The software solution (see Useful Links) is an open source development which is also compatible with RFD900 Modem Tools (see Useful Links) and the 3DR Radio Config (see Useful Links) from 3D Robotics. It is called “SiK” and was created by Mike Smith and improved on by Andrew Tridgell and RFDesign.
A boot loader and interface is available using RFD900 Modem Tools and field upgrade of the modem firmware via the serial port.
The RFD900 Radio Modem is compatible with many configuration methods like the AT Commands and APM Planner. The AT Commands can be used to change parameters such as power levels, air data rates, serial speeds etc.
Integrated support for configuring the RFD900 Radio Modem is supported by the APM Planner, with other GCS solutions in development. Its default serial port settings are as follows:
- 57600 baud rate
- No parity
- 8 data bits
- 1 stop bit
The RFD900 Radio Modem has many software features which include:
- 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 realtime
- Automatic duty cycle throttling based on radio temperature in order to avoid overheating
Air Data Rate
An air speed of 64kps will give a range of about 40km depending on antenna. If the air speed is set to be lower, the range of the wireless link increases but the amount of data that you can send will be limited. Therefore one has to compromise between range and data rate. The data rates that you can choose are only limited to 2, 4, 8, 16, 19, 24, 32, 48, 64, 96, 128, 192 and 250.
The air data rate is chosen depending on:
- the range that you need
- the data rate that you will be sending
- whether you send data in one direction or both
- whether you have enabled ECC or not
- whether you have APM firmware with adaptive flow control
RFD900 can be implemented in either simple pair (V1.x, V2.x) or multipoint network (V2.x Only).
A few notes on the multipoint network:
- In order for Node 1 to communicate with Node 2, it has to be able to see Node 0 (the base) and Node 2
- If Node 4 cannot see Node 0, to communicate with Node 1, it has to be able to see Node 1 and set the SyncAny parameter to 1 (refer to Figure 8.3: RFD900 parameters).
- Please note that there is a maximum number of one node which can have SyncAny = 1 parameter in a network to avoid data corruption.
- More nodes will reduce the bandwidth.