RFDesign RFD900x User manual

www.rfdesign.com.au
Multipoint firmware
User Manual
For use on the RFD x/ux/ux-SMT modems,
Multipoint Firmware versions 2.86+
Features
• Synchronous firmware for 2 or more
modems
• User settable data rates
• Diversity antenna support
RFDesign Pty Ltd
7/1 Stockwell Place
Archerfield, QLD 4108
rfdesign.com.au

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Table of contents
Table of contents..................................................................................................................................... 2
1 Introduction..................................................................................................................................... 3
2 Software/GCS Support.....................................................................................................................4
3 AT commands.................................................................................................................................. 5
3.1 Setting up data encryption...................................................................................................... 9
3.2 Setting the air data rate...........................................................................................................9
4 Multipoint Network....................................................................................................................... 10
4.1 Example network configurations...........................................................................................10
64kbps Airspeed Networks................................................................................................................11
Single network................................................................................................................................... 11
Single network with relay node.........................................................................................................11
125kbps Airspeed Networks..............................................................................................................12
Single network (Maximum 7 non-master nodes)..............................................................................12
Maximum number of nodes per network......................................................................................... 13
Multiple Networks............................................................................................................................. 13
5 Useful links.....................................................................................................................................15
6Document Revision History............................................................................................................15

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1 Introduction
The RFD x and ux radio modems can be loaded with three official firmware releases to achieve
different communication architectures and node topologies. So far, the available firmware versions
are:
Peer-to-peer (P2P)
Multipoint network
Asynchronous mesh
This document describes the configuration of the Multipoint firmware. This firmware version is not
loaded in the RFD900x radio modem by default. This means, you must download it from the website
and flash it to the radio. The download link can be found in section “Useful links”.
The modems feature a boot loader to facilitate field upgrade of the modem firmware via the serial
port. This is most easily performed by using the latest version RFD Modem tools (see “Useful links”)
Figure 1-1 pictures a generic multipoint network. The network requires that one of the devices
assumes a master role to control the timeslot distribution of the surrounding modems.
Node 2
Node 3
Node 4
Node 1
Master
Within master node
range
Figure 1- 1: Multipoint network architecture
As depicted in Figure 1-1, the multipoint network allows each node to be addressed individually.
However, after receiving data it is not possible to identify which node it came from.
Note: Multipoint firmware is not compatible with -EU modems due to limitations the of certificated
modes.
Note: Due to the limited number of channels available on the 868 MHz band the maximum number
of nodes that can be operated may be reduced.
Note: Use of flow control is strongly recommended to prevent data loss or corruption.

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2 Software/GCS Support
Multipoint firmware settings, other than master node settings, can be managed by the modem tools
GUI. All settings can also be configured by AT commands.
Default serial port settings are as follows:
• 57600 baud
• No parity
• 8 data bits
• 1 stop bit
The RFD x and ux series radio modem have many software features including:
• Frequency Hopping Spread Spectrum
• Transparent Serial Link
• Configuration by simple AT commands for local radio, RT Commands for remote radio
• User configurable serial data rates and air data rates
• Error correction routines, MAVLink protocol framing (user selectable)
• MAVLink radio status reporting (Local RSSI, Remote RSSI, Local Noise, Remote Noise)
• Automatic antenna diversity switching on a packet basis in real-time
• Automatic duty cycle throttling based on radio temperature to avoid overheating
Note: Due to limitations of addressability in the firmware SiK features such as RC pass through and
GPIO pin mirroring are not available.

