RFDesign RFD TXMOD User manual

www.rfdesign.com.au
RFD TXMOD
User Manual
PRJ-TXM-MAN-001
RFDesign Pty Ltd
7/1 Stockwell Place
Archerfield, QLD 4108
rfdesign.com.au

RFD TXMOD User Manual
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–Version 1.2 –Status –Issued for use
Document Number –PRJ-TXM-MAN-001
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1
Table of contents
1 Introduction ....................................................................................................................................2
1.1 Product Description ................................................................................................................2
1.2 Getting to know the product ..................................................................................................2
2 RC –TXMOD Compatibility .............................................................................................................4
3 Getting Started................................................................................................................................5
3.1 Radio Controller Configuration...............................................................................................5
3.2 TXMOD Configuration.............................................................................................................5
3.2.1 Configuration Webpage..................................................................................................6
3.2.2 Wi-Fi Configuration.........................................................................................................6
3.2.3 TXMOD Internal RFD900x Modem settings..................................................................12
3.3 Vehicle Modem.....................................................................................................................16
4 Ground control station software ..................................................................................................18
5 Antenna Recommendation...........................................................................................................19
6 Technical Specifications................................................................................................................20
6.1 TXMOD Power Consumption................................................................................................20
6.2 Modem Specification............................................................................................................20
6.3 Wi-Fi Specifications...............................................................................................................21
6.4 TXMOD Radio Controller Interface.......................................................................................22
6.5 TXMOD Compliance..............................................................................................................22
6.6 Physical Dimensions..............................................................................................................23
7 Useful Links ...................................................................................................................................24

RFD TXMOD User Manual
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1Introduction
1.1 Product Description
The RFD TXMOD, or TXMOD, has been designed to work in conjunction with the Taranis X9D Radio
Control Transmitter from FrSky and other compatible controllers. The RFD TXMOD transmits the
PPM stream from the controller to the vehicle via the RF Design long range telemetry modems while
also receiving telemetry data from the aircraft. The telemetry data can be broadcast to a computer
or smart device by the TXMOD’s built in Wi-Fi module.
1.2 Getting to know the product
Figure 2 - TXMOD top (left) and bottom (right) views
Figure 1 - Typical Application Diagram.

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Table 1 - TXMOD Description
#
Description /Note
1
Antenna
connectors
For information about antenna selection refer to section 5 in this document
or to the RFD 900x Modem datasheet linked in section 7.
2
Heat sink
The heatsink, visible through the top cover, is required for proper operation
and should not be covered while the unit is in use.
3
Status LEDs
Red
Blinks slowly a few times - establishing link to a Wi-Fi client.
Blinks rapidly for some time - flashing the modem firmware (using
‘spiffs.bin’ file explained in 3.2.2e)
Solid - device initialisation has completed
Green ∗
Blinking –RFD modem looking for a link
Solid –RFD modem bound to another modem
4
Button
Press 5 times within 5 seconds to reset all Wi-Fi settings to default values.
(Red LED will turn off, blink 3 times and go solid after resetting default Wi-Fi
settings)
5
Tabs
Mechanical clips to lock the TXMOD into the radio control socket.
6
RC and
TXMOD
Interface. ∗∗
a
PPM
Sends RC data into TXMOD.
b
+6 V
6V supply positive terminal (not used by the module)
c
+Bat
Positive battery terminal (supply for the module) ∗∗∗
d
GND
Ground
e
-
Not connected
∗Green LED will be enabled after ‘First Run Wizard’ explained in section section 3.2.2 0.
∗∗Interface between RC and TXMOD is done through a female 0.1” pitch connector.
∗∗∗See Table 2 below for module supply ratings and section 6.1 for the relation between battery voltage and
current draw with different battery types.
Table 2 - TXMOD Supply Ratings
Parameter
Minimum
Maximum
Units
Supply Voltage (+Bat relative to GND)
+5
+18
V
Operating Current Draw
N/A
1.2*
A
∗Rating for TXMOD with RFD modem set for maximum 1W transmit power measured at 5V supply.

