Digi XBS2C XBee ZB module User Manual XBee S2C Users Manual

Digi International Inc XBee ZB module XBee S2C Users Manual

User Manual

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XBee®/XBee‐PRO® SMT ZB RF Modules
XBee®/XBee-PRO® SMT ZB RF Modules
This manual describes the operation of the XBee® /XBee-PRO® SMT ZB RF module, which consists of ZigBee
firmware loaded onto XBee® S2C and S2C PRO hardware. The XBee® /XBee-PRO® SMT ZB RF Modules are
designed to operate within the ZigBee protocol and support the unique needs of low-cost, low-power wireless
sensor networks. The modules require minimal power and provide reliable delivery of data between remote
devices. The modules operate within the ISM 2.4 GHz frequency band.
Digi International Inc.
11001 Bren Road East
Minnetonka, MN 55343 877 912-3444 or 952 912-3444
© 2010 Digi International, Inc.
Page 1
XBee®/XBee‐PRO® SMT ZB RF Modules
http://www.digi.com
© 2010 Digi International, Inc. All rights reserved
No part of the contents of this manual may be transmitted or reproduced in any form or by any means without the
written permission of Digi International, Inc.
ZigBee® is a registered trademark of the ZigBee Alliance.
XBee® and XBee-PRO® are registered trademarks of Digi International, Inc.
Technical Support:
Phone:
Live Chat:
(866) 765-9885 toll-free U.S.A. & Canada
(801) 765-9885 Worldwide
8:00 am - 5:00 pm [U.S. Mountain Time]
www.digi.com
Online Support: http://www.digi.com/support/eservice/login.jsp
Email:
© 2010 Digi International, Inc.
rf-experts@digi.com
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XBee®/XBee‐PRO® SMT ZB RF Modules
Contents
1.
Overview ....................................................................................................................................... 13
Specifications .................................................................................................................................... 13
General Specifications ................................................................................................................... 13
RF Specifications ............................................................................................................................ 13
Electrical Specifications.................................................................................................................. 14
Environmental Specifications ......................................................................................................... 14
Serial Communications Specifications ............................................................................................ 14
Network and Security .................................................................................................................... 15
GPIO Specifications ........................................................................................................................ 15
Agency Approvals .......................................................................................................................... 16
Hardware Specifications for Programmable Variant ....................................................................... 16
What’s New ....................................................................................................................................... 17
Firmware ....................................................................................................................................... 17
Manual .......................................................................................................................................... 17
Pin Signals ......................................................................................................................................... 18
EM357 Pin Mappings ......................................................................................................................... 19
Design Notes ..................................................................................................................................... 19
Power Supply................................................................................................................................. 19
Recommended Pin Connections..................................................................................................... 20
Board Layout ................................................................................................................................. 20
Module Operation for Programmable Variant ................................................................................ 23
XBEE Programmable Bootloader ........................................................................................................ 25
Overview ....................................................................................................................................... 25
Bootloader Software Specifics........................................................................................................ 25
Bootloader Menu Commands ........................................................................................................ 30
Firmware Updates ......................................................................................................................... 31
Output File Configuration .............................................................................................................. 32
1.
RF Module Operation.................................................................................................................... 33
Serial Communications ...................................................................................................................... 33
UART Communications .................................................................................................................. 33
SPI Communications ...................................................................................................................... 34
© 2010 Digi International, Inc.
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XBee®/XBee‐PRO® SMT ZB RF Modules
Serial Buffers ................................................................................................................................. 35
Serial Flow Control ......................................................................................................................... 36
Serial Interface Protocols ............................................................................................................... 36
Modes of Operation .......................................................................................................................... 39
Idle Mode ...................................................................................................................................... 39
Transmit Mode .............................................................................................................................. 39
Receive Mode ................................................................................................................................ 40
Command Mode ............................................................................................................................ 40
Sleep Mode ................................................................................................................................... 42
3. XBee ZigBee Networks ....................................................................................................................... 43
Introduction to ZigBee ....................................................................................................................... 43
ZigBee Stack Layers............................................................................................................................ 43
Networking concepts ......................................................................................................................... 43
Device Types.................................................................................................................................. 43
PAN ID ........................................................................................................................................... 44
Operating Channel ......................................................................................................................... 45
ZigBee Application Layers: In Depth ................................................................................................... 45
Application Support Sublayer (APS)................................................................................................ 45
Application Profiles ........................................................................................................................ 45
Clusters ......................................................................................................................................... 46
Endpoints ...................................................................................................................................... 46
ZigBee Device Profile ..................................................................................................................... 47
ZigBee Device Objects (ZDO) .......................................................................................................... 47
Coordinator Operation ...................................................................................................................... 47
Forming a Network ........................................................................................................................ 47
Channel Selection .......................................................................................................................... 47
PAN ID Selection ............................................................................................................................ 47
Security Policy ............................................................................................................................... 47
Persistent Data .............................................................................................................................. 47
XBee ZB Coordinator Startup ............................................................................................................. 48
Permit Joining ................................................................................................................................ 49
Resetting the Coordinator.............................................................................................................. 49
© 2010 Digi International, Inc.
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XBee®/XBee‐PRO® SMT ZB RF Modules
Leaving a Network ......................................................................................................................... 49
Replacing a Coordinator (Security Disabled Only)........................................................................... 50
Example: Starting a Coordinator .................................................................................................... 50
Example: Replacing a Coordinator (security disabled) .................................................................... 51
Router Operation .............................................................................................................................. 51
Discovering ZigBee Networks ........................................................................................................ 51
Joining a Network ......................................................................................................................... 51
Authentication .............................................................................................................................. 52
Persistent Data.............................................................................................................................. 52
XBee ZB Router Joining ................................................................................................................. 52
Permit Joining ............................................................................................................................... 53
Joining Always Enabled ................................................................................................................. 53
Joining Temporarily Enabled ......................................................................................................... 53
Router Network Connectivity........................................................................................................ 53
Leaving a Network ........................................................................................................................ 55
Resetting the Router ..................................................................................................................... 56
Example: Joining a Network ......................................................................................................... 56
End Device Operation ....................................................................................................................... 56
Discovering ZigBee Networks ........................................................................................................ 56
Joining a Network ......................................................................................................................... 57
Parent Child Relationship .............................................................................................................. 57
End Device Capacity ...................................................................................................................... 57
Authentication .............................................................................................................................. 57
Persistent Data.............................................................................................................................. 57
Orphan Scans ................................................................................................................................ 57
XBee: ZB End Device Joining.......................................................................................................... 57
Parent Connectivity....................................................................................................................... 58
Resetting the End Device .............................................................................................................. 59
Leaving a Network ........................................................................................................................ 59
Example: Joining a Network .......................................................................................................... 59
Channel Scanning.............................................................................................................................. 60
Managing Multiple ZigBee Networks ................................................................................................ 60
© 2010 Digi International, Inc.
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XBee®/XBee‐PRO® SMT ZB RF Modules
Pan ID Filtering.................................................................................................................................. 60
Preconfigured Security Keys.......................................................................................................... 60
Permit Joining ............................................................................................................................... 60
Application Messaging .................................................................................................................. 60
4. Transmission, Addressing, and Routing ............................................................................................ 62
Addressing ........................................................................................................................................ 62
64-bit device Address .................................................................................................................... 62
16-bit Device Address ................................................................................................................... 62
Application Layer Addressing ........................................................................................................ 62
Data Transmission......................................................................................................................... 62
Broadcast Transmissions ............................................................................................................... 62
Unicast Transmissions ................................................................................................................... 63
DATA Transmission Examples ....................................................................................................... 65
RF Packet Routing ............................................................................................................................. 66
Link Status Transmission ................................................................................................................... 67
AODV Mesh Routing ......................................................................................................................... 68
Many-to-One Routing ....................................................................................................................... 70
Source Routing.................................................................................................................................. 71
Acquiring Source Routes ............................................................................................................... 72
Storing Source Routes ....................................................................................................................... 72
Sending a Source Routed Transmission ......................................................................................... 72
Repairing Source Routes ............................................................................................................... 73
Retries and Acknowledgments...................................................................................................... 73
Encrypted Transmissions .................................................................................................................. 74
Maximum RF Payload Size ................................................................................................................ 74
Throughput ....................................................................................................................................... 74
ZDO Transmissions ............................................................................................................................ 75
ZigBee Device Objects (ZDO) ......................................................................................................... 75
Sending a ZDO Command.............................................................................................................. 76
Receiving ZDO Commands and Responses .................................................................................... 76
Transmission Timeouts ..................................................................................................................... 77
Unicast Timeout ............................................................................................................................ 78
© 2010 Digi International, Inc.
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XBee®/XBee‐PRO® SMT ZB RF Modules
Extended Timeout ......................................................................................................................... 78
Transmission Examples ................................................................................................................. 79
5.
Security ......................................................................................................................................... 81
Security Modes ................................................................................................................................. 81
ZigBee Security Model ...................................................................................................................... 81
Network Layer Security ................................................................................................................. 81
Frame Counter .............................................................................................................................. 82
Message Integrity code ................................................................................................................. 82
Network Layer Encryption and Decryption ................................................................................... 82
Network Key Updates ................................................................................................................... 82
APS Layer Security......................................................................................................................... 82
Message Integrity Code................................................................................................................. 83
APS Link Keys ................................................................................................................................ 83
APS Layer Encryption and Decryption ........................................................................................... 83
Network and APS Layer Encryption ............................................................................................... 83
Trust Center .................................................................................................................................. 84
Forming and Joining a secure Network ......................................................................................... 84
Implementing Security on the XBee .................................................................................................. 84
Enabling Security........................................................................................................................... 84
Setting the Network Security Key ................................................................................................. 85
Setting the APS Trust Center Link Key ........................................................................................... 85
Enabling APS Encryption ............................................................................................................... 85
Using a Trust Center ...................................................................................................................... 85
XBee Security Examples .................................................................................................................... 86
Example 1: Forming a network with security (pre-configured link keys) ....................................... 86
Example 1: Forming a network with security (obtaining keys during joining) ............................... 86
6.
Network Commissioning and Diagnostics ..................................................................................... 88
Device Configuration......................................................................................................................... 88
Device Placement ............................................................................................................................. 88
Link Testing ................................................................................................................................... 88
RSSI Indicators .............................................................................................................................. 89
Device Discovery ............................................................................................................................... 89
© 2010 Digi International, Inc.
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XBee®/XBee‐PRO® SMT ZB RF Modules
Network Discovery ........................................................................................................................ 89
ZDO Discovery ............................................................................................................................... 89
Joining Announce .......................................................................................................................... 89
Commissioning Pushbutton and Associate LED ................................................................................. 89
Commissioning Pushbutton .......................................................................................................... 90
Associate LDE ................................................................................................................................ 90
7.
Managing End Devices .................................................................................................................. 93
End Device Operation ....................................................................................................................... 93
Parent Operation .............................................................................................................................. 93
End Device Poll Timeouts .............................................................................................................. 94
Packet Buffer Usage ...................................................................................................................... 94
Non-Parent Device Operation ........................................................................................................... 94
XBee End Device Configuration......................................................................................................... 95
Pin Sleep ....................................................................................................................................... 95
Cyclic Sleep ................................................................................................................................... 97
Transmitting RF Data................................................................................................................... 100
Receiving RF Data........................................................................................................................ 100
IO Sampling ................................................................................................................................. 101
Waking End Devices with the Commissioning Pushbutton.......................................................... 101
Parent Verification ...................................................................................................................... 101
Rejoining ..................................................................................................................................... 101
XBee Router/Coordinator Configuration......................................................................................... 101
RF Packet Buffering Timeout ....................................................................................................... 102
Child Poll Timeout ....................................................................................................................... 102
Transmission Timeout ................................................................................................................. 102
Putting it all Together ..................................................................................................................... 102
Short Sleep Periods ..................................................................................................................... 102
Extended Sleep Periods ............................................................................................................... 103
Sleep Examples ............................................................................................................................... 103
Configure a device to sleep for 20 seconds, but set SN such that the On/Sleep line will remain
deasserted for up to 1 minute..................................................................................................... 103
© 2010 Digi International, Inc.
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XBee®/XBee‐PRO® SMT ZB RF Modules
Configure an end device to sleep for 20 seconds, send 4 IO samples in 2 seconds, and return to
sleep. .......................................................................................................................................... 103
Configure a device for extended sleep: to sleep for 4 minutes. .................................................. 104
8.
XBee Analog and Digital IO Lines................................................................................................. 105
IO Configuration.............................................................................................................................. 105
IO Sampling..................................................................................................................................... 106
Queried Sampling........................................................................................................................ 107
Periodic IO Sampling ................................................................................................................... 108
Change Detection Sampling ........................................................................................................ 108
RSSI PWM ....................................................................................................................................... 108
IO Examples .................................................................................................................................... 109
Example 1: Configure the following IO settings on the XBee....................................................... 109
Example 2: Calculate the PWM counts for a packet received with an RSSI of -84dBm. ............... 109
Example 3: Configure the RSSI/PWM pin to operate for 2 seconds after each received RF packet.
.................................................................................................................................................... 109
9.
API Operation ............................................................................................................................. 110
API Frame Specifications ................................................................................................................. 110
API Operation (AP parameter = 1) ............................................................................................... 110
API Operation-with Escape Characters (AP parameter = 2) ......................................................... 110
API Examples ............................................................................................................................... 112
API UART and SPI Exchanges ........................................................................................................... 112
AT Commands ............................................................................................................................. 112
Transmitting and Receiving RF Data............................................................................................ 113
Remote AT commands ................................................................................................................ 113
Source Routing ............................................................................................................................ 114
Supporting the API .......................................................................................................................... 114
API Frames ...................................................................................................................................... 115
AT Command............................................................................................................................... 115
AT Command-Queue Parameter Value ....................................................................................... 115
ZigBee Transmit Request............................................................................................................. 116
Explicit Addressing ZigBee Command Frame............................................................................... 118
Remote AT Command Request ................................................................................................... 120
© 2010 Digi International, Inc.
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XBee®/XBee‐PRO® SMT ZB RF Modules
Create Source Route ................................................................................................................... 120
AT Command Response .............................................................................................................. 122
Modem Status............................................................................................................................. 122
ZigBee Transmit Status................................................................................................................ 123
ZigBee Receive Packet ................................................................................................................. 124
ZigBee Explicit RX Indicator ......................................................................................................... 125
ZigBee IO Data Sample RX Indicator............................................................................................ 126
XBee Sensor Read Indicator ........................................................................................................ 127
Node Identification Indicator ...................................................................................................... 129
Remote Command Response ...................................................................................................... 130
Over-the-Air Firmware Update Status......................................................................................... 131
Route Record Indicator ............................................................................................................... 132
Many-to-One Route Request Indicator ....................................................................................... 133
Sending ZigBee device objects (ZDO) Commands with the API ................................................... 134
Sending ZigBee Cluster Library (ZCL) Commands with the API .................................................... 136
Sending Public Profile Commands with the API .......................................................................... 139
10.
XBee Command Reference Tables ........................................................................................... 142
Addressing ...................................................................................................................................... 142
Networking ..................................................................................................................................... 143
Security ........................................................................................................................................... 145
RF Interfacing .................................................................................................................................. 146
Serial Interfacing ............................................................................................................................. 148
Serial Interfacing ............................................................................................................................. 149
Diagnostics Interfacing.................................................................................................................... 152
AT Command Options ..................................................................................................................... 153
Sleep Commands ............................................................................................................................ 153
Execution Commands ..................................................................................................................... 154
11.
Module Support ...................................................................................................................... 156
X-CTU Configuration Tool................................................................................................................ 156
Customizing XBee ZB Firmware....................................................................................................... 156
Design Considerations for Digi Drop-In Networking........................................................................ 156
XBee Bootloader ............................................................................................................................. 156
© 2010 Digi International, Inc.
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XBee®/XBee‐PRO® SMT ZB RF Modules
Programming XBee Modules........................................................................................................... 157
Serial Firmware Updates ............................................................................................................. 157
Invoke XBee Bootloader.............................................................................................................. 157
Send Firmware Image ................................................................................................................. 157
Writing Custom Firmware ............................................................................................................... 158
Regulatory Compliance ............................................................................................................... 158
Configuring GPIOs ....................................................................................................................... 159
Detecting XBee vs. XBee-PRO...................................................................................................... 159
12.
Agency Certifications............................................................................................................... 160
United States FCC............................................................................................................................ 160
OEM Labeling Requirements ....................................................................................................... 160
FCC Notices ................................................................................................................................. 160
FCC-Approved Antennas (2.4 GHz) .............................................................................................. 161
RF Exposure................................................................................................................................. 164
Europe (ETSI)................................................................................................................................... 165
OEM Labeling Requirements ....................................................................................................... 165
Restrictions ................................................................................................................................. 165
Declarations of Conformity ......................................................................................................... 165
Approved Antennas .................................................................................................................... 166
XBee RF Module .......................................................................................................................... 166
Canada (IC) ...................................................................................................................................... 167
Transmitters with Detachable Antennas ..................................................................................... 167
Detachable Antenna ................................................................................................................... 167
Australia (C-Tick) ............................................................................................................................. 167
13.
Migrating from XBee S2B to XBee S2C .................................................................................... 168
Pin Mapping.................................................................................................................................... 168
Mounting ........................................................................................................................................ 168
14.
Manufacturing Information..................................................................................................... 170
Recommended Solder Reflow Cycle................................................................................................ 170
Recommended Footprint ................................................................................................................ 171
Flux and Cleaning ............................................................................................................................ 171
Reworking ....................................................................................................................................... 172
© 2010 Digi International, Inc.
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XBee®/XBee‐PRO® SMT ZB RF Modules
15.
Warranty Information ............................................................................................................. 173
1-Year Warranty ............................................................................................................................. 173
Appendix A: Definitions ..................................................................................................................... 174
Definitions ...................................................................................................................................... 174
ZigBee Node Types ...................................................................................................................... 174
ZigBee Protocol ........................................................................................................................... 175
© 2010 Digi International, Inc.
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XBee®/XBee‐PRO® SMT ZB RF Modules
1. Overview
XBee® and XBee-PRO® S2C SMT ZB embedded RF modules provide wireless connectivity to end-point
devices in ZigBee mesh networks. Utilizing the ZigBee PRO Feature Set, these modules are interoperable
with other ZigBee devices, including devices from other vendors. With XBee, users can have their ZigBee
network up-and-running in a matter of minutes without configuration or additional development. The
programmable XBee® and XBee-PRO® S2C SMT ZB modules incorporate a Freescale SO8 microprocessor
for customization and application development.
XBee® and XBee-PRO® ZB Modules are compatible with other devices that use XBee® “ZB" technology.
These include ConnectPort X gateways, XBee® and XBee-PRO® Adapters, XBee Wall Routers, XBee
Sensors, and other products when designated with the "ZB" product name. Devices that do not have the
"ZB" product name, including Digi's line of DigiMesh and 802.15.4 XBee products, are not compatible with
XBee® and XBee-PRO® ZB Modules.
Network interoperability with ZigBee devices from other vendors requires that the ZigBee Feature Set or
ZigBee PRO Feature Set be deployed on all devices. Contact Digi Support for details.
Specifications
General Specifications
Specification
Performance
Dimensions
Operating Temperature
Antenna Options
XBee (S2C)
XBee-PRO (S2C)
0.866 X 1.3" (2.199 X 3.302 cm)
-40 to 85° C (Industrial)
RF Pad, PCB Antenna, or U.FL Connector
RF Specifications
Specification
Performance
Frequency
Number of Channels
Channels
Adjustable Power
Interface immunity
Indoor/Urban Range
Outdoor RF line-of-sight
Range
Transmit Power Output
© 2010 Digi International, Inc.
XBee ® (S2C)
ISM 2.4-2.5GHz
16 Direct Sequence Channels
11 to 26
Yes
XBee-PRO® (S2C)
16
11 to 26
DSSS (Direct Sequence Spread Spectrum)
200 ft
300 Ft
up to 4000 ft (1200m)
Up to 2 miles
6.3mW (8dBm) Boost mode,
2mW (3dBm) Normal mode
Channel 26 max power is 3dBm
360mW (18dBm)
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XBee®/XBee‐PRO® SMT ZB RF Modules
RF Data Rate
Receiver Sensitivity
250,000 bps
-101dBm, Boost mode
-102dBm, Boost mode
-100dBm, Normal mode
99dBm, Normal mode
Electrical Specifications
XBee® (S2C)
XBee-PRO® (S2C)
Supply Voltage
2.1 - 3.6 V
2.2 – 3.6V for Programmable
Version
2.7 -3.6V
Operating Current
(transmit, max output power)
45mA (@3.3V Boost mode)
33mA (@3.3V, Normal mode)
100mA at 18dBm
Specification
Performance
Operating Current
(Receive)
Idle Current (Receiver off)
Power-down Current
31mA (@3.3V Boost mode)
28mA (@3.3V, Normal mode)
9mA
9mA
<1uA @25C
<1uA @ 25C
Environmental Specifications
Specification
Performance
ESD
MSL
ROHS
XBee (S2C)
XBee-PRO (S2C)
3000 V HBM
>4000 V HBM
Compliant
Serial Communications Specifications
The XBee® /XBee-PRO® SMT ZB RF modules support both UART (Universal Asynchronous
Receiver/Transmitter) and SPI (Serial Peripheral Interface, in master or slave mode) serial connections.
UART
The SC1 (Serial Communication Port 1) of the Ember 357 is connected to the UART port.
UART Pin Assignments
Specification
UART Pins
DOUT
DIN/nCONFIG
nCTS/DIO7
nRTS/DIO6
© 2010 Digi International, Inc.
XBee (S2C)
XBee-PRO (S2C)
Module Pin Number
25
29
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XBee®/XBee‐PRO® SMT ZB RF Modules
More information on UART operation is found in the UART section in chapter 2
SPI
The SC2 (Serial Communication Port 2) of the Ember 357 is connected to the SPI port.
SPI Pin Assignments
Specification
SPI Pins
SPI_SCLK/DIO18
SPI_nSSEL/DIO17
SPI_MOSI/DIO16
SPI_MISO/DIO15
XBee (S2C)
XBee-PRO (S2C)
Module Pin Number
14
15
16
17
For more information on SPI operation see the SPI section in chapter 2
Network and Security
Specification
Performance
Supported Network
Topologies
XBee (S2C)
XBee-PRO (S2C)
Point-to-point, Point-to-multipoint,
Peer-to-peer, and Mesh
PAN ID and Addresses, Cluster IDs
and Endpoints (optional)
Addressing Options
GPIO Specifications
The XBee® /XBee-PRO® SMT ZB RF modules have 16 GPIO (General Purpose Input Output) ports available.
Those available will depend on the module configuration as some GPIO pads are consumed by serial
communication, etc.
See GPIO section for more information on configuring and using GPIO ports
Electrical Specification for GPIO pads
Specification
Performance
Voltage Supply
Low Schmitt switching
threshold
High Schmitt switching
threshold
Input current for logic 0
Input current for logic 1
Input pull-up resistor value
© 2010 Digi International, Inc.
XBee (S2C)
XBee-PRO (S2C)
Module Pin Number
2.1 to 3.6V
0.42 to 0.5 X VDD
0.62 to 0.8 X VDD
-0.5uA
0.5uA
29kΩ
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XBee®/XBee‐PRO® SMT ZB RF Modules
Input pull-down resistor value
29kΩ
Output voltage for logic 0
Output voltage for logic 1
0.18 X VDD (Max)
0.82 X VDD (Min)
Output source current for pad
numbers 3, 4, 5, 10, 12, 14,
16, 17, 26, 28, 29, 30, and 32
4mA
Output sink current for pad
numbers 3, 4, 5, 10, 12, 14,
16, 17, 26, 28, 29, 30, and 33
4mA
Output source current for pad
numbers 7,8,24,31, and 33
8mA
Output sink current for pad
numbers 7,8,24,31, and 34
8mA
Total output current (for I/O
Pads)
40mA
Agency Approvals
Specification
Performance
United States (FCC Part
15.247)
Industry Canada (IC)
Europe (DC)
Australia
Japan
XBee (S2C)
XBee-PRO (S2C)
FCC ID: MCQ-XBS2C
FCC ID: MCQ-XBPS2C
IC: 1846A-XBS2C
ETSI
C-Tick
Pending
IC: 1846A-XBPS2C
C-Tick
FCC Approval (USA) Refer to Chapter 12 FCC Requirements. Systems that contain XBee®/ XBee-PRO® ZB RF Modules inherit Digi
Certifications.
Hardware Specifications for Programmable Variant
The following specifications need to be added to the current measurement of the previous table if the module
has the programmable secondary processor. For example, if the secondary processor is running and constantly
collecting DIO samples at a rate while having the RF portion of the XBEE sleeping the new current will be I total
= Ir2 + Is. Where Ir2 is the runtime current of the secondary processor and is the sleep current of the RF
portion of the module of the XBEE-PRO (S2B) listed in the table below.
Specifications of the programmable secondary processor
© 2010 Digi International, Inc.
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XBee®/XBee‐PRO® SMT ZB RF Modules
Optional Secondary Processor Specification
These numbers add to S2C
specifications (Add to RX, TX and Sleep
currents depending on mode of
operation)
Runtime current for 32K running at 20MHz
Runtime current for 32K running at 1MHz
Sleep current
For additional Specifications see Freescale
Datasheet and Manual
+14mA
+1mA
+0.5uA typical
Minimum Reset low pulse time for EM357
VREF Range
26uS
1.8VDC to VCC
MC9S08QE32
What’s New
Firmware
Manual
© 2010 Digi International, Inc.
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XBee®/XBee‐PRO® SMT ZB RF Modules
Pin Signals
Pin Assignments for the XBee S2C and XBee S2C Pro modules
(Low-asserted signals are distinguished with a lower case n before the signal name.)
Pin #
10
11
Name
GND
VCC
DOUT/DIO13
Din/nConfig/DIO14
DIO12
nRESET
RSSI PWM/ DIO10
PWM1/DIO11
reserved
nDTR/SLEEP_RQ/DIO8
GND
Direction
Both
Both
Both
Both
Both
Both
Both
Default State
Output
Input
12
SPI_Attn/nBOOTMODE
Output
Output
13
14
GND
SPI_CLK/DIO18
Both
15
SPI_nSSEL/DIO17
Both
16
SPI_MOSI/DOI16
Both
17
SPI_MOSO/DOI15
Both
18
JTCK/SWCLK
Input
19
JTDO/SWO
Output
20
21
22
23
24
25
26
JTDI
JTMS/SWDIO
GND
reserved
DIO4
nCTS/DIO7
On /SLEEP/DIO9
Input
Both
Both
Both
Output
27
VREF
Input
28
29
30
31
32
33
34
35
36
37
Associate/DIO5
nRTS/DIO6/SCLK2
AD3/DIO3
AD2/DIO2
AD0/DIO0
AD1/DIO2
reserved
GND
RF
reserved
Both
Both
Both
Both
Both
Both
Both
Output
Input
© 2010 Digi International, Inc.
Disabled
Input
Description
Ground
Power Supply
Uart Data out/GPIO
Uart Data In/GPIO
GPIO
Module Reset
RX Signal Strength Indicator/ GPIO
Pulse Width Modulator/GPIO
Do Not Connect
Pin Sleep Control line /GPIO
Ground
Serial Peripheral Interface Attention
Do not tie low on reset
Ground
Serial Peripheral Interface Clock/GPIO
Serial Peripheral Interface not
Select/GPIO
Serial Peripheral Interface Data
Input/GPIO
Serial Peripheral Interface Data
Output/GPIO
JTAG Clock/Serial Wire Clock
JTAG Data Output/Serial Wire Data
Output
JTAG Data Input
Disabled
Output
Output
Disabled
Disabled
Ground
Do Not Connect
GPIO
Clear-to-Send Flow Control/GPIO
Module Status Indicator/GPIO
Not used for EM357. Used for
programmable
secondary processor.
For compatibility with other XBEE
modules, we
recommend connecting this pin to the
voltage reference
if Analog sampling is desired.
Otherwise, connect to GND.
Associate Indicator/GPIO
Request-to-Send Flow Control/GPIO
Analog Input/GPIO
Analog Input/GPIO
Analog Input/GPIO
Analog Input/GPIO
Do Not Connect
Ground
RF IO for RF Pad Variant
Do Not Connect
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XBee®/XBee‐PRO® SMT ZB RF Modules
EM357 Pin Mappings
The Following table shows how the EM357 pins are used on the XBee.
EM357 Pin #
12
18
19
20
21
22
24
25
26
27
29
30
31
32
33
34
35
36
38
41
42
43
EM357 Name
nRst
GPIO PB3
GPIO PA7
GPIO PB4
GPIO PA0/SC2MOSI
GPIO PA1/SC2MOSO
GPIO PA2/SC2SCLK
GPIO PA3/SC2nSSEL
GPIO PA4
GPIO PA5/nBOOTMODE
GPIO PA6
GPIO PB1
GPIO PB2
SWCLK,JTCK
GPIO PC2/JTDO/SWO
GPIO PC3/JTDI
GPIO PC4/JTMS/SWDIO
GPIO PB0
GPIO PC1
GPIO PB7,ADC2
GPIO PB6,ADC1
GPIO PB5,ADC0
XBee Pin #
29
25
16
17
14
15
32
12
18
19
20
21
10
30
31
33
Other Usage
Programming
Programming
Programming
Programming
Programming
Programming
Programming
Temp Sensor on PRO Version
NOTE: Some lines may not go to the external XBEE pads in the programmable secondary processor version
Design Notes
The XBee modules do not specifically require any external circuitry or specific connections for proper
operation. However, there are some general design guidelines that are recommended for help in
troubleshooting and building a robust design.
Power Supply
Poor power supply can lead to poor radio performance especially if the supply voltage is not kept within
tolerance or is excessively noisy. To help reduce noise a 1uF and 8.2pF capacitor are recommended to be
placed as near to pin1 on the PCB as possible. If using a switching regulator for your power supply, switching
frequencies above 500 kHz are preferred. Power supply ripple should be limited to a maximum 250mV peak to
peak.
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XBee®/XBee‐PRO® SMT ZB RF Modules
Note – For designs using the programmable modules an additional 10uF decoupling cap is recommended near
pin 1 of the module. The nearest proximity to pin 1 of the 3 caps should be in the following order: 8.2pf, 1uF
followed by 10uF.
Recommended Pin Connections
The only required pin connections are VCC, GND, DOUT and DIN. To support serial firmware updates, VCC,
GND, DOUT, DIN, RTS, and DTR should be connected.
All unused pins should be left disconnected. All inputs on the radio can be pulled high with 30k internal pull-up
resistors using the PR software command. No specific treatment is needed for unused outputs.
For applications that need to ensure the lowest sleep current, inputs should never be left floating. Use internal
or external pull-up or pull-down resistors, or set the unused I/O lines to outputs.
Other pins may be connected to external circuitry for convenience of operation including the Associate LED
pad (pad 28) and the Commissioning pad (pad 33). The Associate LED pin will flash differently depending on
the state of the module to the network, and a pushbutton attached to pad 33 can enable various join
functions without having to send UART commands. Please see the commissioning pushbutton and associate
LED section in chapter 7 for more details. The source and sink capabilities are limited to 4mA for pad numbers
3, 4, 5, 10, 12, 14, 15, 16, 17, 25, 26, 28, 29, 30, and 32, and 8mA for pad numbers 7, 8, 24, 31, and 33 on the
module.
The VREF pin (pad 27) is not used on this module. For compatibility with other XBee modules, we recommend
connecting this pin to a voltage reference if analog sampling is desired. Otherwise, connect to GND.
Board Layout
XBee modules do not have any specific sensitivity to nearby processors, crystals or other PCB components.
Other than mechanical considerations, no special PCB placement is required for integrating XBee radios except
for those with integral antennas. In general, Power and GND traces should be thicker than signal traces and be
able to comfortably support the maximum currents.
The radios are also designed to be self sufficient and work with the integrated and external antennas without
the need for additional ground planes on the host PCB. However, considerations should be taken on the
choice of antenna and antenna location. Metal objects that are near an antenna cause reflections and may
reduce the ability for an antenna to efficiently radiate. Using an integral antenna in an enclosed metal box will
greatly reduce the range of a radio. For this type of application an external antenna would be a better choice.
External antennas should be positioned away from metal objects as much as possible. Metal objects next to
the antenna or between transmitting and receiving antennas can often block or reduce the transmission
distance. Some objects that are often overlooked are metal poles, metal studs or beams in structures,
concrete (it is usually reinforced with metal rods), metal enclosures, vehicles, elevators, ventilation ducts,
refrigerators and microwave ovens.
Antennas should reside above or away from any metal objects like batteries, tall electrolytic capacitors or
metal enclosures. Antenna elements radiate perpendicular to the direction they point. Thus a vertical
antenna emits across the horizon.
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XBee®/XBee‐PRO® SMT ZB RF Modules
PCB Antennas should not have any ground planes or metal objects above or below the module at the antenna
location. For best results the module should be in a plastic enclosure, instead of metal one. It should be placed
at the edge of the PCB to which it is mounted. The ground, power and signal planes should be vacant
immediately below the antenna section (See drawing for recommended keep out area).
© 2010 Digi International, Inc.
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XBee®/XBee‐PRO® SMT ZB RF Modules
© 2010 Digi International, Inc.
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XBee®/XBee‐PRO® SMT ZB RF Modules
Module Operation for Programmable Variant
The S2C modules with the programmable option have a secondary processor with 32k of flash and 2k of RAM.
This allows module integrators to put custom code on the XBEE module to fit their own unique needs. The
DIN, DOUT, RTS, CTS, and RESET lines are intercepted by the secondary processor to allow it to be in control of
the data transmitted and received. All other lines are in parallel and can be controlled by either the EM357 or
the MC9SO8QE micro (see Block Diagram for details). The EM357 by default has control of certain lines. These
lines can be released by the EM357 by sending the proper command(s) to disable the desired DIO line(s) (see
XBEE Command Reference Tables).
In order for the secondary processor to sample with ADCs, the XBEE pin 27 (VREF) needs to be connected to a
reference voltage.
Digi provides a bootloader that can take care of programming the processor over the air or through the serial
interface. This means that over the air updates can be supported through an XMODEM protocol. The
processor can also be programmed and debugged through a one wire interface BKGD (Pin 9).
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XBee®/XBee‐PRO® SMT ZB RF Modules
© 2010 Digi International, Inc.
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XBee®/XBee‐PRO® SMT ZB RF Modules
XBEE Programmable Bootloader
Overview
The XBee Programmable module is equipped with a Freescale MC9S08QExx application processor. This
application processor comes with a supplied bootloader. The following section describes how to interface the
customer's application code running on this processor to the XBee Programmable module's supplied
bootloader. This section discusses how to initiate firmware updates using the supplied bootloader for wired
and over-the-air updates.
Bootloader Software Specifics
Memory Layout
Figure 1 shows the memory map for the MC9S08QE32 application processor.
The supplied bootloader occupies the bottom pages of the flash from 0xF200 to 0xFFFF. Application code
cannot write to this space.
