Today, I made a port of my old rEmotion 1 Arduino Nano-based firmware to rEmotion 2’s Pico. I used the second core for the stepper motor.

You can build it yourself using PlatformIO. The code is crappy, probably has to be refactored soon, but it works. For now, you can read all the commands in the file https://github.com/an-dr/rEmotion/blob/main/firmware/src/controlcallback.cpp#L19-L29 . 

Basically, they are ASCII codes of 0-6, a, d symbols so you can send them just by pressing a key on your keyboard while connected to the Serial port.

Repository: https://github.com/an-dr/rEmotion