coil_wiring requirements Rpi b/b+ resistance ~750omh x2 (for diods KTIR0411S) resistance ~200omh x2 (for receiver KTIR0411S) a4988 connectors (for power, a4988, wires, etc) stepper motor (12v / 10-15W is better) todo modify pcb (require horizontal flip the a4988 component)