Microhard Systems 00P4 2.4 GHz Spread Spectrum OEM Module User Manual MHX2400MANUA

Microhard Systems Inc 2.4 GHz Spread Spectrum OEM Module MHX2400MANUA

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Operating Manual
MHX-2400
2.4 GHz Spread Spectrum OEM Transceiver
Revision 1.11, December 1, 2000
Microhard Systems Inc.
#110, 1144 - 29th Ave. N.E.
Calgary, Alberta T2E 7P1
Phone: (403) 248-0028
Fax: (403) 248-2762
www.microhardcorp.com
MHX-2400
2.4 GHz
Spread-Spectrum
Embedded Modem
WARNING
In order to comply with the FCC/IC
adopted RF exposure requirements, this
transmitter system will be installed by the
manufacturer's reseller professional.
Installation of all antennas must be
performed in a manner that will provide at
least 20 cm clearance from the front
radiating aperture, to any user or member
of the public.
This manual contains information of proprietary interest to
Microhard Systems Inc. It has been supplied in confidence to
purchasers and users of the MHX-2400, and by accepting this
material the recipient agrees that the contents will not be copied
or reproduced, in whole or in part, without prior written consent
of Microhard Systems Inc.
Microhard Systems Inc. has made every effort to assure that this
document is accurate and complete. However, the company
reserves the right to make changes or enhancements to the
manual and/or the product described herein at any time and
without notice. Furthermore, Microhard Systems Inc. assumes
no liability resulting from any omissions in this document, or
out of the application or use of the device described herein.
Microhard Systems’ products are appropriate for home, office,
or industrial use, but are not authorized for utilization in
applications where failure could result in damage to property or
human injury or loss of life.
The electronic equipment described in this manual generates,
uses, and radiates radio frequency energy. Operation of this
equipment in a residential area may cause radio interference, in
which case the user, at his own expense, will be required to take
whatever measures necessary to correct the interference.
FCC Declaration of Conformity
This device complies with Part 15 of the FCC Rules.
Operation is subject to the following two conditions: (1) this
device may not cause harmful interference, and (2) this
device must accept any interference received including
interference that may caused undesired operation.
Microhard Systems Inc.’s products are warranted against all
failures which occur as a result of defective material or
workmanship within 12 months of purchase by the user. This
warranty does not extend to products that, in the opinion of
Microhard Systems Inc., have been subject to misuse, accidents,
lightning strikes, improper installation or application, nor shall
it extend to units which have, in Microhard Systems Inc.’s
opinion, been opened, tampered with or repaired by an
unauthorized facility.
Microhard Systems Inc.
Leaders in Wireless Telecom
th
#110, 1144 - 29 Ave. N.E.
Calgary, Alberta T2E 7P1
Phone: (403) 248-0028
Fax: (403) 248-2762
www.microhardcorp.com
ii
© 2000 by Microhard Systems Inc., All Rights Reserved.
HyperTerminal is copyrighted by Hilgraeve Inc, and developed for Microsoft.
Microsoft and Windows are registered trademarks of Microsoft Corporation.
pcANYWHERE and Symantec are registered trademarks of Symantec Corp.
All other products mentioned in this document are trademarks or registered
trademarks of their respective holders.
Manual Revision 1.11, December 1, 2000.
MHX-2400 Operating Manual
Contents
1.
2.
3.
A.
B.
C.
D.
F.
G.
H.
Introduction
1.0
Product Overview .............................................................................................................................................................................. 1
1.1
Features.............................................................................................................................................................................................. 1
1.2
About this Manual ............................................................................................................................................................................. 2
Initial Setup and Configuration
2.0
Unpacking and Inspection ................................................................................................................................................................. 3
2.1
Additional Requirements ................................................................................................................................................................... 3
2.2
Connectors and Indicators.................................................................................................................................................................. 3
2.3
Configuration..................................................................................................................................................................................... 6
2.4
Checking the Link............................................................................................................................................................................... 6
Configuration Options
3.0
Command Line Interface.................................................................................................................................................................... 9
3.1
AT Commands................................................................................................................................................................................. 10
A - Answer........................................................................................................................................................................................ 10
E - Command Echo.......................................................................................................................................................................... 10
I - Identification ............................................................................................................................................................................... 10
O - Online Mode .............................................................................................................................................................................. 11
Q - Quiet Mode................................................................................................................................................................................ 11
V - Result Codes Display................................................................................................................................................................. 11
W - Connection Result..................................................................................................................................................................... 11
Z - Reset Modem and load stored configuration .............................................................................................................................. 11
&C - DCD (Data Carrier Detect) ..................................................................................................................................................... 11
&D - DTR (Data Terminal Ready)................................................................................................................................................... 11
&F - Load Factory default configuration ......................................................................................................................................... 12
&K - Handshaking ............................................................................................................................................................................ 12
&S - DSR (Data Set Ready)............................................................................................................................................................. 12
&V - View Configuration ................................................................................................................................................................. 12
&E - Framing Error Check................................................................................................................................................................ 12
&W - Write Configuration to memory ............................................................................................................................................. 12
Sxxx? - Read S register value........................................................................................................................................................... 12
Sxxx=yyy - Set S register value ....................................................................................................................................................... 12
3.2
Command Result Codes................................................................................................................................................................... 13
3.3
S Registers ....................................................................................................................................................................................... 14
S Register 2 - Escape Code ............................................................................................................................................................... 14
S Register 3 - CR Control Code....................................................................................................................................................... 14
S Register 4 - Linefeed Control Code .............................................................................................................................................. 14
S Register 5 - Backspace Control Code ........................................................................................................................................... 14
S Register 101 - Operating Mode..................................................................................................................................................... 15
S Register 102 - Serial Baud Rate.................................................................................................................................................... 17
S Register 103 - Wireless Link Rate ................................................................................................................................................ 17
S Register 104 - Network Address ................................................................................................................................................... 18
S Register 105 - Unit Address.......................................................................................................................................................... 18
S Registers 106 and 206 - Primary and Secondary Hopping Patterns.............................................................................................. 18
S Register 107 - Encryption Key...................................................................................................................................................... 20
S Register 108 - Output Power Level............................................................................................................................................... 20
S Register 109 - Hopping Interval.................................................................................................................................................... 21
S Register 110 - Data Format............................................................................................................................................................ 21
S Registers 111 and 112 - Packet Minimum and Maximum Size..................................................................................................... 22
S Register 116 - Packet Character Timeout ...................................................................................................................................... 22
S Registers 113 and 213 - Packet Retransmission/Packet Retry Limit ............................................................................................. 23
S Register 115 - Packet Repeat Interval........................................................................................................................................... 24
S Register 117 - Modbus Mode ........................................................................................................................................................ 24
S Register 120 and 121- RTS/DCD Framing/Timeout ..................................................................................................................... 25
S Register 123 - RSSI Reading ......................................................................................................................................................... 25
Modem Command Summary ...................................................................................................................................................................... 26
Serial Interface ............................................................................................................................................................................................ 29
Sample Schematic Diagram ........................................................................................................................................................................ 31
Factory Default Settings.............................................................................................................................................................................. 33
Performance Tables...................................................................................................................................................................................... 34
Hopping Tables............................................................................................................................................................................................ 35
Technical Specifications ............................................................................................................................................................................. 36
Glossary ...................................................................................................................................................................................................... 38
1. Introduction
1.0 Product Overview
Congratulations on choosing the MHX-2400 wireless transceiver! Your new
MHX-2400 modem is a state-of-the-art, 2.4 GHz frequency-hopping spreadspectrum communications module. When the MHX-2400 module is
incorporated into the design of new or existing equipment, terminal devices
(DTEs) up to 30 km (or more)1 apart will be capable of establishing highspeed2 communications wirelessly.
MHX-2400 modules provide a practical and reliable alternative to using
traditional analog phone-line modems or “permanent wire” serial cable
(RS-232) connections for data communications between asynchronous serial
equipment. Moreover, wireless data communications using the MHX-2400
module means you will benefit from:
n greater flexibility and freedom to relocate terminal equipment,
n eliminated requirement for access to wire-based transfer media
such as telephone lines,
n the ability to communicate through walls, floors, and many
other obstacles.
While the MHX-2400 module is compact in its design, it delivers power and
convenience and offers quality and dependability. The MHX-2400 module’s
versatility makes it the ideal solution for applications ranging from officeproductivity to industrial data control and acquisition.
While a pair of MHX-2400 modules can link two terminal devices (“point-topoint” operation), multiple MHX-2400 modules can be used together to
create a network of various topologies, including “point-to-multipoint” and
“repeater” operation. Multiple independent networks can operate
concurrently, so it is possible for unrelated communications operations to
take place in the same or a nearby area without sacrificing privacy,
functionality, or reliability.
1.1 Features
Key features of the MHX-2400 module include:
n transmission within a public, license-exempt band of the radio
spectrum3 – this means that it can be used without access fees
(such as those incurred by cellular airtime);
n a serial I/O data port (TTL levels) with handshaking and
hardware flow control, allowing the MHX-2400 module to
interface directly to any microprocessor with an asynchronous
serial interface.
Ideal conditions with clear line-of-sight communications, using high-gain antennas.
Up to 115,200 bits per second (bps).
902-928 MHz, which is license-free within North America; may need to be factory-configured
differently for some countries.