The application code can exist in Flash from address 0x8400 to 0xF1BC. 1k of Flash from 0x8000 to 0x83FF is
reserved for Non Volatile Application Data that will not be erased by the bootloader during a flash update.
A portion of RAM is accessible by both the application and the bootloader. Specifically, there is a shared data
region used by both the application and the bootloader that is located at RAM address 0x200 to 0x215.
Application code should not write anything to AppResetCause or BLResetCause unless informing the
bootloader of the impending reset reason.
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XBee®/XBee‐PRO® SMT ZB RF Modules
© 2010 Digi International, Inc.
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XBee®/XBee‐PRO® SMT ZB RF Modules
Operation
Upon reset of any kind, the execution control begins with the bootloader.
If the reset cause is Power-On reset (POR), Pin reset (PIN), or Low Voltage Detect(LVD) reset the bootloader
will not jump to the application code if the override bits are set to RTS(D7)=1, DTR(D5)=0, and DIN(B0)=0.
Otherwise, the bootloader writes the reset cause "NOTHING" to the shared data region, and jumps to the
Application.
Reset causes are defined in the file common. h in an enumeration with the following definitions:
typedef enum {
BL_CAUSE_NOTHING = 0x0000, //PIN, LVD, POR
BL_CAUSE_NOTHING_COUNT = 0x0001,//BL_Reset_Cause counter
// Bootloader increments cause every reset
BL_CAUSE_BAD_APP = 0x0010,//Bootloader considers APP invalid
} BL_RESET_CAUSES;
typedef enum {
APP_CAUSE_NOTHING = 0x0000,
APP_CAUSE_USE001 = 0x0001,
// 0x0000 to 0x00FF are considered valid for APP use.
APP_CAUSE_USE255 = 0x00FF,
APP_CAUSE_FIRMWARE_UPDATE = 0x5981,
APP_CAUSE_BYPASS_MODE = 0x4682,
APP_CAUSE_BOOTLOADER_MENU = 0x6A18,
} APP_RESET_CAUSES;
Otherwise, if the reset cause is a "watchdog" or other reset, the bootloader checks the shared memory region for
the APP_RESET_CAUSE. If the reset cause is:
1.
2.
3.
"APP_CAUSE_NOTHING" or 0x0000 to 0x00FF, the bootloader increments the  BL_RESET_CAUSES,
verifies that it is still less than BL_CAUSE_BAD_APP, and jumps back to the application. If the
Application does not clear the BL_RESET_CAUSE, it can prevent an infinite loop of running a bad
application that continues to perform illegal instructions or watchdog resets.
"APP_CAUSE_FIRMWARE_UPDATE", the bootloader has been instructed to update the application
"over-the-air" from a specific 64 bit address. In this case, the bootloader will attempt to initiate an
Xmodem transfer from the 64 bit address located in Shared RAM.
"APP_CAUSE_BYPASS_MODE", the bootloader executes bypass mode. This mode passes the  local
UART data directly to the EM250 allowing for direct communication with the EM250. The only way
© 2010 Digi International, Inc.
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XBee®/XBee‐PRO® SMT ZB RF Modules
to exit bypass mode is to reset or power cycle the module. If none of the above is true, the
bootloader will enter "Command mode". In this mode, users can initiate firmware downloads both
wired and over-the-air, check application/bootloader version strings, and enter Bypass mode.
If none of the above is true, the bootloader will enter "Command mode". In this mode, users can initiate firmware
downloads both wired and over-the-air, check application/bootloader version strings, and enter Bypass mode.
Application Version String
Figure 1 shows an "Application version string pointer" area in application flash which holds the pointer to where
the application version string resides. The application's linker command file ultimately determines where this
string is placed in application flash.
It is preferable that the application version string be located at address 0x8400 for MC9S08QE32 parts. The
application string can be any characters terminated by the NULL character (0x00). There is not a strict limit on the
number of characters in the string, but for practical purposes should be kept under 100 bytes including the
terminating NULL character. During an update the bootloader erases the entire application from 0x8400 on. The
last page has the vector table specifically the redirected reset vector. The version string pointer and reset vector
are used to determine if the application is valid.
Application Interrupt Vector Table and Linker Command File
Since the bootloader flash region is read-only, the interrupt vector table is redirected to the region 0xF1C0 to
0xF1FD so that application developers can use hardware interrupts. Note that in order for Application interrupts to
function properly, the Application's linker command file (*.prm extension) must be modified appropriately to allow
the linker to place the developers code in the correct place in memory. For example, the developer desires to use
the serial communications port SCI1 receive interrupt. The developer would add the following line to the
Codewarrior linker command file for the project…
VECTOR ADDRESS 0x0000F1E0 vSci1Rx
This will inform the linker that the interrupt function "vSci1Rx()" should be placed at address 0x0000F1E0. Next,
the developer should add a file to their project "vector_table.c" that creates an array of function pointers to the
ISR routines used by the application…Eg.
extern void _Startup(void);/* _Startup located in Start08.c */
extern void vSci1Rx(void);/* sci1 rx isr */
extern short iWriteToSci1(unsigned char *);
void vDummyIsr(void);
#pragma CONST_SEG VECTORS
void (* const vector_table[])(void) = /* Relocated Interrupt vector table */{
vDummyIsr,/* Int.no. 0 Vtpm3ovf (at F1C0)Unassigned */
vDummyIsr, /* Int.no. 1 Vtpm3ch5 (at F1C2) Unassigned */
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XBee®/XBee‐PRO® SMT ZB RF Modules
vDummyIsr, /* Int.no. 2 Vtpm3ch4 (at F1C4) Unassigned */
vDummyIsr, /* Int.no. 3 Vtpm3ch3 (at F1C6) Unassigned */
vDummyIsr, /* Int.no. 4 Vtpm3ch2 (at F1C8) Unassigned */
vDummyIsr, /* Int.no. 5 Vtpm3ch1 (at F1CA) Unassigned */
vDummyIsr, /* Int.no. 6 Vtpm3ch0 (at F1CC) Unassigned */
vDummyIsr, /* Int.no. 7 Vrtc (at F1CE) Unassigned */
vDummyIsr, /* Int.no. 8 Vsci2tx (at F1D0) Unassigned */
vDummyIsr, /* Int.no. 9 Vsci2rx (at F1D2) Unassigned */
vDummyIsr, /* Int.no. 10 Vsci2err (at F1D4) Unassigned */
vDummyIsr, /* Int.no. 11 Vacmpx (at F1D6) Unassigned */
vDummyIsr, /* Int.no. 12 Vadc (at F1D8) Unassigned */
vDummyIsr, /* Int.no. 13 Vkeyboard (at F1DA) Unassigned */
vDummyIsr, /* Int.no. 14 Viic (at F1DC) Unassigned */
vDummyIsr, /* Int.no. 15 Vsci1tx (at F1DE) Unassigned */
vSci1Rx, /* Int.no. 16 Vsci1rx (at F1E0) SCI1RX */
vDummyIsr, /* Int.no. 17 Vsci1err (at F1E2) Unassigned */
vDummyIsr, /* Int.no. 18 Vspi (at F1E4) Unassigned */
vDummyIsr, /* Int.no. 19 VReserved12 (at F1E6) Unassigned */
vDummyIsr, /* Int.no. 20 Vtpm2ovf (at F1E8) Unassigned */
vDummyIsr, /* Int.no. 21 Vtpm2ch2 (at F1EA) Unassigned */
vDummyIsr, /* Int.no. 22 Vtpm2ch1 (at F1EC) Unassigned */
vDummyIsr, /* Int.no. 23 Vtpm2ch0 (at F1EE) Unassigned */
vDummyIsr, /* Int.no. 24 Vtpm1ovf (at F1F0) Unassigned */
vDummyIsr, /* Int.no. 25 Vtpm1ch2 (at F1F2) Unassigned */
vDummyIsr, /* Int.no. 26 Vtpm1ch1 (at F1F4) Unassigned */
vDummyIsr, /* Int.no. 27 Vtpm1ch0 (at F1F6) Unassigned */
vDummyIsr, /* Int.no. 28 Vlvd (at F1F8) Unassigned */
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XBee®/XBee‐PRO® SMT ZB RF Modules
vDummyIsr, /* Int.no. 29 Virq (at F1FA) Unassigned */
vDummyIsr, /* Int.no. 30 Vswi (at F1FC) Unassigned */
_Startup /* Int.no. 31 Vreset (at F1FE) Reset vector */
};
void vDummyIsr(void){
for(;;){
if(iWriteToSci1("STUCK IN UNASSIGNED ISR\n\r>"));
The interrupt routines themselves can be defined in separate files. The "vDummyIsr" function is used in
conjunction with "iWritetoSci1" for debugging purposes.
Bootloader Menu Commands
The bootloader accepts commands from both the local UART and OTA. All OTA commands sent must be Unicast
with only 1 byte in the payload for each command. A response will be returned to the sender. All Broadcast and
multiple byte OTA packets are dropped to help prevent general OTA traffic from being interpreted as a command
to the bootloader while in the menu.
Bypass Mode – “B”
The bootloader provides a "bypass" mode of operation that essentially connects the SCI1 serial communications
peripheral of the Freescale MCU to the EM357's serial Uart channel. This allows direct communication to the
EM357 radio for the purpose of firmware and radio configuration changes. Once in bypass mode, the XCTU utility
can change modem configuration and/or update EM357 firmware. Bypass mode automatically handles any baud
rate up to 115.2kbps. Note that this command is unavailable when module is accessed remotely.
Update Firmware – “F”
The "F" command initiates a firmware download for both wired and over-the-air configurations. Depending on the
source of the command (received via local UART/SPI, or Over the Air), the download will proceed via wired or overthe-air respectively.
Adjust Timeout for Update Firmware – “T”
The "T" command changes the timeout before sending a NAK by Base-Time*2^(T). The Base-Time for the local
UART is different than the Base-Time for Over the Air. During a firmware update, the bootloader will automatically
increase the Timeout if repeat packets are received or multiple NAKs for the same packet without success occur.
Application Version String – “A”
The "A" command provides the version of the currently loaded application. If no application is present, "Unkown"
will be returned.
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XBee®/XBee‐PRO® SMT ZB RF Modules
Bootloader Version String – “V”
The "V" command provides the version of the currently loaded bootloader.
The version will return a string in the format BLFFF-HHH-XYZ_DDD where FFF represents the Flash size in kilo bytes,
HHH is the hardware, XYZ is the version, and DDD is the preferred XMODEM packet size for updates. Double the
preferred packet size is also possible, but not guaranteed. For example "BL032-2B0-023_064" will take 64 byte CRC
XMODEM payloads and may take 128 byte CRC XMODEM payloads also. In this case, both 64 and 128 payloads are
handled, but the 64 byte payload is preferred for better Over the Air reliability.
Firmware Updates
Wired Updates
A user can update their application using the bootloader in a wired configuration with the following steps…
a. Plug XBee programmable module into a suitable serial port on a PC.
b. Open a hyperterminal (or similar dumb terminal application) session with 9600 baud, no parity, and 8
data bits with one stop bit.
c. Hit Enter to display the bootloader menu.
d. Hit the "F" key to initiate a wired firmware update.
e. A series of "C" characters Will be displayed within the hyperterminal window. At this point, select the
"transfer->send file" menu item. Select the desired flat binary output file. (The file should start at 0x8400
not 0x0000).
f. Select "Xmodem" as the protocol.
g. Click "Send" on the "Send File" dialog. The file will be downloaded to the XBee Programmable module.
Upon a successful update, the bootloader will jump to the newly loaded application.
Over-The-Air Updates
A user can update their application using the bootloader in an "over-the-air" configuration with the following
steps…(This procedure assumes that the bootloader is running and not the application. The EM357 baud rate must
be set to 9600 baud. The bootloader only operates at 9600 baud. The application must be programmed with some
way to support returning to the bootloader in order to support Over the Air (OTA) updates without local
intervention.)
a. The XBee module sending the file OTA (Host module) should be set up with a series 2 XBee module with
transparent mode firmware.
b. The XBee Programmable module receiving the update (remote module) is configured with API
firmware.
c. Open a hyperterminal session to the host module with 9600 baud, no parity, no hardwareflow control,
8 data bits and 1 stop bit.
d. Enter 3 pluses "+++" to place the EM357 in command mode.
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XBee®/XBee‐PRO® SMT ZB RF Modules
e. Set the Host Module destination address to the target module’s 64 bit address that the host module
will update (ATDH aabbccdd, ATDL eeffgghh, ATCN, where aabbccddeeffgghh is the hexa-decimal 64 bit
address of the target module).
f. Hit Enter and the bootloader command menu will be displayed from the remote module. (Note that the
option "B" doesn't exist for OTA)
g. Hit the "F" key to cause the remote module to request the new firmware file over-the-air.
h. The host module will begin receiving "C" characters indicating that the remote module is requesting an
Xmodem CRC transfer. Using XCTU or another terminal program, Select "XMODEM" file transfer. Select
the Binary file to upload/transfer. Click Send to start the transfer. At the con-clusion of a successful
transfer, the bootloader will jump to the newly loaded application.
Output File Configuration
BKGD Programming
P&E Micro provides a background debug tool that allows flashing applications on the MC9S08QE parts through
their background debug mode port. By default, the Codewarrior tool produces an "ABS" output file for use in
programming parts through the background debug interface. The programmable XBee from the factory has the
BKGD debugging capability disabled. In order to debug, a bootloader with the debug interface enabled needs to be
loaded on the secondary processor or a stand-alone app needs to be loaded.
Bootloader Updates
The supplied bootloader requires files in a "flat binary" format which differs from the default ABS file produced.
The Codewarrior tool also produces a S19 output file. In order to successfully flash new applications, the S19 file
must be converted into the flat binary format. Utilities are available on the web that will convert S19 output to
"BIN" outputs. Often times, the "BIN" file conversion will pad the addresses from 0x0000 to the code space with
the same number. (Often 0x00 or 0xFF) These extra bytes before the APP code starts will need to be deleted from
the bin file before the file can be transferred to the bootloader.
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XBee®/XBee‐PRO® SMT ZB RF Modules
1. RF Module Operation
Serial Communications
The XBee RF Modules interface to a host device through a logic-level asynchronous serial port, or a Serial
Peripheral Interface (SPI) port. Through its serial ports, the module can communicate with any logic and
voltage compatible UART or SPI; or through a level translator to any serial device (for example: through a RS232 or USB interface board).
Two wire serial interface (TWI) is also available, but not supported by Digi. For information on the TWI see the
EM357 specification.
UART Communications
UART Data Flow
Devices that have a UART interface can connect directly to the pins of the RF module as shown in the figure
below.
UART Serial Data
Data enters the module UART through the DIN (pin 4) as an asynchronous serial signal. The signal should idle
high when no data is being transmitted. Each data byte consists of a start bit (low), 8 data bits (least significant
bit first) and a stop bit (high). The following figure illustrates the serial bit pattern of data passing through the
module.
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XBee®/XBee‐PRO® SMT ZB RF Modules
Serial communications depend on the two UARTs (the microcontroller's and the RF module's) to be configured
with compatible settings (baud rate, parity, start bits, stop bits, data bits).
The UART baud rate, parity, and stop bits settings on the XBee module can be configured with the BD, NB, and
SB commands respectively. See the command table in chapter 10 for details.
SPI Communications
The XBee modules support SPI communications in the slave mode. Slave mode receives the clock signal and data
from the master and returns data to the master. The SPI port uses the following signals on the XBee:
•
•
•
•
SPI_MOSI (Master Out, Slave In) – inputs serial data from the master
SPI_MISO (Master In, Slave Out) – outputs serial data to the master
SPI_SCLK (Serial Clock) – clocks data transfers on MOSI and MISO
SPI_nSSEL (Slave Select) – enables serial communication with the slave
In this mode the following apply:
•
•
•
Data/Clock rates up to 5MBPS are possible.
Data is MSB first
Frame Format mode 0 is used (see below)
Frame Format for SPI communications
SPI mode is chip to chip communication. Digi does not supply SPI communication option of Device Development
Evaluation Boards.
SPI Operation
When the slave select (SPI_nSSEL) signal is asserted by the master, SPI transmit data is driven to the output pin
SPI_MISO, and SPI data is received from the input pin SPI_MOSI. The SPI_nSSEL pin has to be asserted to enable
the transmit serializer to drive data to the output signal SPI_MISO. A falling edge on SPI_nSSEL resets the SPI slave
shift registers.
If the input buffer is empty, the SPI serializer transmits a busy token (0xFF).
The SPI slave controller must guarantee that there is time to move new transmit data from the transmit buffer into
the hardware serializer. To provide sufficient time, the SPI slave controller inserts a byte of padding at the start of
every new string of transmit data. Whenever the transmit buffer is empty and data is placed into the transmit
buffer the SPI hardware inserts a byte of padding onto the front of the transmission as if this byte was placed there
by software.
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XBee®/XBee‐PRO® SMT ZB RF Modules
Serial Buffers
The XBee modules maintain small buffers to collect received serial and RF data, which is illustrated in the
figure below. The serial receive buffer collects incoming serial characters and holds them until they can be
processed. The serial transmit buffer collects data that is received via the RF link that will be transmitted out
the UART or SPI port.
Serial Receive Buffer
When serial data enters the RF module through the DIN Pin (pin 4), the data is stored in the serial receive buffer
until it can be processed. Under certain conditions, the module may not be able to process data in the serial
receive buffer immediately. If large amounts of serial data are sent to the module, CTS flow control may be
required to avoid overflowing the serial receive buffer.
Cases in which the serial receive buffer may become full and possibly overflow:
1. If the module is receiving a continuous stream of RF data, the data in the serial receive buffer
will not be transmitted until the module is no longer receiving RF data.
2. If the module is transmitting an RF data packet, the module may need to discover the
destination address or establish a route to the destination. After transmitting the data, the
module may need to retransmit the data if an acknowledgment is not received, or if the
transmission is a broad-cast. These issues could delay the processing of data in the serial receive
buffer.
Serial Transmit Buffer
When RF data is received, the data is moved into the serial transmit buffer and sent out the UART or SPI port. If the
serial transmit buffer becomes full enough such that all data in a received RF packet won’t fit in the serial transmit
buffer, the entire RF data packet is dropped.
Cases in which the serial transmit buffer may become full resulting in dropped RF packets
1. If the RF data rate is set higher than the interface data rate of the module, the module could
receive data faster than it can send the data to the host.
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2. If the host does not allow the module to transmit data out from the serial transmit buffer
because of being held off by hardware flow control.
Serial Flow Control
The nRTS and nCTS module pins can be used to provide RTS and/or CTS flow control. CTS flow control provides an
indication to the host to stop sending serial data to the module. RTS flow control allows the host to signal the
module to not send data in the serial transmit buffer out the UART or SPI port. RTS and CTS flow control are
enabled using the D6 and D7 commands.
nCTS Flow Control
If CTS flow control is enabled (D7 command), when the serial receive buffer is 17 bytes away from being full, the
module de-asserts nCTS (sets it high) to signal to the host device to stop sending serial data. nCTS is re-asserted
after the serial receive buffer has 34 bytes of space.
nRTS Flow Control
If RTS flow control is enabled (D6 command), data in the serial transmit buffer will not be sent out the DOUT pin as
long as nRTS is de-asserted (set high). The host device should not de-assert nRTS for long periods of time to avoid
filling the serial transmit buffer. If an RF data packet is received, and the serial transmit buffer does not have
enough space for all of the data bytes, the entire RF data packet will be discarded.
Note: If the XBee is sending data out the UART or SPI port when nRTS is de-asserted (set high), the XBee could
send up to 5 characters out the UART or SPI port after RTS is de-asserted.
Serial Interface Protocols
The XBee modules support both transparent and API (Application Programming Interface) serial interfaces.
Transparent Operation
When operating in transparent mode, the modules act as a serial line replacement. All UART or SPI data received
through the respective ports is queued up for RF transmission. When RF data is received, the data is sent out
through the UART or SPI port. The module configuration parameters are configured using the AT command mode
interface.
Data is buffered in the serial receive buffer until one of the following causes the data to be packetized and
transmitted:
•No serial characters are received for
the amount of time determined by the RO (Packetization Time-out)
parameter. If RO = 0, packetization begins when a character is received.
•The Command Mode Sequence (GT + CC + GT) is received. Any character buffered in the serial receive
buffer before the sequence is transmitted.
•The maximum number of characters that will fit in an RF packet is received.
API Operation
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API operation is an alternative to transparent operation. The frame-based API extends the level to which a host
application can interact with the networking capabilities of the module. When in API mode, all data entering and
leaving the module is contained in frames that define operations or events within the module.
Transmit Data Frames (received through the DIN pin (pin 3)) include:
•RF Transmit Data Frame
•Command Frame (equivalent to AT commands) Receive Data Frames (sent out the DOUT pin (pin 2))
include:
•RF-received data frame •Command response
•Event notifications such as reset, associate, disassociate, etc.
The API provides alternative means of configuring modules and routing data at the host application layer. A host
application can send data frames to the module that contain address and payload information instead of using
command mode to modify addresses. The module will send data frames to the application containing status
packets; as well as source, and payload information from received data packets. The API operation option
facilitates many operations such as the examples cited below:
-> Transmitting data to multiple destinations without entering Command Mode
-> Receive success/failure status of each transmitted RF packet
-> Identify the source address of each received packet
A Comparison of Transparent and API Operation
The following table compares the advantages of transparent and API modes of operation:
Transparent Operation Features
Simple Interface
All received serial data is transmitted unless the module is in command mode.
Easy to support
It is easier for an application to support transparent operation and command mode.
API Operation Features
Easy to manage data
transmissions to
multiple destinations
Transmitting RF data to multiple remotes only requires changing the address in the API frame.
This Process is much faster than transparent operation where the application must enter AT
command mode, change the address, exit command mode, and then transmit data.
Each API transmission can return a transmit status frame indicating the success or reason for
failure
Received data frames
indicate the sender's
address
All received RF data API frames indicate the source address.
Advanced ZigBee
addressing support
API transmit and receive frames can expose ZigBee addressing fields including source and
destination endpoints, cluster ID and profile ID. This makes it easy to support ZDO commands
and public profile traffic.
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Advanced Networking
diagnostics
API frames can provide indication of IO samples from remote devices, and node identification
messages.
Remote Configuration
Set/read configuration commands can be sent to remote devices to configure them as needed
using the API.
As a general rule of thumb, API firmware is recommended when a device:
•sends RF data to multiple destinations
•sends remote configuration commands to manage devices in the network
•receives IO samples from remote devices
•receives RF data packets from multiple devices, and the application needs to know which device sent
which packet
•must support multiple ZigBee endpoints, cluster IDs, and/or profile IDs
•uses the ZigBee Device Profile services.
If the above conditions do not apply (e.g. a sensor node, router, or a simple application), then AT firmware might
be suitable. It is acceptable to use a mixture of devices running API and AT firmware in a network.
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Modes of Operation
Idle Mode
When not receiving or transmitting data, the RF module is in Idle Mode. The module shifts into the other modes of
operation under the following conditions:
•Transmit Mode (Serial data in the serial receive buffer is ready to be packetized)
•Receive Mode (Valid RF data is received through the antenna)
•Sleep Mode (End Devices only)
•Command Mode (Command Mode Sequence is issued)
Transmit Mode
When serial data is received and is ready for packetization, the RF module will exit Idle Mode and attempt to
transmit the data. The destination address determines which node(s) will receive the data.
Prior to transmitting the data, the module ensures that a 16-bit network address and route to the destination node
have been established.
If the destination 16-bit network address is not known, network address discovery will take place. If a route is not
known, route discovery will take place for the purpose of establishing a route to the destination node. If a module
with a matching network address is not discovered, the packet is discarded. The data will be transmitted once a
route is established. If route discovery fails to establish a route, the packet will be discarded.
When data is transmitted from one node to another, a network-level acknowledgement is transmitted back across
the established route to the source node. This acknowledgement packet indicates to the source node that the data
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packet was received by the destination node. If a network acknowledgement is not received, the source node will
re-transmit the data.
It is possible in rare circumstances for the destination to receive a data packet, but for the source to not receive
the network acknowledgment. In this case, the source will retransmit the data, which could cause the destination
to receive the same data packet multiple times. The XBee modules do not filter out duplicate packets. The
application should include provisions to address this potential issue
See Data Transmission and Routing in chapter 4 for more information.
Receive Mode
If a valid RF packet is received, the data is transferred to the serial transmit buffer.
Command Mode
To modify or read RF Module parameters, the module must first enter into Command Mode - a state in which
incoming serial characters are interpreted as commands. Refer to the API Mode section in chapter 9 for an
alternate means of configuring modules.
AT Command Mode
To Enter AT Command Mode:
Send the 3-character command sequence “+++” and observe guard times before and
after the command characters. [Refer to the “Default AT Command Mode Sequence”
below.]
Default AT Command Mode Sequence (for transition to Command Mode):
•No characters sent for one second [GT (Guard Times) parameter = 0x3E8]
•Input three plus characters (“+++”) within one second [CC (Command Sequence
Character) parameter = 0x2B.]
•No characters sent for one second [GT (Guard Times) parameter = 0x3E8]
Once the AT command mode sequence has been issued, the module sends an "OK\r" out the
UART or SPI pad. The "OK\r" characters can be delayed if the module has not finished
transmitting received serial data.
When command mode has been entered, the command mode timer is started (CT command),
and the module is able to receive AT commands on the UART or SPI port.
All of the parameter values in the sequence can be modified to reflect user preferences.
NOTE: Failure to enter AT Command Mode is most commonly due to baud rate
mismatch. By default, the BD (Baud Rate) parameter = 3 (9600 bps).
To Send AT Commands:
Send AT commands and parameters using the syntax shown below.
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To read a parameter value stored in the RF module’s register, omit the parameter field.
The preceding example would change the RF module Destination Address (Low) to “0x1F”. To
store the new value to non-volatile (long term) memory, subsequently send the WR (Write)
command.
For modified parameter values to persist in the module’s registry after a reset, changes must be
saved to non-volatile memory using the WR (Write) Command. Otherwise, parameters are
restored to previously saved values after the module is reset.
Command Response
When a command is sent to the module, the module will parse and execute the command. Upon
successful execution of a command, the module returns an “OK” message. If execution of a
command results in an error, the module returns an “ERROR” message.
Applying Command Changes
Any changes made to the configuration command registers through AT commands will not take
effect until the changes are applied. For example, sending the BD command to change the baud
rate will not change the actual baud rate until changes are applied. Changes can be applied in
one of the following ways:
•The AC (Apply Changes) command is issued.
•AT command mode is exited.
To Exit AT Command Mode:
1.
Send the ATCN (Exit Command Mode) command (followed by a carriage return).
[OR]
2.
If no valid AT Commands are received within the time specified by CT (Command Mode Timeout)
Command, the RF module automatically returns to Idle Mode.
For an example of programming the RF module using AT Commands and descriptions of each
configurable parameter, please see the Command Reference Table chapter.
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Sleep Mode
Sleep modes allow the RF module to enter states of low power consumption when not in use. The XBee RF
modules support both pin sleep (sleep mode entered on pin transition) and cyclic sleep (module sleeps for a fixed
time). XBee sleep modes are discussed in detail in chapter 6.
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3. XBee ZigBee Networks
Introduction to ZigBee
ZigBee is an open global standard built on the IEEE 802.15.4 MAC/PHY. ZigBee defines a network layer above the
802.15.4 layers to support advanced mesh routing capabilities. The ZigBee specification is developed by a growing
consortium of companies that make up the ZigBee Alliance. The Alliance is made up of over 300 members,
including semiconductor, module, stack, and software developers.
ZigBee Stack Layers
The ZigBee stack consists of several layers including the PHY, MAC, Network, Application Support Sublayer (APS),
and ZigBee Device Objects (ZDO) layers. Technically, an Application Framework (AF) layer also exists, but will be
grouped with the APS layer in remaining discussions. The ZigBee layers are shown in the figure below.
A description of each layer appears in the following table:
ZigBee Layer
Description
PHY
Defines the physical operation of the ZigBee device including
receive sensitivity, channel rejection, output power, number
of channels, chip modulation, and transmission rate
specifications. Most ZigBee applications operate on the 2.4
GHz ISM band at a 250kbps data rate. See the IEEE 802.15.4
specification for details.
MAC
Manages RF data transactions between neighboring devices
(point to point). The MAC includes services such as
transmission retry and acknowledgement management, and
collision avoidance techniques (CSMA-CA)
Network
Adds routing capabilities that allow RF data packets to
traverse multiple devices (multiple "hops") to route data from
source to destination (peer to peer).
APS (AF)
Application layer that defines various addressing objects
including profiles, clusters, and endpoints.
ZDO
Application layer that provides device and service discovery
features and advanced network management capabilities.
Networking concepts
Device Types
ZigBee defines three different device types: coordinator, router, and end device.
Node Types / Sample of a Basic ZigBee Network Topology
A coordinator has the following characteristics: it
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•Selects a channel and PAN ID (both 64-bit and 16-bit) to start the network
•Can allow routers and end devices to join the network
•Can assist in routing data
•Cannot sleep--should be mains powered
•Can buffer RF data packets for sleeping end device children.
A router has the following characteristics: it
•Must join a ZigBee PAN before it can transmit, receive, or route data
•After joining, can allow routers and end devices to join the network
•After joining, can assist in routing data
•Cannot sleep--should be mains powered.
•Can buffer RF data packets for sleeping end device children.
An end device has the following characteristics: it
•Must join a ZigBee PAN before it can transmit or receive data
•Cannot allow devices to join the network
•Must always transmit and receive RF data through its parent. Cannot route data.
•Can enter low power modes to conserve power and can be battery-powered.
An example of such a network is shown below:
In ZigBee networks, the coordinator must select a PAN ID (64-bit and 16-bit) and channel to start a network. After
that, it behaves essentially like a router. The coordinator and routers can allow other devices to join the network
and can route data.
After an end device joins a router or coordinator, it must be able to transmit or receive RF data through that router
or coordinator. The router or coordinator that allowed an end device to join becomes the "parent" of the end
device. Since the end device can sleep, the parent must be able to buffer or retain incoming data packets destined
for the end device until the end device is able to wake and receive the data.
PAN ID
ZigBee networks are called personal area networks or PANs. Each network is defined with a unique PAN identifier
(PAN ID). This identifier is common among all devices of the same network. ZigBee devices are either
preconfigured with a PAN ID to join, or they can discovery nearby networks and select a PAN ID to join.
ZigBee supports both a 64-bit and a 16-bit PAN ID. Both PAN IDs are used to uniquely identify a network. Devices
on the same ZigBee network must share the same 64-bit and 16-bit PAN IDs. If multiple ZigBee networks are
operating within range of each other, each should have unique PAN IDs.
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The 16-bit PAN ID is used as a MAC layer addressing field in all RF data transmissions between devices in a
network. However, due to the limited addressing space of the 16-bit PAN ID (65,535 possibilities); there is a
possibility that multiple ZigBee networks (within range of each other) could use the same 16-bit PAN ID. To resolve
potential 16-bit PAN ID conflicts, the ZigBee Alliance created a 64-bit PAN ID.
The 64-bit PAN ID (also called the extended PAN ID), is intended to be a unique, non-duplicated value. When a
coordinator starts a network, it can either start a network on a preconfigured 64-bit PAN ID, or it can select a
random 64-bit PAN ID. The 64-bit PAN ID is used during joining; if a device has a preconfigured 64-bit PAN ID, it will
only join a network with the same 64-bit PAN ID. Otherwise, a device could join any detected PAN and inherit the
PAN ID from the network when it joins. The 64-bit PAN ID is included in all ZigBee beacons and is used in 16-bit
PAN ID conflict resolution.
Routers and end devices are typically configured to join a network with any 16-bit PAN ID as long as the 64-bit PAN
ID is valid. Coordinators typically select a random 16-bit PAN ID for their network.
Since the 16-bit PAN ID only allows up to 65,535 unique values, and since the 16-bit PAN ID is randomly selected,
provisions exist in ZigBee to detect if two networks (with different 64-bit PAN IDs) are operating on the same 16bit PAN ID. If such a conflict is detected, the ZigBee stack can perform PAN ID conflict resolution to change the 16bit PAN ID of the network in order to resolve the conflict. See the ZigBee specification for details.
To summarize, ZigBee routers and end devices should be configured with the 64-bit PAN ID of the network they
want to join. They typically acquire the 16-bit PAN ID when they join a network.
Operating Channel
ZigBee utilizes direct-sequence spread spectrum modulation and operates on a fixed channel. The 802.15.4 PHY
defines 16 operating channels (channels 11 to 26) in the 2.4 GHz frequency band. XBee modules support all 16
channels.
ZigBee Application Layers: In Depth
This section provides a more in-depth look at the ZigBee application stack layers (APS, ZDO) including a discussion
on ZigBee endpoints, clusters, and profiles. Much of the material in this section can introduce unnecessary details
of the ZigBee stack that are not required in many cases.
Skip this section if
•The XBee does not need to interoperate or talk to non-Digi ZigBee devices
•The XBee simply needs to send data between devices.
Read this section if
•The XBee may talk to non-Digi ZigBee devices
•The XBee requires network management and discovery capabilities of the ZDO layer
•The XBee needs to operate in a public application profile (smart energy, home automation, etc.)
Application Support Sublayer (APS)
The APS layer in ZigBee adds support for application profiles, cluster IDs, and endpoints.
Application Profiles
Application profiles specify various device descriptions including required functionality for various devices. The
collection of device descriptions forms an application profile. Application profiles can be defined as "Public" or
"Private" profiles. Private profiles are defined by a manufacturer whereas public profiles are defined, developed,
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and maintained by the ZigBee Alliance. Each application profile has a unique profile identifier assigned by the
ZigBee Alliance.
Examples of public profiles include:
•Home Automation
•Smart Energy
•Commercial Building Automation
The Smart Energy profile, for example, defines various device types including an energy service portal, load
controller, thermostat, in-home display, etc. The Smart Energy profile defines required functionality for each
device type. For example, a load controller must respond to a defined command to turn a load on or off. By
defining standard communication protocols and device functionality, public profiles allow interoperable ZigBee
solutions to be developed by independent manufacturers.
Digi XBee ZB firmware operates on a private profile called the Digi Drop-In Networking profile. However, the API
firmware in the module can be used in many cases to talk to devices in public profiles or non-Digi private profiles.
See the API Operations chapter for details.
Clusters
A cluster is an application message type defined within a profile. Clusters are used to specify a unique function,
service, or action. For example, the following are some clusters defined in the home automation profile:
•On/Off - Used to switch devices on or off (lights, thermostats, etc.)
•Level Control - Used to control devices that can be set to a level between on and off
•Color Control - Controls the color of color capable devices.
Each cluster has an associated 2-byte cluster identifier (cluster ID). The cluster ID is included in all application
transmissions. Clusters often have associated request and response messages. For example, a smart energy
gateway (service portal) might send a load control event to a load controller in order to schedule turning on or off
an appliance. Upon executing the event, the load controller would send a load control report message back to the
gateway.
