Oof, behind on updates; I spent a great Saturday back at the CBA where Jake helped me wake up the rotary axis. We carved a lot of bad circuits and a few good ones; after a few manual touch-ups, one beeped out so I soldered on the appropriate components:

It's not a complicated circuit, just an HC595, a pair of 220-ohm resistor packs, and a handful of yellow 0402 LEDs:

Not yet tested, but no shorts! Tomorrow(ish), I'll drop some wires on the six driver pads and see if I can make some blinkies happen with an external driver IC of some kind.

And more to come! Lots to show: pictures and videos and failures and heatsinks and limit switches and the rest. Slides are now due in a week, but I'd rather not push that, so I may prioritize the talk over updates here for the time being.