3D printers, laser cutters, water jet cutters, robot arms, delta robots, stewart platforms, the Makelangelo: all of these are examples of computer numerical control (CNC) machines. CNC machines need to move accurately and on command. Stepper motors are a great way to move accurately – they move a predictable amount and then stay where you put them. To command the stepper motors we need a way to easily turn our human desires into machine instructions into stepper motor steps. In effect we need our robot brain to be an interpreter. I’m going to show you a simple interpreter written for Arduino that lets you move stepper motors for your robots.