USB

[larsbrinkhoff]

USB stack. Phew!

[larsbrinkhoff]

@ataradov's USB implementation doesn't look like a huge amount of code to port:
https://github.com/ataradov/dgw/blob/master/embedded/usb.c

[larsbrinkhoff]

V-USB may also provide inspiration:
https://github.com/obdev/v-usb

[larsbrinkhoff]

USB in a nutshell:
https://www.beyondlogic.org/usbnutshell/usb1.shtml