When the onboard stepper driver does not have the performance required, the ED1 plugs into any of the Pololu style connectors and connect the stepper control signals to the stepper motor pins. A jumper on the ED1 allows selection of the 4th pin to be either GROUND (default) or 5V. With the ED1 connected, the stepper motor pins become:
- Stepper 2A -> STEP
- Stepper 2B -> ENable
- Stepper 1A -> DIR
- Stepper 1B -> GROUND (or 5V)
The stepper control signals (STEP, DIR, ENable) can then drive an external stepper driver.