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3 AT commands
The Multipoint Firmware supports the Hayes ‘AT’ modem command set for configuration. The AT
command mode can be entered by using the ‘+++’ sequence in a serial terminal connected to the
radio. When doing this, you must allow at least 1 second after any data is sent to be ensure the
request for command mode is not interpreted as data. When you are successfully in the AT
command mode, an ‘OK’ prompt will be displayed on the screen and the RFD900x modem will stop
displaying incoming data from the remote modem. Whilst in command mode, you can use the AT
commands to control the local RFD900x modem or the RT commands to control the remote
modem(s).
To set certain registers to a value, follow these steps:
1. Use the command ATSn=X where nis the register number and Xis the desired value.
2. Use the command AT&W to save the new values to the modem.
3. Use the command ATZ to reboot the modem for changes to take effect.
Table 3-1 shows a gives a list of AT commands and their description.
AT Command
Description
ATI
Returns the radio version
ATI2
Returns the board type (e.g. 131 for x series, 136 for ux modem)
ATI3
Returns board frequency (e.g. 0x0091 for 900MHz 0x0086 for 868MHz)
ATI4
Returns board reversion
ATI5
Returns all user settable EEPROM parameters and their values
ATI5?
Returns all user settable EEPROM parameters and their values and possible
range
ATI6
Displays TDM timing report
ATI7
Displays RSSI signal report
ATI8
Display Device 64-bit hexadecimal unique ID
ATI9
Returns calibration state as “CAL Valid” or “CAL invalid”
ATI10:X
Returns user settable EEPROM parameter X and their values and possible range
ATO
Exits AT command mode
ATSn?
Returns ‘S’ parameter ‘n’
ATSn=X
Sets ‘S’ parameter number ‘n’ to value ‘X’
ATRn?
Returns ‘R’ parameter ‘n’
ATRn=X
Sets ‘R’ parameter number ‘n’ to value ‘X’
ATZ
Reboots the radio
AT&F
Resets all parameters to factory defaults
AT&W
Writes current parameters to EEPROM
AT&UPDATE
Reset and enter boot mode
AT&T
Disables debugging report
AT&T=RSSI
Enables RSSI debugging report
AT&T=TDM
Enables TDM debugging report
AT&E=X
Set new encryption key ‘X’ 128-bit AES (as 16 hex characters 5A02D5BB...)
AT&E?
Shows current encryption key
AT&M?
Current master node settings
AT&MX=A,B
Describes the network configuration. Only set this on master node (NETID=0,
NODEID=1). X is the network number (note must start with 0 as this is the

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synchronising network). A is the start channel ID of the network (this also starts
at 0 and can have values 0,7 or 13). B is the nodecount of the network (i.e. the
number of nodes on the network including the master)
Table 3-1: AT Commands and their description
RT commands are terminal commands that take effect on a remote node. They allow the user to set
or get a remote node’s parameter, for instance, as if they were being set locally. Table 10-2 lists the
RT commands and their respective descriptions.
RT Command
Description
RTI,[x]
Shows the radio version
RTI2,[x]
Shows the board type
RTI3,[x]
Shows board frequency
RTI4,[x]
Shows board version
RTI5,[x]
Shows all user settable EEPROM parameters and their values
RTI5?,[x]
Shows all user settable EEPROM parameters and their possible range
RTI6,[x]
Displays TDM timing report
RTI7,[x]
Displays RSSI signal report
RTI8,[x]
Display Device 64-bit unique ID
RTI9,[x]
Display node ID [multipoint only]
RTO,[x]
Exits AT command mode
RTSn?,[x]
Displays radio 'S' parameter number ‘n’
RTSn=X,[x]
Sets radio 'S' parameter number ‘n’ to ‘X’
RTRn?,[x]
Displays radio 'R' parameter number ‘n’
RTRn=X,[x]
Sets radio 'R' parameter number ‘n’ to ‘X’
RTZ,[x]
Reboots the radio
RT&F,[x]
Resets all parameters to factory defaults
RT&W,[x]
Writes current parameters to EEPROM
RT&UPDATE,[x]
Reset and enter boot mode
RT&P,[x]
Change TDM phase (debug only)
RT&T,[x]
Disables debugging report
RT&T=RSSI,[x]
Enables RSSI debugging report
RT&T=TDM,[x]
Enables TDM debugging report
RT&E=X,[x]
Set new encryption key (128-bit AES in 16 hex bytes e.g. 5A02D5BB...)
RT&E?,[x]
Shows current encryption key
Figure 3-2: RT Commands and their description
Note: ATI5? and RTI5? may not return all parameters due to a buffer overflow in this case use the
ATI10:X command to retrieve the missing parameter information, where X is the parameter number.
Eg ATI10:20, returns
S20:ANT_MODE(N)[0..3]=0{Ant1&2,Ant1,Ant2,Ant1=TX;2=RX,}
RT commands on multipoint network will solicit a response from all available nodes on the network,
the responding node is identified by the x in the brackets, [x] at the start of the line. Commands can
be addressed to an individual node, done by adding ‘ ,[x]’ to the RT command as per the examples
below.
This example describes how to get the radio version of the remote node 2 in a multipoint network
(append,[x] where x is desired node to RTI command):

