Snaggletooth: Shaft encoders are IR reflectance-based sensors mouted inside the gearbox of both servo motors. The sensors read black/white marks painted on the penultimate drive gear. Encoder ticks come in via ADC. Wrote software to count encoder ticks.

Highlights: 100% PWM on a slightly discharged battery yields about 24 ticks per second. 25% PWM yields about 9 tps.

Next: Write feedback-based motor speed control routines. Long term: move to digital encoder sensors.