Murata Electronics North America DNT500P DNT500 900 MHz Transceiver Module User Manual part 1

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DNT500 Series
900 MHz Spread Spectrum Wireless
Industrial Transceivers
Integration Guide
3079 Premiere Pkwy Ste 140
Norcross, Georgia 30097
www.rfm.com
+1 (678) 684-2000
Important Regulatory Information
RFM Product FCC ID: HSW-DNT500P
IC 4492A-DNT500P
Note: This unit 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 when the equipment is operated in a commercial environment. This
equipment generates, uses, and can radiate radio frequency energy and, if not installed and used
in accordance with the instruction manual, may cause harmful interference to radio communications. Operation of this equipment in a residential area is likely to cause harmful interference in
which case the user will be required to correct the interference at their expense.
The DNT500 has been designed to operate with the RWA092R 2 dBi reverse-pin (polarity) SMA sleeved
dipole antenna (U.FL female to reverse-pin SMA female adaptor or equivalent required).
See section 3.10 of this manual for regulatory notices and labeling requirements. Changes or modifications not expressly approved by RFM may void the user’s authority to operate the module.
TABLE OF CONTENTS
1.
INTRODUCTION................................................................................................................ 1
1.1
Why Spread Spectrum?................................................................................................... 1
1.2
Frequency Hopping versus Direct Sequence .................................................................. 2
2.
DNT500 RADIO OPERATION .......................................................................................... 4
Network Synchronization and Registration .................................................................... 4
Transparent and Protocol Serial Port Modes................................................................... 4
RF Data Communications ............................................................................................... 5
RF Transmission Error Control....................................................................................... 5
Network Configurations.................................................................................................. 6
2.5.1 Point-to-Point Network Operation .......................................................................... 6
2.5.2 Point-to-Multipoint Network Operation.................................................................. 7
Full-Duplex Serial Data Communications ...................................................................... 7
Channel Access ............................................................................................................... 7
2.7.1 CSMA Modes.......................................................................................................... 8
2.7.2 TDMA Modes ......................................................................................................... 9
2.7.3 Network Configuration Planning .......................................................................... 10
2.7.4 Serial Port Operation............................................................................................. 12
2.7.5 Sleep Mode............................................................................................................ 13
2.1
2.2
2.3
2.4
2.5
2.6
2.7
3.
DNT500 HARDWARE...................................................................................................... 14
3.1
Specifications ................................................................................................................ 15
3.2
Module Interface ........................................................................................................... 16
3.3
Input Voltages ............................................................................................................... 17
3.4
ESD and Transient Protection ....................................................................................... 17
3.5
Interfacing to 5 V Logic Systems.................................................................................. 18
3.6
Power-On Reset Requirements ..................................................................................... 18
3.7
Analog RSSI Output...................................................................................................... 18
3.8
Mounting and Enclosures.............................................................................................. 18
3.9
Connecting Antennas .................................................................................................... 19
3.10 Labeling and Notices..................................................................................................... 19
4.
PROTOCOL MESSAGES ................................................................................................. 20
4.1
Protocol Message Formats ............................................................................................ 20
4.1.1 Serial message types.............................................................................................. 20
4.1.2 Escape sequence.................................................................................................... 22
4.1.3 CFG select pin....................................................................................................... 23
4.1.4 Flow control .......................................................................................................... 23
4.1.5 Protocol mode data message example................................................................... 23
4.2
Configuration Registers................................................................................................. 23
4.2.1 Bank 0 - Transceiver Setup ................................................................................... 24
4.2.2 Bank 1 - System Settings ...................................................................................... 26
4.2.3 Bank 2 - Status Registers (read only)................................................................... 28
4.2.4 Bank 3 - Serial...................................................................................................... 30
4.2.5
4.2.6
4.2.7
4.2.8
4.2.9
4.2.10
5.
5.1
5.2
5.3
5.4
5.5
5.6
Bank 4 - Host Protocol Settings ........................................................................... 31
Bank 5 - I/O Peripheral Registers ........................................................................ 33
Bank 6 - I/O setup ................................................................................................ 33
Bank FF - Special function................................................................................... 36
Protocol Mode Configuration/Sensor Message Examples.................................... 36
Protocol Mode Event Message Examples............................................................. 37
DNT500 DEVELOPER’S KIT .......................................................................................... 38
DNT500DK Kit Contents.............................................................................................. 38
Additional Items Needed............................................................................................... 38
Developer’s Kit Default Operating Configuration........................................................ 39
Development Kit Hardware Assembly ......................................................................... 39
DNT500 Wizard Utility Program.................................................................................. 41
DNT500 Interface Board Features ................................................................................ 47
6.
Demonstration Procedure ................................................................................................... 50
7.
Troubleshooting.................................................................................................................. 51
8.
8.1
8.2
8.3
9.
APPENDICES.................................................................................................................... 52
Ordering Information .................................................................................................... 52
Technical Support ......................................................................................................... 52
DNT500 Mechanical Specifications ............................................................................. 53
Warranty............................................................................................................................. 55
DNT500
1. INTRODUCTION
The DNT500 series transceivers provide highly reliable wireless connectivity for either
point-to-point or point-to-multipoint applications. Frequency hopping spread spectrum
(FHSS) technology ensures maximum resistance to multipath fading and robustness in
the presence of interfering signals, while operation in the 900 MHz ISM band allows
license-free use in the US, Canada, Australia and New Zealand. The DNT500 supports
all standard serial data rates for host communications from 1.2 to 460.8 kb/s. On-board
data buffering and an error-correcting air protocol provide smooth data flow and simplify the task of integration with existing applications. Key DNT500 features include:
Multipath fading impervious frequency hopping technology with
up to 50 frequency channels
(902 to 928 MHz).
Selectable 0, 10, 19, 24, 27 or
28 dBm transmit power with a
firmware interlock of 19 dBm maximum for 500 kb/s operation.
Supports point-to-point or multipoint applications.
Built-in data scrambling reduces
possibility of eavesdropping.
Meets FCC rules 15.247 for license-free operation.
Nonvolatile memory stores configuration when powered off.
20 mile plus range with omnidirectional antennas.
Dynamic TDMA slot assignment
that maximizes throughput.
Transparent ARQ protocol with
buffering ensures data integrity.
Simple serial interface handles both
data and control at up to 460.8 kb/s.
1.1 Why Spread Spectrum?
A radio transmission channel can be very hostile, corrupted by noise, path loss and
interfering transmissions from other radios. Even in an interference-free environment,
radio performance faces serious degradation through a phenomenon known as multipath fading. Multipath fading results when two or more reflected rays of the transmitted signal arrive at the receiving antenna with opposing phases, thereby partially or
completely canceling the signal. This is a problem particularly prevalent in indoor installations. In the frequency domain, a multipath fade can be described as a frequency-selective notch that shifts in location and intensity over time as reflections
change due to motion of the radio or objects within its range. At any given time, multipath fades will typically occupy 1% - 2% of the band. This means that from a probabilistic viewpoint, a conventional radio system faces a 1% - 2% chance of signal impairment at any given time due to multipath.
Spread spectrum reduces the vulnerability of a radio system to interference from both
jammers and multipath fading by distributing the transmitted signal over a larger region of the frequency band than would otherwise be necessary to send the information. This allows the signal to be reconstructed even though part of it may be lost or
corrupted in transit.
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Figure1
Narrowband vs. spread spectrum in the presence of interference
1.2 Frequency Hopping versus Direct Sequence
The two primary approaches to spread spectrum are direct sequence spread spectrum
(DSSS) and frequency hopping spread spectrum (FHSS), either of which can generally be adapted to a given application. Direct sequence spread spectrum is produced
by multiplying the transmitted data stream by a much faster, noise-like repeating pattern. The ratio by which this modulating pattern exceeds the bit rate of the base-band
data is called the processing gain, and is equal to the amount of rejection the system
affords against narrowband interference from multipath and jammers. Transmitting
the data signal as usual, but varying the carrier frequency rapidly according to a
pseudo-random pattern over a broad range of channels produces a frequency hopping
spectrum system.
Figure 2
Forms of spread spectrum
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DNT500
One disadvantage of direct sequence systems is that due to spectrum constraints and
the design difficulties of broadband receivers, they generally employ only a minimal
amount of spreading (typically no more than the minimum required by the regulating
agencies). For this reason, the ability of DSSS systems to overcome fading and inband jammers is relatively weak. By contrast, FHSS systems are capable of probing
the entire band if necessary to find a channel free of interference. Essentially, this
means that a FHSS system will degrade gracefully as the channel gets noisier while a
DSSS system may exhibit uneven coverage or work well until a certain point and
then give out completely.
Because it offers greater immunity to interfering signals, FHSS is often the preferred
choice for co-located systems. Since direct sequence signals are very wide, they tend
to offer few non-overlapping channels, whereas multiple hoppers may interleave
with less interference. Frequency hopping does carry some disadvantage in that as
the transmitter cycles through the hopping pattern it is nearly certain to visit a few
blocked channels where no data can be sent. If these channels are the same from trip
to trip, they can be memorized and avoided. Unfortunately, this is generally not the
case, as it may take several seconds to completely cover the hop sequence during
which time the multipath delay profile may have changed substantially. To ensure
seamless operation throughout these outages, a hopping radio must be capable of
buffering its data until a clear channel can be found. A second consideration of frequency hopping systems is that they require an initial acquisition period during
which the receiver must lock on to the moving carrier of the transmitter before any
data can be sent, which typically takes several seconds. In summary, frequency hopping systems generally feature greater coverage and channel utilization than comparable direct sequence systems. Of course, other implementation factors such as size,
cost, power consumption and ease of implementation must also be considered before
a final radio design choice can be made.
DNT500 series modules achieve regulatory certification under FHSS rules at air data
rates of 38.4, 115.2 and 200 kb/s. At 500 kb/s, the DNT500 series modules achieve
regulatory certification under “digital modulation” or DTS rules. At 500 kb/s
DNT500 series modules still employ frequency hopping to mitigate the effects of interference and multipath fading, but hop on fewer, more widely spaced frequencies
than at lower data rates.
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2. DNT500 RADIO OPERATION
2.1 Network Synchronization and Registration
As discussed above, frequency hopping radios such as the DNT500 periodically change
the frequency at which they transmit. In order for the other radios in the network to receive the transmission, they must be listening to the frequency over which the current
transmission is being sent. To do this, all the radios in the network must be synchronized
and must be set to the same hopping pattern.
In point-to-point or point-to-multipoint networks, one radio module is designated as the
base station. All other radios are designated remotes. One of the responsibilities of the
base station is to transmit a synchronization signal to the remotes to allow them to synchronize with the base station. Since the remotes know the hopping pattern, once they are
synchronized with the base station, they know which frequency to hop to and when.
Every time the base station hops to a different frequency, it immediately transmits a synchronizing signal.
