Another solution that in my experience seems to work pretty well is what mainsail does. The motion planner runs on a raspberry pi. Theoretically this needs to b

Another solution that in my experience seems to work pretty well is what mainsail does. The motion planner runs on a raspberry pi. Theoretically this needs to be a realtime thing, but in practice the RPi is fast enough to where it's never a bottleneck. The actual stepping of the motors is handled by a more traditional microcontroller board with some very basic firmware. As far as I understand the RPi is sending it (step count, direction, rate) commands. This solves a lot of issues since the microcontroller is doing some really basic things it's well suited for, and the RPi is freed from having hard realtime responsibilities.