The A4988 represents another step toward precise stepper motor control, simplifying wiring down to just two pins instead of the four direction pins used with the L293D and L298N, while adding microstepping capability.
Components needed
An Arduino board, an A4988 driver, a bipolar stepper motor (like the NEMA 17), and an external power supply (8-35V).
Wiring it up
The driver connects to Arduino through just two control pins: the STEP pin (pin 3 in the common example), which receives one pulse per step the motor advances, and the DIR pin (pin 2), which sets the rotation direction (HIGH for one direction, LOW for the opposite). The driver needs two separate power supplies: VDD/GND for logic (3-5.5V), and VMOT/GND to power the motor (8-35V), while the four output pins (1A, 1B, 2A, 2B) connect directly to the motor's coils.
Microstepping
Three selection pins (MS1, MS2, MS3) offer five stepping modes: full, half, quarter, eighth, and sixteenth step. These pins have internal pull-down resistors, meaning leaving them unconnected defaults to full-step mode automatically.
Setting the current limit: a step you can't skip
The driver includes an onboard potentiometer for adjusting the current limit.
You can find A4988 drivers and bipolar stepper motors at Juthour Tech.
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