When a remote is powered on, it rapidly scans the frequency band for the synchronizing
signal. Since the base station is transmitting up to 50 frequencies and the remote is scanning up to 50 frequencies, it can take several seconds for a remote to synchronize with
the base station.
Once a remote has synchronized with the base station, it will request registration information to allow it to join the network. Registration can be handled automatically by the base
station, or it can be controlled by allowing the base station host application to authenticate the remote for registration. When a remote is registered, it receives several network
parameters from the base station, including HopDuration, Nwk_ID, FrequencyBand and
Nwk_Key (see Section 5.2 for parameter details). Note that if a registration parameter is
changed at the base station, it will update the parameter in the remotes over the air.
Among other things, registration allows the tracking of remotes entering and leaving a
network, up to a limit of 255 remotes. The base station builds a table of serial numbers of
registered remotes using their three-byte serial numbers (MAC addresses). To detect if a
remote has gone offline or out of range, the registration is “leased” must be “renewed”
once every 250 hops. Any transmission from a remote running on a leased registration
will renew its lease with the base station.
2.2 Transparent and Protocol Serial Port Modes
DNT500 radios can work in two serial port data modes: transparent and packet protocol.
Transparent formatting is simply the raw user data. Packet protocol formatting uses a
framing character, length byte, addressing, command bytes, etc. Transparent mode operation is especially useful in point-to-point systems that act as simple cable replacements.
In point-to-multipoint systems where the base station needs to send data specifically to
each remote, protocol formatting must be used. Protocol formatting is also required for
configuration commands and responses, and sensor I/O commands and responses. Protocol formatting details are covered in Section 5.
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The DNT500 provides two ways to switch between transparent and protocol modes. If
CFG input Pin 18 on the DNT500 is switched from logic high to low, protocol mode is
invoked. Or if the ASCII escape sequence “DNT500” is sent (without quotation marks) to
the primary serial input following at least a 20 ms pause in data flow, the DNT500 will
switch to the protocol mode. When input Pin 18 is switched from logic low to high, or an
ExitProtocolMode command is sent to the primary serial input, the DNT500 will switch
to transparent operation. Note that if the escape sequence is used to switch to protocol
mode, the sequence will be transmitted before protocol mode is invoked.
When operating in transparent mode, two configuration parameters control when a
DNT500 radio will send the data in its transmit buffer. The MinPacketLength parameter
sets the minimum number of bytes that must be present in the transmit buffer to trigger a
transmission. The TxTimeout parameter sets the maximum time data in the transmit
buffer will be held before transmitting it, even if the number of data bytes is less than
MinPacketLength. The default value for both the MinPacketLength and the TxTimeout
parameters is zero, so that any bytes that arrive in the DNT500 transmit buffer will be
sent on the next hop. As discussed in Section 2.7.3, it is useful to set these parameters to
non-zero values in point-to-multipoint systems where some or all the remotes are in
transparent mode.
2.3 RF Data Communications
At the beginning of each hop, the base station transmits a synchronizing signal. After the
synchronizing signal has been sent, the base will transmit any user data in its transmit
buffer, unless in transparent mode the MinPacketLength and/or TxTimeout parameters
have been set to non-zero. The maximum amount of user data that the base station can
transmit per hop is limited by the BaseSlotSize parameter, which has a maximum value of
232 bytes. If there is no user data or reception acknowledgements (ACKs) to be sent on a
hop, the base station will only transmit the synchronization signal.
The operation for remotes is similar to the base station, but without the synchronizing
signal. The RemoteSlotSize parameter sets the maximum number of user bytes a remote
can transmit on one hop, up to a limit of 243 bytes per hop. The RemoteSlotSize must be
coordinated with the HopDuration and BaseSlotSize parameters and the number of registered remotes, as discussed in Section 2.5.3. The MinPacketLength and TxTimeout parameters operate in a remote in the same manner as in the base station.
2.4 RF Transmission Error Control
The DNT500 supports two error control modes: redundant transmissions and automatic
transmission repeats (ARQ). In both modes, the radio will detect and discard any duplicates of messages it receives so that the host application will only receive one copy of a
given packet. Packet IDs are included in each transmission to allow recipients to identify
if the packet is new or has been received before.
In the redundant transmission mode, packets are repeated a fixed number of times without any acknowledgement (ACK) from the recipient. This error control method is useful
in latency-critical applications such as voice, video and real-time telemetry, where only a
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few transmission repeats can be made before the current data is replaced with new data. It
is wasteful of bandwidth to send ACKs in these types of applications. Redundant transmissions are also used where messages are broadcast to multiple recipients and it is not
practical to receive ACKs from each one.
In ARQ mode, a packet is sent and an acknowledgement is expected on the next hop. If
an acknowledgement is not received, the packet is transmitted again on the next available
hop until either an ACK is received or the maximum number of attempts is exhausted. If
the AttemptLimit parameter is set to its maximum value, a packet transmission will be retried without limit until the packet is acknowledged. This is useful in some point-to-point
cable replacement applications where it is important that data truly be 100% error-free,
even if the destination remote goes out of range temporarily.
2.5 Network Configurations
The DNT500 supports two network configurations: point-to-point and point-tomultipoint. In a point-to-point network, one radio is set up as the base station and the
other radio is set up as a remote. In a point-to-multipoint network, a star topology is used
with the radio set up as a base station acting as the central communications point and all
other radios in the network set up as remotes. In this configuration, all communications
take place between the base station and any one of the remotes. Remotes cannot communicate directly with each other. It should be noted that point-to-point operation is a subset
of the point-to-multipoint operation, so there is no need to specify one or the other.
2.5.1 Point-to-Point Network Operation
Most point-to-point networks act as serial cable replacements and both the base station
and the remote use transparent mode. Unless the MinPacketLength and TxTimeout parameters have been set to non-zero, the base station will send the data in its transmit
buffer on each hop, up to the limit set by the BaseSlotSize parameter, less ACK bytes. If
the base station is buffering more data than can be sent on one hop, the remaining data
will be sent on subsequent hops. The base station adds the address of the remote, a packet
sequence number and error checking bytes to the data when it is transmitted. These additional bytes are not output at the remote in transparent mode. The sequence number is
used in acknowledging successful transmissions and in retransmitting corrupted transmissions. A two-byte CRC and a one-byte checksum allows a received transmission to be
checked for errors. When a transmission is received by the remote, it will be acknowledged if it checks error free. If no acknowledgment is received, the base station will retransmit the same data on the next hop.
In point-to-point operation, by default the remote will send the data in its transmit buffer
on each hop, up to the limit set by its RemoteSlotSize parameter. If desired, the MinPacketLength and TxTimeout parameters can be set to non-zero values, which configures the
remote to wait until the specified amount of data is available or the specified delay had
expired before transmitting. If the remote is buffering more data than can be sent on one
hop, it will send the remaining data in subsequent hops. The remote adds its own address,
a packet sequence number and error checking bytes to the data when it is transmitted.
These additional bytes are not output at the base station if the base station is in transparent mode. When a transmission is received by the base station, it will be acknowledged if
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DNT500
it checks error free. If no acknowledgment is received, the remote will retransmit the
same data on the next hop.
2.5.2 Point-to-Multipoint Network Operation
In a point-to-multipoint network, the base station is usually configured for protocol formatting, unless the applications running on each remote can determine the data’s destination from the data itself. Protocol formatting adds the address of the destination (remote)
and other overhead bytes to the user data. If the addressed remote is using transparent formatting, the destination address and the other overhead bytes are removed. If the remote
is using protocol formatting, the destination address and the other overhead bytes are output with the user data.
A remote can operate in a point-to-multipoint network using either transparent or protocol formatting, as the base station is always the destination. In transparent operation, a
remote will add addressing, a packet sequence number and error checking bytes as in a
point-to-point network. When the base station receives the transmission, it will format the
data to its host according to its formatting configuration. A remote running in transparent
mode in a point-to-multipoint network will often have the MinPacketLength and TxTimeout parameters set to non-zero values to reduce the chance of transmission collisions.
This is covered in more detail in section 2.6.3.
2.6 Full-Duplex Serial Data Communications
From an host application’s perspective, DNT500 serial communications appear full duplex. Both the base station host application and each remote host application can send
and receive serial data at the same time. At the radio level, the base station and remotes
do not actually transmit at the same time. If they did, the transmissions would collide. As
discussed earlier, the base station transmits a synchronization signal at the beginning of
each hop followed by its user data. After the base station transmission, the remotes can
transmit. Each base station and remote transmission may contain all or part of a complete
message from its host application. From an application’s perspective, the radios are
communicating in full duplex since the base station can receive data from a remote before
it completes the transmission of a message to the remote and visa versa.
2.7 Channel Access
The DNT500 provides two methods of channel access: CSMA or TDMA. Each method
supports several options as shown in the table below. The channel access setting is distributed to all remotes in the base station status packet, so changing it at the base station
sets the entire network. Carrier Sense Multiple Access (CSMA) is very effective at handling packets with varying amounts of data and/or packets sent at random times from a
large number of remotes. The DNT500 includes a CSMA polling mode for coordinated
remotes and a CSMA contention mode for uncoordinated and/or reporting remotes. Time
Division Multiple Access (TDMA) provides a scheduled time slot for each remote to
transmit on each hop. The default DNT500 access mode is CSMA polling.
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DNT500
Access Mode
2 (default)
Description
CSMA polling
CSMA contention
TDMA dynamic slots
TDMA fixed slots
TDMA with PTT
Max # of Remotes
1024
1024
up to 15
up to 15
1024
Remote Slot Size
manual
manual
automatic
automatic
automatic
2.7.1 CSMA Modes
When using CSMA, each remote with data to send listens to see if the channel is clear
and then transmits. If the channel is not clear, a remote will wait a random period of time
and listen again. CSMA works best when a large or variable number of remotes transmit
infrequent bursts of data. There is no absolute to the number of remote radios that can be
supported in this mode. For a DNT500 network, a maximum of 255 remotes can be supported if base station join-leave tracking is required, or a maximum of 1024 remotes is
suggested if base station join-leave tracking is not required. The illustration below compares TDMA to CSMA operation.
There are two important parameters related to CSMA operation. The CSMA_MaxBackoff
parameter defines the maximum time that a remote will wait after a collision before attempting to send the packet again (back-off interval). The CSMA_Persistence parameter
sets the probability that a remote will transmit immediately rather than first waiting for a
pre-transmit delay interval. Persistence is a one-byte parameter with a range of 0x00 to
0xFF:
0xFF = 100% probability
0x00 = 0% probability
CSMA polling (Mode 0) is used for point-to-point systems and point-to-multipoint systems where only one remote at a time can receive data to transmit (ModBus, etc.). Since
only one remote will attempt to transmits at a time, the CSMA_Persistence parameter is
fixed at 0xFF for minimum latency. This mode provides maximum throughput since
there is no contention between remotes and the entire portion of the hop frame following
the base station transmission is available for a remote to transmit. The user can set
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DNT500
CSMA_MaxBackoff, BaseSlotSize and RemoteSlotSize parameters when using this mode.