Devices that operate in an application profile (private or public) must respond correctly to all required clusters. For
example, a light switch that will operate in the home automation public profile must correctly implement the
On/Off and other required clusters in order to interoperate with other home automation devices. The ZigBee
Alliance has defined a ZigBee Cluster Library (ZCL) that contains definitions or various general use clusters that
could be implemented in any profile. XBee modules implement various clusters in the Digi private profile. In
addition, the API can be used to send or receive messages on any cluster ID (and profile ID or endpoint). See the
Explicit Addressing ZigBee Command API frame in chapter 3 for details.
Endpoints
The APS layer includes supports for endpoints. An endpoint can be thought of as a running application, similar to a
TCP/IP port. A single device can support one or more endpoints. Each application endpoint is identified by a 1-byte
value, ranging from 1 to 240. Each defined endpoint on a device is tied to an application profile. A device could, for
example, implement one endpoint that supports a Smart Energy load controller, and another endpoint that
supports other functionality on a private profile.
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ZigBee Device Profile
Profile ID 0x0000 is reserved for the ZigBee Device Profile. This profile is implemented on all ZigBee devices. Device
Profile defines many device and service discovery features and network management capabilities. Endpoint 0 is a
reserved endpoint that supports the ZigBee Device Profile. This endpoint is called the ZigBee Device Objects (ZDO)
endpoint.
ZigBee Device Objects (ZDO)
The ZDO (endpoint 0) supports the discovery and management capabilities of the ZigBee Device Profile. A
complete listing of all ZDP services is included in the ZigBee specification. Each service has an associated cluster ID.
The XBee ZB firmware allows applications to easily send ZDO messages to devices in the network using the API. See
the ZDO Transmissions section in chapter 4 for details.
Coordinator Operation
Forming a Network
The coordinator is responsible for selecting the channel, PAN ID (16-bit and 64-bit), security policy, and stack
profile for a network. Since a coordinator is the only device type that can start a network, each ZigBee network
must have one coordinator. After the coordinator has started a network, it can allow new devices to join the
network. It can also route data packets and communicate with other devices on the network.
To ensure the coordinator starts on a good channel and unused PAN ID, the coordinator performs a series of scans
to discover any RF activity on different channels (energy scan) and to discover any nearby operating PANs (PAN
scan). The process for selecting the channel and PAN ID are described in the following sections.
Channel Selection
When starting a network, the coordinator must select a "good" channel for the network to operate on. To do this,
it performs an energy scan on multiple channels (frequencies) to detect energy levels on each channel. Channels
with excessive energy levels are removed from its list of potential channels to start on.
PAN ID Selection
After completing the energy scan, the coordinator scans its list of potential channels (remaining channels after the
energy scan) to obtain a list of neighboring PANs. To do this, the coordinator sends a beacon request (broadcast)
transmission on each potential channel. All nearby coordinators and routers (that have already joined a ZigBee
network) will respond to the beacon request by sending a beacon back to the coordinator. The beacon contains
information about the PAN the device is on, including the PAN identifiers (16-bit and 64-bit). This scan (collecting
beacons on the potential channels) is typically called an active scan or PAN scan.
After the coordinator completes the channel and PAN scan, it selects a random channel and unused 16-bit PAN ID
to start on.
Security Policy
The security policy determines which devices are allowed to join the network, and which device(s) can
authenticate joining devices. See chapter 5 for a detailed discussion of various security policies.
Persistent Data
Once a coordinator has started a network, it retains the following information through power cycle or reset events:
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•PAN ID
•Operating channel
•Security policy and frame counter values
•Child table (end device children that are joined to the coordinator).
The coordinator will retain this information indefinitely until it leaves the network. When the coordinator leaves a
network and starts a new network, the previous PAN ID, operating channel, and child table data are lost.
XBee ZB Coordinator Startup
The following commands control the coordinator network formation process.
Network formation commands used by the coordinator to form a network.
Command
ID
Description
Used to determine the 64-bit PAN ID. If set to 0 (default), a random 64-bit PAN ID
will be selected.
Determines the scan channels bitmask (up to 16 channels) used by the coordinator
when forming a network. The coordinator will perform an energy scan on all
enabled SC channels. It will then perform a PAN ID scan and then form the
network on one of the SC channels
SC
Set the scan duration period. This value determined how long the coordinator
performs an energy scan or PAN ID scan on a given channel.
Set the ZigBee Stack profile for the network.
Enable or disable security in the network.
SD
ZS
EE
NK
Set the network security key for the network. If set to 0 (default), a random
network security key will be used.
KY
Set the trust center link key for the network. If set to 0 (default), a random link key
will be used.
Set the security policy for the network.
EO
Once the coordinator starts a network, the network configuration settings and child table data persist through
power cycles as mentioned in the "Persistent Data" section.
When the coordinator has successfully started a network, it
•Allows other devices to join the network for a time (see NJ command)
•Sets AI=0 •Starts blinking the Associate LED
•Sends an API modem status frame ("coordinator started") out the UART (API firmware only).
These behaviors are configurable using the following commands:
Command
NJ
D5
LT
Description
Sets the permit-join time on the coordinator, measured in seconds.
Enables the Associate LED functionality
Sets the Associate LED blink time when joined. Default is 1 blink per second.
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If any of the command values in the network formation commands table changes, the coordinator will leave its
current network and start a new network, possibly on a different channel. Note that command changes must be
applied (AC or CN command) before taking effect.
Permit Joining
The permit joining attribute on the coordinator is configurable with the NJ command. NJ can be configured to
always allow joining, or to allow joining for a short time.
Joining Always Enabled
If NJ=0xFF (default), joining is permanently enabled. This mode should be used carefully. Once a network has been
deployed, the application should strongly consider disabling joining to prevent unwanted joins from occurring.
Joining Temporarily Enabled
If NJ < 0xFF, joining will be enabled only for a number of seconds, based on the NJ parameter. The timer is started
once the XBee joins a network. Joining will not be re-enabled if the module is power cycled or reset. The following
mechanisms can restart the permit-joining timer:
•Changing NJ to a different value (and applying changes with the AC or CN commands)
•Pressing the commissioning button twice (enables joining for 1 minute)
•Issuing the CB command with a parameter of 2 (software emulation of a 2 button press - enables joining
for 1 minute).
Resetting the Coordinator
When the coordinator is reset or power cycled, it checks its PAN ID, operating channel and stack profile against the
network configuration settings (ID, CH, and ZS). It also verifies the saved security policy against the security
configuration settings (EE, NK, KY). If the coordinator's PAN ID, operating channel, stack profile, or security policy is
not valid based on its network and security configuration settings, then the coordinator will leave the network and
attempt to form a new network based on its network formation command values.
To prevent the coordinator from leaving an existing network, the WR command should be issued after all network
formation commands have been configured in order to retain these settings through power cycle or reset events.
Leaving a Network
There are a couple of mechanisms that will cause the coordinator to leave its current PAN and start a new network
based on its network formation parameter values. These include the following:
•Change the ID command such that the current 64-bit PAN ID is invalid.
•Change the SC command such that the current channel (CH) is not included in the channel mask.
•Change the ZS or any of the security command values (excluding NK).
•Issue the NR0 command to cause the coordinator to leave.
•Issue the NR1 command to send a broadcast transmission, causing all devices in the network to leave
and migrate to a different channel.
•Press the commissioning button 4 times or issue the CB command with a parameter of 4.
Note that changes to ID, SC, ZS, and security command values only take effect when changes are applied (AC or CN
commands).
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Replacing a Coordinator (Security Disabled Only)
In rare occasions, it may become necessary to replace an existing coordinator in a network with a new physical
device. If security is not enabled in the network, a replacement XBee coordinator can be configured with the PAN
ID (16-bit and 64-bit), channel, and stack profile settings of a running network in order to replace an existing
coordinator.
NOTE: Having two coordinators on the same channel, stack profile, and PAN ID (16-bit and 64-bit) can cause
problems in the network and should be avoided. When replacing a coordinator, the old coordinator should be
turned off before starting the new coordinator.
To replace a coordinator, the following commands should be read from a device on the network:
AT Command
OP
OI
CH
ZS
Description
Read the operating 64-bit PAD ID.
Read the operating 16-bit PAN ID.
Read the operating channel.
Read the stack profile.
Each of the commands listed above can be read from any device on the network. (These parameters will be the
same on all devices in the network.) After reading these commands from a device on the network, these
parameter values should be programmed into the new coordinator using the following commands.
AT Command
ID
Description
Set the 64-bit PAN ID to match
the read OP value.
II
Set the initial 16-bit PAN ID to
match the read OI value.
SC
Set the scan channels bitmask to
enable the read operating
channel (CH command). For
example, if the operating channel
is 0x0B, set SC to 0x0001. If the
operating channel is 0x17, set SC
to 0x1000.
ZS
Set the stack profile to match the
read ZS value.
Note: II is the initial 16-bit PAN ID. Under certain conditions, the ZigBee stack can change the 16-bit PAN ID of the
network. For this reason, the II command cannot be saved using the WR command. Once II is set, the coordinator
leaves the network and starts on the 16-bit PAN ID specified by II.
Example: Starting a Coordinator
1. Set SC and ID to the desired scan channels and PAN ID values. (The defaults should suffice.)
2. If SC or ID is changed from the default, issue the WR command to save the changes.
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3. If SC or ID is changed from the default, apply changes (make SC and ID changes take effect) either by
sending the AC command or by exiting AT command mode.
4. The Associate LED will start blinking once the coordinator has selected a channel and PAN ID.
5. The API Modem Status frame ("Coordinator Started") is sent out the UART (API firmware only).
6. Reading the AI command (association status) will return a value of 0, indicating a successful startup.
7. Reading the MY command (16-bit address) will return a value of 0, the ZigBee-defined 16-bit address of
the coordinator.
After startup, the coordinator will allow joining based on its NJ value.
Example: Replacing a Coordinator (security disabled)
1. Read the OP, OI, CH, and ZS commands on the running coordinator.
2. Set the ID, SC, and ZS parameters on the new coordinator, followed by WR command to save these parameter
values.
3. Turn off the running coordinator.
4. Set the II parameter on the new coordinator to match the read OI value on the old coordinator.
5. Wait for the new coordinator to start (AI=0).
Router Operation
Routers must discover and join a valid ZigBee network before they can participate in a ZigBee network. After a
router has joined a network, it can allow new devices to join the network. It can also route data packets and
communicate with other devices on the network.
Discovering ZigBee Networks
To discover nearby ZigBee networks, the router performs a PAN (or active) scan, just like the coordinator does
when it starts a network. During the PAN scan, the router sends a beacon request (broadcast) transmission on the
first channel in its scan channels list. All nearby coordinators and routers operating on that channel (that are
already part of a ZigBee network) respond to the beacon request by sending a beacon back to the router. The
beacon contains information about the PAN the nearby device is on, including the PAN identifier (PAN ID), and
whether or not joining is allowed. The router evaluates each beacon received on the channel to determine if a
valid PAN is found. A router considers a PAN to be valid if the PAN:
•Has a valid 64-bit PAN ID (PAN ID matches ID if ID > 0)
•Has the correct stack profile (ZS command)
•Is allowing joining.
If a valid PAN is not found, the router performs the PAN scan on the next channel in its scan channels list and
continues scanning until a valid network is found, or until all channels have been scanned. If all channels have been
scanned and a valid PAN was not discovered, all channels will be scanned again.
The ZigBee Alliance requires that certified solutions not send beacon request messages too frequently. To meet
certification requirements, the XBee firmware attempts 9 scans per minute for the first 5 minutes, and 3 scans per
minute thereafter. If a valid PAN is within range of a joining router, it should typically be discovered within a few
seconds.
Joining a Network
Once the router discovers a valid network, it sends an association request to the device that sent a valid beacon
requesting a join on the ZigBee network. The device allowing the join then sends an association response frame
that either allows or denies the join.
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When a router joins a network, it receives a 16-bit address from the device that allowed the join. The 16-bit
address is randomly selected by the device that allowed the join.
Authentication
In a network where security is enabled, the router must then go through an authentication process. See the
Security chapter for a discussion on security and authentication.
After the router is joined (and authenticated, in a secure network), it can allow new devices to join the network.
Persistent Data
Once a router has joined a network, it retains the following information through power cycle or reset events:
•PAN ID
•Operating channel
•Security policy and frame counter values
•Child table (end device children that are joined to the coordinator).
The router will retain this information indefinitely until it leaves the network. When the router leaves a network,
the previous PAN ID, operating channel, and child table data are lost.
XBee ZB Router Joining
When the router is powered on, if it is not already joined to a valid ZigBee network, it immediately attempts to find
and join a valid ZigBee network.
Note: The DJ command can be set to 1 to disable joining. The DJ parameter cannot be written with WR, so a power
cycle always clears the DJ setting.
The following commands control the router joining process.
Command
ID
SC
SD
ZS
EE
KY
Description
Sets the 64-bit PAN ID to join. Setting ID=0 allows the router to join any 64-bit PAN
ID.
Set the scan channels bitmask that determines which channels a router will scan to
find a valid network. SC on the router should be set to match SC on the
coordinator. For example, setting SC to 0x281 enables scanning on channels 0x0b,
0x12, and 0x14, in that order.
Set the scan duration, or time that the router will listen for beacons on each
channel.
Sets the stack profile on the device.
Enable or disable security in the network. This must be set to match the EE value
(security policy) of the coordinator.
Set the trust center link key. If set to 0 (default), the link key is expected to be
obtained (unencrypted) during joining.
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Once the router joins a network, the network configuration settings and child table data persist through power
cycles as mentioned in the "Persistent Data" section previously. If joining fails, the status of the last join attempt
can be read in the AI command register.
If any of the above command values change, when command register changes are applied (AC or CN commands),
the router will leave its current network and attempt to discover and join a new valid network. When a ZB router
has successfully joined a network, it:
•Allows other devices to join the network for a time
•Sets AI=0
•Starts blinking the Associate LED
•Sends an API modem status frame ("associated") out the UART (API firmware only).
These behaviors are configurable using the following commands:
Command
NJ
D5
Description
Sets the permit-join time on the router, or the time that it will allow new devices to
join the network, measured in seconds. If NJ=0xFF, permit joining will always be
enabled.
Enables the Associate LED functionality.
Sets the Associate LED blink time when joined. Default is 2 blinks per second
(router).
LT
Permit Joining
The permit joining attribute on the router is configurable with the NJ command. NJ can be configured to always
allow joining, or to allow joining for a short time.
Joining Always Enabled
If NJ=0xFF (default), joining is permanently enabled. This mode should be used carefully. Once a network has been
deployed, the application should strongly consider disabling joining to prevent unwanted joins from occurring.
Joining Temporarily Enabled
If NJ < 0xFF, joining will be enabled only for a number of seconds, based on the NJ parameter. The timer is started
once the XBee joins a network. Joining will not be re-enabled if the module is power cycled or reset. The following
mechanisms can restart the permit-joining timer:
•Changing NJ to a different value (and applying changes with the AC or CN commands)
•Pressing the commissioning button twice (enables joining for 1 minute)
•Issuing the CB command with a parameter of 2 (software emulation of a 2 button press - enables joining
for 1 minute)
•Causing the router to leave and rejoin the network.
Router Network Connectivity
Once a router joins a ZigBee network, it remains connected to the network on the same channel and PAN ID as
long as it is not forced to leave. (See Leaving a Network section for details.) If the scan channels (SC), PAN ID (ID)
and security settings (EE, KY) do not change after a power cycle; the router will remain connected to the network
after a power cycle.
If a router may physically move out of range of the network it initially joined, the application should include
provisions to detect if the router can still communicate with the original network. If communication with the
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original network is lost, the application may choose to force the router to leave the network (see Leaving a
Network section for details). The XBee firmware includes two provisions to automatically detect the presence of a
network, and leave if the check fails.
Power-On Join Verification
The JV command (join verification) enables the power-on join verification check. If enabled, the XBee will attempt
to discover the 64-bit address of the coordinator when it first joins a network. Once it has joined, it will also
attempt to discover the 64-bit address of the coordinator after a power cycle event. If 3 discovery attempts fail,
the router will leave the network and try to join a new network. Power-on join verification is disabled by default
(JV defaults to 0).
Network Watchdog
The NW command (network watchdog timeout) can be used for a powered router to periodically check for the
presence of a coordinator to verify network connectivity. The NW command specifies a timeout in minutes where
the router must receive communication from the coordinator or data collector. The following events restart the
network watchdog timer:
•RF data received from the coordinator
•RF data sent to the coordinator and an acknowledgment was received
•Many-to-one route request was received (from any device)
•Changing the value of NW.
If the watchdog timer expires (no valid data received for NW time), the router will attempt to discover the 64-bit
address of the coordinator. If the address cannot be discovered, the router records one watchdog timeout. Once
three consecutive network watchdog timeouts have expired (3 * NW) and the coordinator has not responded to
the address discovery attempts, the router will leave the network and attempt to join a new network. Anytime a
router receives valid data from the coordinator or data collector, it will clear the watchdog timeouts counter and
restart the watchdog timer. The watchdog timer (NW command) is settable to several days. The network watchdog
feature is disabled by default (NW defaults to 0).
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Leaving a Network
There are a couple of mechanisms that will cause the router to leave its current PAN and attempt to discover and
join a new network based on its network joining parameter values.
These include the following:
•Change the ID command such that the current 64-bit PAN ID is invalid.
•Change the SC command such that the current channel (CH) is not included in the channel mask.
•Change the ZS or any of the security command values.
•Issue the NR0 command to cause the router to leave.
•Issue the NR1 command to send a broadcast transmission, causing all devices in the network to leave
and migrate to a different channel.
•Press the commissioning button 4 times or issue the CB command with a parameter of 4.
Note that changes to ID, SC, ZS, and security command values only take effect when changes are applied (AC or CN
commands).
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Resetting the Router
When the router is reset or power cycled, it checks its PAN ID, operating channel and stack profile against the
network configuration settings (ID, SC, and ZS). It also verifies the saved security policy is valid based on the
security configuration commands (EE, KY). If the router's PAN ID, operating channel, stack profile, or security policy
is invalid, the router will leave the network and attempt to join a new network based on its network joining
command values.
To prevent the router from leaving an existing network, the WR command should be issued after all network
joining commands have been configured in order to retain these settings through power cycle or reset events.
Example: Joining a Network
After starting a coordinator (that is allowing joins), the following steps will cause a router to join the network:
1. Set ID to the desired 64-bit PAN ID, or to 0 to join any PAN.
2. Set SC to the list of channels to scan to find a valid network.
3. If SC or ID is changed from the default, apply changes (make SC and ID changes take effect) by issuing
the AC or CN command.
4. The Associate LED will start blinking once the router has joined a PAN.
5. If the Associate LED is not blinking, the AI command can be read to determine the cause of join failure.
6. Once the router has joined, the OP and CH commands will indicate the operating 64-bit PAN ID and
channel the router joined.
7. The MY command will reflect the 16-bit address the router received when it joined.
8. The API Modem Status frame ("Associated") is sent out the UART (API firmware only).
9. The joined router will allow other devices to join for a time based on its NJ setting.
End Device Operation
Similar to routers, end devices must also discover and join a valid ZigBee network before they can participate in a
network. After an end device has joined a network, it can communicate with other devices on the network. Since
end devices are intended to be battery powered and therefore support low power (sleep) modes, end devices
cannot allow other devices to join, nor can they route data packets.
Discovering ZigBee Networks
End devices go through the same process as routers to discover networks by issuing a PAN scan. After sending the
broadcast beacon request transmission, the end device listens for a short time in order to receive beacons sent by
nearby routers and coordinators on the same channel. The end device evaluates each beacon received on the
channel to determine if a valid PAN is found. An end device considers a PAN to be valid if the PAN:
•Has a valid 64-bit PAN ID (PAN ID matches ID if ID > 0)
•Has the correct stack profile (ZS command)
•Is allowing joining
•Has capacity for additional end devices (see End Device Capacity section below).
If a valid PAN is not found, the end device performs the PAN scan on the next channel in its scan channels list and
continues this process until a valid network is found, or until all channels have been scanned. If all channels have
been scanned and a valid PAN was not discovered, the end device may enter a low power sleep state and scan
again later.
If scanning all SC channels fails to discover a valid PAN, XBee ZB modules will attempt to enter a low power state
and will retry scanning all SC channels after the module wakes from sleeping. If the module cannot enter a low
power state, it will retry scanning all channels, similar to the router. To meet ZigBee Alliance requirements, the end
device will attempt up to 9 scans per minute for the first 5 minutes, and 3 scans per minute thereafter.
Note: The XBee ZB end device will not enter sleep until it has completed scanning all SC channels for a valid
network.
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Joining a Network
Once the end device discovers a valid network, it joins the network, similar to a router, by sending an association
request (to the device that sent a valid beacon) to request a join on the ZigBee network. The device allowing the
join then sends an association response frame that either allows or denies the join. When an end device joins a
network, it receives a 16-bit address from the device that allowed the join. The 16- bit address is randomly
selected by the device that allowed the join.
Parent Child Relationship
Since an end device may enter low power sleep modes and not be immediately responsive, the end device relies
on the device that allowed the join to receive and buffer incoming messages in its behalf until it is able to wake
and receive those messages. The device that allowed an end device to join becomes the parent of the end device,
and the end device becomes a child of the device that allowed the join.
End Device Capacity
Routers and coordinators maintain a table of all child devices that have joined called the child table. This table is a
finite size and determines how many end devices can join. If a router or coordinator has at least one unused entry
in its child table, the device is said to have end device capacity. In other words, it can allow one or more additional
end devices to join. ZigBee networks should have sufficient routers to ensure adequate end device capacity.
In the XBee ZB firmware, a coordinator can support 20 end devices, and a router can support 24 end devices.
In ZB firmware, the NC command (number of remaining end device children) can be used to determine how many
additional end devices can join a router or coordinator. If NC returns 0, then the router or coordinator device has
no more end device capacity. (Its child table is full.)
Also of note, since routers cannot sleep, there is no equivalent need for routers or coordinators to track joined
routers. Therefore, there is no limit to the number of routers that can join a given router or coordinator device.
(There is no "router capacity" metric.)
Authentication
In a network where security is enabled, the end device must then go through an authentication process. See
chapter 5 for a discussion on security and authentication.
Persistent Data
The end device can retain its PAN ID, operating channel, and security policy information through a power cycle.
However, since end devices rely heavily on a parent, the end device does an orphan scan to try and contact its
parent. If the end device does not receive an orphan scan response (called a coordinator realignment command), it
will leave the network and try to discover and join a new network. When the end device leaves a network, the
previous PAN ID and operating channel settings are lost.
Orphan Scans
When an end device comes up from a power cycle, it performs an orphan scan to verify it still has a valid parent.
The orphan scan is sent as a broadcast transmission and contains the 64-bit address of the end device. Nearby
routers and coordinator devices that receive the broadcast check their child tables for an entry that contains the
end device's 64-bit address. If an entry is found with a matching 64-bit address, the device sends a coordinator
realignment command to the end device that includes the end device's 16-bit address, 16-bit PAN ID, operating
channel, and the parent's 64-bit and 16-bit addresses.
If the orphaned end device receives a coordinator realignment command, it is considered joined to the network.
Otherwise, it will attempt to discover and join a valid network.
XBee: ZB End Device Joining
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When an end device is powered on, if it is not joined to a valid ZigBee network, or if the orphan scan fails to find a
parent, it immediately attempts to find and join a valid ZigBee network.
Note: The DJ command can be set to 1 to disable joining. The DJ parameter cannot be written with WR, so a power
cycle always clears the DJ setting.
Similar to a router, the following commands control the end device joining process.
Network joining commands used by an end device to join a network.
Command
ID
Description
Sets the 64-bit PAN ID to join. Setting ID=0 allows the router to join any 64-bit PAN
ID.
Set the scan channels bitmask that determines which channels a router will scan to
find a valid network. SC on the end device should be set to match SC on the
coordinator and router. For example, setting SC to 0x281 enables scanning on
channels 0x0b, 0x12, and 0x14, in that order.
SC
Set the scan duration, or time that the end device will listen for beacons on each
channel.
Sets the stack profile on the device.
Enable or disable security in the network. This must be set to match the EE value
(security policy) of the coordinator.
SD
ZS
EE
Set the trust center link key. If set to 0 (default), the link key is expected to be
obtained (unencrypted) during joining.
KY
Once the end device joins a network, the network configuration settings can persist through power cycles as
mentioned in the "Persistent Data" section previously. If joining fails, the status of the last join attempt can be read
in the AI command register.
If any of these command values changes, when command register changes are applied, the end device will leave
its current network and attempt to discover and join a new valid network.
When a ZB end device has successfully started a network, it
•Sets AI=0
•Starts blinking the Associate LED
•Sends an API modem status frame ("associated") out the UART (API firmware only)
•Attempts to enter low power modes.
These behaviors are configurable using the following commands:
Command
D5
LT
SM, SP, ST,
SN, SO
Description
Enables the Associate LED functionality.
Sets the Associate LED blink time when joined. Default is 2 blinks per second
(router).
Parameters that configure the sleep mode characteristics. (See Managing End
Devices chapter for details.)
Parent Connectivity
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The XBee ZB end device sends regular poll transmissions to its parent when it is awake. These poll transmissions
query the parent for any new received data packets. The parent always sends a MAC layer acknowledgment back
to the end device. The acknowledgment indicates whether the parent has data for the end device or not.
If the end device does not receive an acknowledgment for 3 consecutive poll requests, it considers itself
disconnected from its parent and will attempt to discover and join a valid ZigBee network. (See "Managing End
Devices" chapter for details.)
Resetting the End Device
When the end device is reset or power cycled, if the orphan scan successfully locates a parent, the end device then
checks its PAN ID, operating channel and stack profile against the network configuration settings (ID, SC, and ZS). It
also verifies the saved security policy is valid based on the security configuration commands (EE, KY). If the end
device's PAN ID, operating channel, stack profile, or security policy is invalid, the end device will leave the network
and attempt to join a new network based on its network joining command values.
To prevent the end device from leaving an existing network, the WR command should be issued after all network
joining commands have been configured in order to retain these settings through power cycle or reset events.
Leaving a Network
There are a couple of mechanisms that will cause the end device to leave its current PAN and attempt to discover
and join a new network based on its network joining parameter values. These include the following:
•The ID command changes such that the current 64-bit PAN ID is invalid.
•The SC command changes such that the current operating channel (CH) is not included in the channel
mask.
•The ZS or any of the security command values change.
•The NR0 command is issued to cause the end device to leave.
•The NR1 command is issued to send a broadcast transmission, causing all devices in the network to leave
and migrate to a different channel.
•The commissioning button is pressed 4 times or the CB command is issued with a parameter of 4.
•The end device's parent is powered down or the end device is moved out of range of the parent such
that the end device fails to receive poll acknowledgment messages.
Note that changes to command values only take effect when changes are applied (AC or CN commands).
Example: Joining a Network
After starting a coordinator (that is allowing joins), the following steps will cause an XBee end device to join the
network:
1. Set ID to the desired 64-bit PAN ID, or to 0 to join any PAN.
2. Set SC to the list of channels to scan to find a valid network.
3. If SC or ID is changed from the default, apply changes (make SC and ID changes take effect) by issuing
the AC or CN command.
4. The Associate LED will start blinking once the end device has joined a PAN.
5. If the Associate LED is not blinking, the AI command can be read to determine the cause of join failure.
6. Once the end device has joined, the OP and CH commands will indicate the operating 64-bit PAN ID and
channel the end device joined.
7. The MY command will reflect the 16-bit address the router received when it joined.
8. The API Modem Status frame ("Associated") is sent out the UART (API firmware only).
9. The joined end device will attempt to enter low power sleep modes based on its sleep configuration
commands (SM, SP, SN, ST, SO).
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Channel Scanning
As mentioned previously, routers and end devices must scan one or more channels to discover a valid network to
join. When a join attempt begins, the XBee sends a beacon request transmission on the lowest channel specified in
the SC (scan channels) command bitmask. If a valid PAN is found on the channel, the XBee will attempt to join the
PAN on that channel. Otherwise, if a valid PAN is not found on the channel, it will attempt scanning on the next
higher channel in the SC command bitmask.
The XBee will continue to scan each channel (from lowest to highest) in the SC bitmask until a valid PAN is found or
all channels have been scanned. Once all channels have been scanned, the next join attempt will start scanning on
the lowest channel specified in the SC command bitmask.
For example, if the SC command is set to 0x400F, the XBee would start scanning on channel 11 (0x0B) and scan
until a valid beacon is found, or until channels 11, 12, 13, 14, and 25 have been scanned (in that order). Once an
XBee router or end device joins a network on a given channel, if the XBee is told to leave (see "Leaving a Network"
section), it will leave the channel it joined on and continue scanning on the next higher channel in the SC bitmask.
For example, if the SC command is set to 0x400F, and the XBee joins a PAN on channel 12 (0x0C), if the XBee leaves
the channel, it will start scanning on channel 13, followed by channels 14 and 25 if a valid network is not found.
Once all channels have been scanned, the next join attempt will start scanning on the lowest channel specified in
the SC command bitmask.
Managing Multiple ZigBee Networks
In some applications, multiple ZigBee networks may exist in proximity of each other. The application may need
provisions to ensure the XBee joins the desired network. There are a number of features in ZigBee to manage
joining among multiple networks. These include the following:
•PAN ID Filtering
•Preconfigured Security Keys
•Permit Joining
•Application Messaging
Pan ID Filtering
The XBee can be configured with a fixed PAN ID by setting the ID command to a non-zero value. If the PAN ID is set
to a non-zero value, the XBee will only join a network with the same PAN ID.
Preconfigured Security Keys
Similar to PAN ID filtering, this method requires a known security key be installed on a router to ensure it will join a
ZigBee network with the same security key. If the security key (KY command) is set to a non-zero value, and if
security is enabled (EE command), an XBee router or end device will only join a network with the same security
key.
Permit Joining
The Permit Joining parameter can be disabled in a network to prevent unwanted devices from joining. When a new
device must be added to a network, permit-joining can be enabled for a short time on the desired network. In the
XBee firmware, joining is disabled by setting the NJ command to a value less than 0xFF on all routers and
coordinator devices. Joining can be enabled for a short time using the commissioning push-button (see Network
Commissioning chapter for details) or the CB command.
Application Messaging
If the above mechanisms are not feasible, the application could build in a messaging framework between the
coordinator and devices that join its network. For example, the application code in joining devices could send a
transmission to the coordinator after joining a network, and wait to receive a defined reply message. If the
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application does not receive the expected response message after joining, the application could force the XBee to
leave and continue scanning (see NR parameter).
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4. Transmission, Addressing, and Routing
Addressing
All ZigBee devices have two different addresses, a 64-bit and a 16-bit address. The characteristics of each are
described below.
64-bit device Address
The 64-bit address is a unique device address assigned during manufacturing. This address is unique to each
physical device. The 64-bit address includes a 3-byte Organizationally Unique Identifier (OUI) assigned by the IEEE.
The 64-bit address is also called the extended address.
16-bit Device Address
A device receives a 16-bit address when it joins a ZigBee network. For this reason, the 16-bit address is also called
the "network address". The 16-bit address of 0x0000 is reserved for the coordinator. All other devices receive a
randomly generated address from the router or coordinator device that allows the join. The 16-bit address can
change under certain conditions:
•An address conflict is detected where two devices are found to have the same 16-bit address
•A device leaves the network and later joins (it can receive a different address)
All ZigBee transmissions are sent using the source and destination 16-bit addresses. The routing tables on ZigBee
devices also use 16-bit addresses to determine how to route data packets through the network. However, since
the 16-bit address is not static, it is not a reliable way to identify a device.
To solve this problem, the 64-bit destination address is often included in data transmissions to guarantee data is
delivered to the correct destination. The ZigBee stack can discover the 16-bit address, if unknown, before
transmitting data to a remote.
Application Layer Addressing
ZigBee devices can support multiple application profiles, cluster IDs, and endpoints. (See "ZigBee Application
Layers - In Depth" in chapter 3.) Application layer addressing allows data transmissions to be addressed to specific
profile IDs, cluster IDs, and endpoints. Application layer addressing is useful if an application must •Interoperate
with other ZigBee devices outside of the Digi application profile
•Utilize service and network management capabilities of the ZDO
•Operate on a public application profile such as Home Controls or Smart Energy.
The API firmware provides a simple yet powerful interface that can easily send data to any profile ID, endpoint,
and cluster ID combination on any device in a ZigBee network.
Data Transmission
ZigBee data packets can be sent as either unicast or broadcast transmissions. Unicast transmissions route data
from one source device to one destination device, whereas broadcast transmissions are sent to many or all devices
in the network.
Broadcast Transmissions
Broadcast transmissions within the ZigBee protocol are intended to be propagated throughout the entire network
such that all nodes receive the transmission. To accomplish this, the coordinator and all routers that receive a
broadcast transmission will retransmit the packet three times.
Note: when a router or coordinator delivers a broadcast transmission to an end device child, the transmission is
only sent once (immediately after the end device wakes and polls the parent for any new data). See Parent
Operation section in chapter 6 for details.
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Each node that transmits the broadcast will also create an entry in a local broadcast transmission table. This entry
is used to keep track of each received broadcast packet to ensure the packets are not endlessly transmitted. Each
entry persists for 8 seconds. The broadcast transmission table holds 8 entries.
For each broadcast transmission, the ZigBee stack must reserve buffer space for a copy of the data packet. This
copy is used to retransmit the packet as needed. Large broadcast packets will require more buffer space. This
information on buffer space is provided for general knowledge; the user does not and cannot change any buffer
spacing. Buffer spacing is handled automatically by the XBee module.
Since broadcast transmissions are retransmitted by each device in the network, broadcast messages should be
used sparingly.
Unicast Transmissions
Unicast transmissions are sent from one source device to another destination device. The destination device could
be an immediate neighbor of the source, or it could be several hops away. Unicast transmissions that are sent
along a multiple hop path require some means of establishing a route to the destination device. See the "RF Packet
Routing" section in chapter 4 for details.
Address Resolution
As mentioned previously, each device in a ZigBee network has both a 16-bit (network) address and a 64-bit
(extended) address. The 64-bit address is unique and assigned to the device during manufacturing, and the 16-bit
address is obtained after joining a network. The 16-bit address can also change under certain conditions.
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When sending a unicast transmission, the ZigBee network layer uses the 16-bit address of the destination and each
hop to route the data packet. If the 16-bit address of the destination is not known, the ZigBee stack includes a
discovery provision to automatically discover the destination device's 16-bit address before routing the data.
To discover a 16-bit address of a remote, the device initiating the discovery sends a broadcast address discovery
transmission. The address discovery broadcast includes the 64-bit address of the remote device whose 16-bit
address is being requested. All nodes that receive this transmission check the 64-bit address in the payload and
compare it to their own 64-bit address. If the addresses match, the device sends a response packet back to the
initiator. This response includes the remote's 16-bit address. When the discovery response is received, the initiator
will then transmit the data.
Address Table
Each ZigBee device maintains an address table that maps a 64-bit address to a 16-bit address. When a transmission
is addressed to a 64-bit address, the ZigBee stack searches the address table for an entry with a matching 64-bit
address, in hopes of determining the destination's 16-bit address. If a known 16-bit address is not found, the
ZigBee stack will perform address discovery to discover the device's current 16- bit address.
