To connect stepper motor 28BYJ-48 with DRV8825 stepper driver, the following need to be done:
- Connect RST and SLP to +5v
- STEP and DIR to microcontroller to control direction and speed via PWM pulse
- VMOT should be above 7.5v otherwise DRV8825 undervoltage protection will shut down the driver. 8v seem to be OK.
- Toggling STEP pin with 1ms delay between Lo and Hi will seemingly produce 60rpm.