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2RC –TXMOD Compatibility
The TXMOD has been designed to fit into the rear expansion bay of an FrSky Taranis X9D Plus. It may
be compatible with other transmitters however the determination of this is the user’s responsibility.
Check that the dimensions of the slot and the pin configuration of the connector at the back of your
RC match those specified for the TXMOD. For detailed information on the TXMOD dimensions refer
to section 6.5 and pinout details can be found in Table 1 above
Figure 3 - RC External RF module slot dimensions.

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3Getting Started
The RFD TXMOD setup has five elements.
3.1 Radio Controller (RC) configuration
3.2 TXMOD Wi-Fi access configuration
3.3 TXMOD RFD900x Radio Configuration
3.4 Vehicle (paired) RFD 900x modem configuration
3.5 Ground Control Station (GCS) configuration
3.1 Radio Controller Configuration
a) Enable PPM mode on radio controller
This guide is based on TARANIS X9D PLUS radio controller (RC). Specific instructions on activating the
required mode on other RCs should be sort in the relevant device manufacture’s manual. Please
check the transmitter for RFD TXMOD compatibility and ensure it supports the same interface.
- Switch on the RC and choose the vehicle you intend to operate.
- Navigate to the Model Setup sub-menu
- Scroll down until you find the External RF configuration section, as shown in figure 4.
- Choose “Mode PPM” to enable external PPM stream for the TXMOD.
Figure 4 - PPM mode configuration on TARANIS X9D PLUS RC.
3.2 TXMOD Configuration
- With the RC switched off, remove the rear protective cover from the radio controller and insert the
TXMOD.
- Ensure the TXMOD is inserted fully into the opening and the two tabs have locked in place.
- Switch on and observe the TXMOD’s LEDs. The red LED will blink and then go solid during the
power up sequence, as per the descriptions in Table 1, and the green LED will indicate the state of
the modem link with the modem on the aircraft. Note: The green LED functionality will only be
enabled after the ‘First Run Wizard’, see section 0, is completed; before that it will remain off.
The configuration interface webpage and the communication settings for both the Wi-Fi and the
RFD telemetry links are described throughout this section.

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3.2.1 Configuration Webpage
Figure 6 - Configuration home page
The configuration home page provides basic information on the RF Design TXMOD, such as the
software versions, MAC and IP addresses and links to the various configuration pages. The default
address is http://192.168.4.1/ . This interface allows the user to configure both the Wi-Fi and the
long-range communication settings. Follow the steps described in the following section.
3.2.2 Wi-Fi Configuration
An active Wi-Fi connection is needed to configure the TXMOD. On first power up, the TXMOD will
default to access point mode, with SSID of the format ‘TXMOD-XX-XX-XX’, where the XX are unique
hexadecimal characters relating to the unit MAC address.
a) Connect to TXMOD Access Point
- Use your computer or smart device to search for and connect to the access point Wi-Fi network
generated by the TXMOD (use ‘TXMOD123’ as default password). Note: It may be necessary to
disable mobile data, on tablets and phones, to force the browser to use the TXMOD network.
Figure 7 - Network settings. A) Windows 8.1. B) Android.

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b) First Run Wizard
- Point your preferred browser to the TXMOD IP address (by default http://192.168.4.1/) to access
the configuration homepage of figure 6. Alternatively, it can be accessed by the URL http://TXMOD-
XX-XX-XX.local where the X’s are the same as the X’s in the access point network name. Note: This
second option will require the installation of some support software for correct operation, for detail
please see section 3.2.2 d).
- On the home page, see figure 6, click on ‘Go to First Run Wizard!’ button to access the wizard
shown in figure 8 which will guide you, step by step, to configure your module.
- Power up the remote modem. Note: If the remote RFD900x modem was supplied in kit with the
TXMOD both modems should already have the correct firmware. If not or if TXMOD firmware has
changed due to an update, refer to section 3.3 for a guide on how to update the remote modem
firmware version. The version is displayed on the ‘Device Info’ section of the homepage interface of
figure 6 under ‘Internal modem version:’.
- The modems should lock, indicated by solid green LED on the vehicle modem, if no link is
established, green LED blinking, reset both modems to default settings. If there is an ongoing issue
try resetting the TXMOD by pressing the button on the TXMOD 5 times rapidly, after it has rebooted
the wizard can be restarted.
- Follow the wizard steps
Once the wizard is successfully completed, your device is ready to be used and further configuration
is optional.
Figure 8 - First run wizard
c) Change Network Settings
- Open a web browser and enter the module’s IP address by default in AP mode http://192.168.4.1/
-Click on ‘Wi-Fi/Network Setup’ or ‘General settings’–depending on what firmware version you are
using, to access the Wi-Fi setup interface of figure 9.