Note that a CSMA_Persistence parameter setting of 0xFF would lead to collisions if more
than one remote tried to transmit. Applications where more than one remote can receive
serial data to transmit at the same time, or where periodic reporting and/or event reporting are enabled should not use this mode.
CSMA Contention (Mode 1) provides classical CSMA channel access, and gives the user
control over both the CSMA_MaxBackoff and CSMA_Persistence parameters. This mode
is well-suited for large numbers of uncoordinated remotes, and/or where periodic/event
reporting is used. In addition to CSMA_MaxBackoff and CSMA_Persistence, the user can
set the BaseSlotSize and RemoteSlotSize parameters when using this mode. The following
guidelines are suggested for setting CSMA_Persistence:
•
•
For lightly loaded CSMA contention networks, increase CSMA_Persistence to
0x80 or higher to reduce latency.
For heavily loaded CSMA contention networks, reduce CSMA_Persistence to
0x20 or lower for better throughput.
CSMA modes can optionally track remotes entering and leaving the network for up to
255 remotes. The base station is operated in protocol mode and is configured to generate
a CONNECT message for its host when a remote registers, and a DISCONNECT message when the remote’s registration lease expires.
The base station in a CSMA network can generate CONNECT messages for more than
255 remotes. This allows the host application to track remotes entering and leaving a
large CSMA network by creating a table of MAC addresses and periodically sending a
ping to each remote in the table. Failure to answer the ping indicates the remote is no
longer active in the network.
The CSMA modes work well in many applications, but CSMA does have some limitations, as summarized below:
•
•
Bandwidth is not guaranteed to any remote.
Marginal RF links to some remotes can create a relatively high chance of
collisions in heavily loaded networks.
2.7.2 TDMA Modes
The TDMA modes provide guaranteed bandwidth to some or all of the remotes in the
network. Remotes that register with the base station receive several special parameters,
including ranging information and a specific channel access slot assignment. TDMA registrations are always leased and must be renewed every 250 hops. The DNT500 provides
three different modes of TDMA access, as discussed below.
TDMA Dynamic Slots (Mode 2) is used for general-purpose TDMA applications where
scaling the capacity per slot to the number of active remotes is automatic. Each remote
that registers with the base receives an equal time slice. As new remotes join, the size of
the TDMA slots shrink accordingly. The number of slots, individual slot start times, and
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the RemoteSlotSize are computed automatically by the DNT500 network in this mode.
The user should note that the bandwidth to each remote will change immediately as remotes join and leave the network.
TDMA Fixed Slots (Mode 3) is used for applications that have fixed data throughput requirements, such as isochronous voice or streaming telemetry. The slot start time and the
RemoteSlotSize are computed automatically by the DNT500 network in this mode. The
user must set the number of slots.
TDMA with PTT (Mode 4) supports remotes with a "push-to-talk" feature, also referred
to as "listen-mostly" remotes. This mode uses fixed slot allocations. Remotes can be registered for all but the last slot. The last slot reserved for the group of remotes that are usually listening, but occasionally need to transmit. In essence, the last slot is a shared channel for this group of remotes. When one of them has data to send it keys its transmitter
much like a walkie-talkie, hence the name push-to-talk (PTT).
The slot start time and the RemoteSlotSize are computed automatically by the DNT500
network in this mode. The user must specify the number of slots. The last slot is reserved
for the PTT remotes. The user must configure PTT remotes individually to select Mode 4
operation. The network makes no guarantee that PTT remote transmissions will not collide in the shared slot. The user's application must ensure that no more than one PTT remote is using the slot at a time.
2.7.3 Network Configuration Planning
Some planning is necessary for a DNT500 network to coordinate the RF_DataRate,
HopDuration, BaseSlotSize, RemoteSlotSize, MinPacketLength, TxTimeout and
TDMA_MaxNumSlots parameters to achieve a practical configuration. This is true even
for modes that automatically compute some of these parameters. Each parameter has a
limited range of usable values, as shown in the table below:
Parameter
Useable Range
RF_DataRate
0..3
HopDuration
40..4095
TDMA_MaxNumSlots
1..15
BaseSlotSize
6..232
RemoteSlotSize
3..243
MinPacketLength
0..255
TxTimeOut
0..255
Value
500, 200, 115.2 and 38.4 kb/s
2..204.75 ms (0.05 ms/count)
max number of TDMA slots (MNS) for remotes
max number of user data bytes transmitted per hop
max number of user data bytes transmitted per hop
0..255 bytes
0..255 ms (1 ms/count)
The highest RF data rate, 500 kb/s, provides the highest throughput and the most flexibility with respect to the other parameters. The maximum RF power that can be used at
500 kb/s is 19 dBm. The three lower data rates can run up to 28 dBm of RF power, and
the receiver becomes progressively more sensitive as the data rate is lowered. So for
greatest operating range, one of the three lower RF data rates should be used.
The maximum DNT500 HopDuration setting is about 200 ms regardless of the RF data
rate chosen. For a given data rate, FHSS operation tends to become more robust as hop
duration is reduced. However, running with a shorter hop duration may require setting the
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DNT500
BaseSlotSize and RemoteSlotSize parameters well below their maximum values at the
lower RF data rates. The equation below calculates the minimum hop duration needed at
a given RF data rate for a specific number of remote slots and BaseSlotSize and RemoteSlotSize parameter settings. Support for optimizing a DNT500 configuration for a
specific application is also available from RFM’s Technical Support Group. See Section
10.3. for technical support contact information.
The minimum required hop duration for a DNT500 configuration is:
THD = TBRO + NRS*TRO + TRFB*(BBSS + NRS*BRSS)
Where:
THD
TBRO
NRS
TRO
TRFB
BBSS
BRSS
is the minimum required hop duration in milliseconds
is the base and registration request overhead time for each hop (RF data rate dependent)
is the number of remote slots
is the remote overhead time for each hop (RF data rate dependent)
is the transmission time for one user byte (RF data rate dependent)
is the BaseSlotSize parameter in bytes
is the RemoteSlotSize parameter in bytes
The constants in the equation for each RF data rate are given in the following table:
RF Data Rate
kb/s
38.40
115.2
200
500
TBRO
ms
11.620
4.953
3.540
2.388
TRO
ms
4.817
2.039
1.450
0.970
TRFB
ms
0.2080
0.0694
0.0400
0.0160
For Example 1, consider a point-to-point CSMA Mode 0 system operating at 38.4 kb/s
with the BaseSlotSize parameter set to 133 bytes and the RemoteSlotSize parameter set to
128 bytes. The minimum hop duration needed to support one-hop transmissions of full
slot size messages in both directions for this configuration is:
= 11.620 + 1*4.817 + 0.2080*(133 + 1*128)
= 16.437 + 0.2080*261
= 70.725 ms
The closest programmable hop duration is 70.750 ms.
It should be noted that the base station operating system will commandeer 5 bytes from
the BaseSlotSize allocation in Mode 0 and up to 13 bytes in Mode 1 to send reception acknowledgements (ACKs) back to the remotes. The BaseSlotSize should be sized accordingly. In the above example, the BaseSlotSize parameter is set five bytes larger than the
RemoteSlotSize parameter to accommodate the ACK bytes.
When running a point-to-multipoint network with uncoordinated remotes using CSMA
Mode 1, it is useful to set NRS to a value of 3 or higher in the equation. Although CSMA
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DNT500
does not create reserved time slots for remotes, extending the hop duration this way allows several uncoordinated transmissions of user data and/or periodic/event reports to arrive in the same slot with a relatively few collisions.
The performance of a CSMA Mode 1 system can often be helped by setting the MinPacketLength and TxTimeout parameters on any remotes running transparent mode to
non-zero values, especially if host messages only contain a few bytes each and transmission latency is not critical. For starting point values, set the MinPacketLength equal to the
RemoteSlotSize and TxTimeout to at least three times the hop duration. This will help
avoid excessive transmission collisions due to having many packets transmitted, each carrying only a small amount of user data on top of the relatively large packet overhead
structure.
For Example 2, consider a TDMA Mode 2 or 3 system operating at 500 kb/s. Up to 10
registered remotes need to be accommodated. A BaseSlotSize of 138 bytes is needed, and
each remote needs enough slot time to support a RemoteSlotSize of 64 bytes. The minimum hop duration needed to support this configuration is:
= 2.388 + 10*0.970 + 0.0160*(138 + 10*64)
= 12.088 + 0.0160*778
= 24.536 ms
The closest programmable hop duration is 24.550 ms.
In all TDMA modes, the base station operating system will commandeer one byte from
the BaseSlotSize allocation for each registered remote to send ACKs to the remotes. The
BaseSlotSize and MinPacketLength should be sized accordingly.
2.7.4 Serial Port Operation
DNT500 networks are often used for wireless communication of serial data. The
DNT500 supports serial baud rates from 1.2 to 460.8 kb/s. Listed in the table below are
the supported data rates and their related byte data rates and byte transmission times for
an 8N1 serial port configuration:
Baud Rate
kb/s
1.2
2.4
4.8
9.6
19.2
38.4
115.2
230.4
460.8
Byte Data Rate
kB/s
0.12
0.24
0.48
0.96
1.92
3.84
11.52
23.04
46.08
Byte Transmission Time
ms
8.3333
4.1667
2.0833
1.0417
0.5208
0.2604
0.0868
0.0434
0.0217
To support continuous full-duplex serial port data flow, an RF data rate much higher than
the serial port baud rate is required for FHSS. Radios transmissions are half duplex, and
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DNT500
there are overheads related to hopping frequencies, assembling packets from the serial
port data stream, transmitting them, sending ACK’s to confirm error-free reception, and
occasional transmission retries when errors occur.
For Example 3, consider a CSMA Mode 0 transparent data system operating at 500 kb/s
with the BaseSlotSize parameter set to 133 bytes (128 bytes net after the five byte allocation for sending ACKs) and the RemoteSlotSize parameters set to 128 bytes. The minimum hop duration needed to efficiently support this configuration is:
= 2.388 + 1*0.970 + 0.0160*(133 +1*128)
= 3.358 + 0.0160*261
= 7.534 ms
Setting the hop duration to 7.55 ms, the average full-duplex serial port byte rate that can
be supported under error free conditions is:
128 Bytes /7.55 ms = 16.942 kB/s, or 169.42 kb/s for 8N1
Continuous full-duplex serial port data streams at a baud rate of 115.2 k/bs can be supported by this configuration, provided only occasional RF transmission errors occur. Plan
on an average serial port data flow of 75% of the calculated error-free capacity for general-purpose applications, and 50% of the calculated error-free capacity for RF challenging applications such as vehicle telemetry and heavy industrial process environments.
