This is the Raspberry Pi Pico firmware for the PIcoHPSDR Controller (see https://github.com/cveith/PIcoHPSDR_Controller).
Basically it just collects data from the encoders and i2c bus expanders and translates them to a 8-Bit telegram sent over the serial line to the Raspberry Pi running piHPSDR by John Melton.
Please see https://github.com/g0orx/pihpsdr for more details on his work.