Rotary encoders
I have some micro metal gear motors I've soldered Pololu 3.3V optical rotary encoders onto micro metal gear motors. These have a direct analog output. I thought from a quick read of the instructions they might be tuned to work on digital inputs. If you read all the way to the bottom it suggests using comparators. That's going to be a pain, because what you compare to is going to have to be adjustable. I can't get anywhere near the output voltage Pololu claim, and the two signals have quite different voltages on the one I've experimented with so far. A rotary encoder generates two signals. Going forward, one signal will be 90 degrees forward of the other, and going in reverse, the opposite. The rising edge of one signal can be used to trigger a capture of the other signal which can be used to determine the direction. The capture needs to happen within 1/8th of the period of the encoder signal to be reliable. The motor could run up to 30K RPM, The encoders have 3