Sample Address Table
64-bit Address
16-bit Address
0013 A200 4000 0001
0x4414
0013 A200 400A 3568
0x1234
0013 A200 4004 1122
0xC200
0013 A200 4002 1123
0xFFFE (unknown)
The XBee modules can store up to 20 address table entries. For applications where a single device (e.g.
coordinator) may send unicast transmissions to more than 20 devices, the application should implement an
address table to store the 16-bit and 64-bit addresses for each remote device. Any XBee that will send data to
more than 20 remotes should also use API firmware. The application can then send both the 16-bit and 64-bit
addresses to the XBee in the API transmit frames which will significantly reduce the number of 16-bit address
discoveries and greatly improve data throughput.
If an application will support an address table, the size should ideally be larger than the maximum number of
destination addresses the device will communicate with. Each entry in the address table should contain a 64-bit
destination address and its last known 16-bit address.
When sending a transmission to a destination 64-bit address, the application should search the address table for a
matching 64-bit address. If a match is found, the 16-bit address should be populated into the 16-bit address field of
the API frame. If a match is not found, the 16-bit address should be set to 0xFFFE (unknown) in the API transmit
frame.
The API provides indication of a remote device's 16-bit address in the following frames:
•
All receive data frames
Rx Data (0x90)
Rx Explicit Data (0x91)
IO Sample Data (0x92)
Node Identification Indicator (0x95)
Route Record Indicator (0xA1)
etc.
•
Transmit status frame (0x8B)
The application should always update the 16-bit address in the address table when one of these frames is received
to ensure the table has the most recently known 16-bit address. If a transmission failure occurs, the application
should set the 16-bit address in the table to 0xFFFE (unknown).
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Fragmentation
Each unicast transmission may support up to 84 bytes of RF payload. (Enabling security or using source routing can
reduce this number. See the NP command for details.) However, the XBee ZB firmware supports a ZigBee feature
called fragmentation that allows a single large data packet to be broken up into multiple RF transmissions and
reassembled by the receiver before sending data out its UART or SPI port. This is shown in the image below.
The API transmit frame can include up to 255 bytes of data, which will be broken up into multiple transmissions
and reassembled on the receiving side. If one or more of the fragmented messages are not received by the
receiving device, the receiver will drop the entire message, and the sender will indicate a transmission failure in
the Tx Status API frame.
Applications that do not wish to use fragmentation should avoid sending more than the maximum number of bytes
in a single RF transmission. See the "Maximum RF Payload Size" section for details.
Devices will not receive or reassemble fragmented RF packets if RTS flow control is enabled (D6 command).
DATA Transmission Examples
AT Firmware
To send a data packet in AT firmware, the DH and DL commands must be set to match the 64-bit address of the
destination device. DH must match the upper 4-bytes, and DL must match the lower 4 bytes. Since the coordinator
always receives a 16-bit address of 0x0000, a 64-bit address of 0x0000000000000000 is defined as the
coordinator's address (in ZB firmware). The default values of DH and DL are 0x00, which sends data to the
coordinator.
Example 1: Send a transmission to the coordinator
(In this example, a '\r' refers to a carriage return character.)
A router or end device can send data in two ways. First, set the destination address (DH and DL commands) to
0x00.
1. Enter command mode ('+++')
2. After receiving an OK\r, issue the following commands: a. ATDH0\r b. ATDL0\r c. ATCN\r
3. Verify that each of the 3 commands returned an OK\r response.
4. After setting these command values, all serial characters will be sent as a unicast transmission to the
coordinator.
Alternatively, if the coordinator's 64-bit address is known, DH and DL can be set to the coordinator's 64-bit
address. Suppose the coordinator's address is 0x0013A200404A2244.
1. Enter command mode ('+++')
2. After receiving an OK\r, issue the following commands: a. ATDH13A200\r b. ATDL404A2244\ c. ATCN\r
3. Verify that each of the 3 commands returned an OK\r response.
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4. After setting these command values, all serial characters will be sent as a unicast transmission to the
coordinator.
API Firmware
Use the transmit request, or explicit transmit request frame (0x10 and 0x11 respectively) to send data to the
coordinator. The 64-bit address can either be set to 0x0000000000000000, or to the 64-bit address of the
coordinator. The 16-bit address should be set to 0xFFFE when using the 64-bit address of all 0x00s.
To send an ascii "1" to the coordinator's 0x00 address, the following API frame can be used:
7E 00 0F 10 01 0000 0000 0000 0000 FFFE 00 00 31 C0
If the explicit transmit frame is used, the cluster ID should be set to 0x0011, the profile ID to 0xC105, and the
source and destination endpoints to 0xE8 (recommended defaults for data transmissions in the Digi profile.) The
same transmission could be sent using the following explicit transmit frame:
7E 00 15 11 01 0000 0000 0000 0000 FFFE E8 E8 0011 C105 00 00 31 18
Notice the 16-bit address is set to 0xFFFE. This is required when sending to a 64-bit address of 0x00s.
Now suppose the coordinator's 64-bit address is 0x0013A200404A2244. The following transmit request API frame
(0x10) will send an ASCII "1" to the coordinator:
7E 00 0F 10 01 0013 A200 404A 2244 0000 0000 31 18
Example 2: Send a broadcast transmission
(In this example, a '\r' refers to a carriage return character.)
Perform the following steps to configure a broadcast transmission:
1. Enter command mode ('+++')
2. After receiving an OK\r, issue the following commands: a. ATDH0\r b. ATDLffff\r c. ATCN\r
3. Verify that each of the 3 commands returned an OK\r response
4. After setting these command values, all serial characters will be sent as a broadcast transmission.
API Firmware
This example will use the transmit request API frame (0x10) to send an ASCII "1" in a broadcast transmission.
To send an ascii "1" as a broadcast transmission, the following API frame can be used:
7E 00 0F 10 01 0000 0000 0000 FFFF FFFE 00 00 31 C2
Notice the destination 16-bit address is set to 0xFFFE for broadcast transmissions.
RF Packet Routing
Unicast transmissions may require some type of routing. ZigBee includes several different ways to route data, each
with its own advantages and disadvantages. These are summarized in the table below.
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Routing Approach
Ad hoc On-demand
distance Vector
(AODV) Mesh Routing
Description
Routing paths are created between
source and destination, possibly
traversing multiple nodes ("hops").
Each device knows who to send data to
eventually reaching the destination.
When to Use
Use in networks that will not scale
beyond about 40 destination devices.
Many-to-One Routing
A single broadcast transmission
configured reverse routes on all devices
into the device that sends the broadcast
Useful when many remote devices must
send data to a single gateway or
collector device.
Source Routing
Data packets include the entire route
the packet should traverse to get from
source to destination.
Improves routing efficiency in large
networks (over 40 remote devices)
Note – End devices do not make use of these routing protocols. Rather, an end device sends a unicast transmission
to its parent and allows the parent to route the data packet in its behalf.
Link Status Transmission
Before discussing the various routing protocols, it is worth understanding the primary mechanism in ZigBee for
establishing reliable bi-directional links. This mechanism is especially useful in networks that may have a mixture of
devices with varying output power and/or receiver sensitivity levels.
Each coordinator or router device periodically sends a link status message. This message is sent as a 1-hop
broadcast transmission, received only by one-hop neighbors. The link status message contains a list of neighboring
devices and incoming and outgoing link qualities for each neighbor. Using these messages, neighboring devices can
determine the quality of a bi-directional link with each neighbor and use that information to select a route that
works well in both directions.
For example, consider a network of two neighboring devices that send periodic link status messages. Suppose that
the output power of device A is +18dBm, and the output power of device B is +3dBm (considerably less than the
output power of device A). The link status messages might indicate the following:
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This mechanism enables devices A and B to recognize that the link is not reliable in both directions and select a
different neighbor when establishing routes. (Such links are called asymmetric links, meaning the link quality is not
similar in both directions.)
When a router or coordinator device powers on, it sends link status messages every couple seconds to attempt to
discover link qualities with its neighbors quickly. After being powered on for some time, the link status messages
are sent at a much slower rate (about every 3-4 times per minute).
AODV Mesh Routing
ZigBee employs mesh routing to establish a route between the source device and the destination. Mesh routing
allows data packets to traverse multiple nodes (hops) in a network to route data from a source to a destination.
Routers and coordinators can participate in establishing routes between source and destination devices using a
process called route discovery. The Route discovery process is based on the AODV (Ad-hoc On-demand Distance
Vector routing) protocol.
AODV (Ad-hoc On-Demand Distance Vector) Routing Algorithm
Routing under the AODV protocol is accomplished using tables in each node that store the next hop (intermediary
node between source and destination nodes) for a destination node. If a next hop is not known, route discovery
must take place in order to find a path. Since only a limited number of routes can be stored on a Router, route
discovery will take place more often on a large network with communication between many different nodes.
Node
R3
R5
Destination Address
Router 6
Router 7
Router 8
© 2010 Digi International, Inc.
Next Hop Address
Coordinator
Router 5
Router 6
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When a source node must discover a route to a destination node, it sends a broadcast route request command.
The route request command contains the source network address, the destination network address and a path
cost field (a metric for measuring route quality). As the route request command is propagated through the
network (refer to the Broadcast Transmission), each node that re-broadcasts the message updates the path cost
field and creates a temporary entry in its route discovery table.
Sample Route Request (Broadcast) Transmission Where R3 is Trying to Discover a Route to R6
When the destination node receives a route request, it compares the ‘path cost’ field against previously received
route request commands. If the path cost stored in the route request is better than any previously received, the
destination node will transmit a route reply packet to the node that originated the route request. Intermediate
nodes receive and forward the route reply packet to the source node (the node that originated route request).
Sample Route Reply (Unicast) Where R6 Sends a Route Reply to R3.
Note: R6 could send multiple replies if it identifies a better route.
Retries and Acknowledgments
ZigBee includes acknowledgment packets at both the Mac and Application Support (APS) layers. When data is
transmitted to a remote device, it may traverse multiple hops to reach the destination. As data is transmitted from
one node to its neighbor, an acknowledgment packet (Ack) is transmitted in the opposite direction to indicate that
the transmission was successfully received. If the Ack is not received, the transmitting device will retransmit the
data, up to 4 times. This Ack is called the Mac layer acknowledgment.
In addition, the device that originated the transmission expects to receive an acknowledgment packet (Ack) from
the destination device. This Ack will traverse the same path that the data traversed, but in the opposite direction.
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If the originator fails to receive this Ack, it will retransmit the data, up to 2 times until an Ack is received. This Ack is
called the ZigBee APS layer acknowledgment.
Refer to the ZigBee specification for more details.
Many-to-One Routing
In networks where many devices must send data to a central collector or gateway device, AODV mesh routing
requires significant overhead. If every device in the network had to discover a route before it could send data to
the data collector, the network could easily become inundated with broadcast route discovery messages.
Many-to-one routing is an optimization for these kinds of networks. Rather than require each device to do its own
route discovery, a single many-to-one broadcast transmission is sent from the data collector to establish reverse
routes on all devices. This is shown in the figure below. The left side shows the many broadcasts the devices can
send when they create their own routes and the route replies generated by the data collector. The right side shows
the benefits of many-to-one routing where a single broadcast creates reverse routes to the data collector on all
routers.
The many-to-one broadcast is a route request message with the target discovery address set to the address of the
data collector. Devices that receive this route request create a reverse many-to-one routing table entry to create a
path back to the data collector. The ZigBee stack on a device uses historical link quality information about each
neighbor to select a reliable neighbor for the reverse route.
When a device sends data to a data collector, and it finds a many-to-one route in its routing table, it will transmit
the data without performing a route discovery. The many-to-one route request should be sent periodically to
update and refresh the reverse routes in the network.
Applications that require multiple data collectors can also use many-to-one routing. If more than one data
collector device sends a many-to-one broadcast, devices will create one reverse routing table entry for each
collector.
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In ZB firmware, the AR command is used to enable many-to-one broadcasting on a device. The AR command sets a
time interval (measured in 10 second units) for sending the many to one broadcast transmission. (See the
command table for details.)
Source Routing
In applications where a device must transmit data to many remotes, AODV routing would require performing one
route discovery for each destination device to establish a route. If there are more destination devices than there
are routing table entries, established AODV routes would be overwritten with new routes, causing route
discoveries to occur more regularly. This could result in larger packet delays and poor network performance.
ZigBee source routing helps solve these problems. In contrast to many-to-one routing that establishes routing
paths from many devices to one data collector, source routing allows the collector to store and specify routes for
many remotes.
To use source routing, a device must use the API firmware, and it must send periodic many-to-one route request
broadcasts (AR command) to create a many-to-one route to it on all devices. When remote devices send RF data
using a many-to-one route, they first send a route record transmission. The route record transmission is unicast
along the many-to-one route until it reaches the data collector. As the route record traverses the many-to-one
route, it appends the 16-bit address of each device in the route into the RF payload. When the route record
reaches the data collector, it contains the address of the sender, and the 16-bit address of each hop in the route.
The data collector can store the routing information and retrieve it later to send a source routed packet to the
remote. This is shown in the images below.
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Acquiring Source Routes
Acquiring source routes requires the remote devices to send a unicast to a data collector (device that sends many-to-one route
request broadcasts). There are several ways to force remotes to send route record transmissions.
1.
2.
3.
4.
If the application on remote devices periodically sends data to the data collector, each transmission will force a route
record to occur.
The data collector can issue a network discovery command (ND command) to force all XBee devices to send a network
discovery response. Each network discovery response will be prefaced by a route record.
Periodic IO sampling can be enabled on remotes to force them to send data at a regular rate. Each IO sample would be
prefaced by a route record. (See chapter 8 for details.)
If the NI string of the remote device is known, the DN command can be issued with the NI string of the remote in the
payload. The remote device with a matching NI string would send a route record and a DN response.
Storing Source Routes
When a data collector receives a route record, it sends it out the UART as a Route Record Indicator API frame
(0xA1). To use source routing, the application should receive these frames and store the source route information.
Sending a Source Routed Transmission
To send a source routed transmission, the application should send a Create Source Route API frame (0x21) to the
XBee to create a source route in its internal source route table. After sending the Create Source Route API frame,
the application can send data transmission or remote command request frames as needed to the same
destination, or any destination in the source route. Once data must be sent to a new destination (a destination not
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included in the last source route), the application should first send a new Create Source Route API frame. The XBee
can buffer one source route that includes up to 10 hops (excluding source and destination).
For example, suppose a network exists with a coordinator and 5 routers (R1, R2, R3, R4, and R5) with known
source routes as shown below.
To send a source-routed packet to R3, the application must send a Create Source Route API frame (0x21) to the
XBee, with a destination of R3, and 2 hops (R1 and R2). If the 64- bit address of R3 is 0x0013A200 404a1234 and
the 16-bit addresses of R1, R2, and R3 are:
Device
R1
R2
R3
16-bit Address
0XAABB
0xCCDD
0xEEFF
Then the Create Source Route API frame would be:
7E 0012 21 00 0013A200 404A1234 EEFF 00 02 CCDD AABB 5C
Where:
0x0012 - length
0x21 - API ID (create source route)
0x00 - frame ID (set to 0 always)
0x0013A200 404A1234 - 64-bit address of R3 (destination)
0xEEFF - 16-bit address of R3 (destination)
0x00 - Route options (set to 0)
0x02 - Number of intermediate devices in the source route
0xCCDD - Address of furthest device (1-hop from target)
0xAABB - Address of next-closer device
0x5C - Checksum (0xFF - SUM (all bytes after length))
Repairing Source Routes
It is possible in a network to have an existing source route fail (i.e. a device in the route moves or goes down, etc.).
If a device goes down in a source routed network, all routes that used the device will be broken.
As mentioned previously, source routing must be used with many-to-one routing. (A device that uses source
routing must also send a periodic many-to-one broadcast in order to keep routes fresh). If a source route is broken,
remote devices must send in new route record transmissions to the data collector to provide it with a new source
route. This requires that remote devices periodically send data transmissions into the data collector. See the
earlier "Acquiring Source Routes" section for details.
Retries and Acknowledgments
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ZigBee includes acknowledgment packets at both the Mac and Application Support (APS) layers. When data is
transmitted to a remote device, it may traverse multiple hops to reach the destination. As data is transmitted from
one node to its neighbor, an acknowledgment packet (Ack) is transmitted in the opposite direction to indicate that
the transmission was successfully received. If the Ack is not received, the transmitting device will retransmit the
data, up to 4 times. This Ack is called the Mac layer acknowledgment.
In addition, the device that originated the transmission expects to receive an acknowledgment packet (Ack) from
the destination device. This Ack will traverse the same path that the data traversed, but in the opposite direction.
If the originator fails to receive this Ack, it will retransmit the data, up to 2 times until an Ack is received. This Ack is
called the ZigBee APS layer acknowledgment.
Refer to the ZigBee specification for more details.
Encrypted Transmissions
Encrypted transmissions are routed similar to non-encrypted transmissions with one exception. As an encrypted
packet propagates from one device to another, each device decrypts the packet using the network key, and
authenticates the packet by verifying packet integrity. It then re-encrypts the packet with its own source address
and frame counter values, and sends the message to the next hop. This process adds some overhead latency to
unicast transmissions, but it helps prevent replay attacks. See chapter 5 for details.
Maximum RF Payload Size
XBee ZB firmware includes a command (ATNP) that returns the maximum number of RF payload bytes that can be
sent in a unicast transmission. Querying the NP command, like most other commands, returns a HEXADECIMAL
value. This number will change based on whether security is enabled or not. If security is enabled (EE command),
the maximum number of RF payload bytes decreases since security requires additional overhead.
After reading the NP value, the following conditions can affect the maximum number of data bytes in a single RF
transmission:
•Broadcast transmissions can support 8 bytes more than unicast transmissions.
•If source routing is used, the 16-bit addresses in the source route are inserted into the RF payload space.
For example, if NP returns 84 bytes, and a source route must traverse 3 intermediate hops (3 16-bit
addresses); the total number of bytes that can be sent in one RF packet is 78.
•Enabling APS encryption (API tx option bit set) will reduce the number of payload bytes by 4.
Throughput
Throughput in a ZigBee network can vary by a number of variables, including: number of hops, encryption
enabled/ disabled, sleeping end devices, failures/route discoveries. Our empirical testing showed the following
throughput performance in a robust operating environment (low interference).
Data Throughput*
configuration
1 hop, RR, SD
1 hop, RR, SE
1 hop, RE, SD
1 hop, RE, SE
1 hop, ER, SD
1 hop, ER, SE
Data Throughput
35Kbps
19kBPS
25Kbps
© 2010 Digi International, Inc.
16Kbps
21Kbps
16kKbps
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4 hops, RR, SD
4 hops, RR, SE
10Kpbs
5Kbps
RR = router to router,
RE = router to end device (non-sleeping),
ER = end device (non-sleeping) to router,
SD = security disabled,
SE = security enabled.
4 hops = 5 nodes total,
3 intermediate router nodes
* Data throughput measurements were made setting the serial interface rate to 115200 bps, and measuring the
time to send 100,000 bytes from source to destination. During the test, no route discoveries or failures occurred.
ZDO Transmissions
ZigBee defines a ZigBee Device Objects layer (ZDO) that can provide device and service discovery and network
management capabilities. This layer is described below.
ZigBee Device Objects (ZDO)
The ZigBee Device Objects (ZDO) is supported to some extent on all ZigBee devices. The ZDO is an endpoint that
implements services described in the ZigBee Device Profile in the ZigBee specification. Each service has an assigned
cluster ID, and most service requests have an associated response. The following table describes some common
ZDO services.
Cluster Name
Network Address
Request
Cluster ID
0x0000
Active Endpoints
Request
0x0005
Request a list of endpoints from a
remote device.
LQI request
0x0031
Request data from a neighbor table
of a remote device.
Routing Table
Request
0x0032
Request to retrieve routing table
entries from a remote device.
Network Address
Response
0x8000
Cluster ID
Response that includes the 16-bit
address of a device.
Description
0x8031
Response that includes a neighbor
table data from a remote device.
0x8032
Response that includes routing
table entry data from a remote
device.
Cluster Name
LQI response
Routing Table
Response
© 2010 Digi International, Inc.
Description
Request a 16-bit address of the
radio with a matching 64-bit
address (required parameter).
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Refer to the ZigBee specification for a detailed description of all ZigBee Device Profile services.
Sending a ZDO Command
To send a ZDO command, an explicit transmit API frame must be used and formatted correctly. The source and
destination endpoints must be set to 0, and the profile ID must be set to 0. The cluster ID must be set to match the
cluster ID of the appropriate service. For example, to send an active endpoints request, the cluster ID must be set
to 0x0005.
The first byte of payload in the API frame is an application sequence number (transaction sequence number) that
can be set to any single byte value. This same value will be used in the first byte of the ZDO response. All remaining
payload bytes must be set as required by the ZDO. All multi-byte values must be sent in little endian byte order.
Receiving ZDO Commands and Responses
In XBee ZB firmware, ZDO commands can easily be sent using the API. In order to receive incoming ZDO
commands, receiver application addressing must be enabled with the AO command. (See examples later in this
section.) Not all incoming ZDO commands are passed up to the application.
When a ZDO message is received on endpoint 0 and profile ID 0, the cluster ID indicates the type of ZDO message
that was received. The first byte of payload is generally a sequence number that corresponds to a sequence
number of a request. The remaining bytes are set as defined by the ZDO. Similar to a ZDO request, all multi-byte
values in the response are in little endian byte order.
Example 1: Send a ZDO LQI Request to read the neighbor table contents of a remote.
Looking at the ZigBee specification, the cluster ID for an LQI Request is 0x0031, and the payload only
requires a single byte (start index). This example will send an LQI request to a remote device with a 64-bit
address of 0x0013A200 40401234. The start index will be set to 0, and the transaction sequence number
will be set to 0x76
API Frame:
7E 0016 11 01 0013A200 40401234 FFFE 00 00 0031 0000 00 00 76 00 CE
0x0016 - length
0x11 - Explicit transmit request
0x01 - frame ID (set to a non-zero value to enable the transmit status message, or set to 0 to disable)
0x0013A200 40401234 - 64-bit address of the remote
0xFFFE - 16-bit address of the remote (0xFFFE = unknown). Optionally, set to the 16-bit address of the
destination if known.
0x00 - Source endpoint
0x00 - Destination endpoint
0x0031 - Cluster ID (LQI Request, or Neighbor table request)
0x0000 - Profile ID (ZigBee Device Profile)
0x00 - Broadcast radius
0x00 - Tx Options
0x76 - Transaction sequence number
0x00 - Required payload for LQI request command
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0xCE - Checksum (0xFF - SUM (all bytes after length))
Description:
This API frame sends a ZDO LQI request (neighbor table request) to a remote device to obtain data from
its neighbor table. Recall that the AO command must be set correctly on an API device to enable the
explicit API receive frames in order to receive the ZDO response.
Example 2: Send a ZDO Network Address Request to discover the 16-bit address of a remote.
Looking at the ZigBee specification, the cluster ID for a network Address Request is 0x0000, and the
payload only requires the following:
[64-bit address] + [Request Type] + [Start Index]
This example will send a Network Address Request as a broadcast transmission to discover the 16-bit
address of the device with a 64-bit address of 0x0013A200 40401234. The request type and start index
will be set to 0, and the transaction sequence number will be set to 0x44
API Frame:
7E 001F 11 01 00000000 0000FFFF FFFE 00 00 0000 0000 00 00 44 34124040 00A21300 00 00 33
0x001F – length
0x11 - Explicit transmit request
0x01 - frame ID (set to a non-zero value to enable the transmit status message, or set to 0 to disable)
0x00000000 0000FFFF - 64-bit address for a broadcast transmission
0xFFFE - Set to this value for a broadcast transmission.
0x00 - Source endpoint
0x00 - Destination endpoint
0x0000 - Cluster ID (Network Address Request)
0x0000 - Profile ID (ZigBee Device Profile)
0x00 - Broadcast radius
0x00 - Tx Options
0x44 - Transaction sequence number
0x34124040 00A21300 00 00 - Required payload for Network Address Request command
0x33 - Checksum (0xFF - SUM (all bytes after length))
Description:
This API frame sends a broadcast ZDO Network Address Request to obtain the 16-bit address of a device
with a 64-bit address of 0x0013A200 40401234. Note the bytes for the 64-bit address were inserted in
little endian byte order. All multi-byte fields in the API payload of a ZDO command must have their data
inserted in little endian byte order. Also recall that the AO command must be set correctly on an API
device to enable the explicit API receive frames in order to receive the ZDO response.
Transmission Timeouts
The ZigBee stack includes two kinds of transmission timeouts, depending on the nature of the destination device.
For destination devices such as routers whose receiver is always on, a unicast timeout is used. The unicast timeout
estimates a timeout based on the number of unicast hops the packet should traverse to get data to the destination
device. For transmissions destined for end devices, the ZigBee stack uses an extended timeout that includes the
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unicast timeout (to route data to the end device's parent), and it includes a timeout for the end device to finish
sleeping, wake, and poll the parent for data.
The ZigBee stack includes some provisions for a device to detect if the destination is an end device or not. The
ZigBee stack uses the unicast timeout unless it knows the destination is an end device.
The XBee API includes a transmit options bit that can be set to specify if the extended timeout should be used for a
given transmission. If this bit is set, the extended timeout will be used when sending RF data to the specified
destination. To improve routing reliability, applications should set the extended timeout bit when sending data to
end devices if:
•The application sends data to 10 or more remote devices, some of which are end devices, AND
•The end devices may sleep longer than the unicast timeout
Equations for these timeouts are computed in the following sections.
Note: The timeouts in this section are worst-case timeouts and should be padded by a few hundred milliseconds.
These worst-case timeouts apply when an existing route breaks down (e.g. intermediate hop or destination device
moved).
Unicast Timeout
The unicast timeout is settable with the NH command. The actual unicast timeout is computed as ((50 * NH) +
100). The default NH value is 30 which equates to a 1.6 second timeout.
The unicast timeout includes 3 transmission attempts (1 attempt and 2 retries). The maximum total timeout is
about:
3 * ((50 * NH) + 100).
For example, if NH=30 (0x1E), the unicast timeout is about
3 * ((50 * 30) + 100), or
3 * (1500 + 100), or
* (1600), or
4800 ms, or
4.8 seconds.
Extended Timeout
The worst-case transmission timeout when sending data to an end device is somewhat larger than when
transmitting to a router or coordinator. As described later in chapter 6, RF data packets are actually sent to the
parent of the end device, who buffers the packet until the end device wakes to receive it. The parent will buffer an
RF data packet for up to (1.2 * SP) time.
To ensure the end device has adequate time to wake and receive the data, the extended transmission timeout to
an end device is:
(50 * NH) + (1.2 * SP)
This timeout includes the packet buffering timeout (1.2 * SP) and time to account for routing through the mesh
network (50 * NH).
If an acknowledgment is not received within this time, the sender will resend the transmission up to two more
times. With retries included, the longest transmission timeout when sending data to an end device is:
3 * ((50 * NH) + (1.2 * SP))
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The SP value in both equations must be entered in millisecond units. (The SP command setting uses 10ms units and
must be converted to milliseconds to be used in this equation.)
For example, suppose a router is configured with NH=30 (0x1E) and SP=0x3E8 (10,000 ms), and that it is either
trying to send data to one of its end device children, or to a remote end device. The total extended timeout to the
end device is about:
3 * ((50 * NH) + (1.2 * SP)), or
3 * (1500 + 12000), or
3 * (13500), or
40500 ms, or
40.5 seconds.
Transmission Examples
Example 1: Send a unicast API data transmission to the coordinator using 64-bit address 0, with payload
"TxData".
API Frame:
7E 0014 10 01 00000000 00000000 FFFE 00 00 54 78 44 61 74 61 AB
Field Composition:
0x0014 - length
0x10 - API ID (tx data)
0x01 - frame ID (set greater than 0 to enable the tx-status response)
0x00000000 00000000 - 64-bit address of coordinator (ZB definition)
0xFFFE - Required 16-bit address if sending data to 64-bit address of 0.
0x00 - Broadcast radius (0 = max hops)
0x00 - Tx options 0x54 78 44 61 74 61 - ASCII representation of "TxData" string
0xAB - Checksum (0xFF - SUM (all bytes after length))
Description:
This transmission sends the string "TxData" to the coordinator, without knowing the coordinator device's
64-bit address. A 64-bit address of 0 is defined as the coordinator in ZB firmware. If the coordinator's 64bit address was known, the 64-bit address of 0 could be replaced with the coordinator's 64-bit address,
and the 16-bit address could be set to 0.
Example 2 - Send a broadcast API data transmission that all devices can receive (including sleeping end
devices), with payload "TxData".
API Frame:
7E 0014 10 01 00000000 0000FFFF FFFE 00 00 54 78 44 61 74 61 AD
Field Composition:
0x0014 - length
0x10 - API ID (tx data)
0x01 - frame ID (set to a non-zero value to enable the tx-status response)
0x00000000 0000FFFF - Broadcast definition (including sleeping end devices
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0xFFFE - Required 16-bit address to send broadcast transmission.
0x00 - Broadcast radius (0 = max hops)
0x00 - Tx options 0x54 78 44 61 74 61 - ASCII representation of "TxData" string
0xAD - Checksum (0xFF - SUM (all bytes after length))
Description:
This transmission sends the string "TxData" as a broadcast transmission. Since the destination address is
set to 0xFFFF, all devices, including sleeping end devices can receive this broadcast.
If receiver application addressing is enabled, the XBee will report all received data frames in the explicit
format (0x91) to indicate the source and destination endpoints, cluster ID, and profile ID that each packet
was received on. (Status messages like modem status and route record indicators are not affected.)
To enable receiver application addressing, set the AO command to 1 using the AT command frame (0x08).
Here's how to do this:
API Frame:
7E 0005 08 01 414F 01 65
Field Composition:
0x0005 - length
0x08 - API ID (at command)
0x01 - frame ID (set to a non-zero value to enable AT command response frames)
0x414F - ASCII representation of 'A','O' (the command being issued) 0x01 - Parameter value
0x65 - Checksum (0xFF - SUM (all bytes after length))
Description:
Setting AO=1 is required for the XBee to use the explicit receive API frame (0x91) when RF data packets
are received. This is required if the application needs indication of source or destination endpoint, cluster
ID, and/ or profile ID values used in received ZigBee data packets. ZDO messages can only be received if
AO=1.
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5. Security
ZigBee supports various levels of security that can be configured depending on the needs of the application.
Security provisions include:
•128-bit AES encryption
•Two security keys that can be preconfigured or obtained during joining
•Support for a trust center
•Provisions to ensure message integrity, confidentiality, and authentication.
The first half of this chapter describes various security features defined in the ZigBee-PRO specification, while the
last half illustrates how the XBee and XBee-PRO modules can be configured to support these features
Security Modes
The ZigBee standard supports three security modes – residential, standard, and high security. Residential security
was first supported in the ZigBee 2006 standard. This level of security requires a network key be shared among
devices. Standard security adds a number of optional security enhancements over residential security, including an
APS layer link key. High security adds entity authentication, and a number of other features not widely supported.
XBee ZB modules primarily support standard security, although end devices that support residential security can
join and interoperate with standard security devices. The remainder of this chapter focuses on material that is
relevant to standard security.
ZigBee Security Model
ZigBee security is applied to the Network and APS layers. Packets are encrypted with 128-bit AES encryption. A
network key and optional link key can be used to encrypt data. Only devices with the same keys are able to
communicate together in a network. Routers and end devices that will communicate on a secure network must
obtain the correct security keys.
Network Layer Security
The network key is used to encrypt the APS layer and application data. In addition to encrypting application
messages, network security is also applied to route request and reply messages, APS commands, and ZDO
commands. Network encryption is not applied to MAC layer transmissions such as beacon transmissions, etc. If
security is enabled in a network, all data packets will be encrypted with the network key.
Packets are encrypted and authenticated using 128-bit AES. This is shown in the figure below.
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Frame Counter
The network header of encrypted packets includes a 32-bit frame counter. Each device in the network maintains a
32-bit frame counter that is incremented for every transmission. In addition, devices track the last known 32- bit
frame counter for each of its neighbors. If a device receives a packet from a neighbor with a smaller frame counter
than it has previously seen, the packet is discarded. The frame counter is used to protect against replay attacks.
If the frame counter reaches a maximum value of 0xFFFFFFFF, it does not wrap to 0 and no more transmissions can
be sent. Due to the size of the frame counters, reaching the maximum value is a very unlikely event for most
applications. The following table shows the required time under different conditions, for the frame counter to
reach its maximum value.
Average Transmission Rate
1/second
10/second
Time until 32-bit frame counter expires
136 years
13.6 years
To clear the frame counters without compromising security, the network key can be changed in the network.
When the network key is updated, the frame counters on all devices reset to 0. (See the Network Key Updates
section for details.)
Message Integrity code
The network header, APS header, and application data are all authenticated with 128-bit AES. A hash is performed
on these fields and is appended as a 4-byte message integrity code (MIC) to the end of the packet. The MIC allows
receiving devices to ensure the message has not been changed. The MIC provides message integrity in the ZigBee
security model. If a device receives a packet and the MIC does not match the device’s own hash of the data, the
packet is dropped.
Network Layer Encryption and Decryption
Packets with network layer encryption are encrypted and decrypted by each hop in a route. When a device
receives a packet with network encryption, it decrypts the packet and authenticates the packet. If the device is not
the destination, it then encrypts and authenticates the packet, using its own frame counter and source address in
the network header section.
Since network encryption is performed at each hop, packet latency is slightly longer in an encrypted network than
in a non-encrypted network. Also, security requires 18 bytes of overhead to include a 32-bit frame counter, an 8byte source address, 4-byte MIC, and 2 other bytes. This reduces the number of payload bytes that can be sent in a
data packet.
Network Key Updates
ZigBee supports a mechanism for changing the network key in a network. When the network key is changed, the
frame counters in all devices reset to 0.
APS Layer Security
APS layer security can be used to encrypt application data using a key that is shared between source and
destination devices. Where network layer security is applied to all data transmissions and is decrypted and reencrypted on a hop-by-hop basis, APS security is optional and provides end-to-end security using an APS link key
that only the source and destination device know. APS security can be applied on a packet-by-packet basis. APS
security cannot be applied to broadcast transmissions.
If APS security is enabled, packets are encrypted and authenticated using 128-bit AES. This is shown in the figure
below:
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Message Integrity Code
If APS security is enabled, the APS header and data payload are authenticated with 128-bit AES. A hash is
performed on these fields and appended as a 4-byte message integrity code (MIC) to the end of the packet. This
MIC is different than the MIC appended by the network layer. The MIC allows the destination device to ensure the
message has not been changed. If the destination device receives a packet and the MIC does not match the
destination device’s own hash of the data, the packet is dropped.
APS Link Keys
There are two kinds of APS link keys – trust center link keys and application link keys. A trust center link key is
established between a device and the trust center, where an application link key is established between a device
and another device in the network where neither device is the trust center.