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RTI,2
Table 3-3 shows more details about the parameters that can be set in the RFD900x modem.
Reg
#
S Register
Description
Default
Value
Maximum
Value
Minimum
Value
Must be the
same at both
ends of the
link?
S0
FORMAT
This is for EEPROM version, it should not be
changed
69
n.a.
n.a.
n.a.
S1
SERIAL_SPEED
Serial speed in ‘one-byte form’. Accepted
values are 1, 2, 4, 9, 19, 38, 57, 115, 230,
460,1000 corresponding to 1200bps,
2400bps, 4800bps, 9600bps, 19200bps,
38400bps, 57600bps, 115200bps,
230400bps, 460800bps, and 1000000bps
respectively.
57
1000
1
No
S2
AIR_SPEED
Air data rate in one-byte form, in kbps.
Accepted values are 12, 56, 64, 100, 125,
188, 200, 224, 500, 750.
64
750
12
Yes
S3
NETID
Network ID. It should be the same on all
modems of the network
0
311
0
Yes
S4
TXPOWER
Transmit power in dBm. Maximum is 30dBm
30
30
0
No
S5
ECC
Deprecated. No effect, cannot be changed.
0
0
0
n.a.
S6
RXFRAME
Sets the data type for the modem. 0=Raw,
1=Mavlink2, 2 = SAS
1
2
0
No
S7
OP_RESEND
Deprecated. No effect, cannot be changed.
0
1
0
n.a.
S8
MIN_FREQ3
Min frequency in kHz
922000,
8650004
928000,
8650004
902000,
8690004
Yes
S9
MAX_FREQ3
Max frequency in kHz
928000,
8670004
928000,
8650004
902000,
8690004
Yes
S10
NUM_CHANNELS3
Number of frequency hopping channels. Do
not change as this will affect the spectrum
separation of the nodes
21,74
51,84
2,14
Yes
S11
DUTY_CYCLE
The percentage of time to allow transmit
100
100
10
No
S12
LBT_RSSI
Listen before talk threshold
(This parameter shouldn’t be changed)
0
255
0
Yes
S13
RTSCTS
Ready-to-send and Clear-to-send.
1
1
0
No
S14
Max Window
80
400
20
Yes

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Max transit window size used to limit max
time/latency
S15
Encryption Level
Encryption level 0=off, 1=128bit
0
1
0
Yes
S16 –
S19
RESERVED
Deprecated. No effect.
0
0
0
n.a.
S20
ANT Mode
Set antenna port function. 0= Diversity, 1=A1
only, 2=A2 only, 3= A1 TX and A2 RX
0
3
0
No
S21
GPIO1_3 STATLED
Set GPIO 1.3 to behave the same as the
status LED allowing link lock status to read
from the I/O pin
0
1
0
No
S22
RESERVED
Deprecated. No effect.
0
0
0
n.a.
S23
RATE/FREQBAND
To change bands. Only for locked modems
0
1
0
Yes
S24
NODEID
Node ID. One node must be acting as a
master (NODEID 1, NETID 0) for a multipoint
environment to work.
2
16
1
No
S25
NODEDESTINATION
Remote node ID to communicate with. Set
the value to 255 to broadcast to all nodes.
Cannot be the same as NODEID.
255
2555
1
No
S26
NETCOUNT
The total number of networks on the one
master node. Not applicable to non-master
nodes.
1
106
1
Yes
S27
SERBREAKDETECTMS10
x10 to give time in ms units for break
detection. Set to 0 to turn this feature off.
0
20
0
No
S28
RESERVED
Deprecated. Has no effect.
0
0
0
n.a.
S29
MAX_PACKET
Max air packet (bytes). Advanced feature.
380
120
480
Yes
S30
BUFFSIZE
Max serial buffer (bytes). Advanced feature.
631
256
1920
Yes
R0
TARGET_RSSI
Optimal RSSI value to try to sustain (0
disables the feature)
0
110
0
No
R1
HYSTERESIS_RSSI
Amount of change before power levels
altered
5
15
2
No
Table 3-3: AT parameters
Notes:
1To ensure the correct channel separation this value will change based on frequency band and number of channels. Examples given in the
example configurations.
2Injects RSSI packet when MAVLink protocol used and heartbeat packet detected.
3Some of these values will vary on region locked modems.
4868MHz version.
5The maximum node number is 16 and the value of 255 indicates broadcast, all values between 16 and 255 are not valid.

