Given up on waiting for Makibox, and ordered another printer from eBay, a Sintron Prusa i3 (take that, Jon Buford). It arrived, and I managed to make it work! So I started working on this project again, brand new code is available on GitHub for the new communication protocol. ( I'm using timer interrupt instead of _delay_ms this time, it's much better). Anyway, first images of test prints coming soon!