No USB? No problem. (33c3)

https://media.ccc.de/v/33c3-8031-no_usb_no_problem How to write an open source bit-bang low-speed USB stack running on a sub-$1 Cortex M0+ How to get USB running on an ARM microcontroller that has no built in USB hardware. We'll cover electrical requirements, pin assignments, and microcontroller considerations, then move all the way up the stack to creating a bidirectional USB HID communications layer entirely in software. ['Xobs']