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6The number of networks is based on channel separation requirements and will change based on frequency band and number of channels.
Examples given in the example configurations.
3.1 Setting up data encryption
The 128-bit AES data encryption may be set, enabled and disabled using the AT commands (see
Table 2.1). The encryption key can be any 32-character hexadecimal string.
To encrypt a device, the encryption mode must first be enabled, e.g. by typing ‘ATS15=1’ in the
command terminal. Once the encryption mode is active, an encryption key may be set, e.g. by typing
‘AT&E’ into the command terminal. The encryption key may be of any 32-character hexadecimal
string of the users choosing. Modems with different encryption settings will not communicate.
After entering command mode, send the following commands to set encryption on using an
arbitrary 32-character key:
ATS15=1
AT&E=5AEEF103125C0AA233678909160111CA
AT&W
ATZ
3.2 Setting the air data rate
The default air data rate is 64kps. If the air speed is set lower, the range of the wireless link increases
but the total amount of data that you can send will be reduced. The total amount of data is split
evenly between all the nodes on the network. If the air data rate is set higher the greater throughput
allows for more total data but reduces range. The air data rate must be the same for all nodes on the
network.
The air data rate is chosen depending on:
• The range that you need
• How many nodes you want on each network
• The amount of data that each node will send
It is important that the modem serial data rate must be set to a higher value than the air data rate
serial output data is not lost, as there is limited output buffering in the modem.
To set a 224kbps air data rate, for instance, enter command mode and issue:
ATS2=224
AT&W
ATZ

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4 Multipoint Network
The multipoint firmware is not loaded on the modem by default and will need to be uploaded into
all network modems. Check section “Useful links” for the download link and refer to section “RFD
Modem Tools” to upload the multipoint firmware. After uploading the device, you are required to
choose a master node that will control the radio timeslot allocations.
Node 2
Node 3
Node 4
Node 1
Master
Within master node
range
Figure 4- 2: multipoint network diagram example
At this time the multipoint firmware settings, other than the master nodes configuration, are
supported by the RFD modem tools. Therefore, the master node settings must be made by AT
commands via a terminal programme or the terminal tab of the RFD tools. The list of AT commands
can be found in section three of this manual.
To set up the multipoint network, each device must be assigned a unique Node ID on its network. A
device set as overall master is also mandatory.
By default, the nodes are configured to address all the other nodes in broadcast mode, Node
Destination = 255. To address a specific node, you must set the Node Destination parameter. For
example, to address the data to node 3, you must send the following commands in command mode:
ATS25=3
AT&W
ATZ
A few notes on the multipoint network (see Figure 4-2):
• Based on the topology depicted in Figure 4-2, for Node 3 to communicate with Node 2, Node 1
(the base) and Node 2 must be within the RF range, and
• More nodes will reduce the effective throughput.
• All nodes must remain in range of the Master node.
4.1 Example network configurations
This section will cover the key modem settings for some of the network types that may be desired.
As a general rule lower airspeed will allow for more range but limit the number of nodes/data
throughput that can be used.

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64kbps Airspeed Networks
Single network
Parameter
Value
S1
57
S2
64
S3
0
S4
301
S6
12
S8
922000
S9
928000
S10
21
S11
100
S13
1
S14
80
S15
0
S24
x
S25
y3
1Dependent on range and power requirements. Lower power will reduce range.
2Example setting for sending mavlink data
3Depends on the network structure. Master node must be set to broadcast (255). Other nodes may
be set to address any single node in the network or broadcast mode
x = the node number starting with the master (1) with a maximum in this case of (4) in a three node
one master configuration
y = the address of the target node
Master node specific settings
Parameter
Value
S24
1
S25
255
S26
1
AT&M0= 0, Z where Z is the maximum NodeID used e.g. (4) in a three node one master
configuration.
Single network with relay node
Example network path. Note that the master node has been set as the relay node as all nodes must
be able to see the master and that Vehicle1 will always send messages via the relay even if it is in
range to receive them direct from the GCS
Node name NodeID
Vehicle1 → Relay → GCS 3 → 1 → 2
GCS → Relay → Vehicle1 2 → 1 → 3
GCS → Vehicle1 2 ->3 (When in range)
Vehicle2 → GCS 4 → 2
GCS → Vehicle2 2 → 4
Settings as for single network with the following exceptions
NodeID 1 (Master aka Relay)
Parameter
Value
S25
255
S13
0