APS Layer Encryption and Decryption
Packets with APS layer encryption are encrypted at the source and only decrypted by the destination. Since APS
encryption requires a 5-byte header and a 4-byte MIC, the maximum data payload is reduced by 9 bytes when APS
encryption is used.
Network and APS Layer Encryption
Network and APS layer encryption can both be applied to data. The following figure demonstrates the
authentication and encryption performed on the final ZigBee packet when both are applied.
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Trust Center
ZigBee defines a trust center device that is responsible for authenticating devices that join the network.
The trust center also manages link key distribution in the network.
Forming and Joining a secure Network
The coordinator is responsible for selecting a network encryption key. This key can either be preconfigured or
randomly selected. In addition, the coordinator generally operates as a trust center and must therefore select the
trust center link key. The trust center link key can also be preconfigured or randomly selected.
Devices that join the network must obtain the network key when they join. When a device joins a secure network,
the network and link keys can be sent to the joining device. If the joining device has a pre-configured trust center
link key, the network key will be sent to the joining device encrypted by the link key. Otherwise, if the joining
device is not pre-configured with the link key, the device could only join the network if the network key is sent
unencrypted (“in the clear”). The trust center must decide whether or not to send the network key unencrypted to
joining devices that are not pre-configured with the link key. Sending the network key unencrypted is not
recommended as it can open a security hole in the network. To maximize security, devices should be preconfigured with the correct link key.
Implementing Security on the XBee
If security is enabled in the XBee ZB firmware, devices acquire the network key when they join a network. Data
transmissions are always encrypted with the network key, and can optionally be end-to-end encrypted with the
APS link key. The following sections discuss the security settings and options in the XBee ZB firmware.
Enabling Security
To enable security on a device, the EE command must be set to 1. If the EE command value is changed and changes
are applied (e.g. AC command), the XBee module will leave the network (PAN ID and channel) it was operating on,
and attempt to form or join a new network.
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If EE is set to 1, all data transmissions will be encrypted with the network key. When security is enabled, the
maximum number of bytes in a single RF transmission will be reduced. See the NP command for details.
Note: The EE command must be set the same on all devices in a network. Changes to the EE command should be
written to non-volatile memory (to be preserved through power cycle or reset events) using the WR command.
Setting the Network Security Key
The coordinator must select the network security key for the network. The NK command (write-only) is used to set
the network key. If NK=0 (default), a random network key will be selected. (This should suffice for most
applications.) Otherwise, if NK is set to a non-zero value, the network security key will use the value specified by
NK. NK is only supported on the coordinator.
Routers and end devices with security enabled (ATEE=1) acquire the network key when they join a network. They
will receive the network key encrypted with the link key if they share a pre-configured link key with the
coordinator. See the following section for details.
Setting the APS Trust Center Link Key
The coordinator must also select the trust center link key, using the KY command. If KY=0 (default), the coordinator
will select a random trust center link key (not recommended). Otherwise, if KY is set greater than 0, this value will
be used as the pre-configured trust center link key. KY is write-only and cannot be read.
Note: Application link keys (sent between two devices where neither device is the coordinator) are not supported
in ZB firmware at this time.
Random Trust Center Link Keys
If the coordinator selects a random trust center link key (KY=0, default), then it will allow devices to join the
network without having a pre-configured link key. However, this will cause the network key to be sent
unencrypted over-the-air to joining devices and is not recommended.
Pre-configured Trust Center Link Keys
If the coordinator uses a pre-configured link key (KY > 0), then the coordinator will not send the network key
unencrypted to joining devices. Only devices with the correct pre-configured link key will be able to join and
communicate on the network.
Enabling APS Encryption
APS encryption is an optional layer of security that uses the link key to encrypt the data payload. Unlike network
encryption that is decrypted and encrypted on a hop-by-hop basis, APS encryption is only decrypted by the
destination device. The XBee must be configured with security enabled (EE set to 1) to use APS encryption.
APS encryption can be enabled in API firmware on a per-packet basis. To enable APS encryption for a given
transmission, the "enable APS encryption" transmit options bit should be set in the API transmit frame. Enabling
APS encryption decreases the maximum payload size by 9 bytes.
Using a Trust Center
The EO command can be used to define the coordinator as a trust center. If the coordinator is a trust center, it will
be alerted to all new join attempts in the network. The trust center also has the ability to update or change the
network key on the network.
In ZB firmware, a secure network can be established with or without a trust center. Network and APS layer
encryption are supported if a trust center is used or not.
Updating the Network Key with a Trust Center
If the trust center has started a network and the NK value is changed, the coordinator will update the network key
on all devices in the network. (Changes to NK will not force the device to leave the network.) The network will
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continue to operate on the same channel and PAN ID, but the devices in the network will update their network
key, increment their network key sequence number, and restore their frame counters to 0.
Updating the Network Key without a Trust Center
If the coordinator is not running as a trust center, the network reset command (NR1) can be used to force all
devices in the network to leave the current network and rejoin the network on another channel. When devices
leave and reform then network, the frame counters are reset to 0. This approach will cause the coordinator to
form a new network that the remaining devices should join. Resetting the network in this manner will bring the
coordinator and routers in the network down for about 10 seconds, and will likely cause the 16-bit PAN ID and 16bit addresses of the devices to change.
XBee Security Examples
This section covers some sample XBee configurations to support different security modes. Several AT commands
are listed with suggested parameter values. The notation in this section includes an '=' sign to indicate what each
command register should be set to - for example, EE=1. This is not the correct notation for setting command values
in the XBee. In AT command mode, each command is issued with a leading 'AT' and no '=' sign - for example ATEE1.
In the API, the two byte command is used in the command field, and parameters are populated as binary values in
the parameter field.
Example 1: Forming a network with security (pre-configured link keys)
1. Start a coordinator with the following settings:
a. ID=2234 (arbitrarily selected)
b. EE=1
c. NK=0
d. KY=4455
e. WR (save networking parameters to preserve them through power cycle)
2. Configure one or more routers or end devices with the following settings:
a. ID=2234
b. EE=1
c. KY=4455
d. WR (save networking parameters to preserve them through power cycle)
3. Read the AI setting on the coordinator and joining devices until they return 0 (formed or joined  a
network).
In this example, EE, ID, and KY are set the same on all devices. After successfully joining the secure network, all
application data transmissions will be encrypted by the network key. Since NK was set to 0 on the coordinator, a
random network key was selected. And since the link key (KY) was configured the same on all devices, to a nonzero value, the network key was sent encrypted by the pre-configured link key (KY) when the devices joined.
Example 1: Forming a network with security (obtaining keys during joining)
1. Start a coordinator with the following settings:
a. ID=2235
b. EE=1
c. NK=0
d. KY=0
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e. WR (save networking parameters to preserve them through power cycle)
2. Configure one or more routers or end devices with the following settings:
a. ID=2235
b. EE=1
c. KY=0
d. WR (save networking parameters to preserve them through power cycle)
3. Read the AI setting on the coordinator and joining devices until they return 0 (formed or joined a
network).
In this example, EE, ID, and KY are set the same on all devices. Since NK was set to 0 on the coordinator, a random
network key was selected. And since KY was set to 0 on all devices, the network key was sent unencrypted ("in the
clear") when the devices joined. This approach introduces security vulnerability into the network and is not
recommended.
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6. Network Commissioning and Diagnostics
Network commissioning is the process whereby devices in a mesh network are discovered and configured for
operation. The XBee modules include several features to support device discovery and configuration. In addition to
configuring devices, a strategy must be developed to place devices to ensure reliable routes.
To accommodate these requirements, the XBee modules include various features to aid in device placement,
configuration, and network diagnostics.
Device Configuration
XBee/XBee-PRO ZB modules can be configured locally through serial commands (AT or API), or remotely through
remote API commands. API devices can send configuration commands to set or read the configuration settings of
any device in the network.
Device Placement
For a mesh network installation to be successful, the installer must be able to determine where to place individual
XBee devices to establish reliable links throughout the mesh network.
Link Testing
A good way to measure the performance of a mesh network is to send unicast data through the network from one
device to another to determine the success rate of many transmissions. To simplify link testing, the modules
support a loopback cluster ID (0x12) on the data endpoint (0xE8). Any data sent to this cluster ID on the data
endpoint will be transmitted back to the sender. This is shown in the figure below:
The configuration steps to send data to the loopback cluster ID depend on the firmware type.
AT Firmware
To send data to the loopback cluster ID on the data endpoint of a remote device, set the CI command value to
0x12. The SE and DE commands should be set to 0xE8 (default value). The DH and DL commands should be set to
the address of the remote (0 for the coordinator, or the 64-bit address of the remote). After exiting command
mode, any received serial characters will be transmitted to the remote device, and returned to the sender.
API Firmware
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Send an Explicit Addressing ZigBee Command API frame (0x11) using 0x12 as the cluster ID and 0xE8 as the source
and destination endpoint. Data packets received by the remote will be echoed back to the sender.
RSSI Indicators
It is possible to measure the received signal strength on a device using the DB command. DB returns the RSSI value
(measured in –dBm) of the last received packet. However, this number can be misleading. The DB value only
indicates the received signal strength of the last hop. If a transmission spans multiple hops, the DB value provides
no indication of the overall transmission path, or the quality of the worst link – it only indicates the quality of the
last link and should be used sparingly.
The DB value can be determined in hardware using the RSSI/PWM module pin (pin 6). If the RSSI PWM
functionality is enabled (P0 command), when the module receives data, the RSSI PWM is set to a value based on
the RSSI of the received packet. (Again, this value only indicates the quality of the last hop.) This pin could
potentially be connected to an LED to indicate if the link is stable or not.
Device Discovery
Network Discovery
The network discovery command can be used to discover all Digi modules that have joined a network. Issuing the
ND command sends a broadcast node discovery command throughout the network. All devices that receive the
command will send a response that includes the device’s addressing information, node identifier string (see NI
command), and other relevant information. This command is useful for generating a list of all module addresses in
a network.
When a device receives the node discovery command, it waits a random time before sending its own response.
The maximum time delay is set on the ND sender with the NT command. The ND originator includes its NT setting
in the transmission to provide a delay window for all devices in the network. Large networks may need to increase
NT to improve network discovery reliability. The default NT value is 0x3C (6 seconds).
ZDO Discovery
The ZigBee Device Profile includes provisions to discover devices in a network that are supported on all ZigBee
devices (including non-Digi products). These include the LQI Request (cluster ID 0x0031) and the Network Update
Request (cluster ID 0x0038). The LQI Request can be used to read the devices in the neighbor table of a remote
device, and the Network Update Request can be used to have a remote device do an active scan to discover all
nearby ZigBee devices. Both of these ZDO commands can be sent using the XBee Explicit API transmit frame (0x11).
See the API chapter for details. Refer to the ZigBee specification for formatting details of these two ZDO frames.
Joining Announce
All ZigBee devices send a ZDO Device Announce broadcast transmission when they join a ZigBee network (ZDO
cluster ID 0x0013). These frames will be sent out the XBee's UART as an Explicit Rx Indicator API frame (0x91) if AO
is set to 1. The device announce payload includes the following information:
[Sequence Number] + [16-bit address] + [64-bit address] + [Capability]
The 16-bit and 64-bit addresses are received in little-endian byte order (LSB first). See the ZigBee specification for
details.
Commissioning Pushbutton and Associate LED
The XBee modules support a set of commissioning and LED behaviors to aid in device deployment and
commissioning. These include the commissioning pushbutton definitions and associate LED behaviors. These
features can be supported in hardware as shown below.
Commissioning Pushbutton and Associate LED Functionalities
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Commissioning Pushbutton
The commissioning pushbutton definitions provide a variety of simple functions to aid in deploying devices in a
network. The commissioning button functionality on pin 20 is enabled by setting the D0 command to 1 (enabled by
default).
Button
Presses
If modules is joined to a network
If module is not joined to a
network
• Wakes an end device for 30 seconds
• Sends a node identification broadcast
transmission
• Wakes an end device for 30
seconds
• Blinks a numeric error code on
the Associate pin indicating the
cause of join failure (see section
6.4.2).
• Sends a broadcast transmission to
enable joining on the coordinator and all
devices in the network for 1 minute. (If
joining is permanently enabled on a
device (NJ = 0xFF), this action has no
effect on that device.)
• N/A
• Causes the device to leave the PAN.
• Issues ATRE to restore module
parameters to default values, including
ID and SC.
• The device attempts to join a network
based on its ID and SC settings.
• Issues ATRE to restore module
parameters to default values,
including ID and SC.
• The device attempts to join a
network based on its ID and SC
settings.
Button presses may be simulated in software using the ATCB command. ATCB should be issued with a parameter
set to the number of button presses to execute. (e.g. sending ATCB1 will execute the action(s) associated with a
single button press.)
The node identification frame is similar to the node discovery response frame – it contains the device’s address,
node identifier string (NI command), and other relevant data. All API devices that receive the node identification
frame send it out their UART as an API Node Identification Indicator frame (0x95).
Associate LDE
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The Associate pin (pin 15) can provide indication of the device’s network status and diagnostics information. To
take advantage of these indications, an LED can be connected to the Associate pin as shown in the figure above.
The Associate LED functionality is enabled by setting the D5 command to 1 (enabled by default). If enabled, the
Associate pin is configured as an output and will behave as described in the following sections.
Joined Indication
The Associate pin indicates the network status of a device. If the module is not joined to a network, the Associate
pin is set high. Once the module successfully joins a network, the Associate pin blinks at a regular time interval.
This is shown in the following figure.
The LT command defines the blink time of the Associate pin. If set to 0, the device uses the default blink time
(500ms for coordinator, 250ms for routers and end devices).
Diagnostics Support
The Associate pin works with the commissioning pushbutton to provide additional diagnostics behaviors to aid in
deploying and testing a network. If the commissioning push button is pressed once, and the device has not joined a
network, the Associate pin blinks a numeric error code to indicate the cause of join failure. The number of blinks is
equal to (AI value – 0x20). For example, if AI=0x22, 2 blinks occur.
If the commissioning push button is pressed once, and the device has joined a network, the device transmits a
broadcast node identification packet. If the Associate LED functionality is enabled (D5 command), a device that
receives this transmission will blink its Associate pin rapidly for 1 second.
The following figures demonstrate these behaviors.
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7. Managing End Devices
ZigBee end devices are intended to be battery-powered devices capable of sleeping for extended periods of time.
Since end devices may not be awake to receive RF data at a given time, routers and coordinators are equipped
with additional capabilities (including packet buffering and extended transmission timeouts) to ensure reliable
data delivery to end devices.
End Device Operation
When an end device joins a ZigBee network, it must find a router or coordinator device that is allowing end devices
to join. Once the end device joins a network, a parent-child relationship is formed between the end device and the
router or coordinator that allowed it to join. See chapter 3 for details.
When the end device is awake, it sends poll request messages to its parent. When the parent receives a poll
request, it checks a packet queue to see if it has any buffered messages for the end device. It then sends a MAC
layer acknowledgment back to the end device that indicates if it has data to send to the end device or not.
If the end device receives the acknowledgment and finds that the parent has no data for it, the end device can
return to idle mode or sleep. Otherwise, it will remain awake to receive the data. This polling mechanism allows
the end device to enter idle mode and turn its receiver off when RF data is not expected in order to reduce current
consumption and conserve battery life.
The end device can only send data directly to its parent. If an end device must send a broadcast or a unicast
transmission to other devices in the network, it sends the message directly to its parent and the parent performs
any necessary route or address discoveries to route the packet to the final destination.
Parent Operation
Each router or coordinator maintains a child table that contains the addresses of its end device children. A router
or coordinator that has unused entries in its child table is said to have end device capacity, or the ability to allow
new end devices to join. If the child table is completely filled (such that the number of its end device children
matches the number of child table entries), the device cannot allow any more end devices to join to it.
Since the end device children are not guaranteed to be awake at a given time, the parent is responsible for
managing incoming data packets in behalf of its end device children. If a parent receives an RF data transmission
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destined for one of its end device children, and if the parent has enough unused buffer space, it will buffer the
packet. The data packet will remain buffered until a timeout expires, or until the end device sends a poll request to
retrieve the data.
The parent can buffer one broadcast transmission for all of its end device children. When a broadcast transmission
is received and buffered, the parent sets a flag in its child table when each child polls and retrieves the packet.
Once all children have received the broadcast packet, the buffered broadcast packet is discarded. If all children
have not received a buffered broadcast packet and a new broadcast is received, the old broadcast packet is
discarded, the child table flags are cleared, and the new broadcast packet is buffered for the end device children.
This is demonstrated in the figure below.
When an end device sends data to its parent that is destined for a remote device in the network, the parent
buffers the data packet until it can establish a route to the destination. The parent may perform a route or 16-bit
address discovery in behalf of its end device children. Once a route is established, the parent sends the data
transmission to the remote device.
End Device Poll Timeouts
To better support mobile end devices (end devices that can move around in a network); parent router and
coordinator devices have a poll timeout for each end device child. If an end device does not send a poll request to
its parent within the poll timeout, the parent will remove the end device from its child table. This allows the child
table on a router or coordinator to better accommodate mobile end devices in the network.
Packet Buffer Usage
Packet buffer usage on a router or coordinator varies depending on the application. The following activities can
require use of packet buffers for up to several seconds:
•Route and address discoveries
•Application broadcast transmissions
•Stack broadcasts (e.g. ZDO "Device Announce" messages when devices join a network)
•Unicast transmissions (buffered until acknowledgment is received from destination or retries exhausted)
•Unicast messages waiting for end device to wake.
Applications that use regular broadcasting or that require regular address or route discoveries will use up a
significant number of buffers, reducing the buffer availability for managing packets for end device children.
Applications should reduce the number of required application broadcasts, and consider implementing an external
address table or many-to-one and source routing if necessary to improve routing efficiency.
Non-Parent Device Operation
Devices in the ZigBee network treat data transmissions to end devices differently than transmissions to other
routers and coordinators. Recall that when a unicast transmission is sent, if a network acknowledgment is not
received within a timeout, the device resends the transmission. When transmitting data to remote coordinator or
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router devices, the transmission timeout is relatively short since these devices are powered and responsive.
However, since end devices may sleep for some time, unicast transmissions to end devices use an extended
timeout mechanism in order to allow enough time for the end device to wake and receive the data transmission
from its parent.
If a non-parent device does not know the destination is an end device, it will use the standard unicast timeout for
the transmission. However, provisions exist in the Ember ZigBee stack for the parent to inform the message sender
that the destination is an end device. Once the sender discovers the destination device is an end device, future
transmissions will use the extended timeout. See the XBee Router / Coordinator Configuration section in this
chapter for details.
XBee End Device Configuration
XBee end devices support two different sleep modes:
•Pin Sleep
•Cyclic Sleep.
Pin sleep allows an external microcontroller to determine when the XBee should sleep and when it should wake by
controlling the Sleep_RQ pin. In contrast, cyclic sleep allows the sleep period and wake times to be configured
through the use of AT commands. The sleep mode is configurable with the SM command.
In both pin and cyclic sleep modes, XBee end devices poll their parent every 100ms while they are awake to
retrieve buffered data. When a poll request has been sent, the end device enables the receiver until an
acknowledgment is received from the parent. (It generally takes less than 10ms from the time the poll request is
sent until the acknowledgment is received.) The acknowledgment indicates if the parent has buffered data for the
end device child or not. If the acknowledgment indicates the parent has pending data, the end device will leave the
receiver on to receive the data. Otherwise, the end device will turn off the receiver and enter idle mode (until the
next poll request is sent) to reduce current consumption (and improve battery life).
Once the module enters sleep mode, the On/Sleep pin (pin 26) is de-asserted (low) to indicate the module is
entering sleep mode. If CTS hardware flow control is enabled (D7 command), the CTS pin (pin 25) is de-asserted
(high) when entering sleep to indicate that serial data should not be sent to the module. The module will not
respond to serial or RF data when it is sleeping. Applications that must communicate serially to sleeping end
devices are encouraged to observe CTS flow control.
When the XBee wakes from sleep, the On/Sleep pin is asserted (high), and if flow control is enabled, the CTS pin is
also asserted (low). If the module has not joined a network, it will scan all SC channels after waking to try and find
a valid network to join.
Pin Sleep
Pin sleep allows the module to sleep and wake according to the state of the Sleep_RQ pin (pin 9). Pin sleep mode is
enabled by setting the SM command to 1.
When Sleep_RQ is asserted (high), the module will finish any transmit or receive operations and enter a low power
state. For example, if the module has not joined a network and Sleep_RQ is asserted (high), the module will sleep
once the current join attempt completes (i.e. when scanning for a valid network completes). The module will wake
from pin sleep when the Sleep_RQ pin is de-asserted (low).
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In the figure above, t1, t2, and t3 represent the following events:
•T1 - Time when Sleep_RQ is asserted (high)
•T2 - Time when the XBee enters sleep (CTS state change only if hardware flow control is enabled)
•T3 - Time when Sleep_RQ is de-asserted (low) and the module wakes.
The time between T1 and T2 varies depending on the state of the module. In the worst case scenario, if the end
device is trying to join a network, or if it is waiting for an acknowledgment from a data transmission, the delay
could be up to a few seconds.
When the XBee is awake and is joined to a network, it sends a poll request to its parent to see if the parent has any
buffered data for it. The end device will continue to send poll requests every 100ms while it is awake.
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Demonstration of Pin Sleep
Parent and remote devices must be configured to buffer data correctly and to utilize adequate transmission
timeouts. See the XBee Router / Coordinator Configuration section in this chapter for details.
Cyclic Sleep
Cyclic sleep allows the module to sleep for a specified time and wake for a short time to poll its parent for any
buffered data messages before returning to sleep again. Cyclic sleep mode is enabled by setting the SM command
to 4 or 5. SM5 is a slight variation of SM4 that allows the module to be woken prematurely by asserting the
Sleep_RQ pin (pin 10). In SM5, the XBee can wake after the sleep period expires, or if a high-to-low transition
occurs on the Sleep_RQ pin. Setting SM to 4 disables the pin wake option.
In cyclic sleep, the module sleeps for a specified time, and then wakes and sends a poll request to its parent to
discover if the parent has any pending data for the end device. If the parent has buffered data for the end device,
or if serial data is received, the XBee will remain awake for a time. Otherwise, it will enter sleep mode
immediately.
The On/Sleep line is asserted (high) when the module wakes, and is de-asserted (low) when the module sleeps. If
hardware flow control is enabled (D7 command), the CTS pin will assert (low) when the module wakes and can
receive serial data, and de-assert (high) when the module sleeps.
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In the figure above, t1, t2, and t3 represent the following events:
•T1 - Time when the module wakes from cyclic sleep
•T2 - Time when the module returns to sleep
•T3 - Later time when the module wakes from cyclic sleep.
The wake time and sleep time are configurable with software commands as described in the sections below.
Wake Time (Until Sleep)
In cyclic sleep mode (SM=4 or 5), if serial or RF data is received, the module will start a sleep timer (time until
sleep). Any data received serially or over the RF link will restart the timer. The sleep timer value is settable with the
ST command. While the module is awake, it will send poll request transmissions every 100ms to check its parent
for buffered data messages. The module returns to sleep when the sleep timer expires, or if the SI command is
sent to it. The following image shows this behavior.
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Sleep Period
The sleep period is configured based on the SP, SN, and SO commands. The following table lists the behavior of
these commands.
Command
Range
SP
0x20-oxAF0 (x10ms)
SN
1-0xFFFF
SD
0-0xFF
Description
Configures the sleep period of the
module.
Configures the number of sleep periods
multiplier.
Defines options for sleep mode behavior.
0x02 - Always wake for full ST time
0X04-Enable extended sleep (sleep for full
SP*SN) time)
The XBee module supports both a short cyclic sleep and an extended cyclic sleep that make use of these
commands. These two modes allow the sleep period to be configured according to the application requirements.
Short Cyclic Sleep
In short cyclic sleep mode, the sleep behavior of the module is defined by the SP and SN commands, and the SO
command must be set to 0x00 (default) or 0x02. In short cyclic sleep mode, the SP command defines the sleep
period and is settable up to 28 seconds. When the XBee enters short cyclic sleep, it remains in a low power state
until the SP time has expired.
After the sleep period expires, the XBee sends a poll request transmission to its parent to determine if its parent
has any buffered data waiting for the end device. Since router and coordinator devices can buffer data for end
device children up to 30 seconds, the SP range (up to 28 seconds) allows the end device to poll regularly enough to
receive buffered data. If the parent has data for the end device, the end device will start its sleep timer (ST) and
continue polling every 100ms to receive data. If the end device wakes and finds that its parent has no data for it,
the end device can return to sleep immediately.
The SN command can be used to control when the On/Sleep line is asserted (high). If SN is set to 1 (default), the
On/Sleep line will be set high each time the XBee wakes from sleep. Otherwise, if SN is greater than 1, the
On/Sleep line will only be set high if RF data is received, or after SN wake cycles occur. This allows an external
device to remain powered off until RF data is received, or until a number of sleep periods have expired (SN sleep
periods). This mechanism allows the XBee to wake at regular intervals to poll its parent for data without waking an
external device for an extended time (SP * SN time). This is shown in the figure below.
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Note: SP controls the packet buffer time on routers and coordinators. SP should be set on all router and
coordinator devices to match the longest end device SP time. See the XBee Router / Coordinator Configuration
section for details.
Extended Cyclic Sleep
In extended cyclic sleep operation, an end device can sleep for a multiple of SP time which can extend the sleep
time up to several days. The sleep period is configured using the SP and SN commands. The total sleep period is
equal to (SP * SN) where SP is measured in 10ms units. The SO command must be set correctly to enable extended
sleep.
Since routers and coordinators can only buffer incoming RF data for their end device children for up to 30 seconds,
if an end device sleeps longer than 30 seconds, devices in the network need some indication when an end device is
awake before they can send data to it. End devices that use extended cyclic sleep should send a transmission (such
as an IO sample) when they wake to inform other devices that they are awake and can receive data. It is
recommended that extended sleep end devices set SO to wake for the full ST time in order to provide other
devices with enough time to send messages to the end device.
Similar to short cyclic sleep, end devices running in this mode will return to sleep when the sleep timer expires, or
when the SI command is received.
Transmitting RF Data
An end device may transmit data when it wakes from sleep and has joined a network. End devices transmit directly
to their parent and then wait for an acknowledgment to be received. The parent will perform any required address
and route discoveries to help ensure the packet reaches the intended destination before reporting the
transmission status to the end device.
Receiving RF Data
After waking from sleep, an end device sends a poll request to its parent to determine if the parent has any
buffered data for it. In pin sleep mode, the end device polls every 100ms while the Sleep_RQ pin is de-asserted
(low). In cyclic sleep mode, the end device will only poll once before returning to sleep unless the sleep timer (ST)
is started (serial or RF data is received). If the sleep timer is started, the end device will continue to poll every
100ms until the sleep timer expires.
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The XBee ZB 2x6x firmware includes an adaptive polling enhancement where, if an end device receives RF data
from its parent, it sends another poll after a very short delay to check for more data. The end device continues to
poll at a faster rate as long as it receives data from its parent. This feature greatly improves data throughput to end
devices. When the end device no longer receives data from its parent, it resumes polling every 100ms.
IO Sampling
End devices can be configured to send one or more IO samples when they wake from sleep. To enable IO sampling
on an end device, the IR command must be set to a non-zero value, and at least one analog or digital IO pin must
be enabled for sampling (D0 - D9, P0-P2 commands). If IO sampling is enabled, an end device sends an IO sample
when it wakes and starts the ST timer. It will continue sampling at the IR rate until the sleep timer (ST) has expired.
See chapter 8 for details.
Waking End Devices with the Commissioning Pushbutton
If the commissioning pushbutton functionality is enabled (D0 command), a high-to-low transition on the AD0/
DIO0 pin (pin 33) will cause an end device to wake for 30 seconds. See the Commissioning Pushbutton section in
chapter 7 for details.
Parent Verification
Since an end device relies on its parent to maintain connectivity with other devices in the network, XBee end
devices include provisions to verify its connection with its parent. End devices monitor their link with their parent
when sending poll messages and after a power cycle or reset event as described below.
When an end device wakes from sleep, it sends a poll request to its parent. In cyclic sleep, if RF or serial data is not
received and the sleep timer is not started, the end device polls one time and returns to sleep for another sleep
period. Otherwise, the end device continues polling every 100ms. If the parent does not send an acknowledgment
response to three consecutive poll request transmissions, the end device assumes the parent is out of range, and
attempts to find a new parent.
After a power-up or reset event, the end device does an orphan scan to locate its parent. If the parent does not
send a response to the orphan scan, the end device attempts to find a new parent.
Rejoining
Once all devices have joined a ZigBee network, the permit-joining attribute should be disabled such that new
devices are no longer allowed to join the network. Permit-joining can be enabled later as needed for short times.
This provides some protection in preventing other devices from joining a live network.
If an end device cannot communicate with its parent, the end device must be able to join a new parent to maintain
network connectivity. However, if permit-joining is disabled in the network, the end device will not find a device
that is allowing new joins.
To overcome this problem, ZigBee supports rejoining, where an end device can obtain a new parent in the same
network even if joining is not enabled. When an end device joins using rejoining, it performs a PAN ID scan to
discover nearby networks. If a network is discovered that has the same 64-bit PAN ID as the end device, it will join
the network by sending a rejoin request to one of the discovered devices. The device that receives the rejoin
request will send a rejoin response if it can allow the device to join the network (i.e. child table not full). The rejoin
mechanism can be used to allow a device to join the same network even if permit-joining is disabled.
To enable rejoining, NJ should be set less than 0xFF on the device that will join. If NJ < 0xFF, the device assumes
the network is not allowing joining and first tries to join a network using rejoining. If multiple rejoining attempts
fail, or if NJ=0xFF, the device will attempt to join using association.
XBee Router/Coordinator Configuration
XBee routers and coordinators may require some configuration to ensure the following are set correctly:
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•RF packet buffering timeout
•Child poll timeout
•Transmission timeout.
The value of these timeouts depends on the sleep time used by the end devices. Each of these timeouts is
discussed below.
RF Packet Buffering Timeout
When a router or coordinator receives an RF data packet intended for one of its end device children, it buffers the
packet until the end device wakes and polls for the data, or until a packet buffering timeout occurs. This timeout is
settable using the SP command. The actual timeout is (1.2 * SP), with a minimum timeout of 1.2 seconds and a
maximum of 30 seconds. Since the packet buffering timeout is set slightly larger than the SP setting, SP should be
set the same on routers and coordinators as it is on cyclic sleep end devices. For pin sleep devices, SP should be set
as long as the pin sleep device can sleep, up to 30 seconds.
Note: In pin sleep and extended cyclic sleep, end devices can sleep longer than 30 seconds. If end devices sleep
longer than 30 seconds, parent and non-parent devices must know when the end device is awake in order to
reliably send data. For applications that require sleeping longer than 30 seconds, end devices should transmit an IO
sample or other data when they wake to alert other devices that they can send data to the end device.
Child Poll Timeout
Router and coordinator devices maintain a timestamp for each end device child indicating when the end device
sent its last poll request to check for buffered data packets. If an end device does not send a poll request to its
parent for a certain period of time, the parent will assume the end device has moved out of range and will remove
the end device from its child table. This allows routers and coordinators to be responsive to changing network
conditions. The NC command can be issued at any time to read the number of remaining (unused) child table
entries on a router or coordinator.
The child poll timeout is settable with the SP and SN commands. SP and SN should be set such that SP * SN
matches the longest expected sleep time of any end devices in the network. The actual timeout is calculated as (3
* SP * SN), with a minimum of 5 seconds. For networks consisting of pin sleep end devices, the SP and SN values on
the coordinator and routers should be set such that SP * SN matches the longest expected sleep period of any pin
sleep device. The 3 multiplier ensures the end device will not be removed unless 3 sleep cycles pass without
receiving a poll request. The poll timeout is settable up to a couple of months.
Transmission Timeout
As mentioned in chapter 4, when sending RF data to a remote router, since routers are always on, the timeout is
based on the number of hops the transmission may traverse. This timeout it settable using the NH command. (See
chapter 4 for details.)
Since end devices may sleep for lengthy periods of time, the transmission timeout to end devices also includes
some allowance for the sleep period of the end device. When sending data to a remote end device, the
transmission timeout is calculated using the SP and NH commands. If the timeout occurs and an acknowledgment
has not been received, the source device will resend the transmission until an acknowledgment is received, up to
two more times.
The transmission timeout per attempt is:
3 * ((unicast router timeout) + (end device sleep time)), or
3 * ((50 * NH) + (1.2 * SP)), where SP is measured in 10ms units.
Putting it all Together
Short Sleep Periods
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Pin and cyclic sleep devices that sleep less than 30 seconds can receive data transmissions at any time since their
parent device(s) will be able to buffer data long enough for the end devices to wake and poll to receive the data.
SP should be set the same on all devices in the network. If end devices in a network have more than one SP setting,
SP on the routers and coordinators should be set to match the largest SP setting of any end device. This will ensure
the RF packet buffering, poll timeout, and transmission timeouts are set correctly.
Extended Sleep Periods
Pin and cyclic sleep devices that might sleep longer than 30 seconds cannot receive data transmissions reliably
unless certain design approaches are taken. Specifically, the end devices should use IO sampling or another
mechanism to transmit data when they wake to inform the network they can receive data. SP and SN should be set
on routers and coordinators such that (SP * SN) matches the longest expected sleep time. This configures the poll
timeout so end devices are not expired from the child table unless a poll request is not received for 3 consecutive
sleep periods.
As a general rule of thumb, SP and SN should be set the same on all devices in almost all cases.
Sleep Examples
This section covers some sample XBee configurations to support different sleep modes. Several AT commands are
listed with suggested parameter values. The notation in this section includes an '=' sign to indicate what each
command register should be set to - for example, SM=4. This is not the correct notation for setting command
values in the XBee. In AT command mode, each command is issued with a leading 'AT' and no '=' sign - for example
ATSM4. In the API, the two byte command is used in the command field, and parameters are populated as binary
values in the parameter field.
Example 1
Configure a device to sleep for 20 seconds, but set SN such that the On/Sleep line will remain deasserted for up
to 1 minute.
The following settings should be configured on the end device.
SM = 4 (cyclic sleep) or 5 (cyclic sleep, pin wake)
SP = 0x7D0 (2000 decimal). This causes the end device to sleep for 20 seconds since SP is measured in units of
10ms.
SN = 3. (With this setting, the On/Sleep pin will assert once every 3 sleep cycles, or when RF data is received)
SO = 0
All router and coordinator devices on the network should set SP to match SP on the end device. This ensures that
RF packet buffering times and transmission timeouts will be set correctly.
Since the end device wakes after each sleep period (ATSP), the SN command can be set to 1 on all routers and the
coordinator.
Example 2
Configure an end device to sleep for 20 seconds, send 4 IO samples in 2 seconds, and return to sleep.
