These are examples of how to use the low-level machine.USBDevice class to create custom USB device functionality.
Alternatively, there are usb driver modules in micropython-lib which provide a simpler interface and more built-in functionality.
In this directory:
usb_dfu_device.py implements the USB Device Firmware Update protocol.usb_simple_device.py implements a custom USB protocol, with a matching host program to run on a PC.See comments at the top of each Python file for more details.