MHX-2400 Operating Manual: Chapter 1 Introduction.
n 49 sets of user-selectable pseudo-random hopping patterns,
intelligently designed to offer the possibility of separately
operating multiple networks while providing security, reliability
and high tolerance to interference;
n encryption key with 65536 user-selectable values to maximize
security and privacy of communications;
n built-in CRC-16 error detection and auto re-transmit to provide
100% accuracy and reliability of data;
n ease of installation and use – the MHX-2400 module uses a
subset of standard AT style commands, very similar to those
used by traditional telephone line modems.
While the typical application for the MHX-2400 is to provide a short- to midrange wireless communications link between DTEs, it can be adapted to
almost any situation where an asynchronous serial interface is used and data
intercommunication is required.
1.2 About this Manual
This manual has been provided as a guide and reference for installing and
using MHX-2400 wireless modem modules.
The manual contains
instructions, suggestions, and information which will help you set up and
achieve optimal performance from your equipment using the MHX-2400
module.
It is assumed that users of the MHX-2400 module have either system
integration or system design experience. Chapter 2 details the requirements
and connections of the MHX-2400 module. Chapter 3 describes the AT
command register setup and configuration. The Appendices, including the
Glossary of Terms, are provided as informational references which you may
find useful throughout the use of this manual as well as during the operation
of the wireless modem.
Throughout the manual, you will encounter not only illustrations that further
elaborate on the accompanying text, but also several symbols which you
should be attentive to:
Caution or Warning: Usually advises against some action which could
result in undesired or detrimental consequences.
Point to Remember: Highlights a key feature, point, or step which is worth
noting, Keeping these in mind will make using the MHX-2400 more
useful or easier to use.
Tip: An idea or suggestion is provided to improve efficiency or to make
something more useful.
With that in mind, enjoy extending the boundaries of your communications
with the MHX-2400 module.
MHX-2400 Operating Manual: Chapter 1 Introduction
2. Initial Setup and Configuration
2.0 Unpacking and Inspection
The following items should be found in the shipping carton. Inspect the
contents for any shipping damage. Report damages or shortages to the
distributor from which the unit was purchased. Keep all packing materials in
the event that transportation is required in the future.
Package contents (normal distribution):
MHX-2400 Wireless Modem module
Operating Manual (this document)
2.1 Additional Requirements
Since the MHX-2400 module is a unique product in a class of its own, it will
communicate only with another MHX-2400 module which has been
compatibly configured. Thus, at least two MHX-2400 modules will be
required to establish a wireless communications link.
Additionally, the following requirements should be taken into consideration
when preparing to incorporate the MHX-2400 module in new or existing
designs.
n Small footprint for the MHX-2400 module (e.g., 2.1” W x 3.5” L
x 0.8” H) on the OEM PCB.
n Serial port and control signals from the host microprocessor.
See sample application schematics in Appendix C.
n +5 Vdc supply from the host OEM electronics.
n An external antenna (customer supplied).
2.2 Connectors and Indicators
The MHX-2400 module connects to the host equipment by two single row
header strips on the underside of the unit. This enables the MHX-2400
module to be directly soldered or socketed onto the host equipment
manufacturer’s PCB. The pinout for the module is given in Figure 1.
MHX-2400 Operating Manual: Chapter 2 Initial Setup and Configuration
Top View
Vcc
Vcc
Vcc
Vcc
Vcc
Vcc
Vcc
Radio
Radio
Logic
Logic
Logic
Logic
Logic
N/C
/CONFIG
/RESET
GND
GND
GND
GND
GND
GND
GND
N/C
N/C
N/C
40
20
21
N/C
N/C
N/C
N/C
N/C
N/C
N/C
Rx Mode LED
Tx Mode LED
RSSI LED 3
RSSI LED 2
RSSI LED 1
CTS
RTS
DSR
N/C
DTR
TxD
RxD
DCD
Antenna Connector
Figure 1 - Pinout Diagram
IMPORTANT:
For best performance, it is
strongly recommended to use
a separate, linearly regulated
supply for Vcc Radio. Do
not directly feed a switching
power supply into Vcc
Radio.
For OEM design simplicity,
connect both the radio and
logic Vcc connections
together.
The interface connectors and indicator lights are summarized below:
Vcc Radio - These pins supply power for the MHX-2400’s radio circuitry. Best
performance is achieved by providing linearly regulated voltage to these
pins. It is essential to keep this supply rail as clean as possible preferrably by not directly feeding a switching power supply into Vcc
Radio. In addition, it is recommended that Vcc Radio be regulated as
close to 5.5V as possible (without exceeding 5.5V). Running from a 5V
regulator will decrease the transmitted power by roughly 1dB. The linear
regulator must be rated for at least 800 mA
Vcc Logic - These pins supply power for the MHX-2400’s digital circuitry. It is
recommended you use a linear regulator to feed Vcc Logic. Current
consumption in the logic circuitry is typically 100 mA. The regulator
should be rated for at least 200 mA. To simplify the OEM design, the
Radio Vcc can be connected to the Logic Vcc.
GND - Ground return pins for both Radio and Logic circuitry
/RESET - This momentary active low input signal (100 ms typical) resets the
MHX-2400.
/CONFIG - Leave this pin unconnected. Do NOT ground.
Caution: Using any other power
supply which does not provide the
proper voltage or current could
damage the MHX-2400 module.
Receive Signal Strength Indicator (RSSI) - These active high TTL outputs are
designed to drive LED’s. As the signal strength increases, the number of
active RSSI lines increases, starting with RSSI1. When configured as a
Repeater, the module does not indicate RSSI. The LED’s perform a
“scanning” function, blinking on and off in sequence when a Slave or
Repeater modem is searching for synchronization. The current sourcing
capability of these lines is 20 mA.
MHX-2400 Operating Manual: Chapter 2 Initial Setup and Configuration
Data Port (DCE) - Pins 21 through 28 inclusive. This port is used to interface
the MHX-2400 module to a DTE device and operates at 2400 to 115,200
bps. The levels are active low 5V logic levels, and include (See
Appendix B for a complete description):
Pin No.
Name
Description
I/O
21
DCD
Data Carrier Detect
22
RxD
Receive Data
23
TxD
Transmit Data
24
DTR
Data Terminal Ready
25
NC
No Connect
26
DSR
Data Set Ready
27
RTS
Request to Send
28
CTS
Clear to Send
RX Indicator - This active high output indicates the modem is receiving data
packets with correct CRC, and is designed to drive a LED. When the unit
is configured as a Slave, this LED will typically be on solid under good
operating conditions.
TX Indicator - This active high output is designed to drive a LED, and indicates
the modem is transmitting.
Antenna Connector - The MHX-2400 uses an end launch SMA RF
connector. Microhard Systems can provide the cabling from the
module to the appropriate antenna connector. A suitable antenna must
be used to ensure adequate performance of the MHX-2400 module.
N/C - These pins are reserved for future use. Do not connect to these pins.
MHX-2400 Operating Manual: Chapter 2 Initial Setup and Configuration
2.3 Configuration
Prior to establishing a wireless link, each MHX-2400 module participating in
the link must be correctly configured for compatibility and for the desired
mode of operation.
Network 1
Network topologies consisting of a single Master and virtually any
combination of Slaves and Repeaters may be deployed. The functionality of
any particular MHX-2400 can be configured as follows:
Network 2
Network 3
Network 4
Network 5
Figure 2 - Sample Network
Topologies. Virtually any
Combination of Slaves and
Repeaters May be Used.
n Master Point-to-Point: The module is configured to
communicate with a single Slave, either directly, or through one
or more Repeaters.
n Master Point-to-Multipoint: The module is configured to
communicate with one or more Slaves and/or Repeaters.
n Slave: The module is configured to communicate with one
particular Repeater or Master.
n Repeater: The module is configured to pass information from
either a Master or another Repeater onto subsequent Repeaters
and/or Slaves and vice versa. The Repeater also acts as a Slave
in the sense that, like a Slave, it passes information to/from its
serial port.
All units within a network must be assigned a common Network Address;
thus enabling multiple networks to co-exist in the same vicinity without
unwanted crosstalk between modules. Examples of different network
topologies are shown in Figure 2.
Network 1 shows Point-to-Point
communication between a Master and Slave. Network 2 makes use of a
Repeater to communicate with the Slave. Network 3 illustrates a simple
Point-to-Multipoint network with no Repeaters. Networks 4 and 5 gives
examples of Point-to-Multipoint networks consisting of both Repeaters and
Slaves. There is effectively no restriction to the number of Repeaters and
Slaves that can be added to a network. As seen in Network 4, a Master can
communicate directly with both Slaves and Repeaters. The MHX-2400 has
been designed to allow for additional Repeaters and Slaves to be added to an
existing network without having to reconfigure any units already in the
network. This saves a tremendous amount of time when deploying additional
units in the field.
2.3.1 Quick Start Approach
The MHX-2400 is equipped with four standard factory default settings.
Instead of manually configuring each individual operating parameter, a global
command may be used to quickly configure the modem for a particular type
of operation. For example, to quickly implement Network 1, Factory default
1 would be applied to the Master, and Factory default 2 would be applied to
the Slave. To quickly set up Network 2, apply Factory 1 to the Master,
Factory 3 to the Repeater, and Factory 4 to the Slave. These defaults will get
you started and only ensure that a link can be established, but do not
necessarily provide the best performance.
Optimization of the
communications link is discussed in later sections.
MHX-2400 Operating Manual: Chapter 2 Initial Setup and Configuration
How to Set Up A Simple Network
The MHX-2400 will always be in one of two states:
n Data Mode – When in this state, the modem is listening and talking
to other modems in the network (the modem is online).
n Command Mode – When in this state, the modem is awaiting “AT
Commands” from the serial port. These commands are used to
configure all operating parameters of the modem. When in this
state, the modem is “offline”.