Since SP is measured in 10ms units, and ST and IR are measured in 1ms units, configure an end device with the
following settings:
SM = 4 (cyclic sleep) or 5 (cyclic sleep, pin wake)
SP = 0x7D0 (2000 decimal). This causes the end device to sleep for 20 seconds.
SN = 1
SO = 0
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ST = 0x7D0 (2000 decimal). This sets the sleep timer to 2 seconds.
IR = 0x258 (600 decimal). Set IR to a value greater than (2 seconds / 4) to get 4 samples in 2 seconds. The end
device sends an IO sample at the IR rate until the sleep timer has expired.
At least one analog or digital IO line must be enabled for IO sampling to work. To enable pin 19 (AD1/DIO1) as a
digital input line, the following must be set:
D1 = 3
All router and coordinator devices on the network should set SP to match SP on the end device. This ensures that
RF packet buffering times and transmission timeouts will be set correctly.
Example 3
Configure a device for extended sleep: to sleep for 4 minutes.
SP and SN must be set such that SP * SN = 4 minutes. Since SP is measured in 10ms units, the following settings can
be used to obtain 4 minute sleep.
SM = 4 (cyclic sleep) or 5 (cyclic sleep, pin wake)
SP = 0x7D0 (2000 decimal, or 20 seconds)
SN = 0x0B (12 decimal)
SO = 0x04 (enable extended sleep)
With these settings, the module will sleep for SP * SN time, or (20 seconds * 12) = 240 seconds = 4 minutes.
For best results, the end device should send a transmission when it wakes to inform the coordinator (or network)
when it wakes. It should also remain awake for a short time to allow devices to send data to it. The following are
recommended settings.
ST = 0x7D0 (2 second wake time)
SO = 0x06 (enable extended sleep and wake for ST time)
IR = 0x800 (send 1 IO sample after waking). At least one analog or digital IO sample should be enabled for IO
sampling.
With these settings, the end device will wake after 4 minutes and send 1 IO sample. It will then remain awake for 2
seconds before returning to sleep.
SP and SN should be set to the same values on all routers and coordinators that could allow the end device to join.
This will ensure the parent does not timeout the end device from its child table too quickly.
The SI command can optionally be sent to the end device to cause it to sleep before the sleep timer expires.
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8. XBee Analog and Digital IO Lines
XBee ZB firmware supports a number of analog and digital IO pins that are configured through software commands. Analog and
digital IO lines can be set or queried. The following table lists the configurable IO pins and the corresponding configuration
commands.
Pin name(s)
Module pin
AT
cmd
Command
Range
Dout/DIO13
P3
0, 3-5
DIN/nConfig/DIO14
P4
PWM RSSI/DIO10
P0
0,1, 3-5
PWM1/ DIO11
P1
0, 3-5
DTR/Slp_Rq/DIO8
10
D8
0, 3-5
PTI_DATA/SPI_nAttn/ADC5/DIO19
12
P9
0,1,6
SPI_SClk/DIO18
14
P8
0,1
SPI_nSSel/DIO17
15
P7
0,1
Spi_MOSI/DIO16
16
P6
0,1
Spi_MISO/DIO15
17
P5
0,1
JTMS/SWDIO/DIO12/CD
21
P2
0,3-5
JTRst/DIO4
24
D4
0, 3-5
nCTS/DIO7
25
D7
0,1, 3-7
JTDI/Assoc/DIO5
28
D5
0,1, 3-5
nRTS/DIO6/SClk2
29
D6
0,1, 3-5
AD3/DIO3
30
D3
0,2-5
AD2/DIO2
31
D2
0,2-5
PTI_En/AD1/DIO1
32
D1
0,2-5
AD0/DIO0/Comm
33
D0
0-5
IO Configuration
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To enable an analog or digital IO function on one or more XBee module pin(s), the appropriate configuration
command must be issued with the correct parameter. After issuing the configuration command, changes must be
applied on the module for the IO settings to take effect.
Pin Command Parameter
Description
disabled
Peripheral control
Analog
Data in monitored
Data out default low
Data out default High
RS485 enable low/packet
trace interface
>7
RS485 enable high
Unsupported
Pull-up resistors can be set for each digital input line using the PR command. The PR value updates the state of all
pull-up resistors.
IO Sampling
The XBee ZB modules have the ability to monitor and sample the analog and digital IO lines. IO samples can be
read locally or transmitted to a remote device to provide indication of the current IO line states. (Only API
firmware devices can send remote IO sample data out their UART or SPI ports.)
There are three ways to obtain IO samples, either locally or remotely:
•Queried Sampling
•Periodic Sampling
•Change Detection Sampling.
IO sample data is formatted as shown in the table below
Bytes
Name
Description
Sample Sets
Digital Channel mask
© 2010 Digi International, Inc.
Number of sample sets in the packet. (Always set to 1.)
Digital IO line on the module.
• bit 0 = AD0/DIO0
• bit 1 = AD1/DIO1
• bit 2 = AD2/DIO2
• bit 3 = AD3/DIO3
• bit 4 = JTRst/DIO4
• bit 5 = JTDI/ASSOC/DIO5
• bit 6 = RTS/SCLK2/DIO6
• bit 7 = CTS/GPIO7
• bit 8 = DTR/Slp_Rq/DIO8
• bit 9 = N/A
• bit 10 = PWN/RSSI/DIO10
• bit 11 = PWM1/DIO11
• bit 12 = JTMS/SWDIO/CD/DIO12
• bit 13=DOUT/DIO13
• bit14=DIN/nconfig/DIO14
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Variable
Analog Channel Mask
Sampled Data Set
• bit15=SPI_MISO/DIO15
• bit16=SPI_MOSI/DIO16
• bit17=SPI_nSSEL/DIO17
• bit18=SPI_SCLK/DIO18
For example, a digital channel mask of 0x002F means
DIO0 1, 2, 3, and 5 are enabled as digital IO.
Indicates which lines have analog inputs enabled for
sampling. Each bit in the analog channel mask
corresponds to one analog input channel.
• bit 0 = AD0/DIO0
• bit 1 = AD1/DIO1
• bit 2 = AD2/DIO2
• bit 3 = AD3/DIO3
• bit 7 = Supply Voltage
A sample set consisting of 1 sample for each enabled
ADC and/or DIO channel, which has voltage inputs of
1143.75 and 342.1875mV.
If any digital IO lines are enabled, the first two bytes of
the data set indicate the state of all enabled digital IO.
Only digital channels that are enabled in the Digital
Channel Mask bytes have any meaning in the sample
set. If no digital IO is enabled on the device, these 2
bytes will be omitted.
Following the digital IO data (if any), each enabled
analog channel will return 2 bytes. The data starts with
AIN0 and continues sequentially for each enabled
analog input channel up to AIN3, and the supply voltage
(if enabled) at the end.
The sampled data set will include 2 bytes of digital IO data only if one or more IO lines on the device are configured
as digital IO. If no pins are configured as digital IO, these 2 bytes will be omitted.
The digital IO data is only relevant if the same bit is enabled in the digital IO mask.
Analog samples are returned as 14-bit values. The analog reading is scaled such that 0x0000 represents 0V, and
0x3FF = 1.2V. (The analog inputs on the module cannot read more than 1.2V.) Analog samples are returned in
order starting with AIN0 and finishing with AIN3, and the supply voltage. Only enabled analog input channels
return data as shown in the figure below.
To convert the A/D reading to mV, do the following:
AD(mV) = (A/D reading * 1200mV) / 1024
The reading in the sample frame represents voltage inputs of 1143.75 and 342.1875mV for AD0 and AD1
respectively.
Queried Sampling
The IS command can be sent to a device locally, or to a remote device using the API remote command frame (see
chapter 8 for details). When the IS command is sent, the receiving device samples all enabled digital IO and analog
input channels and returns an IO sample. If IS is sent locally, the IO sample is sent out the UART or SPI port. If the IS
command was received as a remote command, the IO sample is sent over-the-air to the device that sent the IS
command.
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If the IS command is issued in AT firmware, the module returns a carriage return-delimited list containing the
above-listed fields. The API firmware returns an AT command response packet with the IO data included in the
command data portion of the response frame.
The following table shows an example of the fields in an IS response.
Example
0x01
0x0C0C
0x03
0x0408
0x03D0
0x0124
Sample AT Response
[1 sample set]
[Digital Inputs: DIO 2, 3, 10, 11 low]
[Analog Inputs; A/D 0,1]
[Digital input states: DIO 3,10 high, DIO 2,11 low]
[Analog input ADIO 0=0x3D0]
[Analog input ADIO 1=0x120]
Periodic IO Sampling
Periodic sampling allows an XBee/XBee-PRO module to take an IO sample and transmit it to a remote device at a
periodic rate. The periodic sample rate is set by the IR command. If IR is set to 0, periodic sampling is disabled. For
all other values of IR, data will be sampled after IR milliseconds have elapsed and transmitted to a remote device.
The DH and DL commands determine the destination address of the IO samples. DH and DL can be set to 0 to
transmit to the coordinator, or to the 64-bit address of the remote device (SH and SL). Only devices running API
firmware can send IO data samples out their UART. Devices running AT firmware will discard received IO data
samples.
A sleeping end device will transmit periodic IO samples at the IR rate until the ST timer expires and the device can
resume sleeping.
Change Detection Sampling
Modules can be configured to transmit a data sample immediately whenever a monitored digital IO pin changes
state. The IC command is a bitmask that can be used to set which digital IO lines should be monitored for a state
change. If one or more bits in IC is set, an IO sample will be transmitted as soon as a state change is observed in
one of the monitored digital IO lines. Change detection samples are transmitted to the 64-bit address specified by
DH and DL.
RSSI PWM
The XBee module features an RSSI/PWM pin (pin 7) that, if enabled, will adjust the PWM output to indicate the
signal strength of the last received packet. The P0 (P-zero) command is used to enable the RSSI pulse width
modulation (PWM) output on the pin. If P0 is set to 1, the RSSI/PWM pin will output a pulse width modulated
signal where the frequency is adjusted based on the received signal strength of the last packet. Otherwise, for all
other P0 settings, the pin can be used for general purpose IO.
When a data packet is received, if P0 is set to enable the RSSI/PWM feature, the RSSI PWM output is adjusted
based on the RSSI of the last packet. The RSSI/PWM output will be enabled for a time based on the RP command.
Each time an RF packet is received, the RSSI/PWM output is adjusted based on the RSSI of the new packet, and the
RSSI timer is reset. If the RSSI timer expires, the RSSI/PWM pin is driven low. RP is measured in 100ms units and
defaults to a value of 40 (4 seconds).
The RSSI PWM runs at 12MHz and has 2400 total counts (200us period).
RSSI (in dBm) is converted to PWM counts using the following equation:
PWM counts = (41 * RSSI_Unsigned) – 5928
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IO Examples
Example 1: Configure the following IO settings on the XBee
Configure AD1/DIO1 as a digital input with pull-up resistor enabled
Configure AD2/DIO2 as an analog input
Configure DIO4 as a digital output, driving high.
To configure AD1/DIO1 as an input, issue the ATD1 command with a parameter of 3 ("ATD13"). To enable pull-up
resistors on the same pin, the PR command should be issued with bit 3 set (e.g. ATPR8, ATPR1FFF, etc.). The ATD2
command should be issued with a parameter of 2 to enable the analog input ("ATD22"). Finally, DIO4 can be set as
an output, driving high by issuing the ATD4 command with a parameter value of 5 ("ATD45").
After issuing these commands, changes must be applied before the module IO pins will be updated to the new
states. The AC or CN commands can be issued to apply changes (e.g. ATAC).
Example 2: Calculate the PWM counts for a packet received with an RSSI of -84dBm.
RSSI = -84 = 0xAC = 172 decimal (unsigned)
PWM counts = (41 * 172) - 5928
PWM counts = 1124
With a total of 2400 counts, this yields an ON time of (1124 / 2400) = 46.8%
Example 3: Configure the RSSI/PWM pin to operate for 2 seconds after each received RF packet.
First, ensure the RSSI/PWM functionality is enabled by reading the P0 (P-zero) command. It should be set to 1
(default).
To configure the duration of the RSSI/PWM output, set the RP command. To achieve a 2 second PWM output, set
RP to 0x14 (20 decimal or 2 seconds) and apply changes (AC command).
After applying changes, all received RF data packets should set the RSSI timer for 2 seconds.
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9. API Operation
As an alternative to Transparent Operation, API (Application Programming Interface) Operations are available. API
operation requires that communication with the module be done through a structured interface (data is
communicated in frames in a defined order). The API specifies how commands, command responses and module
status messages are sent and received from the module using a UART or SPI Data Frame.
Please note that Digi may add new API frames to future versions of firmware, so please build into your software
interface the ability to filter out additional API frames with unknown Frame Types.
API Frame Specifications
Two API modes are supported and both can be enabled using the AP (API Enable) command. Use the following AP
parameter values to configure the module to operate in a particular mode:
•AP = 1: API Operation
•AP = 2: API Operation (with escaped characters)
API Operation (AP parameter = 1)
When this API mode is enabled (AP = 1), the UART or SPI data frame structure is defined as follows:
UART or SPI Data Frame Structure:
Any data received prior to the start delimiter is silently discarded. If the frame is not received correctly or if the
checksum fails, the module will reply with a module status frame indicating the nature of the failure.
API Operation-with Escape Characters (AP parameter = 2)
When this API mode is enabled (AP = 2), the UART or SPI data frame structure is defined as follows:
UART or SPI Data Frame Structure - with escape control characters:
Escape characters. When sending or receiving a UART or SPI data frame, specific data values must be escaped
(flagged) so they do not interfere with the data frame sequencing. To escape an interfering data byte, insert 0x7D
and follow it with the byte to be escaped XOR’d with 0x20.
Data bytes that need to be escaped:
•0x7E – Frame Delimiter
•0x7D – Escape
•0x11 – XON
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•0x13 – XOFF
Example - Raw UART Data Frame (before escaping interfering bytes): 
0x7E 0x00 0x02 0x23 0x11 0xCB
0x11 needs to be escaped which results in the following frame: 
0x7E 0x00 0x02 0x23 0x7D 0x31 0xCB
Note: In the above example, the length of the raw data (excluding the checksum) is 0x0002 and the checksum of
the non-escaped data (excluding frame delimiter and length) is calculated as: 0xFF - (0x23 + 0x11) = (0xFF - 0x34) =
0xCB.
Length
The length field has a two-byte value that specifies the number of bytes that will be contained in the frame data
field. It does not include the checksum field.
Framed Data
Frame data of the UART or SPI data frame forms an API-specific structure as follows:
UART or SPI Data Frame & API-specific Structure:
The cmdID frame (API-identifier) indicates which API messages will be contained in the cmdData frame (Identifierspecific data). Note that multi-byte values are sent big endian. The XBee modules support the following API
frames:
API Frame Names and Values
API Frame Names
AT Command 0x08
AT Command - Queue Parameter Value
ZigBee Transmit Request
Explicit Addressing ZigBee Command
Frame
Remote Command Request
Create Source Route
AT Command Response
Modem Status
ZigBee Transmit Status
ZigBee Receive Packet (AO=0)
ZigBee Explicit Rx Indicator (AO=1)
ZigBee IO Data Sample Rx Indicator
XBee Sensor Read Indicator (AO=0)
Node Identification Indicator (AO=0)
Remote Command Response
Over-the-Air Firmware Update Status
Route Record Indicator
Many-to-One Route Request Indicator
© 2010 Digi International, Inc.
API ID
0x08
0x09
0x10
0x11
0x17
0x20
0x88
0x8A
0x8B
0x90
0x91
0x92
0x94
0x95
0x97
0xA0
0xA1
0xA3
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Checksum
To test data integrity, a checksum is calculated and verified on non-escaped data.
To calculate: Not including frame delimiters and length, add all bytes keeping only the lowest 8 bits of the result
and subtract the result from 0xFF.
To verify: Add all bytes (include checksum, but not the delimiter and length). If the checksum is correct, the sum
will equal 0xFF.
API Examples
Example: Create an API AT command frame to configure an XBee to allow joining (set NJ to 0xFF). The frame
should look like:
0x7E 0x00 0x05 0x08 0x01 0x4E 0x4A 0xFF 5F
Where 0x0005 = length
0x08 = AT Command API frame type
0x01 = Frame ID (set to non-zero value)
0x4E4A = AT Command ('NJ')
0xFF = value to set command to
0x5F = Checksum
The checksum is calculated as [0xFF - (0x08 + 0x01 + 0x4E + 0x4A + 0xFF)]
Example: Send a remote command to the coordinator to set AD1/DIO1 as a digital input (D1=3) and apply changes
to force the IO update. The API remote command frame should look like:
0x7E 0x00 0x10 0x17 0x01 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0xFF 0xFE 0x02 0x44 0x31 0x03 0x70
Where
0x10 = length (16 bytes excluding checksum)
0x17 = Remote Command API frame type
0x01 = Frame ID
0x0000000000000000 = Coordinator's address (can be replaced with coordinator's actual 64-bit address if
known)
0xFFFE = 16- bit Destination Address
0x02 = Apply Changes (Remote Command Options)
0x4431 = AT command ('D1')
0x03 = Command Parameter (the parameter could also be sent as
0x0003 or 0x00000003)
0x70 = Checksum
API UART and SPI Exchanges
AT Commands
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The following image shows the API frame exchange that takes place at the UART or SPI when sending an AT
command request to read or set a module parameter. The response can be disabled by setting the frame ID to 0 in
the request.
Transmitting and Receiving RF Data
The following image shows the API exchanges that take place at the UART or SPI when sending RF data to another
device. The transmit status frame is always sent at the end of a data transmission unless the frame ID is set to 0 in
the transmit request. If the packet cannot be delivered to the destination, the transmit status frame will indicate
the cause of failure. The received data frame (0x90 or 0x91) is set by the AP command.
Remote AT commands
The following image shows the API frame exchanges that take place at the UART or SPI when sending a remote AT
command. A remote command response frame is not sent out the UART or SPI if the remote device does not
receive the remote command.
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Source Routing
The following image shows the API frame exchanges that take place at the UART or SPI when sending a source
routed transmission.
Supporting the API
Applications that support the API should make provisions to deal with new API frames that may be introduced in
future releases. For example, a section of code on a host microprocessor that handles received serial API frames
(sent out the module's DOUT pin) might look like this:
void XBee_HandleRxAPIFrame(_apiFrameUnion *papiFrame){
switch(papiFrame->api_id){
case RX_RF_DATA_FRAME:
//process received RF data frame break;
case RX_IO_SAMPLE_FRAME:
//process IO sample frame break;
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case NODE_IDENTIFICATION_FRAME:
//process node identification frame break;
default:
//Discard any other API frame types that are not being used break;
API Frames
The following sections illustrate the types of frames encountered while using the API.
AT Command
Frame Type: 0x08
Used to query or set module parameters on the local device. This API command applies changes after executing
the command. (Changes made to module parameters take effect once changes are applied.) The API example
below illustrates an API frame when modifying the NJ parameter value of the module
The above example illustrates an AT command when querying an NJ value.
AT Command-Queue Parameter Value
Frame Type: 0x09
This API type allows module parameters to be queried or set. In contrast to the “AT Command” API type, new
parameter values are queued and not applied until either the “AT Command” (0x08) API type or the AC (Apply
Changes) command is issued. Register queries (reading parameter values) are returned immediately.
Example: Send a command to change the baud rate (BD) to 115200 baud, but don't apply changes yet.
(Module will continue to operate at the previous baud rate until changes are applied.)
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Note: In this example, the parameter could have been sent as a zero-padded 2-byte or 4-byte value.
ZigBee Transmit Request
Frame Type: 0x10
A Transmit Request API frame causes the module to send data as an RF packet to the specified destination.
The 64-bit destination address should be set to 0x000000000000FFFF for a broadcast transmission (to all devices).
The coordinator can be addressed by either setting the 64-bit address to all 0x00s and the 16-bit address to
0xFFFE, OR by setting the 64-bit address to the coordinator's 64-bit address and the 16-bit address to 0x0000. For
all other transmissions, setting the 16-bit address to the correct 16-bit address can help improve performance
when transmitting to multiple destinations. If a 16-bit address is not known, this field should be set to 0xFFFE
(unknown). The Transmit Status frame (0x8B) will indicate the discovered 16-bit address, if successful.
The broadcast radius can be set from 0 up to NH. If set to 0, the value of NH specifies the broadcast radius
(recommended). This parameter is only used for broadcast transmissions.
The maximum number of payload bytes can be read with the NP command.
Note: if source routing is used, the RF payload will be reduced by two bytes per intermediate hop in the source
route. This example shows if escaping is disabled (AP=1).
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Example: The example above shows how to send a transmission to a module where escaping is disabled (AP=1)
with destination address 0x0013A200 40014011, payload "TxData1B". If escaping is enabled (AP=2), the frame
should look like:
0x7E 0x00 0x16 0x10 0x01 0x00 0x7D 0x33 0xA2 0x00 0x40 0x0A 0x01 0x27
0xFF 0xFE 0x00 0x00 0x54 0x78 0x44 0x61 0x74 0x61 0x30 0x41 0x7D 0x33
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The checksum is calculated (on all non-escaped bytes) as [0xFF - (sum of all bytes from API frame type through
data payload)].
Example: Send a transmission to the coordinator without specifying the coordinator's 64-bit address. The API
transmit request frame should look like:
0x7E 0x00 0x16 0x10 0x01 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0xFF 0xFE 0x00 0x00 0x54
0x78 032 0x43 0x6F 0x6F 0x72 0x64 0xFC
Where
0x16 = length (22 bytes excluding checksum)
0x10 = ZigBee Transmit Request API frame type
0x01 = Frame ID (set to non-zero value)
0x0000000000000000 = Coordinator's address (can be replaced with coordinator's actual 64-bit address
if known
0xFFFE = 16-bit Destination Address
0x00 = Broadcast radius
0x00 = Options 0x547832436F6F7264 = Data payload ("Tx2Coord")
0xFC = Checksum
Explicit Addressing ZigBee Command Frame
Frame Type: 0x11
Allows ZigBee application layer fields (endpoint and cluster ID) to be specified for a data transmission.
Similar to the ZigBee Transmit Request, but also requires ZigBee application layer addressing fields to be specified
(endpoints, cluster ID, profile ID). An Explicit Addressing Request API frame causes the module to send data as an
RF packet to the specified destination, using the specified source and destination endpoints, cluster ID, and profile
ID.
The 64-bit destination address should be set to 0x000000000000FFFF for a broadcast transmission (to all devices).
The coordinator can be addressed by either setting the 64-bit address to all 0x00s and the 16-bit address to
0xFFFE, OR by setting the 64-bit address to the coordinator's 64-bit address and the 16-bit address to 0x0000. For
all other transmissions, setting the 16-bit address to the correct 16-bit address can help improve performance
when transmitting to multiple destinations. If a 16-bit address is not known, this field should be set to 0xFFFE
(unknown). The Transmit Status frame (0x8B) will indicate the discovered 16-bit address, if successful.
The broadcast radius can be set from 0 up to NH. If set to 0, the value of NH specifies the broadcast radius
(recommended). This parameter is only used for broadcast transmissions.
The maximum number of payload bytes can be read with the NP command. Note: if source routing is used, the RF
payload will be reduced by two bytes per intermediate hop in the source route.
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Example: Send a data transmission to the coordinator (64-bit address of 0x00s) using a source endpoint of 0xA0,
destination endpoint 0xA1, cluster ID =0x1554, and profile ID 0xC105. Payload will be "TxData".
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Remote AT Command Request
Frame Type: 0x17
Used to query or set module parameters on a remote device. For parameter changes on the remote device to take
effect, changes must be applied, either by setting the apply changes options bit, or by sending an AC command to
the remote.
Example: Send a remote command to change the broadcast hops register on a remote device to 1 (broadcasts go
to 1-hop neighbors only), and apply changes so the new configuration value immediately takes effect. In this
example, the 64-bit address of the remote is 0x0013A200 40401122, and the destination 16-bit address is
unknown.
Create Source Route
Frame Type: 0x21
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This frame creates a source route in the module. A source route specifies the complete route a packet should
traverse to get from source to destination. Source routing should be used with many-to-one routing for best
results.
Note: Both the 64-bit and 16-bit destination addresses are required when creating a source route. These are
obtained when a Route Record Indicator (0xA1) frame is received.
Example: Intermediate hop addresses must be ordered starting with the neighbor of the destination, and working
closer to the source. For example, suppose a route is found between A and E as shown below.
A'B'C'D'E
If device E has the 64-bit and 16-bit addresses of 0x0013A200 40401122 and 0x3344, and if devices B, C, and D
have the following 16-bit addresses:
B = 0xAABB
C = 0xCCDD
D = 0xEEFF
The example above shows how to send the Create Source Route frame to establish a source route between A and
E.
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AT Command Response
Frame Type: 0x88
In response to an AT Command message, the module will send an AT Command Response message. Some
commands will send back multiple frames (for example, the ND (Node Discover) command).
Example: Suppose the BD parameter is changed on the local device with a frame ID of 0x01. If successful
(parameter was valid), the above response would be received.
Modem Status
Frame Type: (0x8A)
RF module status messages are sent from the module in response to specific conditions.
Example: The following API frame is returned when an API coordinator forms a network.
Note: New modem status codes may be added in future firmware releases.
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ZigBee Transmit Status
Frame Type: 0x8B
When a TX Request is completed, the module sends a TX Status message. This message will indicate if the packet
was transmitted successfully or if there was a failure.
Example: Suppose a unicast data transmission was sent to a destination device with a 16-bit address of 0x7D84.
(The transmission could have been sent with the 16-bit address set to 0x7D84 or 0xFFFE.)
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ZigBee Receive Packet
Frame Type: (0x90)
When the module receives an RF packet, it is sent out the UART or SPI using this message type.
Example: Suppose a device with a 64-bit address of 0x0013A200 40522BAA, and 16-bit address 0x7D84 sends a
unicast data transmission to a remote device with payload "RxData". If AO=0 on the receiving device, it would send
the above example frame out its UART or SPI.
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ZigBee Explicit RX Indicator
Frame Type:0x91
When the modem receives a ZigBee RF packet it is sent out the UART or SPI using this message type (when AO=1).
Example: Suppose a device with a 64-bit address of 0x0013A200 40522BAA, and 16-bit address 0x7D84 sends a
broadcast data transmission to a remote device with payload "RxData". Suppose the transmission was sent with
source and destination endpoints of 0xE0, cluster ID=0x2211, and profile ID=0xC105. If AO=1 on the receiving
device, it would send the above frame out its UART or SPI.
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ZigBee IO Data Sample RX Indicator
Frame Type: 0x92
When the module receives an IO sample frame from a remote device, it sends the sample out the UART or SPI
using this frame type (when AO=0). Only modules running API firmware will send IO samples out the UART or SPI.
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Example: Suppose an IO sample is received with analog and digital IO, from a remote with a 64- bit address of
0x0013A200 40522BAA and a 16-bit address of 0x7D84. If pin AD1/DIO1 is enabled as an analog input, AD2/DIO2
and DIO4 are enabled as a digital inputs (currently high), and AD3/ DIO3 is enabled as a digital output (low) the IO
sample is shown in the API example in the table above.
XBee Sensor Read Indicator
Frame Type: 0x94
When the module receives a sensor sample (from a Digi 1-wire sensor adapter), it is sent out the UART or SPI using
this message type (when AO=0).
Example: Suppose a 1-wire sensor sample is received from a device with a 64-bit address of 0x0013A200
40522BAA and a 16-bit address of 0xDD6C. If the sensor sample was taken from a 1-wire humidity sensor, the API
frame could look like this (if AO=0):
For convenience, let's label the A/D and temperature readings as AD0, AD1, AD2, AD3, and T. Using the data in this
example:
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AD0 = 0x0002
AD1 = 0x00CE
AD2 = 0x00EA
AD3 = 0x0052
T = 0x016A
To convert these to temperature and humidity values, the following equations should be used.
Temperature (°C) = (T / 16), for T < 2048 = - (T & 0x7FF) / 16, for T >= 2048
Vsupply = (AD2 * 5.1) / 255
Voutput = (AD3 * 5.1) / 255
Relative Humidity = ((Voutput / Vsupply) - 0.16) / (0.0062)
True Humidity = Relative Humidity / (1.0546 - (0.00216 * Temperature (°C)))
Looking at the sample data, we have:
Vsupply = (234 * 5.1 / 255) = 4.68
Voutput = (82 * 5.1 / 255) = 1.64
Temperature = (362 / 16) = 22.625°C
Relative H = (161.2903 * ((1.64/4.68) - 0.16)) = 161.2903 * (0.19043) = 30.71%
True H = (30.71 / (1.0546 - (0.00216 * 22.625))) = (30.71 / 1.00573) = 30.54%
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Node Identification Indicator
Frame Type: 0x95
This frame is received when a module transmits a node identification message to identify itself (when AO=0). The
data portion of this frame is similar to a network discovery response frame (see ND command).
Example: If the commissioning push button is pressed on a remote router device with 64-bit address 0x0013A200
40522BAA, 16-bit address 0x7D84, and default NI string, the following node identification indicator would be
received.
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Remote Command Response
Frame Type: 0x97
If a module receives a remote command response RF data frame in response to a Remote AT Command Request,
the module will send a Remote AT Command Response message out the UART or SPI. Some commands may send
back multiple frames--for example, Node Discover (ND) command.
Example: If a remote command is sent to a remote device with 64-bit address 0x0013A200 40522BAA and 16-bit
address 0x7D84 to query the SL command, and if the frame ID=0x55, the response is shown in the example API
frame in the table above.
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Over-the-Air Firmware Update Status
Frame Type: 0xA0
The Over-the-Air Firmware Update Status frame provides a status indication of a firmware update transmission
attempt. If a query command (0x01 0x51) is sent to a target with a 64-bit address of 0x0013A200 40522BAA
through an updater with 64-bit address 0x0013A200403E0750 and 16-bit address 0x0000, the following is the
expected response.
If a query request returns a 0x15 (NACK) status, the target is likely waiting for a firmware update image. If no
messages are sent to it for about 75 seconds, the target will timeout and accept new query messages.
If a query returns a 0x51 (QUERY) status, then the target's bootloader is not active and will not respond to query
messages.
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Route Record Indicator
Frame Type: 0xA1
The route record indicator is received whenever a device sends a ZigBee route record command. This is used with
many-to-one routing to create source routes for devices in a network.
Example: Suppose device E sends a route record that traverses multiple hops en route to data collector device A as
shown below.
ABCDE
If device E has the 64-bit and 16-bit addresses of 0x0013A200 40401122 and 0x3344, and if devices B, C, and D
have the following 16-bit addresses:
B = 0xAABB
C = 0xCCDD
D = 0xEEFF
The data collector will send the above API frame out its UART or SPI.
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Many-to-One Route Request Indicator
Frame Type: 0xA3
The many-to-one route request indicator frame is sent out the UART or SPI whenever a many-to-one route request
is received
Example: Suppose a device with a 64-bit address of 0x0013A200 40401122 and 16-bit address of 0x0000 sends a
many-to-one route request. All remote routers with API firmware that receive the many-to-one broadcast would
send the above example API frame out their UART or SPI.
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Sending ZigBee device objects (ZDO) Commands with the API
ZigBee Device Objects (ZDOs) are defined in the ZigBee Specification as part of the ZigBee Device Profile. These
objects provide functionality to manage and map out the ZigBee network and to discover services on ZigBee
devices. ZDOs are typically required when developing a ZigBee product that will interoperate in a public profile
such as home automation or smart energy, or when communicating with ZigBee devices from other vendors. The
ZDO can also be used to perform several management functions such as frequency agility (energy detect and
channel changes - Mgmt Network Update Request), discovering routes (Mgmt Routing Request) and neighbors
(Mgmt LQI Request), and managing device connectivity (Mgmt Leave and Permit Join Request).
The following table shows some of the more prominent ZDOs with their respective cluster identifier. Each ZDO
command has a defined payload. See the "ZigBee Device Profile" section of the ZigBee Specification for details.
ZDO Command
Network Address Request
IEEE Address Request
Node Descriptor Request
Simple Descriptor Request
Active Endpoints Request
Match Descriptor Request
Mgmt LQI Request
Mgmt Routing Request
Mgmt Leave Request
Mgmt Permit Joining Request
Mgmt Network Update Request
Cluster ID
0x0000
0x0001
0x0002
0x0004
0x0005
0x0006
0x0031
0x0032
0x0034
0x0036
0x0038
The Explicit Transmit API frame (0x11) is used to send ZigBee Device Objects commands to devices in the network.
Sending ZDO commands with the Explicit Transmit API frame requires some formatting of the data payload field.
When sending a ZDO command with the API, all multiple byte values in the ZDO command (API payload) (e.g. u16,
u32, 64-bit addresses) must be sent in little endian byte order for the command to be executed correctly on a
remote device.
For an API XBee to receive ZDO responses, the AO command must be set to 1 to enable the explicit receive API
frame.
The following table shows how the Explicit API frame can be used to send an "Active Endpoints" request to
discover the active endpoints on a device with a 16-bit address of 0x1234.
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Sending ZigBee Cluster Library (ZCL) Commands with the API
The ZigBee Cluster Library defines a set of attributes and commands (clusters) that can be supported in multiple
ZigBee profiles. The ZCL commands are typically required when developing a ZigBee product that will interoperate
in a public profile such as home automation or smart energy, or when communicating with ZigBee devices from
other vendors. Applications that are not designed for a public profile or for interoperability applications can skip
this section.
The following table shows some prominent clusters with their respective attributes and commands.
Cluster(Cluster ID)
Basic (0x0000)
Identify (0x0003)
Time (0x000A)
Thermostat (0x0201)
Attributes (Attribute ID)
Application Version (0x0001)
Hardware Version (0x0003)
Model Identifier (0x0005)
Identify Time (0x0000)
Time (0x0000)
Time Status (0x0001)
Time Zone (0x0002)
Local Temperature (0x0000)
Occupancy (0x0002)
Cluster ID
-Reset to defaults
(0x00)
Identify (0x00)
Identify Query (0x01)
-Setpoint raise / lower
(0x00)
The ZCL defines a number of profile-wide commands that can be supported on any profile, also known as general
commands. These commands include the following.
Command (Command ID)
Read Attributes (0x00)
Read Attributes Response (0x01)
Write Attributes (0x02)
Write Attributes Response (0x04)
Configure Reporting (0x06)
Report Attributes (0x0A)
Discover Attributes (0x0C)
Discover Attributes Response (0x0D)
Description
Used to read one or more attributes on a
remote device.
Generated in response to a read
attributes command.
Used to change one or more attributes on
a remote device.
Sent in response to a write attributes
command.
Used to configure a device to
automatically report on the values of one
or more of its attributes.
Used to report attributes when report
conditions have been satisfied.
Used to discover the attribute identifiers
on a remote device.
Sent in response to a discover attributes
command.
The Explicit Transmit API frame (0x11) is used to send ZCL commands to devices in the network. Sending ZCL
commands with the Explicit Transmit API frame requires some formatting of the data payload field.
When sending a ZCL command with the API, all multiple byte values in the ZCL command (API Payload) (e.g. u16,
u32, 64-bit addresses) must be sent in little endian byte order for the command to be executed correctly on a
remote device.
