I'm doing a project for college connecting an app made with app inventor to a Raspberry Pi and then using the RPi to make a printing queue for a Prusa P3 Steel.
The thing is that I already have the comm between the app and the RPi but I need to connect the RPi to the Arduino via USB and select the G-code files that are in the SD card of the Prusa to print. I don't know where should I put the function in the Marlin code or how to manage the serial port read function.
Any ideas?