Most applications do not require continuous serial port data flow. The DNT500 transmit
and receive buffers hold at least 1024 bytes and will accept brief bursts of data at high
baud rates, provided the average serial port data flow such as shown in Example 3 is not
exceeded. It is strongly recommended that the DNT500 host use hardware flow control.
The host must send no more than 32 bytes additional bytes to the DNT500 when the
DNT500 de-asserts the hosts CTS line. In turn, the DNT500 will send no more than one
byte following the host de-asserting its RTS line. Three-wire serial port operation is allowed by connecting the DNT500 CTS output to its RTS input. However, three-wire operation should be limited to applications that send small bursts of data occasionally at an
average serial port data flow less than 50% of the calculated error-free capacity. Data loss
is possible under adverse RF channel conditions when using three-wire serial operation.
2.7.5 Sleep Mode
To save power in applications where a remote transmits infrequently, the DNT500 supports a Sleep Mode. Sleep Mode is entered by switching DTR Pin 11 on the DNT500
from logic low to high. While in Sleep Mode, the DNT500 consumes less than 0.5 mA.
This mode allows a DNT500 to be powered off while its host device remains powered.
After leaving Sleep Mode (Pin 11 low to high), the radio must re-synchronize with the
base station and re-register.
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DNT500
3. DNT500 HARDWARE
D N T 5 0 0 B lo c k D ia g r a m
R S V D
R S V D
A D C _ R E F
R S S I
G P IO 0
G P IO 1
G P IO 2
G P IO 3
P W M A
F ilte r
P W M B
1 0
F ilte r
C L K
S I
D T R
1 1
A D C X
1 2
A D C Y
A D C Z
1 3
E X _ S Y N C
1 5
U A R T 1 _ R X D
1 6
U A R T 1 _ T X D
1 7
C F G
1 8
V C C
1 9
G N D
2 0
P W R
4 3
S O
M ic r o c o n tr o lle r
C S n
R a d io
T /R
T /R
F ilte r
P K T D E T
4 2
4 1
IN T
P R E
1 4
3 3
3 6
3 7
3 8
3 9
4 0
B O O T _ L O A D
3 5
/R E S E T
S P I_ S C L K
U A R T 0 _ T X D
3 4
S P I_ M IS O
3 2
S P I_ M O S I
3 1
V M O D
3 0
S P I_ N S S
2 9
U A R T 0 _ C T S
2 8
U A R T 0 _ R X D
2 7
R S V D
2 6
U A R T 0 _ R T S
2 5
R S V D
2 4
R S V D
2 3
A C T
2 2
D C D
2 1
G P IO 5
R e g
R S V D
3 .6 V
G P IO 4
R e g
G N D
3 .3 V
The major components of the DNT500 include a 900 MHz FHSS transceiver and a 32-bit
microcontroller. The DNT500 operates in the frequency band of 902 to 928 MHz. There
are 32 selectable hopping patterns including patterns compatible the frequency allocations in the US, Canadian, Australian and New Zealand. The DNT500 has six selectable
RF output power levels: 0, 10, 19, 24, 27 and 28 dBm. Also, there are four selectable RF
transmission rates: 38.4, 115.2, 200 and 500 kb/s. The power level is firmware interlocked to a maximum of 19 dBm at 500 kb/s to assure regulatory compliance.
The DNT500 includes a low-noise preamplifier protected by two SAW filters, providing
an excellent blend of receiver sensitivity and out-of-band interference rejection.
The DNT500 provides a variety of hardware interfaces. There are two UART serial ports,
one for data and a second for diagnostics. The data port supports baud rates from 1.2 to
460.8 kb/s and the diagnostic port supports baud rates from 38.4 to 460.8 kb/s. Other
hardware interfaces include an SPI interface, three 10-bit ADC inputs, two 8-bit resolution PWM (DAC) outputs, and six general purpose digital I/O ports. Four of the digital
I/O ports support an optional interrupt-from-sleep mode when configured as inputs. A
3.6 Vdc signal can be switched on the RF output port for diversity antenna control. The
radio is available in two mounting configurations. The DNT500 is designed for solder reflow mounting. The DNT500P is designed for plug-in connector mounting.
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R F IO
DNT500
3.1 Specifications
The DNT500 specifications are listed in the table below:
Characteristic
Sym Notes
Operating Frequency Range
Minimum
Typical
Maximum
Units
927.25
MHz
902.75
FCC 15.247 FHSS
38.4, 115.2 and 200 kb/s, up to 28 dBm
FCC 15.247 Digital Modulation (DSS)
500 kb/s, up to 19 dBm
Number of Hopping Patterns
32
Hop Dwell Time
200
Number of RF Channels
ms
50
RF Data Transmission Rates
38.4, 115.2, 200 and 500
kb/s
-108
dBm
-94
dBm
0, 10, 19, 24, 27, 28
dBm
50
Ω
Receiver Sensitivity
10-5 BER @ 38.4 kb/s
-5
10 BER @ 500 kb/s
Transmitter RF Output Power Levels
Optimum Antenna Impedance
RF Connection
U.FL Connector or PCB Pad
Network Topologies
Point-to-Point, Point-to-Multipoint, Mesh
Access Schemes
TDMA and CSMA
Number of Network Nodes
TDMA
15
CSMA
1024
ADC Input Range
ADC Input Resolution
3.3
10
Signal Source Impedance for ADC Reading
PWM (DAC) Output Range
PWM (DAC) Output Resolution
Primary Serial Port Baud Rates
bits
10
KΩ
3.3
bits
1.2, 2.4, 4.8, 9.6, 19.2, 38.4, 115.2, 230.4, 460.8
kb/s
38.4, 115.2, 230.4, 460.8
kb/s
Diagnostic Serial Port Baud Rates
Digital I/O:
Logic Low Input Level
-0.5
0.8
Logic High Input Level
3.3
Logic Input Internal Pull-up Resistor
50
200
KΩ
Logic Input Internal Pull-down Resistor
Power Supply Voltage Range
VCC
50
180
KΩ
+3.3
+5.5
Vdc
10
mVP-P
Power Supply Voltage Ripple
Receive Mode Current
mA
50
Transmit Mode Current
900
mA
DTR High Sleep Current
0.5
mA
Operating Temperature Range
-40
85
Operating Relative Humidity Range
10
90
1. RF output power is interlocked in firmware to a maximum of 19 dBm at the 500 kb/s RF data rate to assure compliance
with regulatory requirements.
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DNT500
3.2 Module Interface
Electrical connections to the DNT500 are made through the I/O pads and through the I/O
pins on the DNT500P. The hardware I/O functions are detailed in the table below:
Pad
Name
Description
RSVD
Reserved pad. Leave unconnected.
RSVD
Reserved pad. Leave unconnected.
ADC_REF
RSSI
GPIO0
Configurable digital I/O port 0. When configured as an input, an internal pull-up resistor can be
selected and interrupt from sleep can be invoked. When configured as an output, the power-on
state is also configurable.
GPIO1
Configurable digital I/O port 1. Same configuration options as GPIO0.
GPIO2
Configurable digital I/O port 2. Same configuration options as GPIO0.
GPIO3
Configurable digital I/O port 3. Same configuration options as GPIO0.
PWM0
Pulse-width modulated output 0 with internal low-pass filter. Provides an 8-bit DAC resolution.
10
PWM1
Pulse-width modulated output 1 with internal low-pass filter. Provides an 8-bit DAC resolution.
11
SLEEP
Default functionality is active high module sleep input. When switched low after sleep, the
module executes a power-on reset.
12
ADC0
10-bit ADC input 0. Full scale reading is referenced to the ADC_REF input.
13
ADC1
10-bit ADC input 1. Full scale reading is referenced to the ADC_REF input.
14
ADC2
10-bit ADC input 2. Full scale reading is referenced to the ADC_REF input.
15
EX_SYNC
16
DIAG_TX
Diagnostic output (for factory use).
17
DIAG_RX
Diagnostic input (for factory use).
18
/CFG
Protocol selection input. Leave unconnected when using software commands to select transparent/protocol mode (default is transparent mode). Logic low selects protocol mode, logic high
selects transparent mode.
19
VCC
Power supply input, +3.3 to +5.5 Vdc.
20
GND
Power supply and signal ground. Connect to the host circuit board ground.
21
GND
Power supply and signal ground. Connect to the host circuit board ground.
22
GPIO4
Configurable digital I/O port 4. When configured as an input, an internal pull-up resistor can be
selected. When configured as an output, the power-on state is configurable.
23
GPIO5
Configurable digital I/O port 5. Same configuration options as GPIO4.
24
RSVD
Reserved pad. Leave unconnected.
25
ACT
Data activity output, logic high when data is being transmitted or received.
26
/DCD
Default functionality is data carrier detect output, which provides a logic low on a remote when
the module is locked to FHSS hopping pattern and logic low on a base station when at least
one remote is connected to it.
ADC supply and external full scale reference voltage input. Voltage range is 2.4 to 3.3 Vdc.
Connect pad 34 to this input to reference the ADC full scale reading to the module’s 3.3 V
regulated supply.
Analog voltage proportional to received signal strength, range 0 to 3.3 V.
Optional rising-edge triggered input for synchronizing co-located base stations. See ExternalSyncEn on Page 25 for additional details.
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DNT500
Pad
Name
Description
27
RSVD
Reserved pad. Leave unconnected.
28
RSVD
Reserved pad. Leave unconnected.
29
RSVD
Reserved pad. Leave unconnected.
30
/UART0_RTS
Default functionality is UART flow control input for the module’s host. A logic low allows data
flow from the module to the host; a logic high blocks data flow from the module to the host.
31
UART0_RXD
UART received data output to host from module.
32
UART0_TXD
UART host data input to be transmitted by module.
33
/UART0_CTS
34
VMOD
35
SPI_NSS
UART flow control output from the module to the host. A logic low should allow data flow from
the host; a logic high should block data flow from the host.
Module’s +3.3 V regulated supply output. Connect to pad 3 to support 3.3 V full scale and/or
ratiometric ADC readings, etc. Current drain on this output should be no greater than 5 mA.
Active low SPI enable (slave). This input must be held low for the duration of an SPI transmission.
36
SPI_MOSI
SPI port data output.
37
SPI_MISO
SPI port data input.
38
SPI_SCLK
SPI port clock signal.
39
/RESET
40
BOOT_LOAD
41
GND
RF ground (DNT500 only). Connect to the host circuit board ground plane.
42
RFIO
Alternate RF port to the U.FL connector (DNT500 only). The antenna can be connected to this
port with a 50 Ω stripline or coaxial cable. Leave unconnected when using the U.FL connector.
43
GND
RF ground (DNT500 only). Connect to the host circuit board ground plane.
Active low module hardware reset.
Logic high at power up enables module boot loader. Hold low for normal operation.
