sweet, that looks like a pretty neat little project. I've turned up some more on VPW and PWM, they both use "bit symbols", so it's not the fact that the bus is high or low that matters, it's for how long the bus is high or low (in microseconds). This is going to be interesting, I got started on the code to generate the necessary pulses. Here's some more reading material for those interested in the timings for bits:
Third draft of Eval Eng article
The one of interest for PWM is the very last table at the bottom of the page.