The expansion board can be used for engraving machine, 3D printer driver extension plate, a total of four stepper motor driver module slot. (Moto Sako does not contain the A4988 stepper motor driver module, need to be in the store to purchase another) It can be driven by 4 road into the motor, and each step electric machine only need two IO mouth. That is to say, six IO mouth can be a very good management, the three step stepper motor use very convenient.