To implement the very basic network illustrated in Figure 2, Network 1,
n Plug the modem into the development board and connect a straight-
through serial cable between the development board and the
terminal (e.g., your PC)
Connect an antenna cable and antenna to the module.
Configure the unit to Factory Setting 1 by typing AT&F1 .
This puts the unit into Master Point-to-Multipoint mode.
Store these settings to memory by typing AT&W .
Put the modem into Data Mode by typing ATA . There are
other ways to enter Data Mode, which are discussed in Chapter 3.
Perform the above steps for the second unit, using the command
AT&F2 instead of AT&F1. This will configure the second unit as a
Slave.
The units should now be communicating. Remember, the parameters defined
by AT&F1 and AT&F2 will likely not be the most ideal for your application,
but will quickly allow you to test the units. A complete summary of the
settings defined by AT&F1,2,3 and 4 can be found in Appendix D. Factory
Default Settings.
Warning: Using an antenna that
is inappropriate for use with the
MHX-2400 module could result in
undesired performance, and may
damage the unit. It is the user’s
responsibility to ensure the
antenna has adequate lightning
protection.
Settings are not immediately stored in non-volatile memory, therefore, the
command &W is issued to store the current configuration into non-volatile
memory. Settings are retained even after powering down. All user selectable
parameters for the MHX-2400 are described in detail in Chapter 3:
Configuration Options.
2.4 Checking the Link
To check if the units are communicating, observe the LED indicators on the
development board. If the link is good, up to three RSSI outputs on the Slave
modem should be active; and if the link is absent (due to a fault at one end or
another, such as misconfiguration), the outputs will be in either “scanning
mode” or inactive.
Characters typed at the Master terminal should appear at the Slave’s terminal,
and vice versa. Also, verify that the RX LED blinks as packets of data are
received at the Master modem. As data is sent from Slave to Master, the RX
indicator should blink on as correct packets of data are received. It is
recommended that if MHX-2400 modules will be deployed in a field where
large distances separate the units, the modems should be configured and
tested in close proximity (e.g., in the same room) first to ensure a good link
can be established and settings are correct.
This will facilitate
troubleshooting, should problems arise.
MHX-2400 Operating Manual: Chapter 2 Initial Setup and Configuration
3. Configuration Options
3.0 Command Line Interface
The MHX-2400 modem can be easily configured to meet a wide range of
needs and applications. You can have your modem perform a variety of
functions by sending it instructions (in the form of commands). Sending a
command overrides the modem’s operating characteristics.
Your modem must be in Command Mode for it to execute a command. If
you send characters when the modem is in Data Mode, the modem transmits
the characters over the air.
Depending on its settings, the modem will either power up in Command
Mode or Data Mode. Normally, when first received from the factory, the
unit will power up in Command Mode.
You can place the modem into Data Mode either by
1.
Issuing the answer command
2.
Issuing the online command
You can place the modem into Command Mode either by
The escape sequence will not
be accepted unless both the
MHX-2400 and the terminal
are set to the same baud rate
1.
Sending the escape sequence
2.
Toggling the DTR line (depending on the &D parameter see pg 11).
To enter a command line and have your modem execute it, use the following
procedure:
1.
With your modem in the Command Mode, type AT. These characters,
known as the attention characters, must be typed at the beginning of
each command line.
2.
Type the command(s). Include any parameters required by the
command. To make the command line more readable, you can insert as
many spaces as desired. The command line holds up to 16 characters,
not including the AT prefix.
3.
Press the ENTER key. Your modem executes the command line and
sends you a word response (usually OK).
Refer to Appendix A (page
19) for a summary of the
modem commands
Configuration options are
not stored in non-volatile
memory until the WRITE
command (&W) is executed
For example, to set the Operating Mode S101 register to Master Point-toMultipoint mode, enter the following command line; AT S101 = 1 .
To display what a register is currently set to, enter the following command
line; AT Sxxx? . The modem will output the value of the register.
MHX-2400 Operating Manual: Chapter 3 Configuration Options
Note: If you want to send more than one command line, wait for a response
before entering the AT prefix at the start of the next command line.
To re-execute the previous command, enter A/. The modem will execute
the previous command line.
When in Command Mode, the modem “autobauds”, meaning that it will
automatically adjust to the baud rate of the terminal. You may change the
terminal baud rate while in Command Mode without losing communication
with the modem.
For the AT command protocol, an escape sequence consists of three
consecutive escape codes preceded and followed by at least 1 second of
inactivity. Typically, the ‘+’ character is used as the escape code.
+++
preceded and followed by 1 second of inactivity
Note that the terminal must be configured to the same baud rate as the
modem in order for the mode to recognize the escape sequence. The
modem is unable to “autobaud” while in Data Mode.
3.1 AT Commands
Several AT Commands are supported by the MHX-2400 module. The
following is a short description of all available commands. ‘*’ denotes
standard factory settings. All of the following commands must be preceded
by “AT”
Answer
The A command causes the modem to attempt to connect with another
remote modem (Type ATA ).
Command Echo
Your modem is preset to return (or echo) commands to the host
microprocessor when in Command Mode.
E0
*E1
No Command Echo
Command Echo
Identification
The I command returns various modem information settings.
I1
I2
I3
I4
I5
I6
I7
Product Code (MHX-2400)
Issue ROM Check (OK or ERROR)
Product Identification (Firmware Version)
Firmware Date
Firmware Copyright
Firmware Time
Serial Number
MHX-2400 Operating Manual: Chapter 3 Configuration Options
O
On-line Mode
The O command attempts to put the modem online and communicate with a
remote modem.
Quiet Mode
Your modem is preset to send responses when it executes commands, and
there after to keep the host informed of its status.
*Q0
Q1
Enable modem responses
Disable modem responses
Result Codes display
Your modem can either display result codes as words or numbers.
V0
*V1
Display Result Codes as numbers
Display Result Codes as words
Connection Result
The W command returns your modem to the Data Mode from the Command
Mode
*W0
W1
W2
Reports computer (DTE) baud rate as CONNECT xxxx
Reports computer (DTE) rate and wireless rate between
modems as CARRIER xxxx.
Reports modem (DCE) baud rate as CONNECT xxxx
Reset and load stored configuration
The Z command resets the modem and loads the stored configuration.
&C
DCD (Data Carrier Detect)
The &C command controls the modem’s DCD output signal to the host
microprocessor. This command determines when the DCD is active.
&C0
*&C1
&C2
&D
DCD is always ON
DCD on when modems are synchronized. DCD is always
on when unit is configured as Master.
DCD used for output data framing and Modbus mode.
See page 25 for details.
DTR (Data Terminal Ready)
The &D command controls what action the modem performs when the DTR
input line is toggled. The DTR input is controlled by the host
microprocessor.
*&D0
&D1
&D2
&D3
10
DTR line is ignored
Not Supported
DTR disconnects and switches to Command Mode
DTR disconnects and resets modem. Modem will remain
in this state until DTR again goes active.
MHX-2400 Operating Manual: Chapter 3 Configuration Options
&F
&F1
Master
Load Factory Default Configuration
The &F command resets the modem and loads the default factory
configuration.
&F2
&F1
Slave
&F2
&F3
&F1
Master
&F3
Repeater
&F4
&F4
Slave
&K
Master Point-to-Multipoint. Designed to communicate
with modems configured as &F2 or &F3.
Slave. Designed to communicate with another modem
configured as &F1.
Repeater. Designed to communicate with modems
configured as &F1 and &F4.
Slave working with factory default Repeater and factory
default Master. Communicates directly with Repeater
configured as &F3.
Handshaking
The &K command controls the handshaking between the modem and host
microprocessor.
&K0
&K2
*&K3
&S
Disable handshaking
RTS/CTS input data framing. See page 25 for details.
Enable hardware handshaking (RTS/CTS)
DSR (Data Set Ready)
The &S command controls the DSR line for the modem, and determines
when it is active
&S0
*&S1
&V
DSR is always ON
DSR is ON in Data Mode, OFF in Command Mode
View Configuration
The &V command displays the current (DTE) baud rate, and all setable
modem parameters including S register values.
&E
Framing Error Check
This command enables or disables Framing Error Check. When enabled,
the modem looks for the stop bit. If the stop bit is absent, the byte is thrown
out. When enabled, the modem also does a parity check. Note that the data
format (number of data bits, parity type, and number of stop bits) is defined
by S register 110.
*&E0
&E1
&W
Disable Framing Error Check
Enable Framing Error Check
Write Configuration to Memory
The &W command stores the active configuration into the modem’s nonvolatile memory.
Sxxx?
Read S register value
This command causes the modem to display the current setting of S register
xxx.
Sxxx=yyy
Set S register value (see section 3.3 S-Registers)
This command sets the specified S register to a value specified by yyy.
MHX-2400 Operating Manual: Chapter 3 Configuration Options
11
3.2 Command Result Codes
The MHX-2400 module can either display the results of a command as
either text strings or numerical data. The following chart shows resulting
text string and corresponding numeric result.
10
12
13
14
15
17
18
33
62
64
12
OK
NO CARRIER
ERROR
CONNECT 2400
CONNECT 3600
CONNECT 4800
CONNECT 7200
CONNECT 9600
CONNECT 14400
CONNECT 19200
CONNECT 28800
CONNECT 38400
CONNECT 57600
CONNECT 115200
CARRIER 45000
CARRIER 20000
MHX-2400 Operating Manual: Chapter 3 Configuration Options
3.3 S Registers
S Register 0 - Auto Answer
If this register is set to zero, the modem will power up in command mode. If
this register is non-zero, the modem will power up in data mode.