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NodeID 2 (aka GCS)
Parameter
Value
S25
255
NodeID 3 (aka Vehicle1)
Parameter
Value
S25
1
NodeID 4 (aka Vehicle2)
Parameter
Value
S25
2
Note that for the Master (Relay) only, the flow control is disabled. This node also requires that the
RX and TX pin of the UART (pin 7 and 9) must be connected.
125kbps Airspeed Networks
Single network (Maximum 7 non-master nodes)
Parameter
Value
S1
115
S2
125
S3
0
S4
301
S6
12
S8
922000
S9
928000
S10
21
S11
100
S13
1
S14
40
S15
0
S24
x
S25
y3
1Dependent on range and power requirements. Lower power generally lowers range.
2Example setting for sending mavlink data
3Depends on the network structure. Master node must be set to broadcast (255). Other nodes may
be set to address any single node in the network or broadcast mode
x = the node number starting with the master (1) with a maximum in this case of (4) in a three node
one master configuration
y = the address of the target node
Master node specific settings
Parameter
Value
S24
1
S25
255
S26
1
AT&M0= 0, Z where Z is the maximum NodeID used e.g. (4) in a three node one master
configuration.

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Maximum number of nodes per network
The maximum number of nodes that can be used on a network is determined by the total
throughput, related to the airspeed minus overheads etc., and the required node throughput,
recommended to be at least 12-14kbps for basic mavlink telemetry. The number of nodes is the
throughput divided by needed node throughput.
Example throughput measurements
Airspeed
Approx total
throughput
Nodes per
network
Approx node
throughput
64
43
3
14.3
125
78
7
11.1
200
115.5
9
12.8
224
119.5
9
13.2
500
188.6
14
13.4
750
238.9
16
14.9
Note: The above table is based on throughput measurements and does not indicate these node
counts have been fully verified in working networks and meant as illustration of node counts scaling
verses the airspeed settings.
Encryption has a negative effect on the total available throughput.
Airspeed
Approx total
throughput
Approx total throughput
with encryption
125
78
75
Multiple Networks
It is possible to run multiple networks of the same configuration at the same time to enable support
for more nodes. There will still only be one master node (network 0, node 1) and all nodes will need
to be in range of the master for synchronisation. Node 1 on NetworkIDs other than 0 will act as
normal nodes and need no master node setting configurations. Nodes will only see other nodes on
the same NetworkID.
The theoretical NetworkID minimum frequency separation for networks is approximately 1200kHz
on 900 version modems and approximately 1050kHz on 868 version modems. The NetworkIDs of
these networks would be separated by the number of channels required to meet this separation
frequency. The channel bandwidth, in kHz, is the (Max Freq - Min Freq) / Num Channels.
e.g.
For default frequency and number of channels on a 900x modem
928000 - 922000 / 21 = 285.7 kHz channel bandwidth
Therefore, the minimum number of channels for required network separation is 5, so valid
NetworkIDs would be 0, 5, 10, 15 etc.

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Note: These are theoretical values and have not been fully verified as working networks.
A tested network example is given below using the 125kbps airspeed example basic settings.
The NetworkIDs values are 0,7 and 13 so:
Parameter
Value
S3
Y
Where Y is the NetworkID e.g 0, 7 or 13 here
The following settings will be needed for the master node.
Parameter
Value
S26
A
Where A is the number of networks e.g 3 here
AT&M0= 0, Z0 where Z0 is the maximum NodeID used in NetworkID 0
AT&M1= 7, Z1 where Z1 is the maximum NodeID used in NetworkID 7
AT&M2= 13, Z2 where Z2 is the maximum NodeID used in NetworkID 13

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5 Useful links
RDF900x/ux and RFD868x/ux modem Firmware
The firmware is the same for both the 868x/900x modems and can be found at.
http://files.rfdesign.com.au/firmware/
RFD TOOLS
http://files.rfdesign.com.au/tools/
Documentation (including FAQ)
http://files.rfdesign.com.au/docs/
Store
http://store.rfdesign.com.au
FTDI Cable documentation
http://www.ftdichip.com/Support/Documents/DataSheets/Cables/DS_TTL-232R_CABLES.pdf
6 Document Revision History
Version
Date
Changes
1.0
20/08/2018
Release document
1.1
01/04/2021
Updates to reflect latest firmware