I got started on writing the firmware using PlatformIO. I've been trying to be more organized with my folder structure and making a better effort at encapsulating all my code properly so I've been trying to contain a lot of the IO and setup functionality inside its own custom library. I just got the audio shield setup working and am nicely polling all my knobs and buttons (with debouncing). Not terribly exciting, but still happy with the results!
I also got started on a pretty straightforward synth engine. 2 Oscillators, 1 noise generator, ADSR envelopes for filter and amp. Likely will change as I move further along, but it'll do for now.