S Registers 2 through 5
cannot be stored to nonvolatile memory.
S Register 2 - Escape Code
This register contains the ASCII value of the escape character.
The default value (decimal 43) is equivalent to the ASCII character ‘+’.
Values greater than 127 disable the escape feature and prevent you from
returning to the Command Mode. This register cannot be stored to nonvolatile memory. If the modem is reset, or powered down, the default value
is restored.
Default is ‘+’ (decimal 43).
S Register 3 - CR Control Code
This register contains the ASCII value of the carriage return character.
This is the character that is used to end the command line and is also the
character that appears after the modem sends a response. This register
cannot be stored to non-volatile memory. If the modem is reset, or powered
down, the default value is restored.
Default is ‘CR’ (decimal 13).
S Register 4 - Linefeed Control Code
Register S4 sets the ASCII value of the linefeed character.
The modem sends the linefeed character after sending a carriage return
character when sending text responses. This register cannot be stored to
non-volatile memory. If the modem is reset, or powered down, the default
value is restored.
Default is ‘LF’ (decimal 10).
S Register 5 - Backspace Control Code
Register S5 sets the ASCII value of the backspace character.
This character is both the character created by entering BACKSPACE and
the character echoed to move the cursor to the left. This register cannot be
stored to non-volatile memory. If the modem is reset, or powered down, the
default value is restored.
Default is ‘BS’ (decimal 8).
MHX-2400 Operating Manual: Chapter 3 Configuration Options
13
S Register 101 - Operating Mode
The Operating Mode (register S101) partly defines the “personality” of the
MHX-2400 module. Allowable settings for this register are 1 through 4 as
follows:.
•
•
•
•
Only one Master can exist
for each network.
S101=1
S101=2
S101=3
S101=4
Master Point to Multipoint
Master Point to Point
Slave
Repeater
The default for this register depends on which factory default is selected as
shown below:
•
•
•
•
Default for Factory Setting &F1 is 1 (Master Point-to-Multipoint)
Default for Factory Setting &F2 is 3 (Slave)
Default for Factory Setting &F3 is 4 (Repeater)
Default for Factory Setting &F4 is 3 (Slave)
1)Master - Point to Multipoint. In any given network, there
is always only one Master. All other units should be configured as either
Slaves or Repeaters. When defined as a Point-to-Multipoint Master, the
modem broadcasts data to all Slaves and Repeaters in the network, and is
also the ultimate destination for data transmitted by all Slaves and
Repeaters. In addition, the Master defines the following network parameters
to be utilized by all other modems in the network (See the appropriate
sections for a complete description of these parameters):
n Maximum Packet Size (S112)
n Minimum Packet Size (S111)
n Wireless Link Rate (S103)
n Hop Interval (S109)
2)Master - Point to Point. This mode of operation is identical
to Master Point-to-Multipoint, with the exception that the Master only
broadcasts to one particular Slave or Repeater. The modem with which
communication occurs is defined by the Unit Address (S105). For example,
if a Slave has been assigned Unit Address 100, and the Master wishes to
communicate with that Slave, the Master must also be assigned a Unit
Address of 100. If there are Repeaters in the network, they will pass the
packet through to the Slave, and vice versa. Because Repeaters also have
Slave functionality (i.e., a Repeater can be connected to a terminal), the
Master can choose to communicate solely with a Repeater. This would be
accomplished by assigning the same Unit Address to both the Master and
the Repeater.
14
MHX-2400 Operating Manual: Chapter 3 Configuration Options
3)Slave. Up to 65534 Slaves may exist in a network, all of which
communicate with the common Master (either directly or via Repeater(s)).
Slaves cannot directly communicate with other Slaves, nor can they
acknowledge packets of data sent by the Master. Clearly this would cause
conflicts when there are multiple Slaves. The Master does, however, send
acknowledgements to all messages it receives from Slaves. The Master
initiates communications by sending a broadcast message to all Slaves. All
Slaves are free to respond in a “Slotted ALOHA” fashion, meaning that each
Slave can choose one of several windows in which to transmit. If there
happens to be two Slaves attempting to talk at the same time, the Master
may not receive the data, and the Slaves therefore would not get an
acknowledgement. At this point, the Slaves would attempt to get the
information through at random time intervals, thus attempting to avoid any
more conflicts. Special parameters which control the Slave’s response
characteristics can be modified with S Registers S115 and S213.
Network 50
Hop Pattern 2
PHP=1
Master
PHP=1
SHP=2
PHP=2
Slave
Repeater
Hop Pattern 1
Figure 3 - Repeater
Operation
Hop Pattern 3
Repeater Slave
PHP=2 PHP=3
SHP=3
Master
PHP=1
HopPattern 1
Repeater
PHP=1
SHP=2
Slave
PHP=2
4) Repeater. A more precise title would be Repeater/Slave, because a
Repeater also has much of the same functionality as a Slave. A terminal can
be connected at the Repeater location and communicate with the Master
terminal. There is no restriction to the number of Repeaters in a network,
allowing for communication over virtually limitless distances. The presence
of one Repeater in a network automatically degrades system throughput by
half. Additional Repeaters, regardless of the quantity, do not diminish
system throughput any further. To understand Repeater operation, consider
the module as belonging to two hopping patterns at the same time: The
Primary Hopping Pattern and the Secondary Hopping Pattern. In Figure 3,
the Master belongs to Hopping Pattern 1, and communicates with the
Repeater on this hopping pattern. The Slave belongs to Hopping Pattern 2,
and communicates with the Repeater on this hopping pattern. The whole
system belongs to Network 50 (i.e., all units must be assigned the same
Network Address (S104), which in this case was selected to be 50. Note
that Slaves and Master only communicate on their respective Primary
Hopping Pattern. Repeaters communicate on the Primary Hopping Pattern
when communicating with the Master (or with another Repeater between
itself and the Master). Repeaters communicate on their Secondary Hopping
Pattern when communicating with Slaves (or with another Repeater between
itself and the Slaves). Figure 4 shows another example.
If the Repeater is not also being used as a Slave (there is no DTE connected
to the serial port), it is recommended that the Repeater’s baud rate be set to
115K, and that handshaking be disabled (&K0). This will help ensure a
smooth flow of data through the network.
Hop Pattern 2
Figure 4 - A Network
Utilizing Three Hopping
Patterns
If there is no DTE connected
to the Repeater, turn off
handshaking (&K0) and set
the baud rate to 115K.
MHX-2400 Operating Manual: Chapter 3 Configuration Options
15
S Register 102 - Serial Baud Rate
The Serial Baud Rate is the current speed that the modem is using to
communicate with the DTE. When the AT command prefix is issued, the
modem performs an ‘autobaud’ operation and determines what the current
DTE baud rate is set to. The S register value returns the current setting of
the DTE baud rate.
The possible values are:
*1
10
11
115200
57600
38400
28800
19200
14400
9600
7200
4800
3600
2400
It is generally advisable to choose the highest rate that your terminal
equipment will handle to maximize performance, unless a limitation on the
available bandwidth is desired. If the DTE is a personal computer, the port
can usually be used reliably at 115200. It is not possible to write values to
this register, since the instant another AT command is issued, the register
will revert to the current baud rate. Therefore, it is advisable to operate in
Command Mode at the desired baud rate for Data Mode.
The Master determines the
Wireless Link Rate. This
setting on all other modems
is ignored..
S Register 103 - Wireless Link Rate
The Wireless Link Rate is the speed and optimization method for which
modems will communicate over the RF link. It is only necessary to set this
parameter on the Master unit. Units configured as Repeaters and Slaves will
ignore this setting, and adjust automatically to the rate of the Master.
The allowable settings are:
*4
Fast without Forward Error Correction
Fast with Forward Error Correction
Depending on the application requirements, each mode will provide
different throughput and performance. Appendix E. Performance Tables
give some indication of the performance to be expected in each mode.
In general, Forward Error Correction (FEC) reduces throughput, but in some
environments will actually increase throughput. FEC can reduce the number
of bad data packets, and hence reduce the need to retransmit.
16
MHX-2400 Operating Manual: Chapter 3 Configuration Options
S Register 104 - Network Address
Select a Network Address
and assign it to all units
which will be included in the
network.
The Network Address defines the membership to which individual units can
be a part of. By establishing a network under a common Network Address,
the network can be isolated from any other concurrently operating network.
As well, the Network Address provides a measure of privacy and security.
Only those units which are members of the network will participate in the
communications interchange. Valid values for the Network Address range
from 0 to 65535, inclusive.
To enhance privacy and reliability of communications where multiple
networks may operate concurrently in close proximity, it is suggested that an
atypical value be chosen – perhaps something meaningful yet not easily
selected by chance or coincidence.
Default is 1.
Use the same Unit Address
on both units for point-topoint mode. In multipoint
mode, set each Slave and
Repeater to a different Unit
Address.
Valid Unit Addresses are 1
to 65535.
S Register 105 - Unit Address
In point-to-point operation, the Unit Address on both the Master and Slave
(or Repeater) units must be the same. In a multipoint system, the Unit
Address uniquely identifies each Slave and Repeater from one another.
