The intent of this library is to allow FT8/FT4 encoding and decoding in standalone environments (i.e. without a PC or RPi), e.g. automated beacons or SDR transceivers. It's also my learning process, optimization problem and source of fun.
The decoder is designed with memory and computing efficiency in mind, in order to be usable with a fast enough microcontroller. It is shown to be working on STM32F7 boards fast enough for real work, but the embedded application itself is beyond this repository. This repository provides an example decoder which can decode a 15-second WAV file on a desktop machine or SBC. The decoder needs to access the whole 15-second window in spectral magnitude representation (the window can be also shorter, and messages can have varying starting time within the window). The example FT8 decoder can work with slightly less than 200 KB of RAM.
Encoding and decoding works for both FT8 and FT4. For encoding and decoding, there is a console application provided for each, which serves mostly as test code, and could be a starting point for your potential application on an MCU. The console apps should run perfectly well on a RPi or a PC/Mac. I don't provide a concrete example for a particular MCU hardware here, since it would be very specific.
You can generate 15-second WAV files with your own messages as a proof of concept or for testing purposes. They can either be played back or opened directly from WSJT-X. To do that, run ```make```. Then run ```gen_ft8``` (run it without parameters to check what parameters are supported). Currently messages are modulated at 1000-1050 Hz.
You can decode 15-second (or shorter) WAV files with ```decode_ft8```. This is only an example application and does not support live processing/recording. For that you could use third party code (PortAudio, for example).
The public part of FT4/FT8 implementation is included in this repository under ft4_ft8_public.
Of course in moments of frustration I have looked up the original WSJT-X code, which is mostly written in Fortran (http://physics.princeton.edu/pulsar/K1JT/wsjtx.html). However, this library contains my own original DSP routines and a different implementation of the decoder which is suitable for resource-constrained embedded environments.