3.3 Input Voltages
DNT500 radio modules can operated from an unregulated DC input (Pad/Pin 19) in the
range of 3.3 (trough) to 5.5 V (peak) with a maximum ripple of 5% over the temperature
range of -40 to 85 C. Applying AC, reverse DC, or a DC voltage outside the range given
above can cause damage and/or create a fire and safety hazard. Further, care must be
taken so logic inputs applied to the radio stay within the voltage range of 0 to 3.3 V. Signals applied to the analog inputs must be in the range of 0 to ADC_REF(Pad/Pin 3). Applying a voltage to a logic or analog input outside of its operating range can damage the
DNT500 module.
3.4 ESD and Transient Protection
The DNT500 and DNT500P circuit boards are electrostatic discharge (ESD) sensitive.
ESD precautions must be observed when handling and installing these components. Installations must be protected from electrical transients on the power supply and I/O lines.
This is especially important in outdoor installations, and/or where connections are made
to sensors with long leads. Inadequate transient protection can result in damage and/or
create a fire and safety hazard.
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DNT500
3.5 Interfacing to 5 V Logic Systems
All logic signals including the serial ports on the DNT500 are 3.3 V signals. To interface
to 5 V signals, the resistor divider network shown below must be placed between the 5 V
signal outputs and the DNT500 signal inputs. The output voltage swing of the DNT500
3.3 V signals is sufficient to drive 5 V logic inputs.
5 V
L o g ic
D N T 5 0 0
2 .2 K
4 .3 K
3.6 Power-On Reset Requirements
The DNT500 has an internal reset circuit that generates and maintains the DNT500 in a
reset state until the power supply voltage reaches 3.3 volts for 100 milliseconds. This reset circuit protects the radio and non-volatile memory from brown-out voltage conditions.
If devices that communicate with the DNT500 have shorter reset periods, an allowance
must be made to allow the DNT500 to come out of reset. Commands and data sent before
the DNT500 is out of reset will be ignored.
3.7 Analog RSSI Output
Pin 4 on the DNT500 provides a 0.3 to 3.0 V output proportional to received signal
strength in dB, as follows:
VRSSI = 0.03*SRF + 3.6
Where:
VRSSI
SRF
is the RSSI output in volts, over the range of 0.3 to 3.0 V
is the RF signal strength in dBm, over the range of -110 to -20 dBm
The analog RSSI output on a DNT500 remote represents the signal strength of the last
base station transmission received. The RSSI output on a base station represents the signal strength of the last remote transmission heard.
3.8 Mounting and Enclosures
DNT500 radio modules are mounted by reflow soldering them to a host circuit board.
DNT500P modules are mounted by plugging their pins into a set of mating connectors on
the host circuit board. Refer to the DNT500 data sheet for a suitable solder reflow profile
and details of the connectors for the DNT500P.
DNT500 radio module enclosures must be made of plastics or other materials with low
RF attenuation to avoid compromising antenna performance. Metal enclosures are not
suitable as they will block antenna radiation and reception. Outdoor enclosures must be
water tight, such as a NEMA 4X enclosure.
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DNT500
3.9 Connecting Antennas
A U.FL miniature coaxial connector is the primary RF connection point on the DNT500,
and the only RF connection point on the DNT500P. On the DNT500, it is also possible to
connect an antenna using a stripline from pad 42 instead of the U.FL connector. It is important that this connection be implemented as a 50 ohm stripline trace. A short coaxial
jumper cable should be used to connect to between the U.FL connector on the DNT500P
and the host circuit board U.FL connector. The host PCB U.FL connector should connect
to the antenna or antenna connector with a 50 ohm stripline trace. The design details of
the stripline are covered in the DNT500 Data Sheet.
3.10 Labeling and Notices
DNT500 FCC Certification - The DNT500 hardware has been certified for operation under FCC Part 15 Rules, Section 15.247. The antenna(s) used for this transmitter must be
installed to provide a separation distance of at least 20 cm from all persons and must not
be co-located or operating in conjunction with any other antenna or transmitter.
DNT500 FCC Notices and Labels - 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 cause undesired operation.
A clearly visible label is required on the outside of the user’s (OEM) enclosure stating
that this product contains a DNT500 transceiver assembly, FCC ID: HSW-DNT500P.
WARNING: This device operates under Part 15 of the FCC rules. Any modification to
this device, not expressly authorized by RFM, Inc., may void the user’s authority to operate this device.
Canadian Department of Communications Industry Notice - IC: 4492A-DNT500P
This apparatus complies with Health Canada’s Safety Code 6 / IC RSS 210.
ICES-003
This digital apparatus does not exceed the Class B limits for radio noise emissions from
digital apparatus as set out in the radio interference regulations of Industry Canada.
Le present appareil numerique n’emet pas de bruits radioelectriques depassant les limites
applicables aux appareils numeriques de Classe B prescrites dans le reglement sur le
brouillage radioelectrique edicte par Industrie Canada.
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DNT500
4. PROTOCOL MESSAGES
4.1 Protocol Message Formats
The DNT500 is configured and controlled through a series of protocol mode messages.
All protocol mode messages have a common header format:
SOP
Length
PktType
3…
variable number of arguments …
LRC*
The scale above is in bytes. General comments:
•
The Start-of-Packet (SOP) character, 0xFB, is used to distinguish the beginning of a
message and to assure synchronization in the event of a glitch on the serial port at
startup.
•
The Length byte is defined as the length of the remainder of the message following
the length byte itself (or the length of the entire message - 2). If the LRC is enabled, it
is included in the length.
•
The Packet Type (PktType) byte specifies the type of message. It is a bitfield-oriented
specifier, decoded as follows:
Bits
Bit
Bit
Bits
7-6
3-0
Reserved for future use
Event - set to indicate this message is an event
Reply - set to indicates this message is a reply
Type - indicates the message type/command
As indicated, the lower 4 bits (3-0) specify a message type. Bit 4 is a modifier indicating that the message is a command or a reply. A reply message has the original command type in bits 3:0, with bit 4 set to one.
•
Arguments vary in size and number depending on the type of message and whether it
is a message sent from the host or is a reply from the radio; see the table provided below for reference.
•
The LRC is an optional checksum byte that verifies the integrity of the message received. It is the two's complement of the sum of all the bytes in the message. If the
sum is larger than 1 byte, only the LSB is used. For example, 0xFB 0x05 0x04 0x01
0x0A 0x00 0x01 → LRC = 0xF0.
Messages that are generated on the serial interface by the user are referred to as host
messages. Messages that are generated by the radio are referred to as reply messages.
For many message types, there is a reply message that corresponds to a host message.
For example, when the host sends a TxData message, the radio will reply to indicate
the status of the transmission, whether it succeeded or failed. Some message types are
host-only or reply-only; please refer to the table for specifics.
4.1.1 Serial message types
Each message generally has two forms, a command from the host and a reply from the
radio. Depending on the direction, they have different arguments as shown in the table
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DNT500
below. Event messages from the radio such as receive data packets or status announcements make up a third category of messages. To assist in interpreting the command-reply
data flow, the direction is indicated by Bit 4 in the message type. For example, an EnterProtocolMode command from the host is message type 0x00, and the EnterProtocolModeReply from the radio is message type 0x10. Event messages, including RxData,
RxEvent and ANNOUNCE, packets are indicated by setting Bit 5 high in the type byte. If
multiple arguments are to be provided, they are to be concatenated in the order shown.
Little-Endian byte format is used for all multi-byte arguments, where the lowest order
byte is the left byte of the argument and the highest order byte in the right byte of the argument.
Message Type Code
Command
Reply
Event
0x00
Description
Direction
Arguments
EnterProtocolMode
from Host
"DNT500"
0x10
EnterProtocolModeReply
from Radio
none
0x01
ExitProtocolMode
from Host
none
0x11
ExitProtocolModeReply
from Radio
none
0x02
SoftwareReset
from Host
BootSelect
0x12
SoftwareResetReply
from Radio
none
0x03
GetRegister
from Host
Reg, Bank, Span
0x13
GetRegisterReply
from Radio
Reg, Bank, Span,Val
0x04
SetRegister
from Host
Reg, Bank, Span, Val
0x14
SetRegisterReply
from Radio
none
0x05
TxData
from Host
Addr, Data
0x15
TxDataReply
from Radio
TxStatus, Addr, RSSI
0x26
RxData
from Radio
Addr, RSSI, Data
0x27
Announce
from Radio
AnnStatus, add'l fields
0x28
RxEvent
from Radio
Addr, RSSI, Reg, Bank,
Span,Val
0x0A
GetRemoteRegister
from Host
Addr, Reg, Bank, Span
0x1A
GetRemoteRegisterReply
from Radio
TxStatus, Addr, RSSI,
Reg, Bank, Span, Val*
0x0B
SetRemoteRegister
from Host
Addr, Reg, Bank, Span, Val
0x1B
SetRemoteRegisterReply
from Radio
TxStatus, Addr, RSSI
0x2F
Instrumentation
from Radio
DiagInfo
*If TxStatus is non-zero in a GetRemoteRegisterReply, the Reg, Bank, Span and Val bytes will not be
present in the message
Arguments:
Reg
= Register location (1 byte).
Bank = Register bank, which provides logical isolation from other data regions (1 byte).
Span = Number of bytes of register data to get or set; must align to a parameter boundary (1 byte).
Val
= Value to read/write to/from register (see table for size and acceptable range).
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Data = User data (variable size, 0 to 128 bytes).
Addr = MAC address of the sender for a reply or event, or recipient for a command (3 bytes).
TxStatus = Result of last TxData operation (1 byte).
0 = Acknowledgement received.
1 = No acknowledgement received.
2 = (Remote) Not linked.
3 = Recipient holding for flow control.
RSSI = RSSI, range 0x01 to 0xFE. Values 0x00 & 0xFF have special meanings (1 byte).
0x00 = No RSSI measured because no ACK was received.
0xFF = No RSSI measured because packet was relayed.
NwkID = Network identifier of network joined (1 byte).
BaseMacAddr = MAC address of base that the remote joined (3 bytes).
BootSelect = Code indicating whether to do a normal reset or a reset to the bootloader (1 byte).
(0 = normal reset, 1 = reset to bootloader)
AnnStatus = Status announcement (1 byte).
Additional fields are also reported depending on the status code:
Status code
Add'l fields
A0
A1
A2
A3
A4
A5
A7
Radio has completed startup initialization.
none
Base: Network formed, ready for data.
NwkID
Base: A remote has joined me.
MacAddr (0xFF if none)
Remote: Joined a network, ready for data.
NwkID, BaseMacAddr, Range
Remote: Exited network (base is out of range). NwkID
Remote: Base has restarted.
none
Base: Remote has left the network.
Addr
Status codes for error conditions
Add'l fields
E0 = Protocol error -- invalid message type.
E1 = Protocol error -- invalid argument.
E2 = Protocol error -- general error.
E3 = Protocol error -- parser timeout.
E4 = Protocol error -- register is read-only.