Each unit in a multipoint system must have a unique Unit Address ranging
from 1 to 65535. Do not use 0 as a Unit Address, and do not use a Unit
Address more than once within the same Network. This is required because
the Master must be able to acknowledge each unit individually, based on the
Unit Address.
S Register 106 - Primary Hopping Pattern
S Register 206 - Secondary Hopping Pattern
Since the MHX-2400 is a frequency-hopping modem, the carrier frequency
changes periodically according to one of 49 pseudo-random patterns,
defined by the Primary and Secondary Hopping Patterns. Valid entries for
each are 0 through 50.
The concept of Primary and Secondary Hopping Patterns was introduced in
the discussion of S Register 101 (Operating Mode).
Using the designations M[a,] Rx[a,b] and Sx[a] where:
- M indicates Master;
- R indicates Repeater;
- S indicates Slave;
- x is the Unit Address;
- a is the primary hopping pattern; and,
- b is the secondary hopping pattern;
MHX-2400 Operating Manual: Chapter 3 Configuration Options
17
the following diagrams illustrate the methodology for deploying simple to
complicated networks:
Master
Slave
Master
Repeater
Master
Repeater1
M[1]
←→
S1[1]
M[1]
←→
R1[1,2]
←→
S2[2]
M[1]
←→
R1[1,2]
←→
R2[2,3]
←→
S3[3]
M[1]
←→
R1[1,2]
←→
R2[2,3]
←→
R3[3,4]
←→
S4[4]
Slave
Repeater2
Slave
It is reasonable to consider a Repeater as being both a Slave and a Master,
alternating between Primary and Secondary Hopping Patterns as the unit
changes channel.
Consider R1 in the illustration below.
When
communicating with the Master, R1 is acting like a Slave on Primary
Hopping Pattern 1. When communicating with R2 and S4, R1 is acting like
a Master on Secondary Hopping Pattern 2. If multiple Repeaters are used,
they should have different Secondary Hopping Patterns:
←→
R1[1,2]
M[1]
Slaves and Masters do not
use Secondary Hopping
Patterns
←→
R2[2,5]
←→
S4[2]
←→
R5[1,3]
←→
R6[3,6]
←→
R8[1,4]
←→
S9[4]
←→
S3[5]
←→
S7[6]
Note that all units have a unique Unit Address.
Remember to assign a
unique Unit Address (1 to
65535) to each unit in the
system
Networks of any complexity can be created by linking multiple Repeaters
and Slaves:
←→
R1[1,2]
←→
M[1]
←→
S2[2]
←→
S3[2]
←→
R5[3,6]
R4[1,3]
←→
←→
S11[1]
←→
S12[1]
R8[3,7]
←→
S6[6]
←→
S7[6]
←→
R9[7,8]
←→
S10[8]
With a limitation of 51 hopping patterns, one might suspect that there is a
limitation to the number of repeaters in a system. However, if the units are
far enough away from one another, hopping patterns may be reused in
different sections of the network, without causing interference.
18
MHX-2400 Operating Manual: Chapter 3 Configuration Options
S Register 107 - Encryption Key
All units within a network
must use the same
encryption key.
The Encryption Key provides a measure of security and privacy of
communications by rendering the transmitted data useless without the
correct key on the receiver. Valid Encryption Keys range from 0 to 65535.
Keep in mind that all units within the network must use the same key for
communications to succeed.
S Register 108 - Output Power Level
The Output Power Level determines at what power the MHX-2400
transmits. The super-sensitive MHX-2400 can operate with very low power
levels, so it is recommended that the lowest power necessary is used; using
excessive power contributes to unnecessary “RF pollution”.
The allowable settings are:
*2
10 mW
50 mW
100 mW
250 mW
1W
500 mW
750 mW
Ideally, you should test the communications performance between units
starting from a low power level and working upward until the RSSI is
sufficiently high and a reliable link is established. Although the conditions
will vary widely between applications, typical uses for some of the settings
are described below:
Power
Use
For in-building use, typically provides a link up to 300 feet on the
same floor or up/down a level. Outdoors, distances of 10 km can be
achieved if high-gain (directional) antennas are placed high above
ground level and are in direct line-of-sight.
50 mW 200-500 ft indoors, 8-15 km* outdoors.
100 mW 400-800 ft indoors, 15-25 km* outdoors.
1000 mW Typically provides communications up to a distance of 1000 feet or
(1 W) more in-building on the same floor or up/down a few levels,
depending on building construction (wood, concrete, steel, etc.). In
ideal line-of-sight conditions, up to 30 km* or more can be
achieved. Note that only an antenna with a gain of no more than 6
dBi may be used. Any higher is a violation of FCC rules. See
IMPORTANT warning below.
* These outdoor distances assume antennas are mounted at least 100 ft
above ground level
10 mW
MHX-2400 Operating Manual: Chapter 3 Configuration Options
19
IMPORTANT:
FCC Regulations allow up to 36 dBi effective radiated power (ERP).
Therefore, the sum of the transmitted power (in dBm), the cabling loss
and the antenna gain cannot exceed 36 dBi.
1 mW = 0 dBm
10 mW = 10 dBm
100 mW = 20 dBm
1000 mW = 30 dBm
For example, when transmitting 1 Watt (30 dBm), with cabling losses of
2 dB, the antenna gain cannot exceed 36 - 30 + 2 = 8 dBi. If an antenna
with a gain higher than 8 dBi were to be used, the power setting must
be adjusted appropriately. Violation of FCC regulations can result in
severe fines.
The hopping interval is
controlled by the master.
The slave and repeater units
will use the hopping interval
setting from the master.
S Register 109 - Hopping Interval
This option determines the frequency at which the modems change channel.
Note that the Master controls this parameter for the entire network. This
setting is ignored in units configured as Slaves or Repeaters.
The allowable settings are:
*8
8 msec
12 msec
16 msec
20 msec
30 msec
45 msec
80 msec
120 msec
See Appendix E for optimal Hopping Interval settings in relation to packet
size and link rate.
S Register 110 - Data Format
This register determines the format of the data on the serial port. Allowable
settings are:
*1
10
11
20
8 bits, No Parity, 1 Stop
8 bits, No Parity, 2 Stop
8 bits, Even Parity, 1 Stop
8 bits, Odd Parity, 1 Stop
7 bits, No Parity, 1 Stop
7 bits, No Parity, 2 Stop
7 bits, Even Parity, 1 Stop
7 bits, Odd Parity, 1 Stop
7 bits, Even Parity, 2 Stop
7 bits, Odd Parity, 2 Stop
9 bits, No Parity, 1 Stop
MHX-2400 Operating Manual: Chapter 3 Configuration Options
S Register 111 - Packet Minimum Size
S Register 112 - Packet Maximum Size
S Register 116 - Packet Character Timeout
These settings determine the conditions under which the modem will
transmit accumulated data over the air.
S Register 111 - Minimum Size
Valid entries for this register are 1 to 255 bytes, which defines the minimum
number of bytes to receive from the DTE before encapsulating them in a
packet and transmitting over the air.
The Minimum and
Maximum Packet Size is
controlled by the Master.
The Slave and Repeater units
will use the Minimum and
Maximum Packet Size
setting from the Master.
Note that the minimum packet size for all modems in the network is
determined by the Master only. This setting is ignored in all Slave and
Repeater modems. The default is 1 byte.
S Register 112 - Maximum Size
This setting has a range of 2 to 255, and defines the maximum number of
bytes from the DTE which should be encapsulated in a packet. This value
should be greater than the minimum packet size, but not smaller than is
necessary for reliable communications. If the wireless link is consistently
good and solid, a maximum size of 255 will yield the best throughput
(depending on the higher level protocols of the connected equipment).
However, if the link is poor (e.g., experiencing excessive interference) and
data is frequently retransmitted, the maximum packet size should be
reduced. This decreases the probability of errors within packets, and
reduces the amount of traffic in the event that retransmissions are required.
Note that the maximum packet size for all modems in the network is
determined by the Master only. This setting is ignored in all Slave and
Repeater modems. The default is 255 bytes.
S Register 116 - Packet Character Timeout
This register has valid entries of 0 to 254 milliseconds. The Packet
Character Timeout timer looks for gaps in the data being received from the
DTE. The timer is only activated after the Minimum Packet Size has been
accumulated in the modem. After which, if the timer detects a gap in the
data exceeding the Packet Character Timeout value, the modem will
transmit the data.
The MHX-2400 will accumulate data in its buffers from the DTE until one
of the following requirements is met (whichever occurs first):
•
The Maximum Packet Size (in bytes) has been accumulated;
•
The Minimum Packet Size has been accumulated AND the Packet
Character Timeout interval has elapsed.
The default for the Packet Character Timeout is 9 ms. If set to 0 ms, the
unit will buffer exactly the minimum packet size before transmitting.
MHX-2400 Operating Manual: Chapter 3 Configuration Options
21
S Register 113 - Packet Retransmissions
This register applies to both Master and Repeater operation. It does not
apply to Slave operation. The Master will retransmit each data packet
exactly the number of times defined by the Packet Retransmissions
parameter. The Master retransmits once at the beginning of each hopping
interval until the limit is reached. This parameter is not necessary in Slave
units since all Slaves receive acknowledgement from the Master. As
discussed previously, the Repeater effectively behaves as both a Master and
a Slave. When the Repeater is tuned to its Secondary Hopping Pattern
(acting as a Master), the Packet Retransmissions Parameter comes into play.
The Repeater will re-send packets of data on to Slaves or other Repeaters
exactly the number of times defined by the Packet Retransmissions
parameter.
Recipients of the packet will discard any duplicates The valid settings for
this parameter are 0 to 255 retransmissions. The default is 2.
S Register 213 - Packet Retry Limit
Packet Retry Limit is analogous to Packet Retransmissions, but specifically
applies to Slaves and Repeaters. This parameter is not used by the Master.
Because the Slave has the advantage of receiving acknowledgements from
the Master, it is not necessary to blindly retransmit each packet. If the Slave
does not get an acknowledgement on the next hop, it will retransmit its
packet. This will continue until the Packet Retry Limit is reached or an
acknowledgement is received. If the limit is reached, the modem will give
up and discard the data. Valid settings are 0 to 255 retries. The default
value is 2.
The Repeater makes use of this parameter when it is tuned to its Primary
Hopping Pattern and is acting like a Slave.
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MHX-2400 Operating Manual: Chapter 3 Configuration Options
S Register 115 - Packet Repeat Interval
A parameter that is specific to Slaves and Repeaters is the Packet Repeat
Interval.
The allowable settings are 1 through 255. The default is 1.
This parameter defines a range of random numbers that the Slave will use as
the next slot in which it will attempt to send the packet. For example, if this
register is set to 7, the Slave will choose a number between one and seven as
the next slot in which to transmit. Suppose the random number generator
picks 5, then the Slave will transmit in the fifth time slot. A Slave will
transmit a maximum of once per hopping interval, however, depending on
the duration of the hopping interval and the maximum packet size, more
than one slot per hop is potentially available. The Slave will transmit more
frequently when a Repeat Interval with a smaller range is selected. Choose
1 to have the Slave transmit in the first available slot. Choose higher
intervals for less frequent transmission, or to avoid collisions between many
Slaves in the system.
S Register 117 - Modbus Mode
Modbus Mode allows for the MHX-2400 to be fully Modbus compatible.
Please contact Microhard Systems for assistance when configuring the unit
for Modbus operation. Optimal Modbus settings rely on several other S
Register parameters.
The allowable settings for this register are:
*0
Disabled
Enabled
MHX-2400 Operating Manual: Chapter 3 Configuration Options
23
S Register 120 - RTS/DCD Framing
S Register 121 - DCD Timeout
The MHX-2400 supports two special types of data framing:
•
•
Input (or RTS/CTS) Data Framing; and,
Output (or DCD) Data Framing
Input Data Framing is enabled by configuring the Handshaking Parameter as
&K2. This type of framing makes use of the S120 parameter as illustrated
in Figure 5. Parameter S120 can be set to any value between 0 and 254 ms.
RTS
CTS
TXD
Data going into MHX-910
0 to 1 ms
S120 (ms)
Figure 5 - Input Data Framing
To enable output (DCD) data framing, set the Data Carrier Detect parameter
as &C2. This type of framing uses both S120 and S121 registers as shown
in Figure 6. Valid ranges for each parameter are 0 to 254 ms.
DCD
RXD
Data leaving MHX-910
S120 (ms)
S121 (ms)
Figure 6 - Output Data Framing
S Register 123 - RSSI Reading
This register displays the average signal strength in dBm over the previous
four hop intervals. Valid RSSI readings apply only to units configured as
Slave or Repeater.
24
MHX-2400 Operating Manual: Chapter 3 Configuration Options
MHX-2400 Operating Manual: Chapter 3 Configuration Options
25
A. Modem Command Summary
The following provides a command summary for the MHX-2400 module. Factory settings are denoted with a ‘*’.
AT Commands
Answer
Command Echo
E0 No Echo
* E1 Command Echo
Identification
I0 Product Code
I2 ROM Checksum test
I3 Firmware Version
I4 Firmware Date
I5 Copyright
I6 Firmware Time
On-line Mode
Quiet Mode
* Q0 Enables Result Codes
Q1 Disables Result Codes
Result Codes Display
V0 Display as Numbers
* V1 Display as Words
Connection Result
* W0 Reports DTE as CONNECT xxxx
W1 Reports computer (DTE) rate and wireless rate
between modems as CARRIER xxxx.
W2 Reports DCE as CONNECT xxxx
Reset and load stored configuration
&C
DCD (Data Carrier Detect)
&C0 DCD is always on
* &C1 DCD is on when modems are synchronized
&C2 DCD used for output data framing
&D
DTR (Data Terminal Ready)
&D0 DTR ignored
* &D2 DTR disconnects and switches to command
&D3 DTR disconnects and resets modem
&F
Load Factory Default
&F1 Master
&F2 Slave
&F3 Repeater
&F4 Slave through Repeater
&K
Handshaking
&K0 Disable Handshaking
&K2 RTS/CTS Input Framing
* &K3 Enable Handshaking
&S
DSR (Data Set Ready)
&S0 DSR is always on
* &S1 DSR on in data, off in command mode
&V
View Configuration
&W
Write configuration to memory
Sxx?
Read S register value
Sxx=yy Set S register value
Result Codes
OK
12
CONNECT 9600
NO CARRIER
13
CONNECT 14400
ERROR
14
CONNECT 19200
CONNECT 2400
15
CONNECT 28800
CONNECT 3600
17
CONNECT 38400
CONNECT 4800
18
CONNECT 57600
10
CONNECT 7200
33
CONNECT 115200
64
CARRIER 20000
62
CARRIER 45000
26
S Registers
S0
Auto Answer [0...255]
0 = power up in Command Mode,
non-zero = power up in Data Mode
S2
Escape code [0...255] default ‘+’
S3
CR character [0...255] default
S4
Line Feed [0...255] default
S5
Backspace [0...255] default
S101
Operating Mode
1 - Master Point to Multipoint
2 - Master Point to Point
3 - Slave
4 - Repeater
S102
Serial Baud Rate
*1 = 115200, 2 = 57600, 3 = 38400
4 = 28800, 5 = 19200, 6 = 14400
7 = 9600, 8 = 7200, 9 = 4800,
10 = 3600, 11 = 2400
S103
Wireless Link Rate
2 = Fast w/o FEC
*4 = Fast with FEC
S104
Network Address [0...65535]
S105
Unit Address [1...65535]
S106
Primary Hopping Pattern [0...50]
S206
Secondary Hopping Pattern [0...50]
S107
Encryption Key [0...65535]
S108
Output Power Level
0 = 10 mW, 1 = 50 mW, *2 = 100 mW, 3 = 250 mW
4 = 500 mW, 5 = 750 mW, 6 = 1W
S109
Hopping Interval
1 = 8 msec, 2 = 12 msec, 3 = 16 msec,
4 = 20 msec, 5 = 30 msec, 6 = 45 msec,
7 = 80 msec, *8 = 120 msec
S110
Data Format
* 1 = 8N1, 2 = 8N2, 3 = 8E1, 4 = 8O1
5 = 7N1, 6 = 7N2, 7 = 7E1, 8 = 7O1
9 = 7E2, 10 = 7O2, 11 = 9N1
S111
Packet Minimum Size [1...Maximum Size]
S112
Packet Maximum Size [2...255]
S113
Packet Retransmissions [0...255]
S213
Packet Retry Limit [0...255]
S115
Packet Repeat Interval [1..255]
Default = 1
S116
Packet Character Timeout [0...254 ms]
S117
Modbus Mode
*0 = Disabled, 1 = Enabled
S120
RTS/DCD Framing Interval [0...254 ms]
S121
DCD Timeout [0...254 ms]
MHX-2400 Operating Manual: Appendix A. Modem Command Summary
MHX-2400 Operating Manual: RS-232 Interface and Cables
27
B. Serial Interface
The MHX-2400 module uses 8 pins on the header connector for
asynchronous serial I/O. The interface conforms to standard RS-232 signals
without level shifting, so direct connection to a host microprocessor is
possible.
The signals in the asynchronous serial interface are described below:
DCD Data Carrier Detect - Output from Modem - When asserted (TTL low),
DCD informs the DTE that a communications link has been established with
another MHX-2400.
Modem
(DCE)


←
←


←

Host
Microprocessor
Signal
(DTE)
DCD
RX
TX
DTR
SG
DSR
RTS
CTS
→ IN
→ IN
 OUT
 OUT
→ IN
→ IN
 OUT
→ IN
Arrows denote the direction that
signals are asserted (e.g., DCD
originates at the DCE and tells the
DTE that a carrier is present).
RX
Receive Data - Output from Modem - Signals transferred from the MHX2400 are received by the DTE via RX.
TX
Transmit Data - Input to Modem - Signals are transmitted from the DTE via
TX to the MHX-2400.
DTR Data Terminal Ready - Input to Modem - Asserted (TTL low) by the DTE to
inform the modem that it is alive and ready for communications.
SG
Signal Ground - Provides a ground reference for all signals transmitted by
both DTE and DCE.
DSR
Data Set Ready - Output from Modem - Asserted (TTL low) by the DCE to
inform the DTE that it is alive and ready for communications. DSR is the
modem’s equivalent of the DTR signal.
RTS
Request to Send - Input to Modem - A “handshaking” signal which is
asserted by the DTE (TTL low) when it is ready. When hardware
handshaking is used, the RTS signal indicates to the DCE that the host can
receive data.
CTS
Clear to Send - Output from Modem - A “handshaking” signal which is
asserted by the DCE (TTL low) when it has enabled communications and
transmission from the DTE can commence. When hardware handshaking is
used, the CTS signal indicates to the host that the DCE can receive data.
Notes: It is typical to refer to RX and TX from the perspective of the DTE. This should be
kept in mind when looking at signals relative to the modem (DCE); the modem
transmits data on the RX line, and receives on TX.
