I have the preliminary software working for the hihat. Things are reasonably good, although there are still a few bugs / annoyances. I realize that it will never be as expressive as an acoustic hihat, but I can still try :-)
The pedal uses 6 IR photo transistors to sense the position of the hihat pedal. In practice this hardware can differentiate between about 4 or 5 different states (Tightly closed, closed, loose, half open, open). If you were to add more transistors and change the orientation of where they are located you could get more positional accuracy; 5 is plenty for my needs currently (finding hihat samples with that many different variations would be difficult at best, and even if I could find them would probably take up most of the space on the memory chip).
On that note... does anyone know of a good free source of HiHat samples? I need samples recorded at different velocities and at different pedal positions. I have found a couple of very nice sets on freesound.org (both by quartertone; one of these is the one playing in this video); however the longer sounds are cut off / looped for use with a sequencer. Unfortunately looped cymbals just don't sound right to me. I would prefer to have a set that lets the open cymbals taper off over time naturally; or at least for longer than about 4 seconds, which is what these samples do.
Anyway, without further ado, here is the demo video of the hihat, after one day's worth of software.
If you have any thoughts, suggestions, or (best of all) sources of high quality hi hat samples, I would love to hear it!