E8 = UART receive buffer overflow.
E9 = UART receive overrun.
EA = UART framing error.
none
none
none
none
none
none
none
none
JoinAddr = MAC address of radio joining (3 bytes).
Range = Range measurement of radio joining. (1 byte).
4.1.2 Escape sequence
The escape sequence is a sequence of bytes that the user can input in transparent mode to
switch the radio to configuration mode. In the DNT500, we define the EnterProtocolMode command as the ASCII escape sequence “DNT500” (quotation marks are not part
of the sequence). A radio that is already in protocol mode will respond to this command
the same way as a radio that is in transparent mode. For the escape sequence to be recognized, byte flow must pause at least 20 ms before the escape sequence is sent.
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DNT500
4.1.3 CFG select pin
A falling edge on the CFG pin is the equivalent of entering the escape sequence to invoke
the protocol mode. A rising edge on the CFG pin is the equivalent to sending the exit protocol command.
4.1.4 Flow control
There are two flow control signals between the radio and the host, RTS and CTS. See
Section 2.7.4 for flow control details.
4.1.5 Protocol mode data message example
For Example 4, ASCII text “Hello World” is sent from the base station to a remote using
a TxData command. The MAC address of the remote is 0x000102. The protocol formatting for the host message is:
0xFB 0x0F 0x05 0x02 0x01 0x00 0x48 0x65 0x6C 0x6C 0x6F 0x20 0x57 0x6F 0x72 0x6C 0x64
There are 15 bytes following the length byte, so the length byte is set to 0x0F. Note that
the 0x000102 MAC address is entered in Little-Endian byte order 0x02 0x01 0x00.
When an ACK to this message is received from the remote, the base station outputs a
TxDataReply message to its host:
0xFB 0x06 0x15 0x00 0x02 0x01 0x00 0x80
The 0x00 TxStatus byte value indicates the ACK reception from the remote. The RSSI
value is 0x80.
If the remote is in protocol mode, the received message is output in the following format:
0xFB 0x10 0x26 0x02 0x01 0x00 0x8A 0x48 0x65 0x6C 0x6C 0x6F 0x20 0x57 0x6F 0x72 0x6C
0x64
The message is output as an 0x26 event. Note that the RSSI value 0x8A is inserted between the remote’s MAC address and the “Hello World” user data.
4.2 Configuration Registers
The configuration registers supported by the DNT500 are described below. Registers are
sorted into banks according to similarity of function.
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4.2.1 Bank 0 - Transceiver Setup
Bank Loc'n
Name
Size in
R/W bytes Range
00
00
00
01
DeviceMode
RF_DataRate
R/W1
R/W
00
00
00
00
00
00
02
04
05
15
16
18
HopDuration
InitialNwkID
SecurityKey
SleepMode
SleepInterval
TxPower
R/W
R/W
R/W
R/W
R/W
R/W
00
00
00
00
19
1A
1B
1C
ExternalSyncEn
DiversityMode
JoinPermit
UserTag
R/W
R/W
R/W
R/W
Default, Options
0..2
0..4
0 = Remote, 1= Base, 2 = PTT Remote
0 = 500, 1 = 200, 2 = 115.2, 3 = 38.4 kb/s,
0xFF = auto
2 4..4000 10 ms (0x00C8)
1 0..255 0xFF = broadcast
16 0..2128 0 = security disabled
1 0..1
0 = off, 1 = timer, 2 = interrupt
2 0..216 0 = off
1 0..5
1 = 10 dBm; 0 = 1, 2 = 19, 3 = 24, 4 = 27,
5 = 28 dBm
1 0..1
0 = disabled, 1 = input, 2 = output
1 0..1
0=0V
1 0..1
0 = no join, 1 = remotes (default), 2 =any
16
"DNT500"
Note: These settings are individual to each module.
DeviceMode
Selects the operating mode for the radio: remote, base, or PTT remote (listen mostly remote). Note that the setting takes effect immediately.
RF_DataRate
This sets the over-the-air RF data rate. Radios with different RF rates cannot intercommunicate. The following codes are defined:
0x00 = 500 kb/s
0x01 = 200 kb/s
0x02 = 115.2 kb/s
0x03 = 38.4 kb/s
0xff = auto (default)
A setting of "auto" will cause a remote to scan all 4 possible RF rates for a network to
join. A base set to "auto" will run at the maximum rate of 500 kb/s. A change to this setting on the base will trigger an epoch change to reboot the network.
HopDuration
This sets the duration of the hop frame. The duration is set as a 12-bit value,
0.05 ms/count.
InitialNwkID
Selects the initial network ID that the radio will start (if a base) or join (if a remote). A
value of 0xFF instructs a remote to operate in 'promiscuous mode' and join any network it
finds (if set for a base, this will select the default network of 0x00.) The network ID also
sets the base frequency at which the hopping pattern starts, as illustrated by the following
equation:
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FrequencyIndex[n] = HoppingPattern[n + 2*NetworkID mod 32]
This allows the user to coordinate frequency spacing of co-located networks to maintain a
constant separation as they hop.
SecurityKey
This sets the 128-bit AES encryption key that will be used. The intent is for this to act
like a password that all radios in the network are configured with. To protect the key, this
is a write-only parameter for the user, unless the manufacturing write enable is set, in
which case it is also readable. Refer to the section on Encryption for further information.
SleepMode
Sets the sleep mode.
SleepInterval
Sets the sleep interval as the number of superframes that a remote will sleep between
wake intervals. A superframe interval is 64 hops.
TxPower
Sets the transmit power level:
0 dBm or 1 mW
10 dBm or 10 mW (default)
19 dBm or 79.4 mW
24 dBm or 250 mW
27 dBm or 500 mW
28 dBm or 1000 mW (1 W)
When the data rate is set to 500 kb/s, the firmware interlocks the transmit power level to
19 dBm or less to comply with FCC regulations.
ExternalSyncEn
Enables the external sync input. This option allows a base radio's hopframes to be triggered by an external synchronization signal. Valid settings are 0 = disabled, 1 = sync pin
is input, 2 = sync pin is an output. This last mode allows a base radio to source the sync
signal for another radio.
DiversityMode
The DNT500 supports the following diversity antenna switching options:
0 = 0 V on the diversity pin (default)
1 = 3.3 V on the diversity pin
2 = 0 - 3.3 V toggle on every hop frame
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JoinPremit
Valid parameter on a base only. Controls whether remote nodes are permitted to join the
base. Parameter values are 0 = no joining permitted, 1 = remotes only may join, 2 = remotes or routers may join (future function).
UserTag
This is a user definable field intended for use as a location description or other identifying tag such as a “friendly name”.
4.2.2 Bank 1 - System Settings
Bank
Loc'n
Size in
Name
R/W
bytes
Range
Default; Options
01
00
FrequencyBand
R/W
0..1
01
01
01
01
01
01
01
01
01
01
01
02
03
04
05
06
07
08
09
0A
AccessMode
BaseSlotSize
LeasePeriod
ARQ_Mode
ARQ_AttemptLimit
TDMA_MaxSlots
CSMA_Persistence
CSMA_MaxBackoff
MaxPropDelay
EpochMode
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0..4
6..232
0..250
0..1
0..16
0..15
0..255
0..255
0..255
0..1
0x00 = North America;
0x01 = Australia, 0xFF = auto
2 = TDMA Dynamic Slots
20 bytes
5 s (0 to disable)
0 = ARQ, 1 = redundant TX
5 attempts
8 slots
0xFF
5 ms
50 µs (~4 miles)
0 = use previous; 1 = increment
2 = random
Note: The base station propagates these setting to all remotes.
FrequencyBand
This sets the range of frequencies over which the radio will operate. Two settings are defined: North America (902-928 MHz) and Australia-New Zealand (915-928 MHz).
AccessMode
This sets the channel access mode that remotes will use to communicate with the base:
Access Mode
2 (default)
Description
CSMA polling
CSMA contention
TDMA dynamic slots
TDMA fixed slots
TDMA with PTT
Max # of Remotes
1024
1024
up to 15
up to 15
1024
Remote Slot Size
manual
manual
automatic
automatic
automatic
BaseSlotSize
This sets the size of the base slot. This number is specified in terms of the number of application payload bytes that can be supported. This value excludes the message length
byte, the BASE_STATUS packet, the checksum and CRC bytes, and a presumed
REG_REPLY packet. The BaseSlotSize indicates the number of bytes that are available
for MAC and network ACKs, plus user data packets. This number does not include the
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DNT500
overhead required for headers of these packets, which must be factored into the slot size
budget. To ensure that there is never a restriction on when registration or renewal may
take place, space for a registration reply packet is always assumed. If this packet is not
needed on a given hop, this space is unused.
LeasePeriod
This sets the duration for network address leases that remotes may receive from the base.
If a period of zero is specified, then lease and network address functions are disabled.
ARQ_Mode
This sets the ARQ mode for delivery of application messages. In full ARQ mode, an
ACK is expected from the receiving radio for each message addressed and sent to it. If no
ACK is received, up to ARQ_AttemptLimit, efforts to send the data will be made, after
which the message is discarded. In redundant transmit mode, each message is sent exactly ARQ_AttemptLimit times. No ACKS are sent or expected. This is primarily useful
in cases where the number of attempts is 2 or 3, the data flow is time-critical, and the
overhead of sending ACKs is not desired.
ARQ_AttemptLimit
This sets the maximum number of attempts that will be made to send a data packet on the
RF link. Setting this parameter to the maximum value of 15 is a flag value indicating that
there should be no limit to the number of attempts to send each packet (infinite number of
attempts). This mode is intended for point-to-point networks in serial data cable replacement applications where absolutely no packets can be lost.
TDMA_MaxNumSlots
In TDMA access modes, this sets the number of slots that are allowed. In fixed slot
mode, this allocates the number of slots directly. In dynamic slot mode, this sets the
maximum number of slots that may be allocated according to the number of remotes that
are registered.
CSMA_Persistence
In CSMA mode, this sets the 'persistence' parameter, or probability that a remote will
transmit when it senses an open channel. Please refer to the section on Channel Access
for more information.
CSMA_MaxBackoff
In CSMA mode, this sets the maximum length of time that a remote will back off for after a failed transmit attempt. Please refer to the section on Channel Access for more information.
MaxPropDelay
This is the maximum propagation delay that remotes and base will use in their slot timing
calculations, in units of microseconds. This is used to pad the amount of time dedicated
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DNT500
to the signup slot. Increasing this value will subtract slightly from the overall slot time
available to remotes for sending data.
EpochMode
This is a base-only parameter that governs how the base will select an epoch number at
startup when it creates a network. In mode 0, the base will read the epoch number from
NVRAM. In mode 1, it reads the value from NVRAM and increments it (and stores the
result). In mode 2, it will generate a random epoch number at every startup.
