A high speed stepper mottor driver. I struggled through a lot of frustrating designs that could never drive any of my stepper motors at more than 3 or 4 revolutions per second. I wondered how the pros could extract so much better performance out of the same motors. Then I stumbled across a reference design developed by MicroChip( http://ww1.microchip.com/downloads/en/AppNotes/01307A.pdf ).
MicroChip, being a microcontroller company, is interested in selling their PIC chips and not at all hesitant to show how you can get superb performance out of a stepper motor.
After studying their design I rolled my own. I use a different driver stage, and my code is quite different but the core method is the same. Thank you Microchip.

The source code:
https://www.dropbox.com/s/x7kjzvohlcusqfv/dsPIC33%20Stepper%20Driver%20Source.zip?dl=0

Schematics:
http://www.dr-iguana.com/prj_StepperDriver/files/schematic.pdf