As fallout from a conversation about I2C and the Adafruit NeoTrellis, here is a small code example which wraps an OSC sender and receiver around a NeoTrellis so you can talk to it.

https://github.com/rhaleblian/neotrellis-osc

This has been used with some success with Pure Data and C projects. The example itself really is no more than the underlying projects' examples, fused, with a tiny bit of Bela-centricity. If it's useful, hits a practical usability level and gets some feedback it can be improved and debugged.

Big caveat is that you need a newer Python than the one on the Bela. I have one which I can share and should think of a smart place to post it for download.

(@Lia)

Added a link in the README where the version of Python in question (3.9, built on the current Bela image) can be downloaded. Please do not try to replace the existing Python with this one! This one is meant to live in /opt/python3.9 and only be used to make a virtualenv for this specific application.

I'm not super happy about this heavy hammer; in the future it might eventually be unnecessary.

Added minimal C code which listens for NeoTrellis messages and prints the key and its state.