4.2.3 Bank 2 - Status Registers (read only)
Bank
02
02
02
02
02
02
02
02
02
02
02
02
02
02
02
02
02
02
02
Loc'n
00
03
04
05
06
07
08
09
0A
0B
0C
0D
0E
0F
10
11
12
14
15
Name
MacAddress
CurrNwkAddress
CurrNwkID
CurrRF_DataRate
CurrFreqBand
LinkStatus
RemoteSlotSize
TDMA_NumSlots
TDMA_SlotStart
TDMA_CurrSlot
HardwareVersion
FirmwareVersion
FirmwareBuildNum
Epoch
SuperframeCount
RSSI_Idle
RSSI_Last
CurrAttemptLimit
CurrRangeDelay
R/W
Size in
bytes
Range
0..224
0..255
0..255
0..4
0..1
0..1
0..255
0..15
0..255
0..15
0..255
0..255
0..216
0..255
0..255
0..255
0..255
0..255
0..255
Default
fixed value
as set
as set
as set
as set
current status
current size
as set
current setting
current slot
0x00 = DNT500 rev A
current firmware load
current firmware load
as set
current value
as set
as set
as set
as set
MacAddress
Returns the radio's unique 24-bit MAC address.
CurrNwkAddress
Returns the radio's current network address, if any. Some special values should be noted.
The base always reports 0x00. If a remote does not have a network address, either because lease mode is not enabled or it has not yet received one, it reports 0xFF. This returns the network ID of the network that the radio is currently assigned to or connected
to. A value of 0xFF means the radio is in promiscuous mode and scanning for a network
but has not yet joined one.
CurrNwkID
This returns the network ID of the network that the radio is currently assigned to or connected to. A value of 0xFF means the radio is in promiscuous mode and scanning for a
network but has not yet joined one.
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DNT500
CurrRF_DataRate
This returns the RF data rate of the network that the radio is currently assigned to or connected to. A value of 0xFF means the radio is scanning for a network but has not yet
joined one.
CurrFreqBand
This returns the frequency band of the network that the radio is currently assigned to or
connected to. A value of 0xFF means the radio is scanning for a network but has not yet
joined one.
LinkStatus
This returns the radio's current connection status to the network. The following codes are
defined:
0 = initializing
1 = unlinked, scanning for network
2 = linked
RemoteSlotSize
This returns the current remote slot size, defined as the maximum possible user data payload size in bytes. In TDMA modes where the slot size is automatically computed, this
value is read-only. In manual TDMA mode and CSMA mode, this value must be set by
the user. This value excludes the message length byte, REMT_STATUS packet, and
checksum and CRC bytes. It indicates the number of bytes available for REMT_DATA
and/or REMT_DATA_EXTs. It does not include the overhead bytes required for these
packets, which must be figured into the slot size budget.
TDMA_NumSlots
In TDMA access modes, this returns the number of slots currently allocated.
TDMA_CurrSlot
This returns the current TDMA slot number. in modes where the slot position is automatically computed. In modes where this number is not applicable, the value is read as
0xFF.
TDMA_SlotStart
This returns the current TDMA slot position. In TDMA modes where the slot position is
automatically computed, this value is read-only.
HardwareVersion
This returns an identifier indicating the type of radio. A value of 0x00 is defined for the
DNT500 Rev A hardware.
FirmwareVersion
This returns the firmware version of the radio in 2-digit BCD format.
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DNT500
FirmwareBuildNum
This returns the firmware build number, in binary format.
Epoch
Returns the current epoch number.
SuperframeCount
Returns the current superframe count. The superframe counter increments every 64 hops.
RSSI_Idle
Returns the last measurement of RSSI made during a time when the RF channel was idle.
May be used to detect interferers. Read-only.
RSSI_Last
Returns the last measurement of RSSI made during receipt of an RF packet with valid
CRC. Used for network commissioning and diagnostic purposes.
CurrAttemptLimit
This returns the value of ARQ_AttemptLimit currently in use (depending on the selected
ARQ_Mode, it may not always match the local EEPROM value).
CurrRangeDelay
This returns the current propagation delay for this remote as measured from the base.
4.2.4 Bank 3 - Serial
Bank
03
03
03
Loc'n
00
01
03
Name
SerialRate
SerialParams
SerialControls
R/W
R/W
R/W
R/W
Size in
bytes Range
2 0..216
1 0..7
1 0..7
Default
115.2 kb/s (0x0004)
8N1
0X07
SerialRate
This sets the serial rate divisor according to the following formula:
Serial rate in b/s = 460800/SerialRate
Serial rate division setting for commonly used baud rates are:
Setting
0x0000
0x0001
0x0002
0x0004
0x0006
0x0008
0x000C
0x0010
 2008 by RF Monolithics, Inc.
Serial rate
460.8 kb/s
460.8 kb/s
230.4 kb/s
115.2 kb/s (default)
76.8 kb/s
57.6 kb/s
38.4 kb/s
28.8 kb/s
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0x0018
0x0030
0x0060
0x00C0
0x0180
19.2 kb/s
9.6 kb/s
4.8 kb/s
2.4 kb/s
1.2 kb/s
Note that if a value of 0x0000 is specified, the maximum data rate of 460.8 kb/s will be
selected.
SerialParams
This sets the serial mode options for parity and stop bits:
Setting
0x00
0x01
0x02-03
0x04
0x05
0x06
0x07
Mode
No parity, 8 data bits, 1 stop bit
No parity, 8 data bits, 2 stop bits
Reserved
Even parity, 8 data bits, 1 stop bit
Even parity, 8 data bits, 2 stop bits
Odd parity, 8 data bits, 1 stop bit
Odd parity, 8 data bits, 2 stop bits
Note that 8-bit data with no parity is capable of carrying 7-bit data with parity for compatibility without loss of generality for legacy applications that may require it.
SerialControls
This register affects the way the radio responds to the various serial control lines. Enabling or disabling response to some serial control signals can facilitate communicating
with devices that support only a reduced serial interface. The register is defined as a bitmask, with the following options:
bits 7..3 Reserved
bit 2
Base DCD mode.
1 = The base will only assert DCD when at least one remote is registered (default).
0 = The base always asserts DCD, regardless of whether any remotes are attached.
bit 1
RTS enable.
1 = Radio will respond to changes on the RTS control line (default).
0 = Radio ignores the RTS pin and assumes flow control is always asserted.
bit 0
SLEEP enable.
1 = Radio will respond to changes on the SLEEP (DTR) control line (default)
0 = Radio ignores the SLEEP (DTR) pin and is always in the awake state.
4.2.5 Bank 4 - Host Protocol Settings
Bank
04
04
04
04
04
Loc'n
00
01
02
03
04
Name
ProtocolMode
ProtocolOptions
TxTimeout
MinPacketLength
StartupAnnEn
 2008 by RF Monolithics, Inc.
R/W
R/W
R/W
R/W
R/W
R/W
Size in
bytes
31
Range
0..1
Default; Options
0 = transparent; 1 = protocol
0..255
0..255
0..1
5 ms
1 byte
0 = disabled; 1 = enabled
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04
04
04
05
06
07
TransLinkAnnEn
EscapeSequenceEn
TransPtToPtMode
R/W
R/W
R/W
0..1
0..2
0..1
0 = disabled; 1 = LINK announce
0 = enabled; 1 = startup, 2 = anytime
0 = multipoint, 1 = point-to-point
ProtocolMode
Selects the host protocol mode. The default is 0, which is transparent mode, meaning the
radio conveys whatever characters that are sent to it transparently, without requiring the
host to understand or conform to the DNT500's built-in protocol. This setting is recommended for point-to-point applications for legacy applications such as wire replacements
where another serial protocol may already exist. Setting this parameter to 1 enables the
DNT500 host protocol, which is recommended for point-to-multipoint applications and is
preferred for new designs. It is not necessary to define the same protocol mode for all radios in a network. For example, it is frequently useful to configure all the remotes for
transparent mode and the base for protocol mode. Note that it is possible for the host to
switch the radio from transparent mode to protocol mode and back if desired by transmitting a special "escape sequence" code. See the section on the serial host protocol for more
information.
ProtocolOptions
This is a bitmask that selects various options for the protocol mode. Default is 0x01.
bit 7
bits 2..6
bit 1
bit 0
Enable output of Instrumentation packets.
reserved
Enable LRC checksum byte in serial protocol.
Enable output of Announce packets.
TxTimeout
This sets the transmit timeout used for determining message boundaries in transparent
data mode. Units are in milliseconds. The default is that a message boundary is determined whenever there is more than a 5 ms gap detected between consecutive characters.
MinPacketLength
This sets the minimum message length used for determining packet boundaries in transparent data mode. The default is one byte.
TransLinkAnnEn
This enables a link announcement function for transparent mode. Whenever link is acquired or dropped, the strings "" or "" are sent to the host.
EscapeSequenceEn
Enables or disables the escape sequence which can be used to switch from transparent
mode to protocol mode. Enabled by default. Valid settings are 0 = disabled, 1 = one
chance at startup, 2 = enabled at any time.
TransPtToPtMode
This controls the behavior for addressing packets in transparent mode. When this setting
is zero (default), in transparent mode the base will direct packets to the broadcast address.
This is useful for point-to-multipoint where the base is sending data to multiple remotes,
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DNT500
for instance in applications where a wireless link is replacing an RS-485 serial bus. When
this setting is one, in transparent mode the base will direct packets to the last remote that
registered with it. This is useful for point-to-point networks where there are only two
endpoints, for instance in applications where a simple serial cable is being replaced.
4.2.6 Bank 5 - I/O Peripheral Registers
Bank
05
05
05
05
05
05
05
05
05
05
05
Loc'n
00
01
02
03
04
05
06
07
08
09
0A
Name
GPIO0
GPIO1
GPIO2
GPIO3
GPIO2
GPIO3
ADC0
ADC1
ADC2
PWM0
PWM1
Size in
bytes
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Range
in bits
10
10
10
Default
N/A
N/A
N/A
GPIO0..5
Writing to these registers sets the corresponding driver for pins that are enabled outputs.
Writing to pins that are enabled as inputs enables or disables the internal pull-up. Reading
these registers returns the current level detected on the corresponding pin.
ADC0..2
Read-only, returns the current 10-bit ADC reading for the selected register. See the discussion of the ADC_SampleIntvl parameter below.
PWM0..1
Sets the PWM (DAC) outputs. The DC voltage derived from the integrated low-pass filters on the PWM output provides and effective DAC resolution of 8 bits. The range of
this parameter is 0x0000 to 0x0100.