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Note: When sending ZCL commands, the AO command should be set to 1 to enable the explicit receive API frame.
This will provide indication of the source 64- and 16-bit addresses, cluster ID, profile ID, and endpoint information
for each received packet. This information is required to properly decode received data.
The following table shows how the Explicit API frame can be used to read the hardware version attribute from a
device with a 64-bit address of 0x0013A200 40401234 (unknown 16-bit address). This example uses arbitrary
source and destination endpoints. Recall the hardware version attribute (attribute ID 0x0003) is part of the basic
cluster (cluster ID 0x0000). The Read Attribute general command ID is 0x00.
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In the above example, the Frame Control field (offset 23) was constructed as follows:
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Name
Bits
Example Value Description
Frame Type
0-1
Manufacturer Specific
Direction
Disable Default Response
00 - Command acts across the entire
profile
0 - The manufacturer code field is omitted
from the ZCL Frame Header.
0 - The command is being sent from the
client side to the server side.
0 - Default response not disabled
Reserved
5-7
Set to 0.
See the ZigBee Cluster Library specification for details.
Sending Public Profile Commands with the API
Commands in public profiles such as Smart Energy and Home Automation can be sent with the XBee API using the
Explicit Transmit API frame (0x11). Sending public profile commands with the Explicit Transmit API frame requires
some formatting of the data payload field. Most of the public profile commands fit into the ZigBee Cluster Library
(ZCL) architecture as described in the previous section.
The following table shows how the Explicit API frame can be used to send a demand response and load control
message (cluster ID 0x701) in the smart energy profile (profile ID 0x0109) in the revision 14 Smart Energy
specification. The message will be a "Load Control Event" (command ID 0x00) and will be sent to a device with 64bit address of 0x0013A200 40401234 with a 16-bit address of 0x5678. The event will start a load control event for
water heaters and smart appliances, for a duration of 1 minute, starting immediately.
Note: When sending public profile commands, the AO command should be set to 1 to enable the explicit receive
API frame. This will provide indication of the source 64- and 16-bit addresses, cluster ID, profile ID, and endpoint
information for each received packet. This information is required to properly decode received data.
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In the above example, the Frame Control field (offset 23) was constructed as follows:
Name
Bits
Example Value Description
Frame Type
0-1
Manufacturer Specific
Direction
Disable Default Response
00 - Command is specific to a cluster
0 - The manufacturer code field is omitted
from the ZCL Frame Header.
0 - The command is being sent from the
server side to the client side.
0 - Default response not disabled
Reserved
5-7
Set to 0.
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10. XBee Command Reference Tables
Addressing
Addressing Commands
AT
Command
DH
DL
MY
MP
NC
SH
SL
NI
SE
DE
CI
NP
DO
Name and Description
Destination Address High.Set/Get the upper 32 bits of the 64-bit destination
address. When combined with DL, it defines the 64-bit destination address for data
transmission. Special definitions for DH and DL include 0x000000000000FFFF
(broadcast) and 0x0000000000000000 (coordinator).
Destination Address Low. Set/Get the lower 32 bits of the 64-bit destination
address. When combined with DH, it defines the 64-bit destination address for data
transmissions. Special definitions for DH and DL include 0x000000000000FFFF
(broadcast) and 0x0000000000000000 (coordinator).
16-bit Network Address. Read the 16-bit network address of the module. A value of
0xFFFE means the module has not joined a ZigBee network
16-bit Parent Network Address. Read the 16-bit network address of the module's
parent. A value of 0xFFFE means the module does not have a parent.
Number of Remaining Children. Read the number of end device children that can
join the device. If NC returns 0, then the device cannot allow any more end device
children to join.
Serial Number High. Read the high 32 bits of the module's unique 64-bit address.
Serial Number Low. Read the low 32 bits of the module's unique 64-bit address.
Node Identifier. Stores a string identifier. The register only accepts printable ASCII
data. In AT Command Mode, a string cannot start with a space. A carriage return
ends the command. Command will automatically end when maximum bytes for the
string have been entered. This string is returned as part of the ND (Node Discover)
command. This identifier is also used with the DN (Destination Node) command. In
AT command mode, an ASCII comma (0x2C) cannot be used in the NI string
Source Endpoint. Set/read the ZigBee application layer source endpoint value. This
value will be used as the source endpoint for all data transmissions. SE is only
supported in AT firmware. The default value 0xE8 (Data endpoint) is the Digi data
endpoint
Destination Endpoint. Set/read Zigbee application layer destination ID value. This
value will be used as the destination endpoint all data transmissions. DE is only
supported in AT firmware. The default value (0xE8) is the Digi data endpoint.
Cluster Identifier. Set/read Zigbee application layer cluster ID value. This value will
be used as the cluster ID for all data transmissions. CI is only supported in AT
firmware. The default value0x11 (Transparent data cluster ID).
Maximum RF Payload Bytes. This value returns the maximum number of RF
payload bytes that can be sent in a unicast transmission. If APS encryption is used
(API transmit option bit enabled), the maximum payload size is reduced by 9 bytes.
If source routing is used (AR < 0xFF), the maximum payload size is reduced further.
Note: NP returns a hexadecimal value. (e.g. if NP returns 0x54, this is equivalent to
84 bytes)
Device Type Identifier. Stores a device type value. This value can be used to
differentiate different XBee-based devices. Digi reserves the range 0 - 0xFFFFFF. For
example, Digi currently uses the following DD values to identify various ZigBee
products: 0x30001 - ConnectPort X8 Gateway 0x30002 - ConnectPort X4 Gateway
0x30003 - ConnectPort X2 Gateway 0x30005 - RS-232 Adapter 0x30006 - RS-485
Adapter 0x30007 - XBee Sensor Adapter 0x30008 - Wall Router 0x3000A - Digital I/O
Adapter 0x3000B - Analog I/O Adapter 0x3000C - XStick 0x3000F - Smart Plug
0x30011 - XBee Large Display 0x30012 - XBee Small Display
Node
Type
Parameter
Range
Default
CRE
0 - 0xFFFFFFFF
CRE
0 - 0xFFFFFFFF
0xFFFF(Coordinator)
0 (Router/End
Device)
CRE
CR
CRE
CRE
0 - 0xFFFE
[read-only]
0 - 0xFFFE
[read-only]
0xFFFE
0xFFFE
0 - MAX_CHILDREN
(maximum varies)
read-only
0 - 0xFFFFFFFF 
[read-only]
0 - 0xFFFFFFFF
[read-only]
factory-set
factory-set
CRE
20-Byte printable 
ASCII string
ASCII space
character (0x20)
CRE
0 - 0xFF
0xE8
CRE
0 - 0xFF
0xE8
CRE
0 - 0xFFFF
0x11
CRE
0 - 0xFFFF
[read-only]
CRE
0 - 0xFFFFFFFF
0x30000
Node types that support the command: C=Coordinator, R=Router, E=End Device
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Networking
Networking Commands
AT
Command
CH
ID
OP
NH
BH
OI
NT
NO
SC
SD
Name and Description
Operating Channel. Read the channel number used for transmitting and receiving
between RF modules. Uses 802.15.4 channel numbers. A value of 0 means the device
has not joined a PAN and is not operating on any channel.
Extended PAN ID. Set/read the 64-bit extended PAN ID. If set to 0, the coordinator
will select a random extended PAN ID, and the router / end device will join any
extended PAN ID. Changes to ID should be written to non-volatile memory using the
WR command to preserve the ID setting if a power cycle occurs.
Operating Extended PAN ID. Read the 64-bit extended PAN ID. The OP value reflects
the operating extended PAN ID that the module is running on. If ID > 0, OP will equal
ID.
Maximum Unicast Hops. Set / read the maximum hops limit. This limit sets the
maximum broadcast hops value (BH) and determines the unicast timeout. The
timeout is computed as (50 * NH) + 100 ms. The default unicast timeout of 1.6
seconds (NH=0x1E) is enough time for data and the acknowledgment to traverse
about 8 hops.
Broadcast Hops. Set/Read the maximum number of hops for each broadcast data
transmission. Setting this to 0 will use the maximum number of hops.
Operating 16-bit PAN ID. Read the 16-bit PAN ID. The OI value reflects the actual 16bit PAN ID the module is running on.
Node Discovery Timeout. Set/Read the node discovery timeout. When the network
discovery (ND) command is issued, the NT value is included in the transmission to
provide all remote devices with a response timeout. Remote devices wait a random
time, less than NT, before sending their response.
Network Discovery options. Set/Read the options value for the network discovery
command. The options bitfield value can change the behavior of the ND (network
discovery) command and/or change what optional values are returned in any
received ND responses or API node identification frames. Options include: 0x01 =
Append DD value (to ND responses or API node identification frames) 002 = Local
device sends ND response frame when ND is issued.
Scan Channels. Set/Read the list of channels to scan. Coordinator - Bit field list of
channels to choose from prior to starting network. Router/End Device - Bit field list
of channels that will be scanned to find a Coordinator/ Router to join. Changes to SC
should be written using WR command to preserve the SC setting if a power cycle
occurs.
Bit (Channel): 0 (0x0B) 4 (0x0F) 8 (0x13) 12 (0x17)
1 (0x0C) 5 (0x10) 9 (0x14) 13 (0x18)
2 (0x0D) 6 (0x11) 10 (0x15) 14 (0x19)
3 (0x0E) 7 (0x12) 11 (0x16) 15 (0x1A)
Scan Duration. Set/Read the scan duration exponent. Changes to SD should be
written using WR command. Coordinator - Duration of the Active and Energy Scans
(on each channel) that are used to determine an acceptable channel and Pan ID for
the Coordinator to startup on. Router / End Device - Duration of Active Scan (on
each channel) used to locate an available Coordinator / Router to join during
Association. Scan Time is measured as:(# Channels to Scan) * (2 ^ SD) * 15.36ms - The
number of channels to scan is determined by the SC parameter. The XBee can scan
up to 16 channels (SC = 0xFFFF).
Sample Scan Duration times (13 channel scan):
If SD = 0, time = 0.200 sec
SD = 2, time = 0.799 sec
SD = 4, time = 3.190 sec
SD = 6, time = 12.780 sec
Note: SD influences the time the MAC listens for beacons or runs an energy scan on a
given channel. The SD time is not a good estimate of the router/end device joining
time requirements. ZigBee joining adds additional overhead including beacon
processing on each channel, sending a join request, etc. that extend the actual joining
time.
© 2010 Digi International, Inc.
Node
Type
Parameter Range
Default
CRE
XBee
0, 0x0B - 0x1A
(Channels 11-26)
XBee-PRO
0, 0x0B - 0x18
(Channels 11-26)
[read-only]
CRE
00xFFFFFFFFFFFFFFFF
CRE
0x01 0xFFFFFFFFFFFFFFFF
[read-only]
CRE
0 - 0xFF
0x1E
CRE
0 - 0x1E
CRE
0 - 0xFFFF
[read-only]
CRE
0x20 - 0xFF [x 100
msec]
0x3
C (60d)
CRE
0 - 0x03 [bitfield]
CRE
XBee
1 - 0xFFFF [bitfield]
XBee-PRO
1 - 0xFFF [bitfield]
1FFE
CRE
0 - 7 [exponent]
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Networking Commands
AT
Command
ZS
NJ
JV
NW
JN
AR
Name and Description
ZigBee Stack Profile. Set / read the ZigBee stack profile value. This must be set the
same on all devices that should join the same network.
Node Join Time. Set/Read the time that a Coordinator/Router allows nodes to join.
This value can be changed at run time without requiring a Coordinator or Router to
restart. The time starts once the Coordinator or Router has started. The timer is reset
on power-cycle or when NJ changes.
Channel Verification. Set/Read the channel verification parameter. If JV=1, a router
will verify the coordinator is on its operating channel when joining or coming up from
a power cycle. If a coordinator is not detected, the router will leave its current
channel and attempt to join a new PAN. If JV=0, the router will continue operating on
its current channel even if a coordinator is not detected.
Network Watchdog Timeout. Set/read the network watchdog timeout value. If NW
is set > 0, the router will monitor communication from the coordinator (or data
collector) and leave the network if it cannot communicate with the coordinator for 3
NW periods. The timer is reset each time data is received from or sent to a
coordinator, or if a many-to-one broadcast is received.
Join Notification. Set / read the join notification setting. If enabled, the module will
transmit a broadcast node identification packet on power up and when joining. This
action blinks the Associate LED rapidly on all devices that receive the transmission,
and sends an API frame out the UART of API devices. This feature should be disabled
for large networks to prevent excessive broadcasts.
Aggregate Routing Notification. Set/read time between consecutive aggregate route
broadcast messages. If used, AR should be set on only one device to enable many-toone routing to the device. Setting AR to 0 only sends one broadcast
© 2010 Digi International, Inc.
Node
Type
Parameter Range
Default
CRE
0-2
CR
0 - 0xFF
[x 1 sec]
0XFF
(always allows
joining)
0 - Channel
verification disabled
1 - Channel
verification enabled
0 - 0x64FF
[x 1 minute]
(up to over 17 days)
0 (disabled)
RE
0-1
CR
0 - 0xFF
0 - 0xFF
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Security
Security Commands
AT
Command
EE
EO
NK
KY
Name and Description
Encryption Enable. Set/Read the encryption enable setting.
Encryption Options. Configure options for encryption. Unused option bits should be
set to 0. Options include:
0x01 - Send the security key unsecured over-the-air during joins
0x02 - Use trust center (coordinator only)
Network Encryption Key. Set the 128-bit AES network encryption key. This
command is write-only; NK cannot be read. If set to 0 (default), the module will select
a random network key.
Link Key. Set the 128-bit AES link key. This command is write only; KY cannot be
read. Setting KY to 0 will cause the coordinator to transmit the network key in the
clear to joining devices, and will cause joining devices to acquire the network key in
the clear when joining.
© 2010 Digi International, Inc.
Node
Type
Parameter Range
Default
CRE
0 - Encryption
disabled
1 - Encryption
enabled
CRE
0 - 0xFF
128-bit value
CRE
128-bit value
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RF Interfacing
RF Interfacing Commands
AT
Command
Name and Description
Node
Type
Parameter Range
Default
XBee (boost mode)
Channel 11-25
0 = 0 dBm
1 = 2 dBm
2 = 4 dBm
3 = 6 dBm
4 = 8 dBm
XBee (boost mode)
Channel 26
0 = 0 dBm
1 = 2 dBm
2 = 3 dBm
3 = 3dBm
4 = 3 dBm
PL
Power Level. Select/Read the power level at which the RF module transmits
conducted power. For XBee-PRO (S2B) Power Level 4 is calibrated and the other
power levels are approximate.
XBee
(Normal mode)
Channel 11-25
0 = -3 dBm
1 = -1 dBm
2 = 1 dBm
3 = 3 dBm
4 = 5 dBm
CRE
XBee
(Normal mode)
Channel 26
0 = -3 dBm
1 = -1 dBm
2 = 1 dBm
3 = 3 dBm
4 = 3 dBm
XBee-PRO
Channel 11-25
0 = 10 dBm
1 = 12 dBm
2 = 14 dBm
3 = 16 dBm
4 = 18 dBm
XBee-PRO
Channel 26
0 = 3 dBm
1 = 3 dBm
2 = 3 dBm
3 = 3 dBm
4 = 3 dBm
PM
DB
Power Mode. Set/read the power mode of the device. Enabling boost mode will
improve the receive sensitivity by 1dB and increase the transmit power by 2dB Note:
Enabling boost mode on the XBee-PRO (S2) will not affect the output power. Boost
mode imposes a slight increase in current draw. See section 1.2 for details.
Received Signal Strength. This command reports the received signal strength of the
last received RF data packet. The DB command only indicates the signal strength of
the last hop. It does not provide an accurate quality measurement for a multihop
link. DB can be set to 0 to clear it. The DB command value is measured in -dBm. For
example if DB returns 0x50, then the RSSI of the last packet received was -80dBm. As
of 2x6x firmware, the DB command value is also updated when an APS
© 2010 Digi International, Inc.
CRE
0-1,  0= -Boost
mode disabled,
1= Boost mode
enabled
CRE
0 - 0xFF Observed
range for XBee-PRO:
0x1A - 0x58 For
XBee: 0x 1A - 0x5C
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acknowledgment is received.
PP
Peak Power. Read the dBm output when maximum power is selected (PL4).
© 2010 Digi International, Inc.
CRE
0x0-0x12
[read only]
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XBee®/XBee‐PRO® SMT ZB RF Modules
Serial Interfacing
Serial Interfacing Commands
AT Command
Name and Description
Node
Type
AP
API Enable. Enable API Mode. The AP command is only supported when using API firmware: 21xx (API
coordinator), 23xx (API router), 29xx (API end device).
CRE
AO
API Options. Configure options for API. Current options select the type of receive API frame to send out the Uart
for received RF data packets.
CRE
BD
Interface Data Rate. Set/Read the serial interface data rate for communication between the module serial port
and host. Any value above 0x07 will be interpreted as an actual baud rate. When a value above 0x07 is sent, the
closest interface data rate represented by the number is stored in the BD register.
CRE
NB
Serial Parity. Set/Read the serial parity setting on the module.
CRE
SB
RO
Stop Bits. Set/read the number of stop bits for the UART. (Two stop bits are not supported if mark parity is
enabled.)
Packetization Timeout. Set/Read number of character times of inter-character silence required before
packetization. Set (RO=0) to transmit characters as they arrive instead of buffering them into one RF packet The
RO command is only supported when using AT firmware: 20xx (AT coordinator), 22xx (AT router), 28xx (AT end
device).
CRE
DIO7 Configuration. Select/Read options for the DIO7 line of the RF module.
CRE
D6
DIO6 Configuration. Configure options for the DIO6 line of the RF module.
CRE
1.
1-2
1 = API-enabled
2 = API-enabled
(w/escaped control
characters)
0 - Default receive API
indicators enabled
1 - Explicit Rx data
indicator API frame
enabled (0x91)
3 - enable ZDO
passthrough of ZDO
requests to the UART
which are not supported
by the stack, as well as
Simple_Desc_req,
Active_EP_req, and
Match_Desc_req.
0-7
(standard baud rates)
0 = 1200 bps
1 = 2400
2 = 4800
3 = 9600
4 = 19200
5 = 38400
6 = 57600
7 = 115200
0x80 - 0xE1000 (nonstandard rates up to
921kbps)
0 = No parity
1 = Even parity
2 = Odd parity
3 = Mark parity
0 = 1 stop bit
1 = 2 stop bits
0 - 0xFF
[x character times]
CRE
D7
Default
Parameter Range
0 = Disabled
1 = CTS Flow Control
3 = Digital input
4 = Digital output, low
5 = Digital output, high
6 = RS-485 transmit
enable (low enable) 7 = RS485 transmit enable (high
enable)
0 = Disabled
1 = RTS flow control 3 =
Digital input
4 = Digital output, low
5 = Digital output, high
Node types that support the command: C = Coordinator, R = Router, E = End Device
© 2010 Digi International, Inc.
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XBee®/XBee‐PRO® SMT ZB RF Modules
Serial Interfacing
Serial Interfacing Commands
AT
Command
IR
IC
Name and Description
IO Sample Rate. Set/Read the IO sample rate to enable periodic sampling. For
periodic sampling to be enabled, IR must be set to a non-zero value, and at least one
module pin must have analog or digital IO functionality enabled (see D0-D8, P0-P2
commands). The sample rate is measured in milliseconds.
IO Digital Change Detection. Set/Read the digital IO pins to monitor for changes in
the IO state. IC works with the individual pin configuration commands (D0-D8, P0-P2).
If a pin is enabled as a digital input/output, the IC command can be used to force an
immediate IO sample transmission when the DIO state changes. IC is a bitmask that
can be used to enable or disable edge detection on individual channels. Unused bits
should be set to 0. Bit (IO pin): 0 (DIO0)4 (DIO4)8 (DIO8) 1 (DIO1) 5 (DIO5) 9 (DIO9) 2
(DIO2) 6 (DIO6) 10 (DIO10) 3 (DIO3) 7 (DIO7) 11 (DIO11)
Node
Type
Parameter Range
Default
CRE
0, 0x32:0xFFFF (ms)
CRE
0 - 0xFFFF
P0
PWM0 Configuration. Select/Read function for PWM0.
CRE
P1
DIO11 Configuration. Configure options for the DIO11 line of the RF module.
CRE
P2
DIO12 Configuration. Configure options for the DIO12 line of the RF module.
CRE
P3
DIO13 Configuration. Set/Read function for DIO13.
CRE
P4
DIO14 Configuration. UART Data In
CRE
P5
DIO15 Configuration. Set for SPI function
CRE
P6
DIO16 Configuration. Set for SPI function
CRE
P7
DIO17 Configuration. Set for SPI function
CRE
P8
DIO18 Configuration. Set for SPI function
CRE
P9
DIO19 Configuration. Set for SPI function
CRE
© 2010 Digi International, Inc.
1 = RSSI PWM
3 - Digital input,
monitored
4 - Digital output,
default low
5 - Digital output,
default high
0 - Unmonitored
digital input
3- Digital input,
monitored
4- Digital output,
default low
5- Digital output,
default high
0 - Unmonitored
digital input
3- Digital input,
monitored
4- Digital output,
default low
5- Digital output,
default high
0 - Unmonitored
digital input
3- Digital input,
monitored
4- Digital output,
default low
5- Digital output,
default high
3-Digital Input,
monitored
(not set-able)
0-Unmonitored
digital input
1-SPI MISO
0-Unmonitored
digital input
1-SPI MOSI
0-Unmonitored
digital input
1-SPI nSSEL
0-Unmonitored
digital input
1-SPI SCLK
0-Unmonitored
digital input
1-SPI nATTN
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XBee®/XBee‐PRO® SMT ZB RF Modules
Serial Interfacing Commands
AT
Command
Name and Description
Node
Type
D0
AD0/DIO0 Configuration. Select/Read function for AD0/DIO0.
CRE
D1
AD1/DIO1 Configuration. Select/Read function for AD1/DIO1
CRE
D2
AD2/DIO2 Configuration. Select/Read function for AD2/DIO2
CRE
D3
AD3/DIO3 Configuration. Select/Read function for AD3/DIO3.
CRE
D4
DIO4 Configuration. Select/Read function for DIO4.
CRE
D5
DIO5 Configuration. Configure options for the DIO5 line of the RF module.
CRE
D6
DIO6 Configuration. Configure options for the DIO5 line of the RF module.
CRE
© 2010 Digi International, Inc.
Parameter Range
Default
1 – Commissioning
button enabled
2-Analog input,
single ended
3 - Digital input,
monitored
4 - Digital output,
default low
5 - Digital output,
default high
0 - Unmonitored
digital input
2-Analog input,
single ended
3- Digital input,
monitored
4- Digital output,
default low
5- Digital output,
default high
0 - Unmonitored
digital input
2-Analog input,
single ended
3- Digital input,
monitored
4- Digital output,
default low
5- Digital output,
default high
0 - Unmonitored
digital input
3- Digital input,
monitored
4- Digital output,
default low
5- Digital output,
default high
0 - Unmonitored
digital input
3- Digital input,
monitored
4- Digital output,
default low
5- Digital output,
default high
0 = Disabled
1 = Associated
indication LED
3 = Digital input
4 = Digital output,
default low
5 = Digital output,
default high
0 = Disabled
1 = RTS indication
3 = Digital input
4 = Digital output,
default low
5 = Digital output,
default high)
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XBee®/XBee‐PRO® SMT ZB RF Modules
Serial Interfacing Commands
AT
Command
Name and Description
Node
Type
D7
DIO7 Configuration. Configure options for the DIO5 line of the RF module.
CRE
D8
DIO8 Configuration. Configure options for the DIO5 line of the RF module.
CRE
LT
PR
RP
%V
V+
TP
Assoc LED Blink Time. Set/Read the Associate LED blink time. If the Associate LED
functionality is enabled (D5 command), this value determines the on and off blink
times for the LED when the module has joined a network. If LT=0, the default blink
rate will be used (500ms coordinator, 250ms router/end device). For all other LT
values, LT is measured in 10ms.
Pull-up Resistor. Set/read the bit field that configures the internal pull-up resistor
status for the I/O lines. "1" specifies the pull-up resistor is enabled. "0" specifies no
pullup.(30k pull-up resistors)
Bits:*
0 - DIO4 (Pin 11)
1 - AD3 / DIO3 (Pin 17)
2 - AD2 / DIO2 (Pin 18)
3 - AD1 / DIO1 (Pin 19)
4 - AD0 / DIO0 (Pin 20)
5 - RTS / DIO6 (Pin 16)
6 - DTR / Sleep Request / DIO8 (Pin 9)
7 - DIN / Config (Pin 3)
8 - Associate / DIO5 (Pin 15)
9 - On/Sleep / DIO9 (Pin 13)
10 - DIO12 (Pin 4)
11 - PWM0 / RSSI / DIO10 (Pin 6)
12 - PWM1 / DIO11 (Pin 7)
13 - CTS / DIO7 (Pin 12)
RSSI PWM Timer. Time the RSSI signal will be output on the PWM after the last RF
data reception or APS acknowledgment.. When RP = 0xFF, output will always be on.
Supply Voltage. Reads the voltage on the Vcc pin. Scale by 1200/1024 to convert to
mV units. For examplee, a %V reading of 0x900 (2304 decimal) represents 2700mV or
2.7OV.
Voltage Supply Monitoring. The voltage supply threshold is set with the V+
command. If the measured supply voltage falls below or equal to this threshold, the
supply voltage will be included in the IO sample set. V+ is set to 0 by default (do not
include the supply voltage). Scale mV units by 1024/1200 to convert to internal units.
For example, for a 2700mV threshold enter 0x900.
Given the operating Vcc ranges for different platforms, and scaling by 1024/1200, the
useful parameter ranges are:
XBee 2100-3600 mV 0,0x0700-0x0c00
XBee-PRO 2700-3400 mV, 0,0x0a00-0x0b55
Reads the module temperature in Degrees Celsius. Accuracy +/- 7 degrees. 1° C =
0x0001 and -1° C = 0xFFFF. Command is only available in PRO S2B.
© 2010 Digi International, Inc.
Parameter Range
Default
0 = Disabled
1 = CTS indication
3 = Digital input
4 = Digital output,
default low
5 = Digital output,
default high)
0 - Unmonitored
digital input
3- Digital input,
monitored
4- Digital output,
default low
5- Digital output,
default high
3,4
CRE
0, 0x0A - 0xFF (100 2550 ms)
CRE
0 - 0x3FFF
0 - 0x1FFF
CRE
0 - 0xFF [x 100 ms]
0x28 (40d)
CRE
-0x-0xFFFF
[read only]
CRE
0-0xFFFF
CRE
0x0-0xFFFF
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XBee®/XBee‐PRO® SMT ZB RF Modules
Diagnostics Interfacing
Diagnostics Commands
AT
Command
VR
HV
AL
TP
1.
Name and Description
Firmware Version. Read firmware version of the module.
The firmware version returns 4 hexadecimal values (2 bytes) "ABCD". Digits ABC are
the main release number and D is the revision number from the main release. "B" is a
variant designator.
XBee and XBee-PRO ZB modules return:
firmware versions.
XBee and XBee-PRO ZNet modules return:
firmware versions. ZNet firmware is not compatible with ZB firmware.
Hardware Version. Read the hardware version of the module.
This command can be used to distinguish among different hardware platforms. The
upper byte returns a value that is unique to each module type. The lower byte
indicates the hardware revision.
XBee ZB and XBee ZNet modules return the following (hexadecimal) values:
0x19xx - XBee module
0x1Axx - XBee-PRO module
Association Indication. Read information regarding last node join request:
0x00 - Successfully formed or joined a network. (Coordinators form a network,
routers and end devices join a network.)
0x21 - Scan found no PANs
0x22 - Scan found no valid PANs based on current SC and ID settings
0x23 - Valid Coordinator or Routers found, but they are not allowing joining (NJ
expired)
0x27 - Node Joining attempt failed (typically due to incompatible security settings)
0x2A - Coordinator Start attempt failed‘
0x2B - Checking for an existing coordinator
0xAB - Attempted to join a device that did not respond.
0xAC - Secure join error - network security key received unsecured
0xAD - Secure join error - network security key not received
0xAF - Secure join error - joining device does not have the right preconfigured link
key
0xFF - Scanning for a ZigBee network (routers and end devices)
Note: New non-zero AI values may be added in later firmware versions. Applications
should read AI until it returns 0x00, indicating a successful startup (coordinator) or
join (routers and end devices)
Reads the module temperature in Degrees Celsius. Accuracy +/- 7 degrees. 1° C =
0x0001 and -1° C = 0xFFFF. Command is only available in PRO S2B.
Node
Type
Parameter Range
Default
CRE
0 - 0xFFFF [readonly]
Factory-set
CRE
0 - 0xFFFF [readonly]
Factory-set
CRE
0 - 0xFF [readonly]
CRE
0x0-0xFFFF
Node types that support the command: C = Coordinator, R = Router, E = End Device
© 2010 Digi International, Inc.
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XBee®/XBee‐PRO® SMT ZB RF Modules
AT Command Options
AT Command Options Commands
AT
Command
Node
Type
Parameter Range
Default
CRE
2 - 0x028F [x 100
ms]
0x64 (100d)
CRE
CRE
1 - 0x0CE4 [x 1 ms]
(max of 3.3 decimal
sec)
0x3E8
(1000d)
CRE
0 - 0xFF
0x2B
(‘+’ ASCII)
Node
Type
Parameter Range
Default
RE
0-Sleep disabled
(router)
1-Pin sleep enabled
4-Cyclic sleep
enabled
5 - Cyclic sleep, pin
wake
0 - Router 4 - End
Device
CRE
1 - 0xFFFF
0x20 - 0xAF0 x 10ms
(Quarter second
resolution)
0x20
0 - 0xFF
0 - 0xFFFF (x 1ms)
0 - 0x1770 (10msec)
Command Mode Timeout. Set/Read the period of inactivity (no valid commands
received) after which the RF module automatically exits AT Command Mode and
returns to Idle Mode.
Exit Command Mode. Explicitly exit the module from AT Command Mode.
CT
CN
Guard Times. Set required period of silence before and after the Command Sequence
Characters of the AT Command Mode Sequence (GT + CC + GT). The period of silence
is used to prevent inadvertent entrance into AT Command Mode.
between Guard Times of the AT Command Mode Sequence (GT + CC + GT). The AT
Command Mode Sequence enters the RF module into AT Command Mode. The CC
command is only supported when using AT firmware: 20xx (AT coordinator), 22xx (AT
router), 28xx (AT end device).
GT
CC
1.
Name and Description
Node types that support the command: C = Coordinator, R = Router, E = End Device
Sleep Commands
Sleep Commands
AT
Command
Name and Description
SM
Sleep Mode Sets the sleep mode on the RF module. An XBee loaded with router
firmware can be configured as either a router (SM set to 0) or an end device (SM > 0).
Changing a device from a router to an end device (or vice versa) forces the device to
leave the network and attempt to join as the new device type when changes are
applied
SN
SP
SO
Command
WH
Number of Sleep Periods. Sets the number of sleep periods to not assert the
On/Sleep pin on wakeup if no RF data is waiting for the end device. This command
allows a host application to sleep for an extended time if no RF data is present
Sleep Period. This value determines how long the end device will sleep at a time, up
to 28 seconds. (The sleep time can effectively be extended past 28 seconds using the
SN command.) On the parent, this value determines how long the parent will buffer a
message for the sleeping end device. It should be set at least equal to the longest SP
time of any child end device.
Sleep Options. Configure options for sleep. Unused option bits should be set to 0.
Sleep options include:
0x02 - Always wake for ST time
0x04 - Sleep entire SN *
SP time Sleep options should not be used for most applications. See chapter 6 for
more information.
Wake Host. Set/Read the wake host timer value. If the wake host timer is set to a
non-zero value, this timer specifies a time (in millisecond units) that the device
should allow after waking from sleep before sending data out the UART or
transmitting an IO sample. If serial characters are received, the WH timer is stopped
immediately.
SI
Sleep Immediately. See Execution Commands table below..
PO
Polling Rate. Sets the polling rate for the end device.
© 2010 Digi International, Inc.
0x00 (100 msec)
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XBee®/XBee‐PRO® SMT ZB RF Modules
Execution Commands
Where most AT commands set or query register values, execution commands cause an action to be executed on
the module. Execution commands are executed immediately and do not require changes to be applied.
Execution Commands
AT
Command
AC
WR
RE
FR
NR
SI
CB
ND
Name and Description
Apply Changes. Applies changes to all command registers causing queued command
register values to be applied. For example, changing the serial interface rate with the
BD command will not change the UART interface rate until changes are applied with
the AC command. The CN command and 0x08 API command frame also apply
changes.
Write. Write parameter values to non-volatile memory so that parameter
modifications persist through subsequent resets. Note: Once WR is issued, no
additional characters should be sent to the module until after the "OK\r" response is
received. The WR command should be used sparingly. The EM250 supports a limited
number of write cycles.*
Restore Defaults. Restore module parameters to factory defaults.
Software Reset. Reset module. Responds immediately with an OK status, and then
performs a software reset about 2 seconds later.
Network Reset. Reset network layer parameters on one or more modules within a
PAN. Responds immediately with an “OK” then causes a network restart. All network
configuration and routing information is consequently lost.
If NR = 0: Resets network layer parameters on the node issuing the command.
If NR = 1: Sends broadcast transmission to reset network layer parameters on all
nodes in the PAN.
Sleep Immediately. Cause a cyclic sleep module to sleep immediately rather than
wait for the ST timer to expire.
Commissioning Pushbutton. This command can be used to simulate commissioning
button presses in software. The parameter value should be set to the number of
button presses to be simulated. For example, sending the ATCB1 command will
execute the action associated with 1 commissioning button press.
Node Discover. Discovers and reports all RF modules found. The following
information is reported for each module discovered.
MY
SH
SL
NI (Variable length)
PARENT_NETWORK ADDRESS (2 Bytes)
DEVICE_TYPE (1 Byte: 0=Coord, 1=Router, 2=End Device)
STATUS (1 Byte: Reserved)
PROFILE_ID (2 Bytes)
MANUFACTURER_ID (2 Bytes)
After (NT * 100) milliseconds, the command ends by returning a . ND also
accepts a Node Identifier (NI) as a parameter (optional). In this case, only a module
that matches the supplied identifier will respond.
If ND is sent through the API, each response is returned as a separate
AT_CMD_Response packet. The data consists of the above listed bytes without the
carriage return delimiters. The NI string will end in a "0x00" null character. The radius
of the ND command is set by the BH command.
© 2010 Digi International, Inc.
Node
Type
Parameter Range
Default
CRE
CRE
CRE
CRE
CRE
0 -1
optional 20-Byte 
NI or MY value
CRE
CRE
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XBee®/XBee‐PRO® SMT ZB RF Modules
Execution Commands
AT
Command
Name and Description
Node
Type
Parameter Range
Default
DN
Destination Node. Resolves an NI (Node Identifier) string to a physical address (casesensitive). The following events occur after the destination node is discovered: 
1. DL & DH are set to the extended (64-bit) address of the module with the matching
NI (Node Identifier) string.
