Since I have some basic USART to play with, I would say ADC, SPI, SWI. I was actually able to run the Unity test that doesn't involve ADC using USART1 at A9&A10 for printing: Testing... Wokwi CLI v0.6.5 (2d0131707d12) Connected to Wokwi Simulation API 1.0.0-20230819-g3661476...