Stepper motor is an electromechanical device that converts electrical pulses into discrete mechanical movements. In this tutorial, I will explain how to control a unipolar stepper motor using STM32F103 microcontroller. If you don’t know the basic of the stepper motor, I suggest you to read this post. To interface a stepper motor from a microcontroller, we can’t directly drive it with GPIO pins because GPIO pins have maximum current that can sink or source from it. To overcome this problem, we can use driver circuit. The driver circuit for unipolar stepper motor can be built by using 4 transistors to drive large current to the 4 wires of a stepper motor. It also can be built with ULN2003 IC. This is the circuit for driving a unipolar stepper motor from STM32F103 by using ULN2003 IC.