“DCE” and “modem” are often synonymous since a modem is typically a DCE device.
“DTE” is, in most applications, a device such as a host microprocessor.
MHX-2400 Operating Manual: Appendix B Serial Interface
29
30
MHX-2400 Operating Manual: Appendix B Serial Interface
C. Sample Schematic Diagram
The following is a sample microprocessor implementation with a MICROCHIP PIC 16C74 and the MHX-2400. The MHX2400 performs no level shifting on the serial port, so direct connection to the host microprocessor is possible.
DO NOT CONNECT THE MHX-2400 TO RS 232 DRIVER OUTPUTS. DAMAGE TO THE UNIT MAY RESULT.
On this implementation, the onboard SCI of the PIC 16C74 is directly connected pins 2 and 3 of the MHX-2400. The bidirectional Port D is used for asserting or monitoring control signals from the MHX-2400.
The RESET and CONFIG signals are momentary active low signals asserted by the host microprocessor.
RESET initializes the MHX-2400 and places the system in a known state. This signal should be set high after the host
microprocessor has been reset.
The CONFIG line is reserved for factory use. This signal should be set high.
PIC16C74
MHX-900
RC7
RC6
RXD
TXD
RD0
RD1
RD2
RD3
RD4
DCD
DTR
DSR
RTS
CTS
RD5
RD6
CONFIG
RESET
32
31
Power Connections not shown
MHX-2400 Operating Manual: Appendix C Sample Schematic Diagram
31
32
MHX-2400 Operating Manual: Appendix C Sample Schematic Diagram
D. Factory Default Settings
AT&F1 - Master Default Settings
AT&F3 - Repeater Default Settings
E1, Q0, V1, W0, S0=0, S2=43, S3=13, S4=10, S5=8
E1, Q0, V1, W0, S0=1, S2=43, S3=13, S4=10, S5=8
DCD
DTR
Framing
Handshaking
DSR
Operating Mode
Serial Baud Rate
Wireless Link Rate
Network Address
Unit Address
Primary Hop Pattern
Encryption Key
Output Power
Hop Interval
Data Format
Packet Minimum Size
Packet Maximum Size
Packet Retransmissions
&C1 (On)
&D0 (DTR is ignored)
&E0 (Disabled)
&K3 (Enabled)
&S1 (On in Data, Off in Command)
S101=1 (Master P-MP)
S102=1 (115kbaud)
S103=4 (Fast, FEC)
S104=1
S105=1
S106=0
S107=1
S108=2 (100mW)
S109=8
S110=1 (8N1)
S111=1
S112=255
S113=2
DCD
DTR
Framing
Handshaking
DSR
Operating Mode
Serial Baud Rate
Wireless Link Rate
Network Address
Unit Address
Primary Hop Pattern
Encryption Key
Output Power
Hop Interval
Data Format
Packet Minimum Size
Packet Maximum Size
Packet Retransmissions
&C1 (On when modems are synced)
&D0 (DTR is ignored)
&E0 (Disabled)
&K3 (Enabled)
&S1 (On in Data, Off in Command)
S101=4 (Repeater)
S102=1 (115kbaud)
S103=4 (Fast, FEC) (Set by Master)
S104=1
S105=3
S106=0
S107=1
S108=2 (100mW)
S109=8 (Set by Master)
S110=1 (8N1)
S111=1 (Set by Master)
S112=255 (Set by Master)
S113=2
Packet Repeat Interval
Character Timeout (ms)
Modbus Mode
RTS/DCD Framing (ms)
DCD Timeout (ms)
Secondary Hop Pattern
Packet Retry Limit
S115=1 (Don’t Care)
S116=8
S117=0
S120=0
S121=0
S206=2 (Don’t Care)
S213=2 (Don’t Care)
Packet Repeat Interval
Character Timeout (ms)
Modbus Mode
RTS/DCD Framing (ms)
DCD Timeout (ms)
Secondary Hop Pattern
Packet Retry Limit
S115=1
S116=8
S117=0
S120=0
S121=0
S206=2
S213=2
AT&F2 - Slave Default Settings
AT&F4 -Slave Through Repeater Default Settings
E1, Q0, V1, W0, S0=1, S2=43, S3=13, S4=10, S5=8
E1, Q0, V1, W0, S0=1, S2=43, S3=13, S4=10, S5=8
DCD
DTR
Framing
Handshaking
DSR
Operating Mode
Serial Baud Rate
Wireless Link Rate
Network Address
Unit Address
Primary Hop Pattern
Encryption Key
Output Power
Hop Interval
Data Format
Packet Minimum Size
Packet Maximum Size
Packet Retransmissions
&C1 (On when modems are synced)
&D0 (DTR is ignored)
&E0 (Disabled)
&K3 (Enabled)
&S1 (On in Data, Off in Command)
S101=3 (Slave)
S102=1 (115kbaud)
S103=4 (Fast, FEC) (Set by Master)
S104=1
S105=2
S106=0
S107=1
S108=2 (100mW)
S109=8 (Set by Master)
S110=1 (8N1)
S111=1 (Set by Master)
S112=255 (Set by Master)
S113=2 (Don’t Care)
DCD
DTR
Framing
Handshaking
DSR
Operating Mode
Serial Baud Rate
Wireless Link Rate
Network Address
Unit Address
Primary Hop Pattern
Encryption Key
Output Power
Hop Interval
Data Format
Packet Minimum Size
Packet Maximum Size
Packet Retransmissions
&C1 (On when modems are synced)
&D0 (DTR is ignored)
&E0 (Disabled)
&K3 (Enabled)
&S1 (On in Data, Off in Command)
S101=3 (Slave)
S102=1 (115kbaud)
S103=4 (Fast, FEC) (Set by Master)
S104=1
S105=4
S106=2
S107=1
S108=2 (100mW)
S109=8 (Set by Master)
S110=1 (8N1)
S111=1 (Set by Master)
S112=255 (Set by Master)
S113=2 (Don’t Care)
Packet Repeat Interval
Character Timeout (ms)
Modbus Mode
RTS/DCD Framing (ms)
DCD Timeout (ms)
Secondary Hop Pattern
Packet Retry Limit
S115=1
S116=9
S117=0
S120=0
S121=0
S206=2 (Don’t Care)
S213=2
Packet Repeat Interval
Character Timeout (ms)
Modbus Mode
RTS/DCD Framing (ms)
DCD Timeout (ms)
Secondary Hop Pattern
Packet Retry Limit
S115=1
S116=8
S117=0
S120=0
S121=0
S206=2 (Don’t Care)
S213=2
MHX-2400 Operating Manual: Appendix D. Factory Default Settings
33
34
MHX-2400 Operating Manual: Appendix D Factory Default Settings
E. Performance Tables
The scope of this appendix is to find the best possible performance and maximum packet size at different modes of
operation. The setup assumes a baud rate of 115k, no retries and no retransmissions..
Slave to Master
Communication.
(No Repeater)
Link Rate = Fast
NO FEC
Slave to Master
Communication.
(No Repeater)
Link Rate = Fast
WITH FEC
Repeater to
Master Direct
Communication.
Link Rate = Fast
NO FEC
Repeater to
Master Direct
Communication.
Link Rate = Fast
WITH FEC
Slave to Master
Through One or
More Repeaters.
Link Rate = Fast
NO FEC
Slave to Master
Through One or
More Repeaters.
Link Rate = Fast
WITH FEC
Hop
Interval
1 (8 ms)
2 (12 ms)
3 (16 ms)
4 (20 ms)
5 (30 ms)
6 (45 ms)
7 (80 ms)
8 (120 ms)
1 (8 ms)
2 (12 ms)
3 (16 ms)
4 (20 ms)
5 (30 ms)
6 (45 ms)
7 (80 ms)
8 (120 ms)
1 (8 ms)
2 (12 ms)
3 (16 ms)
4 (20 ms)
5 (30 ms)
6 (45 ms)
7 (80 ms)
8 (120 ms)
1 (8 ms)
2 (12 ms)
3 (16 ms)
4 (20 ms)
5 (30 ms)
6 (45 ms)
7 (80 ms)
8 (120 ms)
1 (8 ms)
2 (12 ms)
3 (16 ms)
4 (20 ms)
5 (30 ms)
6 (45 ms)
7 (80 ms)
8 (120 ms)
1 (8 ms)
2 (12 ms)
3 (16 ms)
4 (20 ms)
5 (30 ms)
6 (45 ms)
7 (80 ms)
8 (120 ms)
Optimal Packet
Size (bytes)
14
66
110
154
255
255
255
255
34
54
76
130
210
255
255
N/A
22
44
101
178
255
255
N/A
N/A
16
43
80
174
255
N/A
22
43
93
174
255
255
N/A
N/A
N/A
14
40
80
Throughput
(kbps)*
20
52
66
74
83
56
31
21
22
28
32
38
43
30
20
N/A
13
21
32
39
31
21
N/A
N/A
12
16
20
20
N/A
13
21
31
38
31
21
N/A
N/A
N/A
12
16
174
255
19
20
MHX-2400 Operating Manual: Appendix E. Performance Tables
35
36
MHX-2400 Operating Manual: Appendix E. Performance Tables
F. Hopping Patterns
This Appendix provides a guide for selecting appropriate hopping patterns (S106,S206). There
are 49 hopping patterns: Patterns have been designed to notch out certain segments of the ISM
band.