4.2.7 Bank 6 - I/O setup
Bank
06
06
06
06
06
06
06
06
06
06
06
Loc'n
00
01
02
03
04
05
06
07
09
0B
0D
Name
Size in Range
R/W bytes in bits
Default; Options
GPIO_Dir
GPIO_Init
GPIO_Alt
GPIO_MessageMode
GPIO_SleepMode
GPIO_SleepDDR
GPIO_SleepState
PWMA_Init
PWMB_Init
ADC_SampleIntvl
ADC0 ThresholdLo
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0 (all inputs)
0 (all zeros)
0x08 = use GPIO3 for RS485 enable
GPIO messages disabled
0 = off; 1 = use sleep I/O states
0 (all inputs)
0 (all zeros)
0x0000
0x0000
0x0001 (10 ms)
0x0000
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06
06
06
06
06
06
06
06
0F
11
13
15
17
19
1A
1E
ADC0_ThresholdHi
ADC1_ThresholdLo
ADC1_ThresholdHi
ADC2_ThresholdLo
ADC2_ThresholdHi
IO_ReportEnable
IO_ReportInterval
IO_ReportAddress
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
10
10
10
10
10
0..1
32
24
0x03FF
0x0000
0x03FF
0x0000
0x03FF
0 = off
0x00007530 (every 30,000 hops)
0x000000
GPIO_DIR
This is a bitmask that sets whether the GPIOs are inputs (0) or outputs (1). The default is
all inputs.
GPIO_Init
This is a bitmask that sets the initial value for any GPIOs which are enabled as outputs.
For GPIOs enabled as inputs, this sets the initial pull-up setting.
PWM0_Init
This sets the initial value for PWM0 at startup.
PWM1_Init
This sets the initial value for PWM1 at startup.
GPIO_Alt
Provides and alternate function for GPIO3 as an RS-485 driver enable.
GPIO_MessageMode
This register enables a message to be sent to the base station whenever one of the GPIOs
is triggered. If the radio is asleep, it will be awakened while the particular GPIO is asserted.
Bit
Option
7-6
Message type for GPIO_3
5-4
Message type for GPIO_2
3-2
Message type for GPIO_1
1-0
Message type for GPIO_0
Message options:
0b00: Disabled
Events are ignored and the radio is not awakened from sleep
0b01: Button Message
An event message is sent reporting the state of the corresponding GPIO
input. The state will be 0b0 since I/Os are triggered on logic low.
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DNT500
0b10: Module I/O Message
An event message is sent reporting the states of the entire I/O register
bank
0b11: Registration Message
A registration packet is sent to the base station.
GPIO_SleepMode
Enables setting of GPIOs to the designated direction and state whenever a device is
asleep.
GPIO_SleepDDR
When GPIO_SleepMode is enabled, the three LSBs of this byte are used to set the direction of the GPIOs during a device's sleep period. This enables the user to provide alternate configurations during sleep that will help minimize current consumption. Bits 0..2
correspond to GPIO0..GPIO2.
GPIO_SleepState
When GPIO_SleepMode is enabled, the three LSBs of this byte are used to set the output
state of the GPIOs during a device's sleep period. This enables the user to provide alternate configurations during sleep that will help minimize current consumption. Bits 0..2
correspond to GPIO0..GPIO2.
ADC_SampleIntvl
The ADC_SampleIntvl sets the interval between the beginning of one ADC read cycle
and the next ADC read cycle. The three ADC inputs are read on each ADC read cycle.
An ADC_SampleIntvl count equals 10 ms.
ADC0..2_ThresholdLo/Hi
These values define thresholds to trigger an I/O report based on ADC measurements. If
I/O reporting is enabled, single EVENT report containing the contents of the I/O bank is
generated when a threshold is crossed. Reporting is "edge-triggered" with respect to
threshold boundaries, not "level-triggered"; i.e., if the measurement remains there, additional reports are not triggered until the value crosses the threshold again. The thresholds
are met whenever one of the following inequalities are satisfied:
ADCx < ADCx_ThresholdLo
ADCx > ADCx_ThresholdHi
IO_ReportEnable
When enabled, this causes a remote to periodically send an EVENT message to its base
containing the contents of the I/O bank.
IO_ReportInterval
When periodic I/O reporting is enabled, this sets the interval between reports. The default
is once every 30000 hops (every 5 minutes, at the default 10 ms hop duration).
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DNT500
IO_ReportAddress
Address to send I/O reports. Usually the base station address.
4.2.8 Bank FF - Special function
This bank contains two user functions, UcReset and MemorySave.
Bank
Loc'n
Name
R/W bytes Range
Description
FF
00
UcReset
0..90
FF
FF
MemorySave
0..1
00 = reset, 1 = clear status/address and
reset, 0x5A = reset with factory defaults
0 = load factory defaults, 1 = save settings
to EEPROM
UcReset
Writing a value of 0x00 to this location forces a software reset of the microcontroller.
Writing a value of 0x01 resets the Link Status and erases any assigned Network Address
before resetting. Writing a value of 0x5A forces a factory default before resetting. Writing any other value returns an error.
MemorySave
Writing a zero to this location clears all registers back to factory defaults. Writing a one
to this location commits the current register settings to EEPROM. When programming
registers, all changes are considered temporary until this command is executed.
4.2.9 Protocol Mode Configuration/Sensor Message Examples
For Example 5, the host configures the base station to transmit 24 dBm of RF power using the SetRegister command, 0x04. The TxPower parameter is stored in bank 0x00, register 0x18. A one-byte parameter value of 0x03 selects the 24 dBm power level. The protocol formatting for the command is:
0xFB 0x05 0x04 0x18 0x00 0x01 0x03
Note the order of the bytes in the command argument: register, bank, span, parameter
value. When the base station receives the command it updates the parameter setting and
return a SetRegisterReply message as follows:
0xFB 0x02 0x17 0x14
In order for this new RF power setting to persist through a base station power down,
MemorySave must be invoked. This is done by setting a one-byte parameter in register
0xFF of bank 0xFF to 0x01 with another SetRegister command:
0xFB 0x05 0x04 0xFF 0xFF 0x01 0x01
The base station will write the current parameter values to EEPROM and return a SetRegisterReply message:
0xFB 0x01 0x14
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DNT500
For Example 6, the base station host requests an ADC1 reading from a remote using the
GetRemoteRegister command, 0x0A. The MAC address of the remote is 0x000102. The
current ADC1 measurement is read from register 0x07 in bank 0x05. The ADC reading
spans two bytes. The protocol formatting for this command is:
0xFB 0x07 0x0A 0x02 0x01 0x00 0x07 0x05 0x02
Note the remote MAC address 0x000102 is entered in Little-Endian byte order, 0x02
0x01 0x00. The ADC reading is returned in a GetRemoteRegisterReply message:
0xFB 0x0B 0x1A 0x00 0x02 0x01 0x00 0x80 0x07 0x05 0x02 0xFF 0x02
Substantial information is returned in the message. The last two byes of the message give
the ADC reading in Little-Endian format, 0xFF 0x02. The ADC reading is thus 0x02FF.
The RSSI value is the byte following the address, 0x80. The TxStatus byte to the right of
the GetRemoteRegisterReply Packet Type is 0x00, showing the packet was acknowledged
on the RF channel.
4.2.10 Protocol Mode Event Message Examples
For Example 4, input GPIO2 (only) is configured to initiate an event message on remote
0x000102. This is done by configuring one-byte parameter GPIO_MessageMode with a
SetRemoteRegister command. GPIO_MessageMode is register 0x03 of bank 0x06. Bits
4-5 control GPIO2 event messaging. Button Message mode is chosen, which sends the
state of GPIO2, located in register 0x02 of bank 0x05, when a high-to-low transition occurs on GPIO2 (Button Message always reports a low state). The required GPIO_MessageMode bit pattern is 00010000b or 0x10. The protocol formatting for this command
is:
0xFB 0x08 0x0B 0x02 0x01 0x00 0x03 0x06 0x01 0x10
The GPIO_MessageMode parameter is updated and SetRemoteRegisterReply is returned:
0xFB 0x06 0x1B 0x00 0x02 0x01 0x00 0x8F
The RSSI value is the byte following the address, 0x8F. The TxStatus byte to the right of
the GetRemoteRegisterReply Packet Type is 0x00, showing the packet was acknowledged
on the RF channel. In order for this new GPIO_MessageMode setting to persist through a
base station power down, MemorySave must be invoked, as discussed in Example 5.
When a high-to-low “button push” transition occurs on GPIO2, remote 0x001002 will
send the following RxEvent message to the base station host:
0xFB 0x09 0x28 0x02 0x01 0x00 0x8E 0x02 0x05 0x01 0x00
The message is output as a PktType 0x28 RxEvent. Note that the RSSI value 0x8E is inserted between the remote’s MAC address and the register address byte. Register 0x02 in
bank 0x05 uniquely identifies GPIO2 as the source of the event message.
 2008 by RF Monolithics, Inc.
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DNT500
5. DNT500 DEVELOPER’S KIT
Figure 5.1 shows the main contents of a DNT500DK Developer’s kit:
Figure 5.1
5.1 DNT500DK Kit Contents
The kit contains the following items:
•
•
•
•
•
•
•
•
•
Two DNT500P Radios
Two DNT500 Interface Boards
Two 9 V Wall Plug Power Suppliers, 120/240 VAC
Two U.FL RF Jumper Cables
Two RJ-45 to DB-9F Cable Assemblies
Two A/B USB Cables
One RJ-11 to DB-9F Cable Assembly
Two 900 MHz Dipole Antennas
One DNT500 Documentation and Software CD
5.2 Additional Items Needed
To operate the kit, the following additional items are needed:
•
Two PCs with Microsoft Windows® XP or Vista Operating System
To fully test the kit’s functionality, the PCs should be equipped with high-speed serial
ports capable of operation at 460.8 kb/s.
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DNT500
5.3 Developer’s Kit Default Operating Configuration
The default operating configuration of the DNT500DK developer’s kit is TDMA Mode 2,
point-to-point, with transparent serial data at 115.2 kb/s, 8N1. One DNT500P is preconfigured as a base station and the other as a remote. The defaults can be overridden to test
other operating configurations using the DNT500 Wizard utility discussed in Section 5.5.
The default RF power setting is 10 dBm, which is suitable for side-by-side operation. The
RF power level should be set higher as needed for longer range operation. Note that setting the RF power to a high level when doing side-by-side testing will overload the
DNT500P receiver and cause erratic operation.
5.4 Development Kit Hardware Assembly
Observe ESD precautions when handling the kit circuit boards. Referring to Figure 5.4.1,
confirm each DNT500P is correctly plugged into an interface board, with the radio oriented so that its U.FL connector is next to the U.FL connector on the interface board.
Check each radio’s alignment in the socket on the interface board. No pins should be
hanging out over the ends of the connector. Next, install the U.FL jumper cables between
the U.FL connectors on the radios and the interface boards. Then install the dipole antennas. As shown in Figure 5.4.2, confirm there is a jumper on pins J14. The interface
boards can now be powered by the 9 V wall plug transformer power supplies (the interface boards can also be run for a short time from the 9 V batteries for range testing, etc.).
Figure 5.4.1
 2008 by RF Monolithics, Inc.
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---

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