Motors

A4988 stepper driver with ESP32

The A4988 lets an ESP32 run a bipolar stepper motor with just two signals: STEP moves one step and DIR sets the direction. The small module has the power stage, current limiting and microstepping, so all the code has to do is send pulses.

Set the current limit before you connect anything valuable. Use Vref = Imot × 8 × Rs, where Rs is the sense resistor on your board. That value varies between clones, with 0.05, 0.068 and 0.1 Ω all seen. Measure Vref with the small trimmer and read the resistor marking instead of copying a value from a forum. Datasheet ratings look high, but expect about 1 A per phase without strong cooling, and up to 1.5 A with a heatsink and a fan.

Never unplug a motor while the driver is powered, because that can kill the driver. Motor power is separate, from about 8 V upward, and needs a large capacitor near the driver. Logic runs from the ESP32's 3.3 V. Step pulses must keep coming, so on a display board do not generate them in the same loop that redraws the screen. Use a timer or the second core, or the motor will stutter.

#include <AccelStepper.h>

const int STEP_PIN = 5, DIR_PIN = 6;
AccelStepper stepper(AccelStepper::DRIVER, STEP_PIN, DIR_PIN);

void setup() {
  stepper.setMaxSpeed(800);       // steps per second
  stepper.setAcceleration(400);
  stepper.moveTo(1600);
}

void loop() {
  if (stepper.distanceToGo() == 0) stepper.moveTo(-stepper.currentPosition());
  stepper.run();                  // call as often as possible
}

Use this information at your own risk. It is for general guidance only: the example code compiles, but it has not been tested on every part, and modules differ between sellers. Check the manufacturer's data before you build. Product names belong to their owners, and LCD Ultra Pro is not affiliated with them. See our Terms.