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- Change the desired settings and press save.
- Finalise the changes by power cycling the TXMOD. Note: Changes to the network settings may
require a change to the Wi-Fi connection that you use in order to connect, e.g. selecting the new Wi-
Fi name, or forcing the system to forget an old network password.
Figure 9 -WiFi settings configuration page on firmware version 1.4. Some of the options will not be available on older
firmware versions.
Table 2 –WiFi Settings/General settings parameters description
Parameter
Description
Wi-Fi mode
This sets the module to act as an access point (default) or as a station on an
existing access point, such as a home network.
AP SSID
Is the SSID used for creating the Access Point (AP).
AP Password
This is the password that will be used for the access point. It must be a
minimum of 8 character long
Wi-Fi Channel
Allows the user to set the channel as per the Wi-Fi 802.11 standard definitions
this can be used as needed to prevent interference or meet the requirements of
the network that the module is joining. The default is channel 11. The most
commonly used channel set is 1, 6 and 11.
StationSSID
The SSID of the network that the TXMOD should attempt to join.
Station
Password
The password of the network that the TXMOD should attempt to join.

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Parameter
Description
Station IP
The static IP address to assign the TXMOD when joining the network. (Note this
may require appropriate settings to be made on the network router. Once
assigned as a station the landing page for the TXMOD settings becomes the
Station IP address that was assigned.)
Station
Gateway
The Gateway IP address of the network that the TXMOD should attempt to join.
Station Subnet
The Subnet Mask of the network that the TXMOD should attempt to join as a
station.
Host Port
This is the UDP host port number. This is the port that you will direct a
connection to in UDP mode
Client Port
This is the UDP client port number.
Baudrate
Baud rate of the serial link with the modem. It must match the modem serial
speed setting to allow the two to communicate.
S.PORT output
enable
You might enable S.PORT passthrough if your hardware supports it. This allows
the Mavlink telemetry data to be converted and displayed on compatible RC
transmitter. You can modify the original TXMOD hardware to enable that
feature or use the TXMOD2 that supports it out-of-the-box.
Battery 1
capacity
This parameter is used to set the battery 1 capacity to be displayed in your RC
transmitter screen if the S.PORT output is enabled.
Battery 2
capacity
This parameter is used to set the battery 2 capacity to be displayed in your RC
transmitter screen if the S.PORT output is enabled.
d) TXMOD as a station
Using the TXMOD on an existing Wi-Fi network, e.g. to provide telemetry data to a GCS while still
allowing access to the internet, for example to download maps, can be done a couple of ways
Basic users
Supporting software requirements:
For Windows and Linux users this will require the installation of a support software like Bonjour
Services from Apple for Windows (https://support.apple.com/kb/DL999?locale=en_US) and Avahi
for Linux. Windows users may also need to use Chrome (or Chrome based) browser as this has good
support for the Apple software.
Procedure:
Once the supporting software is installed.
- Connect to the TXMOD in default AP mode go to Wi-Fi settings
- Choose ‘Station’ in ‘Wi-Fi Mode’, set the correct SSID (in StationSSID) and password of the network
in “Station Password”, leave “Station IP”, “Station Gateway” and “Station Subnet Mask” as 0.0.0.0
then press “Save”
- Finally reboot the device.
You can connect the to the Wi-Fi network with the TXMOD on it then open the browser and enter
the following address http://TXMOD-XX-XX-XX.local where the X’s are the same as the X’s in the
access point network name. If you cannot access using the URL, you will have to log into your router