2. OK (or ERROR)\r is returned.
3. Command Mode is exited to allow immediate communication

1.
The 16-bit network and 64-bit extended addresses are returned in an API
Command Response frame.
If there is no response from a module within (NT * 100) milliseconds or a parameter
is not specified (left blank), the command is terminated and an “ERROR” message is
returned. In the case of an ERROR, Command Mode is not exited. The radius of the
DN command is set by the BH command.
CRE
up to 20-Byte
printable ASCII
string
IS
Force Sample Forces a read of all enabled digital and analog input lines.
CRE
1S
XBee Sensor Sample. Forces a sample to be taken on an XBee Sensor device. This
command can only be issued to an XBee sensor device using an API remote
command.
RE
Node types that support the command: C = Coordinator, R = Router, E = End Device
© 2010 Digi International, Inc.
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XBee®/XBee‐PRO® SMT ZB RF Modules
11. Module Support
This chapter provides customization information for the XBee/XBee-PRO ZB modules. In addition to providing an
extremely flexible and powerful API, the XBee and XBee-PRO ZB modules are a robust development platform that
have passed FCC and ETSI testing. Developers can customize default parameters, or even write or load custom
firmware for Ember's EM357 chip.
X-CTU Configuration Tool
Digi provides a Windows X-CTU configuration tool for configuring module parameters and updating firmware. The
XCTU has the capability to do the following:
•Discover all XBee devices in the network
•Update firmware on a local module (requires USB or serial connection)
•Read or write module configuration parameters on a local or remote device
•Save and load configuration profiles containing customized settings.
Contact Digi support for more information about the X-CTU.
Customizing XBee ZB Firmware
Once module parameters are tested in an application and finalized, Digi can manufacture modules with specific,
customer-defined configurations for a nominal fee. These custom configurations can lock in a firmware version or
set command values when the modules are manufactured, eliminating the need for customers to adjust module
parameters on arrival. Alternatively, Digi can program custom firmware, including Ember's EZSP UART image, into
the modules during manufacturing. Contact Digi to create a custom configuration.
Design Considerations for Digi Drop-In Networking
XBee/XBee-PRO embedded RF modules contain a variety of features that allow for interoperability with Digi's full
line of Drop-in Networking products. Interoperability with other "DIN" products can offer these advantages:
•Add IP-connectivity to your network via Cellular, Ethernet or WiFi with a ConnectPort X Gateway.
•Extend the range of your network with the XBee Wall Router.
•Make deployment easy by enabling the Commissioning Pushbutton (pin 20) and AssociateLED (pin 15) to
oper-ate with the Network Commissioning Tool software.
•Interface with standard RS-232, USB, Analog & Digital I/O, RS-485, and other industrial devices using
XBee Adapters.
•Monitor and manage your network securely from remote locations with iDigi Platform.
•We encourage you to contact our technical representatives for consideration, implementation, or design
review of your product for interoperability with Digi's Drop-in Networking solutions.
XBee Bootloader
XBee modules use a modified version of Ember’s bootloader. This bootloader version supports a custom entry
mechanism that uses module pins DIN (pin 3), DTR / SLEEP_RQ (pin 9), and RTS (pin 16). To invoke the bootloader,
do the following:
© 2010 Digi International, Inc.
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XBee®/XBee‐PRO® SMT ZB RF Modules
1. Set DTR / SLEEP_RQ low (TTL 0V) and RTS high.
2. Send a serial break to the DIN pin and power cycle or reset the module.
3. When the module powers up, DTR / SLEEP_RQ and DIN should be low (TTL 0V) and RTS should be high.
4. Terminate the serial break and send a carriage return at 115200bps to the module.
5. If successful, the module will send the Ember bootloader menu out the DOUT pin at 115200bps.
6. Commands can be sent to the bootloader at 115200bps.
Note: Hardware flow control should be disabled when entering and communicating with the EM250 bootloader.
Programming XBee Modules
Firmware on the XBee and XBee-PRO ZB modules can be updated through one of two means:
•Serially
•SIF header.
Each method is described below.
Serial Firmware Updates
Serial firmware updates make use of the XBee custom bootloader which ships in all units. This modified bootloader
is based on Ember's standalone bootloader, but with a modified entry mechanism. The modified entry mechanism
uses module pins 4, 10, and 30 (DIN, DTR, and RTS respectively).
The X-CTU program can update firmware serially on the XBee and XBee-PRO ZB modules. Contact Digi support for
details.
If an application requires custom firmware to update the XBee firmware serially, the following steps are required.
Invoke XBee Bootloader
See the "XBee Bootloader" section above for steps to invoke the bootloader
Send Firmware Image
After invoking the bootloader, the Ember bootloader will send the bootloader menu characters out the UART at
115200 bps. The application should do the following to upload a firmware image.
1. Look for the bootloader prompt "BL >" to ensure the bootloader is active
2. Send an ASCII "1" character to initiate a firmware update
3. After sending a "1", the EM250 waits for an XModem CRC upload of an .ebl image over the serial line at
115200 bps. The .ebl file must be sent to the EM250 in order.
If no serial transaction is initiated within a 60 second timeout period, the bootloader times out and returns to the
menu. If the upload is interrupted with a power cycle or reset event, the EM250 will detect an invalid application
image and enter bootloader mode. The entire ebl image should be uploaded again to recover. If an error occurs
while uploading, the EM250 bootloader returns an error code from the following table:
© 2010 Digi International, Inc.
Page 157
XBee®/XBee‐PRO® SMT ZB RF Modules
Hex Error
Code
0x21
0x22
0x23
0x24
0x25
0x26
0x27
0x41
0x42
0x43
0x44
0x45
0x46
0x47
0x48
0x49
0x4A
0x4B
0x4C
0x4D
Description
The bootloader encountered an error while trying to parse the Start of
Header (SOH) character in the XModem frame.
The bootloader detected an invalid checksum in the XModem frame.
The bootloader encountered an error while trying to parse the high
byte of the CRC in the XModem frame.
The bootloader encountered an error while trying to parse the low
byte of the CRC in the XModem frame.
The bootloader encountered an error in the sequence number of the
current XModem frame.
The frame that the bootloader was trying to parse was deemed
incomplete (some bytes missing or lost).
The bootloader encountered a duplicate of the previous XModem
frame.
No .ebl header was received when expected.
Header failed CRC.
File failed CRC.
Unknown tag detected in .ebl image.
Invalid .ebl header signature.
Trying to flash odd number of bytes.
Indexed past end of block buffer.
Attempt to overwrite bootloader flash.
Attempt to overwrite SIMEE flash.
Flash erase failed.
Flash write failed.
End tag CRC wrong length.
Received data before query request/response
Writing Custom Firmware
The XBee/XBee-PRO module can be used as a hardware development platform for the EM250. Custom firmware
images can be developed around the EmberZNet 2.5.x and 3.x mesh stacks (for the EM250) and uploaded to the
XBee.
Warning: If programming firmware through the SIF interface, be aware that uploading firmware through the SIF
header can potentially erase the XBee bootloader. If this happens, serial firmware updates will not work.
Regulatory Compliance
XBee modules are FCC and ETSI certified for operation on all 16 channels. The EM357 output power can be
configured up to 8dBm with boost mode enabled.
XBee-PRO modules are certified for operation on 15 of the 16 band channels (channels 11 - 25). The scan channels
mask of XBee-PRO devices must be set in the application to disable the upper two channels (e.g. 0x01FFF800). The
XBee-PRO contains power compensation circuitry to adjust the output power near 18dBm. For best results, the
EM357 should be configured with an output power level of -4dBm. The end product is responsible to adhere to
these requirements.
© 2010 Digi International, Inc.
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Configuring GPIOs
Most of the remaining sections in this chapter describe how to configure GPIO to function correctly in custom
applications that run on the XBee and XBee-PRO modules. In order for the GPIO to be configurable, the application
must set the GPIO_CFG register to enable the appropriate GPIO. The following table lists values for configuring the
GPIO pins. Other functionality is affected by these settings. See the EM357 datasheet from Ember for a complete
listing of functionality.
GPIO Mode
GPIO_PxCFGH/L
Description
Analog
0x0
Analog input or output. When in analog mode, the digital input (GPIO_PxIN)
always reads 1.
Input (floating)
0x4
Digital input without an internal pull up or pull down. Output is disabled.
Input (pull-up or
pull-down)
0x8
Digital input with an internal pull up or pull down. A set bit in GPIO_PxOUT
selects pull up and a cleared bit selects pull down. Output is disabled.
Output (push-pull)
0x1
Push-pull output. GPIO_PxOUT controls the output.
Output (opendrain)
0x5
Open-drain output. GPIO_PxOUT controls the output. If a pull up is required,
it must be external.
Alternate Output
(push-pull)
0x9
Push-pull output. An onboard peripheral controls the output.
Alternate Output
(open-drain)
0xD
Open-drain output. An onboard peripheral controls the output. If a pull up is
required, it must be external.
The GPIO CFG command is used to configure the functionality of the GPIOs. The GPIOs are configured in 3 ports (A, B and C).
For example, to Configure port A for all input (floating) the following command would be used:
GPIOCFG PA 44444444.
To configure Port B with GPIO 0,2,4, and 6 for Output (open-drain), and the other GPIOs in port B for output(push-pull) the
following would be used:
GPIOCFG PB 51515151.
For more information on configuring and setting GPIOs consult the EM357 specification.
Detecting XBee vs. XBee-PRO
For some applications, it may be necessary to determine if the code is running on an XBee or an XBee-PRO device.
The GPIO1 pin on the EM357 is used to identify the module type (see table 1-03 in chapter 1). GPIO1 is connected
to ground on the XBee module. The following code could be used to determine if a module is an XBee or XBeePRO:
GPIO_DIRCLRL = GPIO(1);// Set GPIO1 as an input
GPIO_PUL |= GPIO(1);// Enable GPIO1 pull-up resistor
ModuleIsXBeePro = (GPIO_INL & GPIO(1));//ModuleIsXBeePro > 0 if XBee-PRO, =0 if non-PRO.
© 2010 Digi International, Inc.
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XBee®/XBee‐PRO® SMT ZB RF Modules
12. Agency Certifications
United States FCC
The XBee RF Module complies with Part 15 of the FCC rules and regulations. Compliance with the labeling
requirements, FCC notices and antenna usage guidelines is required.
To fulfill FCC Certification, the OEM must comply with the following regulations:
1. The system integrator must ensure that the text on back side of the module is placed on the outside of
the final product.
2. XBee RF Module may only be used with antennas that have been tested and approved for use with this
module [refer to the antenna tables in this section].
OEM Labeling Requirements
WARNING: The Original Equipment Manufacturer (OEM) must ensure that FCC labeling requirements
are met. This includes a clearly visible label on the outside of the final product enclosure that displays
the contents shown in the figure below.
Required FCC Label for OEM products containing the XBee S2C RF Module
Contains FCC ID: MCQ-XBS2C
The enclosed device complies with Part 15 of the FCC Rules. Operation is subject to the following two conditions:
(i.) this device may not cause harmful interference and (ii.) this device must accept any interference received,
including interference that may cause undesired operation.
Required FCC Label for OEM products containing the XBee-PRO S2C RF Module
Contains FCC ID: MCQ-XBPS2C
The enclosed device complies with Part 15 of the FCC Rules. Operation is subject to the following two conditions:
(i.) this device may not cause harmful interference and (ii.) this device must accept any interference received,
including interference that may cause undesired operation.
FCC Notices
IMPORTANT: The XBee and XBee PRO RF Module have been certified by the FCC for use with other products
without any further certification (as per FCC section 2.1091). Modifications not expressly approved by Digi could
void the user's authority to operate the equipment.
© 2010 Digi International, Inc.
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XBee®/XBee‐PRO® SMT ZB RF Modules
IMPORTANT: OEMs must test final product to comply with unintentional radiators (FCC section 15.107 & 15.109)
before declaring compliance of their final product to Part 15 of the FCC Rules.
IMPORTANT: The RF module has been certified for remote and base radio applications. If the module will be used
for portable applications, the device must undergo SAR testing.
This equipment has been tested and found to comply with the limits for a Class B digital device, pursuant to Part
15 of the FCC Rules. These limits are designed to provide reasonable protection against harmful interference in a
residential installation. This equipment generates, uses and can radiate radio frequency energy, and if not installed
and used in accordance with the instructions, may cause harmful interference to radio communications. However,
there is no guarantee that interference will not occur in a particular installation.
If this equipment does cause harmful interference to radio or television reception, which can be determined by
turning the equipment off and on, the user is encouraged to try to correct the interference by one or more of the
following measures: Re-orient or relocate the receiving antenna, Increase the separation between the equipment
and receiver, Connect equipment and receiver to outlets on different circuits, or Consult the dealer or an
experienced radio/TV technician for help.
FCC-Approved Antennas (2.4 GHz)
The XBee and XBee-PRO RF Module can be installed utilizing antennas and cables constructed with non-standard
connectors (RPSMA, RPTNC, etc.).
The modules are FCC approved for fixed base station and mobile applications for the channels indicated in the
tables below. If the antenna is mounted at least 20cm (8 in.) from nearby persons, the application is considered a
mobile application. Antennas not listed in the table must be tested to comply with FCC Section 15.203 (Unique
Antenna Connectors) and Section 15.247 (Emissions).
XBee RF Modules: XBee RF Modules have been tested and approved for use with all the antennas listed in the
tables below. (Cable-loss IS required when using gain antennas as shown below.)
The antennas in the tables below have been approved for use with this module. Digi does not carry all of these
antenna variants. Contact Digi Sales for available antennas.
© 2010 Digi International, Inc.
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XBee®/XBee‐PRO® SMT ZB RF Modules
Antennas approved for use with the XBee and XBee-PRO RF Modules (Cable-loss is not required.)
OMNI-DIRECTIONAL ANTENNAS for All Available Channels
Part
Number
Type (Description)
Integrated PCB antenna
29000294
A24HASM-450
A24HABSM
A24HABUF-P5I
A24HASM-525
A24-QI
A24-F2NF
A24-F3NF
A24-F5NF
A24-F8NF
A24-F9NF
A24-F10NF
A24-F12NF
A24-F15NF
A24-W7NF
A24-M7NF
Integral PCB antenna
Dipole (Half-wave
articulated RPSMA-4.5")
Dipole (Articulated RPSMA)
Dipole (Half-wave bulkhead
mount U.FL s/ 5" pigtail)
Dipole (Half-wave
articulated RPSMA-5.25")
Monopole (Integrated Whip)
Omin-Directional (Fiberglass
base station)
Omin-Directional (Fiberglass
base station)
Omin-Directional (Fiberglass
base station)
Omin-Directional (Fiberglass
base station)
Omin-Directional (Fiberglass
base station)
Omin-Directional (Fiberglass
base station)
Omin-Directional (Fiberglass
base station)
Omin-Directional (Fiberglass
base station)
Omin-Directional ( base
station)
Omin-directional (Magmount base station)
© 2010 Digi International, Inc.
Gain
dBi
-0.5
dBi
2.1
dBi
2.1
dBi
2.1
dBi
2.1
dBi
1.5
dBi
2.1
dBi
3.0
dBi
5.0
dBi
8.0
dBi
9.5
dBi
10
dBi
12
dBi
15
dBi
7.2
dBi
7.2
dBi
Min
Separation
Minimum Cable
Loss/Power
Reduction/Attenuation
Required
Fixed/Mobile
20 cm
N/A
Fixed/Mobile
20 cm
N/A
Fixed
20 cm
N/A
Fixed
20 cm
N/A
Fixed/Mobile
20 cm
N/A
Fixed
20 cm
N/A
Fixed/Mobile
20 cm
N/A
Fixed/Mobile
20 cm
N/A
Fixed/Mobile
20 cm
N/A
Fixed
20 cm
N/A
Fixed
2m
N/A
Fixed
2m
N/A
Fixed
2m
N/A
Fixed
2m
N/A
Fixed
2m
N/A
Fixed
2m
N/A
Fixed
2m
N/A
Application
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XBee®/XBee‐PRO® SMT ZB RF Modules
Antennas approved for use with the XBee and XBee-PRO RF Modules (Cable-loss is not required.)
PANEL CLASS ANTENNAS for All Available Channels
Part Number
Type (Description)
A24-P8SF
Flat Panel
A24-P8NF
Flat Panel
A24-P13NF
Flat Panel
A24-P14NF
Flat Panel
Gain
8.5
dBi
8.5
dBi
13
dBi
14
dBi
Application
Min
Separation
Minimum Cable
Loss/Power
Reduction/Attenuation
Required
Fixed
2m
N/A
Fixed
3m
N/A
Fixed
4m
N/A
Fixed
5m
N/A
Antennas approved for XBee and XBee-PRO RF Module Channels 11-25
YAGI CLASS ANTENNAS for Channel 11-25
Part Number
Type (Description)
Gain
Application
Min
Separation
Minimum Cable
Loss/Power
Reduction/Attenuation
Required
A24-Y6NF
Yagi (6 element)
8.8dBi
Fixed
2m
N/A
A24-Y7NF
Yagi (7 element)
Fixed
2m
N/A
A24-Y9NF
Yagi (9 element)
Fixed
2m
N/A
A24-Y10NF
Yagi (10 element)
Fixed
2m
N/A
A24-Y12NF
Yagi (12element)
Fixed
2m
N/A
A24-Y13NF
Yagi (13 element)
Fixed
2m
N/A
A24-Y15NF
Yagi (15 element)
Fixed
2m
N/A
A24-Y16NF
Yagi (16 element)
Fixed
2m
N/A
A24-Y16RM
Yagi (16 element, RPSMA connector)
Fixed
2m
N/A
A24-Y18NF
Yagi (18 element)
Fixed
2m
N/A
A24-P15NF
Flat Panel
Fixed
2m
N/A
A24-P16NF
Flat Panel
Fixed
2m
N/A
A24-19NF
Flat Panel
9.0 dBi
10.0
dBi
11.0
dBi
12.0
dBi
12.0
dBi
12.5
dBi
13.5
dBi
13.5
dBi
15.0
dBi
15.0
dBi
16.0
dBi
19.0
dBi
Fixed
2m
N/A
© 2010 Digi International, Inc.
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XBee®/XBee‐PRO® SMT ZB RF Modules
Antennas approved for XBee and XBee-PRO RF Module Channel 26
YAGI CLASS ANTENNAS for Channel 26
Part Number
Type (Description)
Gain
Application
Min
Separation
Minimum Cable
Loss/Power
Reduction/Attenuation
Required
A24-Y6NF
Yagi (6 element)
8.8dBi
Fixed
2m
N/A
A24-Y7NF
Yagi (7 element)
Fixed
2m
N/A
A24-Y9NF
Yagi (9 element)
Fixed
2m
N/A
A24-Y10NF
Yagi (10 element)
Fixed
2m
N/A
A24-Y12NF
Yagi (12element)
Fixed
2m
N/A
A24-Y13NF
Yagi (13 element)
Fixed
2m
0.5 dB
A24-Y15NF
Yagi (15 element)
Fixed
2m
1 dB
A24-Y16NF
Yagi (16 element)
Fixed
2m
2 dB
A24-Y16RM
Yagi (16 element, RPSMA connector)
Fixed
2m
7.5 dB
A24-Y18NF
Yagi (18 element)
Fixed
2m
9 dB
A24-P15NF
Flat Panel
Fixed
2m
4.5 dB
A24-P16NF
Flat Panel
Fixed
2m
10 dB
A24-19NF
Flat Panel
9.0 dBi
10.0
dBi
11.0
dBi
12.0
dBi
12.0
dBi
12.5
dBi
13.5
dBi
13.5
dBi
15.0
dBi
15.0
dBi
16.0
dBi
19.0
dBi
Fixed
2m
13 dB
* If using the RF module in a portable application (for example - if the module is used in a handheld device and
the antenna is less than 20cm from the human body when the device is in operation): The integrator is responsible
for passing additional SAR (Specific Absorption Rate) testing based on FCC rules 2.1091 and FCC Guidelines for
Human Exposure to Radio Frequency Electromagnetic Fields, OET Bulletin and Supplement C. The testing results
will be submitted to the FCC for approval prior to selling the integrated unit. The required SAR testing measures
emissions from the module and how they affect the person.
RF Exposure
WARNING: To satisfy FCC RF exposure requirements for mobile transmitting devices, a
separation distance of 20 cm or more should be maintained between the antenna of this device
and persons during device operation. To ensure compliance, operations at closer than this
distance are not recommended. The antenna used for this transmitter must not be co-located
in conjunction with any other antenna or transmitter.
The preceding statement must be included as a CAUTION statement in OEM product manuals in order to alert
users of FCC RF Exposure compliance.
© 2010 Digi International, Inc.
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XBee®/XBee‐PRO® SMT ZB RF Modules
Europe (ETSI)
The XBee RF Module has been certified for use in several European countries. For a complete list, refer to
www.digi.com
If the XBee RF Modules are incorporated into a product, the manufacturer must ensure compliance of the final
product to the European harmonized EMC and low-voltage/safety standards. A Declaration of Conformity must be
issued for each of these standards and kept on file as described in Annex II of the R&TTE Directive.
Furthermore, the manufacturer must maintain a copy of the XBee user manual documentation and ensure the
final product does not exceed the specified power ratings, antenna specifications, and/or installation requirements
as specified in the user manual. If any of these specifications are exceeded in the final product, a submission must
be made to a notified body for compliance testing to all required standards.
OEM Labeling Requirements
The 'CE' marking must be affixed to a visible location on the OEM product.
CE Labeling Requirements
The CE mark shall consist of the initials "CE" taking the following form:
•If the CE marking is reduced or enlarged, the proportions given in the above graduated drawing must be
respected. •The CE marking must have a height of at least 5mm except where this is not possible on
account of the nature of the apparatus.
•The CE marking must be affixed visibly, legibly, and indelibly.
Restrictions
France: Outdoor use limited to 10 mW EIRP within the band 2454-2483.5 MHz.
Norway: Norway prohibits operation near Ny-Alesund in Svalbard. More information can be found at the Norway
Posts and Telecommunications site (www.npt.no).
Declarations of Conformity
© 2010 Digi International, Inc.
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XBee®/XBee‐PRO® SMT ZB RF Modules
Digi has issued Declarations of Conformity for the XBee RF Modules concerning emissions, EMC and safety. Files
can be obtained by contacting Digi Support.
Important Note:
Digi does not list the entire set of standards that must be met for each country. Digi customers assume full
responsibility for learning and meeting the required guidelines for each country in their distribution market. For
more information relating to European compliance of an OEM product incorporating the XBee RF Module, contact
Digi, or refer to the following web sites:
CEPT ERC 70-03E - Technical Requirements, European restrictions and general requirements: Available at
www.ero.dk/.
R&TTE Directive - Equipment requirements, placement on market: Available at www.ero.dk/.
Approved Antennas
When integrating high-gain antennas, European regulations stipulate EIRP power maximums. Use the following
guidelines to determine which antennas to design into an application.
XBee RF Module
The following antennas types have been tested and approved for use with the XBee Module: XBee® ZB RF Modules
© 2010 Digi International, Inc. 151
Antenna Type: Yagi
RF module was tested and approved with 15 dBi antenna gain with 1 dB cable-loss (EIRP Maximum of 14 dBm).
Any Yagi type antenna with 14 dBi gain or less can be used with no cable-loss.
Antenna Type: Omni-Directional
RF module was tested and approved with 15 dBi antenna gain with 1 dB cable-loss (EIRP Maximum of 14 dBm).
Any Omni-Directional type antenna with 14 dBi gain or less can be used with no cable-loss.
Antenna Type: Flat Panel
RF module was tested and approved with 19 dBi antenna gain with 4.8 dB cable-loss (EIRP Maximum of 14.2 dBm).
Any Flat Panel type antenna with 14.2 dBi gain or less can be used with no cable-loss.
XBee RF Module
The following antennas have been tested and approved for use with the embedded XBee RF Module:
- Dipole (2.1 dBi, Omni-directional, Articulated RPSMA, Digi part number A24-HABSM)
- PCB Antenna (0 dBi)
© 2010 Digi International, Inc.
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XBee®/XBee‐PRO® SMT ZB RF Modules
Canada (IC)
Labeling Requirements
Labeling requirements for Industry Canada are similar to those of the FCC. A clearly visible label on the outside of
the final product enclosure must display the following text:
Contains Model XBee Radio, IC: 1846A-XBS2C
The integrator is responsible for its product to comply with IC ICES-003 & FCC Part 15, Sub. B - Unintentional
Radiators. ICES-003 is the same as FCC Part 15 Sub. B and Industry Canada accepts FCC test report or CISPR 22 test
report for compliance with ICES-003.
If it contains an XBee-PRO (S2) RF Module, the clearly visible label on the outside of the final product enclosure
must display the following text:
Contains Model XBee PRO Radio, IC: 1846A-XBPS2C
Transmitters with Detachable Antennas
This device has been designed to operate with the antennas listed in the previous table and having a maximum of
17.5 dB. Antennas not included in this list or having a gain greater than 17.5 dB are strictly prohibited for use with
this device. The required antenna impedance is 50 ohms.
Detachable Antenna
To reduce potential radio interference to other users, the antenna type and gain should be so chosen that the
equivalent, istropically radiated power (e.i.r.p.) is not more than permitted for successful communication.
Australia (C-Tick)
These modules comply with requirements to be used in end products in Australia. All products with EMC and radio
communications must have a registered C-Tick mark. Registration to use the compliance mark will only be
accepted from Australian manufacturers or importers, or their agent, in Australia.
In order to have a C-Tick mark on an end product, a company must comply with a or b below.
a. have a company presence in Australia.
b. have a company/distributor/agent in Australia that will sponsor the importing of the end product.
Contact Digi for questions related to locating a contact in Australia.
© 2010 Digi International, Inc.
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13. Migrating from XBee S2B to XBee S2C
The XBee S2C and XBee-PRO S2C are designed to be compatible with the XBeeS2B and XBee-PRO S2B. The S2C
modules have all the features of the S2B modules and offer the increased feature set described in this users guide.
For further information on the S2B see the XBee®/XBee-PRO® ZB RF Modules user’s guide available at
www.digi.com.
Pin Mapping
Mapping of the S2C pins to the S2B pins is shown in the table below. The pin names are from the S2C SMT
module.
S2C Pin
10
11
12
13
14
15
16
17
18
19
Name
GND
VCC
DOUT/DIO13
Din/nConfig/DIO14
DIO12
nRESET
RSSI PWM/ DIO10
PWM1/DIO11
reserved
nDTR/SLEEP_RQ/DIO8
GND
SPI_Attn/nBOOTMODE
GND
SPI_CLK/DIO18
SPI_nSSEL/DIO17
SPI_MOSI/DOI16
SPI_MOSO/DOI15
JTCK/SWCLK
JTDO/SWO
S2B Pin
10
S2C Pin
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
Name
JTDI
JTMS/SWDIO
GND
reserved
DIO4
nCTS/DIO7
On /SLEEP/DIO9
VREF
Associate/DIO5
nRTS/DIO6/SCLK2
AD3/DIO3
AD2/DIO2
AD0/DIO0
AD1/DIO2
reserved
GND
RF
reserved
S2B Pin
11
12
13
14
15
16
17
18
19
20
Mounting
One of the important differences between the S2C and S2B modules is the way they mount to the PCB. The S2B is
designed with through hole pins, while the S2C is designed with Surface Mount Technology (SMT). As such
different mounting techniques may be required.
Digi International has designed a footprint which will allow either module to be attached to a PCB. The layout is
shown below.
© 2010 Digi International, Inc.
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XBee®/XBee‐PRO® SMT ZB RF Modules
The round holes in the diagram are for the S2B, and the semi-oval pads are for the S2C. Pin 1 of the S2B in the
diagram is lined up with pin 1 of the S2C, but the pins are actually offset by one pad (see Pin Mapping above). By
using diagonal traces to connect the appropriate pins, the layout will work for both modules.
Information on attaching the S2C SMT module is included in Chapter 14 below.
© 2010 Digi International, Inc.
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XBee®/XBee‐PRO® SMT ZB RF Modules
14.
Manufacturing Information
The XBee S2C and XBee-PRO S2C are designed for surface mount on the OEM PCB. The S2C modules are designed
with castellated pad to allow for easy solder attach inspection. The pads are all located on the edge of the module,
so no hidden solder joints are used with these modules.
Recommended Solder Reflow Cycle
The recommended solder reflow cycle is shown below. The Chard shows the temperature setting and the time to
reach the temperature. The cooling cycle is not shown.
Time
(sec)
30
60
90
120
150
180
210
Temperature
(°C)
65
100
135
160
195
240
260
The maximum temperature should not exceed 260 °C.
The module will reflow during this cycle, and must not be reflowed with the shield down. Care should be taken not
to jar the module while the solder is molten, as parts inside the module can be removed from their required
locations.
Hand soldering is possible and should be done in accordance with approved standards.
© 2010 Digi International, Inc.
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XBee®/XBee‐PRO® SMT ZB RF Modules
Recommended Footprint
In order to surface mount the XBee S2C modules, it is recommended that you use the PCB footprint shown below.
The solder footprint should be matched to the copper pads, but may need to be adjusted depending on the
specific needs of assembly and product standards.
While the underside of the XBee S2C/XBee-PRO S2B do not contain any holes, and is mostly coated with solder
resist, it is recommended that the copper layer directly below the module be left open to avoid unintended
contacts. These modules have a ground plane in the middle on the back side for shielding purposes which can be
affected by copper traces directly under the module.
Flux and Cleaning
It is recommended that a “No Clean” solder past be used in assembling these modules. This will eliminate the
clean step and insure that unwanted residual flux in not left under the module where it is difficult to remove. In
addition:
© 2010 Digi International, Inc.
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XBee®/XBee‐PRO® SMT ZB RF Modules
•
•
Cleaning with liquids can result in liquid remaining under the shield or in the gap between the module and
OEM PCB. This can lead to unintended connections between the pads of the module.
The residual moisture and flux residue under the module are not easily seen during an inspection process.
Factory recommended best practice is to use a “no clean” solder paste to avoid the issues above and insure proper
module operation.
Reworking
The module may be removed from the OEM PCB by the use of a hot air rework station, or hot plate. Care should
be taken not to overheat the module. During rework, the module temperature may rise above its internal solder
melting point and care should be taken not to dislodge internal components from their intended positions.
Rework should never be performed on the module itself. The module has been optimized to give the best possible
performance, and reworking the module itself will void warranty coverage.
© 2010 Digi International, Inc.
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XBee®/XBee‐PRO® SMT ZB RF Modules
15.
Warranty Information
1-Year Warranty
XBee RF Modules from Digi International, Inc. (the "Product") are warranted against defects in materials and
workmanship under normal use, for a period of 1-year from the date of purchase. In the event of a product failure
due to materials or workmanship, Digi will repair or replace the defective product. For warranty service, return the
defective product to Digi International, shipping prepaid, for prompt repair or replacement.
The foregoing sets forth the full extent of Digi International's warranties regarding the Product. Repair or
replacement at Digi International's option is the exclusive remedy. THIS WARRANTY IS GIVEN IN LIEU OF ALL
OTHER WARRANTIES, EXPRESS OR IMPLIED, AND DIGI SPECIFICALLY DISCLAIMS ALL WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL DIGI, ITS SUPPLIERS OR
LICENSORS BE LIABLE FOR DAMAGES IN EXCESS OF THE PURCHASE PRICE OF THE PRODUCT, FOR ANY LOSS OF USE,
LOSS OF TIME, INCONVENIENCE, COMMERCIAL LOSS, LOST PROFITS OR SAVINGS, OR OTHER INCIDENTAL, SPECIAL
OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE PRODUCT, TO THE FULL
EXTENT SUCH MAY BE DISCLAIMED BY LAW. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF
INCIDENTAL OR CONSEQUENTIAL DAMAGES. THEREFORE, THE FOREGOING EXCLUSIONS MAY NOT APPLY IN ALL
CASES. This warranty provides specific legal rights. Other rights which vary from state to state may also apply.
© 2010 Digi International, Inc.
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XBee®/XBee‐PRO® SMT ZB RF Modules
Appendix A: Definitions
Definitions
ZigBee Node Types
Coordinator
A node that has the unique function of forming a network. The coor-dinator is responsible for establishing
the operating channel and PAN ID for an entire network. Once established, the coordinator can form a
network by allowing routers and end devices to join to it. Once the network is formed, the coordinator
functions like a router (it can participate in routing packets and be a source or destination for data
packets).
-- One coordinator per PAN
-- Establishes/Organizes PAN
-- Can route data packets to/from other nodes
-- Can be a data packet source and destination
-- Mains-powered Refer to the XBee coordinator section for more information.
Router
A node that creates/maintains network information and uses this information to determine the best route
for a data packet. A router must join a network before it can allow other routers and end devices to join
to it. A router can participate in routing packets and is intended to be a mains-powered node.
-- Several routers can operate in one PAN
-- Can route data packets to/from other nodes
-- Can be a data packet source and destination
-- Mains-powered Refer to the XBee router section for more information.
End device
End devices must always interact with their parent to receive or transmit data. (See ‘joining definition.)
They are intended to sleep periodically and therefore have no routing capacity. An end device can be a
source or destination for data packets but cannot route packets. End devices can be battery-powered and
offer low-power operation.
-- Several end devices can operate in one PAN
-- Can be a data packet source and destination
-- All messages are relayed through a coordinator or router
-- Lower power modes
© 2010 Digi International, Inc.
Page 174
XBee®/XBee‐PRO® SMT ZB RF Modules
ZigBee Protocol
PAN
Personal Area Network - A data communication network that includes a coordinator and one or more
routers/end devices.
Joining
The process of a node becoming part of a ZigBee PAN. A node becomes part of a network by joining to a
coordinator or a router (that has previously joined to the network). During the process of joining, the
node that allowed joining (the parent) assigns a 16-bit address to the joining node (the child).
Network Address
The 16-bit address assigned to a node after it has joined to another node. The coordinator always has a
network address of 0.
Operating Channel
The frequency selected for data communications between nodes. The operating channel is selected by
the coordinator on power-up.
Energy Scan
A scan of RF channels that detects the amount of energy present on the selected channels. The
coordinator uses the energy scan to determine the operating channel.
Route Request
Broadcast transmission sent by a coordinator or router throughout the network in attempt to establish a
route to a destination node.
Route Reply
Unicast transmission sent back to the originator of the route request. It is initiated by a node when it
receives a route request packet and its address matches the Destination Address in the route request
packet.
Route Discovery
The process of establishing a route to a destination node when one does not exist in the Routing Table. It
is based on the AODV (Ad-hoc On-demand Distance Vector routing) protocol.
ZigBee Stack
ZigBee is a published specification set of high-level communication protocols for use with small, lowpower modules. The ZigBee stack provides a layer of network functionality on top of the 802.15.4
specification. For example, the mesh and routing capabilities available to ZigBee solutions are absent in
the 802.15.4 protocol.
© 2010 Digi International, Inc.
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