Pattern Number
Spectrum Used
0-7
2.4012 - 2.4824 GHz
8 - 10
2.4012 - 2.4312 GHz
11 - 13
2.4052 - 2.4352 GHz
14 - 16
2.4092 - 2.4392 GHz
17 - 19
2.4132 - 2.4432 GHz
20 - 22
2.4172 - 2.4472 GHz
23 - 25
2.4212 - 2.4512 GHz
26 - 28
2.4252 - 2.4552 GHz
29 - 31
2.4292 - 2.4592 GHz
32 - 34
2.4332 - 2.4632 GHz
35 - 37
2.4372 - 2.4672 GHz
38 - 40
2.4412 - 2.4712 GHz
41 - 43
2.4452 - 2.4752 GHz
44 - 46
2.4492 - 2.4792 GHz
47 - 48
2.4520 - 2.4820 GHz
Patterns 44 to 48 may be manually edited by entering AT&H at the Command Line. Each pattern must use a channel
only once, and must consist of exactly 76 channels. There are 202 channels available ranging from Channel 1 at
2.4016 GHz up to Channel 202 at 2.4820 GHz
MHX-2400 Operating Manual: Appendix F. Hopping Patterns
37
38
MHX-2400 Operating Manual: Appendix F. Hopping Patterns
G. Technical Specifications
Electrical/Physical
Data Interface
Asynchronous Serial Port, TTL Levels
Signals
Sig. Gnd, TX, RX, DCD, DSR, DTR, RTS, CTS
Bandwidth / Data Rate
2,400 - 115,200 bps, uncompressed half-duplex,
Approx. 100 kbps sustained in intelligent asymmetrical full-duplex
transmission mode
Communications Range1
30 kilometres (19 miles)
Power Requirements
5 VDC, 1.0 Amp
Power Consumption
700 mA max, 450 mA typical at 1W transmit; 200 mA receive
Operating Frequency
2.4000 GHz to 2.4835 GHz
System Gain
135 dB
Sensitivity
-105 dBm
Output Power
10, 50, 100, 250, 500, 750, 1000mW (user-selectable)
Spreading Code
Frequency Hopping
Hopping Patterns
20 pseudo-random, user-selectable
Error Detection
CRC-16 with auto re-transmit
Error Correction
Dimensions (LxWxH)
User-selectable Forward Error Correction (FEC)
Encl: 3.5” x 2.1” x 1.” (90 mm x 53 mm x 25 mm)
Weight
75 grams
Operating Environment
Temperature: -40 to +70°C
Humidity: 5 to 95%, non-condensing
Storage Temperature
-40 to 90°C
1. Clear line-of-sight, elevated high-gain antennas.
MHX-2400 Operating Manual: Appendix G. Technical Specifications
39
40
MHX-2400 Operating Manual: Appendix G. Technical Specifications
H. Glossary
Terminology Used in the MHX-2400 Operating Manual
Asynchronous communications A method of
telecommunications in which units of single bytes
of data are sent separately and at an arbitrary time
(not periodically or referenced to a clock). Bytes
are “padded” with start and stop bits to distinguish
each as a unit for the receiving end, which need
not be synchronized with the sending terminal.
Attenuation
The loss of signal power through
equipment, lines/cables, or other transmission
devices. Measured in decibels (dB).
Bandwidth The information-carrying capacity of a
data transmission medium or device, usually
expressed in bits/second (bps).
Baud
Unit of signaling speed equivalent to the
number of discrete conditions or events per
second. If each signal event represents only one
bit condition, then baud rate equals bits per
second (bps) – this is generally true of the serial
data port, so baud and bps have been used
interchangeably in this manual when referring to
the serial port; this is not always the case during
the DCE-to-DCE communications, where a
number of modulation techniques are used to
increase the bps rate over the baud rate.
Bit
The smallest unit of information in a binary
system, represented by either a 1 or 0.
Abbreviated “b”.
Bits per second (b/s or bps) A measure of data
transmission rate in serial communications. Also
see baud.
Byte A group of bits, generally 8 bits in length. A
byte typically represents a character of data.
Abbreviated “B”.
Characters per second (cps) A measure of data
transmission rate for common exchanges of data.
A character is usually represented by 10 bits: an 8bit byte plus two additional bits for marking the
start and stop. Thus, in most cases (but not
always), cps is related to bits per second (bps) by
a 1:10 ratio.
CRC (Cyclic Redundancy Check) An error-detection
scheme for transmitted data. Performed by using
a polynomial algorithm on data, and appending a
checksum to the end of the packet. At the
MHX-2400 Operating Manual: Appendix H. Glossary
receiving end, a similar algorithm is performed
and checked against the transmitted checksum.
Crossover cable (Also known as rollover, null-
modem, or modem-eliminator cable) A cable
which allows direct DTE-to-DTE connection
without intermediate DCEs typically used to
bridge the two communicating devices. Can also
be used to make cabled DCE-to-DCE connections.
The name is derived from “crossing” or “rolling”
several lines, including the TX and RX lines so
that transmitted data from one DTE is received on
the RX pin of the other DTE and vice-versa.
Data Communications Equipment (DCE, also
referred to as Data Circuit-Terminating
Equipment, Data Set) A device which facilitates a
communications connection between Data
Terminal Equipment (DTEs). Often, two or more
compatible DCE devices are used to “bridge”
DTEs which need to exchange data. A DCE
performs signal encoding, decoding, and
conversion of data sent/received by the DTE, and
transmits/receives data with another DCE.
Common example is a modem.
Data Terminal Equipment
(DTE) An enddevice which sends/receives data to/from a DCE,
often providing a user-interface for information
exchange. Common examples are computers,
terminals, and printers.
dBm
Stands for “Decibels referenced to one
milliwatt (1 mW)”. A standard unit of power
level commonly used in RF and communications
(n/10)
work. n dBm is equal to 10
milliwatt, so
0dBm = 1mW, -10dBm = 0.1mW, -20dBm =
0.01mW, etc.
DCE See Data Communications Equipment.
DTE See Data Terminal Equipment.
Flow Control
A method of moderating the
transmission of data so that all devices within the
communications link (DTEs and DCEs) transmit
and receive only as much data as they can handle
at once. This prevents devices from sending data
which cannot be received at the other end due to
conditions such as a full buffer or hardware not in
a ready state. This is ideally handled by hardware
using flow-control and handshaking signals, but
41
can be controlled also by software using X-ON/XOFF (transmitter on/off) commands.
Frequency-hopping
A type of spread spectrum
communication whereby the carrier frequency
used between transmitter and receiver changes
repeatedly in a synchronized fashion according to
a specified algorithm or table. This minimizes
unauthorized
jamming
(interference)
and
interception of telecommunications.
Full-duplex
Where data can be transmitted,
simultaneously
and
independently,
bidirectionally.
Half duplex
Exists when the communications
medium supports bi-directional transmission, but
data can only travel in one direction at the same
time.
Handshaking
A flow-control procedure for
establishing data communications whereby
devices indicate that data is to be sent and await
appropriate signals that allow them to proceed.
Line-of-sight
Condition in which a transmitted
signal can reach its destination by travelling a
straight path, without being absorbed and/or
bounced by objects in its path.
Master The station which controls and/or polls one
or more Slave stations in a point-to-point or pointto-multipoint network. Often functions as a server
or hub for the network.
Non-volatile memory
Memory which retains
information which is written to it.
Null modem cable See Crossover cable.
Point-to-point A simple communications network
in which only two DTEs are participants.
Point-to-multipoint
A communications network
in which a Master DTE communicates with two or
more Slave DTEs.
Repeater A device which automatically amplifies
or restores signals to compensate for distortion
and/or attenuation prior to retransmission. A
repeater is typically used to extend the distance
for which data can be reliably transmitted using a
particular medium or communications device.
many newer devices use a compact 9-pin
connector with only the essential signaling lines
used in asynchronous serial communications.
Lines have two possible states: “high” (on, active,
asserted, carrying +3 to +25 V) or “low” (off,
inactive, disasserted, carrying -3 to -25 V).
RTU
(Remote Terminal Unit) A common term
describing a DTE device which is part of a widearea network. Often a RTU performs data I/O and
transmits the data to a centralized station.
Serial communications
A common mode of
data transmission whereby character bits are sent
sequentially, one at a time, using the same
signaling line.
Contrast with parallel
communications where all bits of a byte are
transmitted at once, usually requiring a signal line
for each bit.
Shielded cable
Interface medium which is
internally shrouded by a protective sheath to
minimize external electromagnetic interference
(“noise”).
Slave A station which is controlled and/or polled by
the Master station for communications. Typically
represents one end of a point-to-point connection,
or one of the terminal nodes in a point-tomultipoint network. Often a RTU is linked by a
Slave DCE.
Spread spectrum
A method of transmitting a
signal over a wider bandwidth (using several
frequencies) than the minimum necessary for the
originally narrowband signal. A number of
techniques are used to achieve spread spectrum
telecommunications, including frequency hopping.
Spread spectrum provides the possibility of
sharing the same band amongst many users while
increasing the tolerance to interference and noise,
and enhancing privacy of communications.
Throughput A measure of the rate of data trans-
mission passing through a data communication
system, often expressed as bits or characters per
second (bps or cps).
RS-232
(Recommended Standard 232; more
accurately, RS-232C or EIA/TIA-232E) Defined
by the EIA, a widely known standard electrical
and physical interface for linking DCEs and DTEs
for serial data communications. Traditionally
specifies a 25-pin D-sub connector, although
42
MHX-2400 Operating Manual: Appendix H . Glossary

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