No Closed-Loop Spindle Control with Working Encoder

Thanks for all the assistance. I got the closed-loop spindle control working now and did some preliminary PID tuning so I can use the entire RPM range.

Not sure about the quadrature encoder issues I'm having but with counter-mode it's working. I think this'll be good enough for now.

If quadrature mode is not working well, it suggests that there is significant
quadrature distortion in the encoder (duty cycle not 50% and A-B phase
difference not 90 degrees)

You can check this by running at a constant low speed and plotting the
A/B encoder inputs in halscope