Stall Detection

This implementation employs three methods of stall detection:

• Zero-cross time-out using the TCA1 CMP2 interrupt
• Using a zero-cross delta limit. This means that if the motor has any abrupt changes on the time in which the zero cross is detected, based on the previous one, then the motor is considered stalled.
• Most likely, during a stall, the current through the windings will rise considerably and get over the overcurrent limit

The most sensitive part of stall detection is at start-up. When the motor is accelerated in Open Loop mode and switching to Closed Loop, the system might get a false response that the zero cross is valid, even though the BEMF is a result of the magnetic coupling between the driven and the undriven coils, and not the voltage induced in the coils by the moving magnet.