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and find what IP was assigned to the TXMOD. You will be able to access the TXMOD interface by
typing the IP in a web browser.
Advanced users
The module must be set up by:
- Choosing ‘Station’ in ‘Wi-Fi Mode’
- Setting the correct SSID (in StationSSID) and password of the network in “Station Password”.
- Find the Gateway and Subnet mask of the network then to write the appropriate values in ‘Station
Gateway’, ‘Station Subnet’. Network information such as the Subnet Mask and Gateway address can
be found on a network connected device. For instance, in windows launch a command prompt, type
‘ipconfig’ and press enter. Information similar to figure 10 will be shown. In Linux based devices
typing ‘ifconfig’ to the terminal should give similar results.
Note: Assigning the ‘Station IP’ will require that a static IP is set on the DHCP server, normally the
network router, this is to ensure the device will be at a known address on the network. This new
address will replace the default 192.168.4.1 of access point mode.
Figure 10 – Command Prompt.
Default Gateway ->‘Station Gateway’
Subnet Mask ->‘Station Subnet’
e) Firmware Update:
Updating the TXMOD requires two different files; the ‘firmware.bin’ and the ‘spiffs.bin’ files.
- Download files. Follow the links in section 7
- On the browser configuration landing page shown in figure 6, select ‘Update Firmware’ and follow
the on-screen commands to flash them onto the device.
- The firmware.bin should be uploaded first
- Second upload the spiffs.bin. These files must not be uploaded and flashed simultaneously.
- Power-cycle the device, this will automatically update firmware on the RFD900x modem if
required.

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Figure 11 TXMOD update page

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f) Wi-Fi Troubleshooting:
In some cases, user connection settings may prevent devices from accessing the Wi-Fi addresses.
Some basic troubleshooting.
- Remove the existing network settings from the device memory
- Reset the wireless adaptor
- Turn off mobile data and disconnect other networking devices such as LAN cables.
- In other cases, OS tools such as the Windows Network Diagnostics may help.
If you forget your settings or the device is not available on the network, it is possible to reset the
TXMOD to its default Wi-Fi settings.
- Pressing the button 5 times rapidly while the device is powered up to initiate a factory reset of the
TXMOD and the internal modem.
- Set up the device again as per earlier instructions.
3.2.3 TXMOD Internal RFD900x Modem settings
The TXMOD has an RFD900x series modem internally pre-configured with factory parameters, see
figure 12. A description of this parameters can be found in Table 3 - RFD900x parameters. For
further information regarding the internal modem refer to the RFD900x Peer to Peer Firmware and
RFDesign Modem 900x Datasheet documents using the links in section 7.
Table 3 - RFD900x parameters from RFD900x Peer-to-peer V3.X User Manual V1.3.pdf
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. It is set by the firmware
Firmware
dependant
N/A
N/A
No
S1
SERIAL_SPEED
Serial speed in ‘one-byte form’. Accepted
values are 1, 2, 4, 9, 19, 38, 57, 115, 230,
460 and 1000 corresponding to 1200bps,
2400bps, 4800bps, 9600bps, 19200bps,
38400bps, 57600bps, 115200bps,
230400bps, 460800bps and 1000000bps
respectively.
57
1000
1
No
S2
AIR_SPEED1
Air data rate in ‘one-byte form’. Accepted
values are 12, 56, 64, 100, 125, 200, 224,
500 and 750 corresponding to 12000bps,
56000bps 64000bps, 100000bps,
125000bps, 200000bps, 250000bps,
224000bps, 500000bps and 750000bps
respectively.
64/2004,8
750
12
Yes
Reg
#
S Register
Description
Default
Value
Maximum
Value
Minimum
Value
Must be the same
at both ends of
the link?

