The cdcarduino library provides support for Arduino USB CDC ACM boards such as the Uno and Mega 2560. The library detects Arduino boards based on their USB Vendor ID and Product ID. Methods to reset ...
Hook your Pi 400 up to your PC somehow, using a USB Type-C cable into the power port of the Pi. Anker make good ones- I used a 3m white one for my tests. Our USB-C to USB-A is great if you're using a ...