gabonator
commented
3 years ago I was considering support for uknown protocols, but there are more reasons why this would be too challenging:
- The main feature for the rf toolkit is analyse and synthesize - you can receive a packet, modify it and send it out. There is no similar device or pc application that does this. This requires the app to "understand" the received signal
- Implementing new protocol is quite easy, so the community could contribute to this project and add support for new devices, here is code for FA-Twin-Plus weather station
- The device has very limited resources - storing arbitrary packets would consume too much RAM. Currently we only store few numbers needed to reconstruct the packet (type of device + temperature + humidity + device id...)
- There are two ways how to transmit data with CC1101 - either you use one of the input pins as OOK modulation input, or you transfer the paket through SPI interface. I decided to use SPI interface, because the application doesnt need to handle precise timing, you just let the transceiver to transmit the binary stream at specified speed from byte buffer provided through SPI
- For transmitting packets over SPI we need to know what is the shortest pulse duration, or we need to know what is the greatest common divisor of all possible pulse lengths to be able to construct the bitstream. And this is not possible with arbitrary protocols, we need to simply quantize the durations somehow
Of course we can add some universal analyser for manchester coding, gap coding and other common modulation types. There is one application that helps you identifying the protocol type WaveAlchemy, but it is very experimental and since we have CC1101 webusb rf analyser application I stopped the development of WaveAlchemy, because web browser offers much more options for analysis of unknown protocols
To analyse new protocols I use this workflow:
- Use spectrum analyser with directional antenna to identify new signal source and its precise frequency (not necessary, you can guess the frequency until you get stable signal)
- Use computer and Webusb rf analyser to catch few packets tuned at this frequency. This application integrates RTL433 library which has support for more than 400 protocols and if it will recoginze your signal, your are lucky
- Add new protocol to the Rf toolkit application based on the RTL433 decoder
- Check the decoder with packets from webusb rf analyser using unit test (https://github.com/gabonator/LA104/blob/master/system/apps_featured/80_rftool/test/test.cpp) - it tries to decode array of microsecond intervals and then encode it back and decode again to verify if decoder and encoder is consistent
For recording arbitrary packets I would rather make separate application (or continue developing WaveAlchemy app), but I am afraid that we cannot use the CC1101 in direct modulation mode using its GPIO pin, because there is no extra GPIO pin on LA104.
So for now we can keep this issue open until someone (or I) adds support for generic modulations.
cypresstwist
BG7UHS
art9tem
RChadwick7
The RF potential for this looks fantastic, but after adding a CC1101 board, I realized I don't have any compatible devices that are automatically recognized. It would be great if unrecognized devices could still be recorded, analyzed, and played back.