Assume a microcontroller and a motor amplifier/driver. The micro generates step and direction signals which the driver uses to move the motor. I have a design on my bench right now that uses an Allegro driver and an SiLabs micro. The motor itself uses a 24V supply and the Allegro part's digital inputs are TTL compatible. (A regulator is used to knock the 24V down to 5V for the Allegro's logic supply input.)

I put fast optoisolators between the micro and the Allegro part and that keeps things calm. You just want to keep the ugly motor return currents separate from the logic and sensitive sensor return currents.

The 24V return and the micro supply return get tied together in a star ground at the power-supply inlet.

-a