Setup and troubleshooting for RFD900x communications
Intro
The RFD900x is a radio modem (receiver and transmitter) made by RFDesign. It operates at a frequency ~900 MHz.
You can get one for $100 - https://store.rfdesign.com.au/rfd-900x-modem/
Official documentation (detailed pinout, power levels, performance data) - https://files.rfdesign.com.au/Files/documents/RFD900x%20DataSheet%20V1.2.pdf
LEDs
The RFD900x has two LEDs - one green and one red. The lights are indicators for the status of the device.
Blinking Green - the RFD is ready to connect
Solid Green - the RFD is connected
Blinking Red - if the RFD is blinking red after being successfully connected, it is transmitting data. If it's blinking red immediately after being powered, something is broken. See the Flashing section below.
Solid Red - the RFD is in firmware update mode
No light - underpowered cable or you forgot to plug it in
Usage
You can operate an RFD using a Windows computer and a Pixhawk flight controller. You will need to have Mission Planner installed on your computer. Always keep the heatsink exposed to open air and the antennas vertical and horizontal as shown below. The signal will be strongest in the direction of the blue line.
To access the RFD from a computer, you will need an FTDI cable with IO pins configured for 3.3V. On an FTDI cable, the orange and yellow wires are output and input, respectively. Please double check the voltage on these wires to make sure the RFD won't be damaged via overvoltage. Pixhawk I/O on TELEM1 and TELEM2 is 3.3V by default.
Once both RFDs are blinking green, you are ready to connect. Open Ardupilot, select a COM# port in the top right, set the baud rate to 57600 and press connect.
Flashing
Flashing is the process of uploading new firmware to a device. It's necessary when the old firmware is broken, outdated, or missing. If the RFD is blinking red, it could mean the firmware needs to be replaced. Follow the steps below to flash the modem
Download firmware at https://files.rfdesign.com.au/firmware/
Download RFDTools at https://files.rfdesign.com.au/tools/
Open RFDTools.exe, then connect to your modem over an FTDI cable rated for 3.3V IO.
Short pads 9&16:
The modem's upper LED will light solid red.
Select the correct COM Port and set Baud to 57600, then click Connect. Keep the pads shorted as you start uploading firmware. If everything goes right, power cycle the modem and it should blink green.
Have fun! 😉
