This is an Arduino sketch, to be run on a Pro Micro (ATMEGA32U4) board, that turns it into a USB serial adapter for Martin Barr's UPURS.
It works very well with UPURS. I couldn't get it to work reliably with UPURSFS (HostFS:UPURS); I suspect there are bugs in my code to calculate when it's safe to send a byte.
TODO: Investigate this more. 8bitkick has apparently got it working reliably on an Arduino MKR1000, which uses an ATSAMD21 core at 48MHz. I'd like to have it running rock-solid on an ATMEGA32U4, because no level shifting is required, and keeping the component count to a minimum is very much in line with the UPURS philosophy.
Discussion on the Stardot forums.
