Using a magnetic encoder to get speed of a motor

[jaysun]

We have a magnetic encoder mounted to a test motor and, using the magnetic encoder example code, we get a nice sawtooth signal that gives us a position. However, we cannot just calculate the speed of the motor using (current_position - last_position)/time because we would calculate an erroneous speed when the position loops from 360 degrees to 0 degrees.

Any ideas on how to work around this to calculate the speed of the motor?