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S3
NETID
Network ID.
25
255
0
Yes
S4
TXPOWER1
Transmit power in dBm.
30
30
0
No
S5
ECC2
Enables or disables the Golay error
correcting code.
0
1
0
Yes
S6
MAVLINK3
Enables or disables the MAVLink framing
and reporting
1
1
0
No
S7
OP_RESEND
Opportunistic resend allows the node to
resend packets if it has spare bandwidth
0
1
0
No
S8
MIN_FREQ1
Min frequency in KHz
915000
/8680004,8
927000
/8700004
902000
/8650004,8
Yes
S9
MAX_FREQ1
Max frequency in KHz
928000
/8700004
928000
/8700004
903000
/8650004,8
Yes
S10
NUM_CHANNELS1
Number of frequency hopping channels
20/14,8
518/84,8
1
Yes
S11
DUTY_CYCLE1
The percentage of time to allow transmit
100
100
10
No
S12
LBT_RSSI1
Listen before talk threshold
0
220
25
Yes
S13
RTSCTS
Ready-to-send and Clear-to-send flow
control.
0
1
0
No
S14
Max Window
Max transit window size used to limit max
time/latency if required otherwise will be
set automatically
131
400
20
Yes
S15
Encryption Level
Encryption level 0=off, 1=128bit AES
0
1
0
Yes
S16
GPIO1.1 R/C input
Set GPIO 1.1 (pin 15) as R/C(PPM) input
0
1
0
No
S17
GPIO1.1 R/C output
Set GPIO 1.1 (pin 15) as R/C(PPM) output
0
1
0
No
S18
GPIO1.1 SBUS input7
Set GPIO 1.1 (pin 15) as R/C(PPM) input
0
1
0
No
S19
GPIO1.1 SBUS output7
Set GPIO 1.1 (pin 15) as R/C(PPM) output
0
1
0
No
S20
ANT_MODE
0= Diversity, 1= Antenna 1 only, 2=
Antenna 2 only, 3= Antenna 1 TX and
antenna 2 RX
0
3
0
No
Reg
#
S Register
Description
Default
Value
Maximum
Value
Minimum
Value
Must be the same
at both ends of
the link?
S21
GPIO1.3 Status LED output
0
1
0
No

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Set GPIO 1.3 (pin 12) as output with state
that mirrors the status LED on the modem
S22
GPIO1.0 485 TX control output6
Set GPIO 1.0 (pin 13) as control signal on
DINIO and RS485 interface boards.
0
1
0
No
S23
Rate and Frequency Band
Switches between valid settings for the
frequencies, channels and airspeeds that
can be set on compliant modems ensuring
compliance is maintained. See section 3.4
for FCC-related information.
0
3
0
Yes
R0
TARGET_RSSI
Optimal RSSI value to try to sustain (255/08
disables the feature) V3.09 and earlier this
is based on RSSI figures. After v3.12 this
changes to being based on receiver dBm
255/1108
50/08
255/08
No
R1
HYSTERESIS_RSSI
Amount of change before power levels
altered. V3.09 and earlier this is based on
RSSI figures. After v3.12 this changes to
being based on receiver dBm
50/158
20/28
50/58
No
Table 3: RFD900x SiK firmware parameters
Notes:
1The listed values are the full range of options available on unrestricted modems. The range of settings available may be altered on
compliant systems to maintain compliance to the appropriate standards
2ECC - Software Detection and correction, extra packet information, twice the packet length, is sent to allow the recovery of corrupted
packets. Disabled in version 3.15 and up. Error detection is handled by CRC since at least version 3.01
3Injects RSSI packet when MAVLink protocol used and heartbeat packet detected.
4868 modems
5Experimental feature settings not currently available
6This setting controls modem functionality linked with 485 interface and DINIO products it is not intended for use outside of this
application.
7Version 3.09 the SBUS function is mapped to GPIO1.3
8Version 3.15 and up
a) Modifying parameters with the TXMOD web interface
The modem settings, described in Table 3, can be viewed and modified on the TXMOD and on any
remote modem connected to it by using the browser interface introduced in Section 3.2.2.
To do so, point your preferred browser to the module’s IP address to access the TXMOD web
interface.
- Click on ‘RFD900x Radio Settings’ to access the modem’s setup interface. Note: If the TXMOD has
not been paired yet with any other modem, the remote side will appear empty and the message
“Sorry no parameters available” will be shown.

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Figure 12 - TXMOD modem configuration page.
- Settings can be refreshed using the ‘Load Fresh Parameters’ button.
- Parameters can be adjusted in the text boxes as required
- Apply changes using the ‘Save Params’ button. Note: Changes on the AIR_SPEED, NETID,
MIN_FREQ, MAX_FREQ and NUM_CHANNELS parameters should be applied to remote radio settings
as well to avoid losing the radio link.

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3.3 Vehicle Modem
The TXMOD bundle should come supplied with a vehicle modem that has the required firmware
version. If that is the case, the easiest way to configure it is through the browser interface explained
in section 3.2.3.
However if the modem is not the one supplied with the kit, or the TXMOD firmware has been
updated, or the modems are not connecting, the vehicle modem can be should be configured or
updated with an FTDI cable and the RFD900 Tools.
- Connect the FTDI cable. The black wire of the FTDI, i.e. pin 1, should connect to pin 1 on the lower
row of modem header
- Ensure the jumper is fitted as per figure 13. The jumper should connect the second and third pins,
aka pin 4 and 6, on the top row of the modem header.
Figure 13 - Modem connected to FTDI cable (pins 1,3,5,7,9,11) to enable serial communications. *Jumper connection (pins
4&6).
To configure the modem using the RFD900 tools. Download and install the software using the links
on section 7 if it is not installed on your computer yet.

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Figure 14 – Vehicle modem configuration on RFD900 tools.
- Ensure the firmware on the vehicle modem is the same as the one on the TXMOD.
- Update firmware if required by clicking on ‘Upload Firmware’ and choose the *.bin file Note:
Firmware can be download through the links in section 7.
- Wait until the process finishes (a message will appear at the bottom of the page)
- Reboot the modem.
- Use the interface to configure the parameters. Note: The AIR_SPEED, NETID, TXPOWER,
MIN_FREQ, MAX_FREQ and NUM_CHANNELS parameters should be the same as the ones in the
TXMOD modem.
- Set modem GPIO1.1 as a PPM output. Note: This allows the modem pin 15 to output the PPM
stream received from the TXMOD modem. This will be configured automatically by the First Run
Wizard.
- Save the settings to the modem.
If the modem has been configured correctly it will be able to link with the TXMOD modem, indicated
by a solid green LED on both devices. From this point onwards the FTDI cable is no longer required to
configure the vehicle modem. Instead this can be done over the air via the TXMOD using the
browser interface described in section 3.2.2 as long as the modem in the vehicle and TXMOD are
linked. Note: Firmware updates to the vehicle modem can only be done by means of the FTDI cable.
Settings on the modem can be defaulted by means of the reset to defaults button.

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4Ground control station software
Once the modem and Wi-Fi communications are configured it is possible to use the telemetry data
stream. The example in this section uses Mission Planner for Windows and Tower for Android. Other
software can be used provided it supports Transmission Control Protocol (TCP) or User Datagram
Protocol (UDP).
- Connect your computer or smart device to the configured Wi-Fi network; that is either the TXMOD
Access Point or the linked network when using the module as a station.
- Open Mission Planner on your computer or Tower App on your Android device
- Choose TCP or UDP and press the button “CONNECT” as per figure 15.
- When prompted, enter the IP address and port number in the pop-up boxes. Default values in AP
mode are IP 192.168.4.1, TCP port number 23 and UDP 14550. After that, if properly connected,
telemetry data should be available, and the control software should run missions as normal.
- Parameters should start loading provided that the TXMOD is properly bond to the modem on the
aircraft (solid green LED) and both devices are powered up.
Figure 15 – Mission planner connection options.
Figure 16 - Tower configuration on Android.

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5Antenna Recommendation
Any antenna with a male RPSMA fitting 50 Ohm impedance and matched to the 902-928MHz or
868MHz ISM band can be used. The recommended antenna for the TXMOD is the 3 dBi half wave
dipole which is provided in the kit and is available for purchase on the RFDesign store.
Figure 17 -: 900MHz Half Wave Dipole Antenna 3 dBi.
When assembling and disassembling the TXMOD from the transmitter, be aware the antenna may
have to be removed then reattached due to mechanical interference.