What is SuperbitRF?
SuperbitRF is a project to design our own datalink/radio receiver. The ultimate goal is to get the receiver to work with our own datalink modem and also normal DSM2/DSMX transmitters. But the main focus is to get a very small datalink which will be integrated in the autopilot PCB.
How does it work
In general you will have either a usb datalink modem or a DSM2/DSMX transmitter which can be binded to the datalink/radio receiver on the autopilot. During the binding process the receiver will know if it is binding to a usb datalink(in DSMX or DSM2 mode), DSM2 transmitter or a DSMX transmitter. After binding the receiver tries to keep in sync with the usb datalink or transmitter and will forward the packets received to either the paparazzi datalink or the radio control.
The SuperbitRF usb modem uses the normal DSM2/DSMX protocl, which can be chosen inside the firmware. For more information on how the DSM2 and the DSMX protocol works, look at DSM.
The source code
The firmware for the SuperbitRF USB modem is open source and can be found at Github SuperbitRF Firmware. The source code of the datalink receiver inside the paparazzi autopilot isn't made yet but will come later.
- 02/07/2013 - After some simple logic analysing we figured out the faulths and now we have a working SPI connection between the superbitRF and the paparazzi Lisa M. Already implemented the binding procedure inside paparazzi and we are receiving packets, but we didn't implement the handling of the binding packet.
- 01/07/2013 - We connected a cyrf6936 chip directly to the spi bus of a Lisa M and are trying to receive the MFG id, manufacturer id, from the cyrf6936. Having some problems with that so we are going to sniff the spi connection and the reset pin with a logic analyser.
- 28/06/2013 - We sniffed a normal dsm2 receiver spi bus connection to the cyrf6936 chip and found the errors in our own protocol. We are now able to bind to a normal DSM2 and DSMX transmitter trough DSM2 and receive the channels. The next step is to implement DSMX and make our own datalink work together with a normal transmitter. (We used saleae logic with a simple php script to analyze the cyrf6936 spi connection)
- 20/06/2013 - Hacked the SITL(NPS) of paparazzi to enable a hardware datalink and tested the Quad Lisa M simulator with normal telemetry. Everything worked great, tweaked some of the timings of the receiver and transsmitter, and we now have a relaible datalink!
- 19/06/2013 - Made the datalink more relaible, and both the receiver and transmitter know when a packet is lost and resends it. Als did manage to get a simple datalink with an AR.Drone 2.
- 18/06/2013 - We currently have a datalink working between two SuperbitRF usb modems. It isn't that reliable yet, but we are working on improving it. We can already bind to a normal DSM2/DSMX transmitter, but can't get the syncing to work. We are also working on testing the datalink transfer rate and testing how paparazzi handles the packet loss you have with a unreliable radio datalink.
- 11/06/2013 - Received the SuperbitRF usb modems and did some simple testing with blinking light and receiving the radio chip ID.
- Piotr (working on the hardware)
- Bart Remes
- Freek van Tienen (working on the software)