[Ether]

Backlash, torsional windup, and sensor resolution make a gearbox-mounted sensor a very poor choice for commutation. You want the commutation sensor mounted internally to sense the shaft position near the rotor for best results.

Trapezoidal commutation is not that hard to code if you are using motors with Hall commutation sensors. Interrupt on change of Hall states and flip the appropriate FETs in the 3-half-bridge driver circuit. Just make sure the rest of your code is written properly so that you have very low software latency.