I am currently working on the design for a PID speed controller for a Brush less DC motor (200 RPM max speed). My feedback mechanism is a IR motor encoder which spits out a PWM signal with a frequency that depends on the speed of the motor. I am trying to figure out how to calculate the frequency of the PWM signal being fed into the microcontroller. Any ideas or sources I could use?
Check previous discussion on motor control and tachometer frequency measurement here: