Smooth Stepper Motor Control with ESP32

4 min readJul 3, 2024

Controlling a stepper motor precisely is crucial in many applications, from 3D printers to CNC machines.

The ESP32, with its dual-core architecture, offers an excellent opportunity to handle real-time stepper motor control and other logic simultaneously without compromising performance.

In this article, we will explore how to achieve smooth stepper motor control by using FreeRTOS tasks and separate cores on the ESP32.

Why Use Separate Cores?

The ESP32 features two Xtensa LX6 microprocessor cores. By assigning the stepper motor control to one core and the other logic to the second core, we can ensure that the motor runs smoothly without being interrupted by other tasks.

This setup minimizes jitter and enhances the reliability of the stepper motor movements.

Hardware Setup

First, ensure you have the following components,

ESP32 development board
Stepper motor
Stepper motor driver (e.g., A4988/ DRV8825/TB6600)
Power supply
Jumper Wires

Wiring

Software Implementation

Let’s break down the code to control the stepper motor using FreeRTOS tasks on the ESP32.

Complete Code

// Define pin numbers
#define stepPin 16
#define dirPin 17
#define enablePin 18

// Stepper settings
const int stepsPerRevolution = 1600;
const int gearRatio = 80;
const int stepsPerDegree = (stepsPerRevolution * gearRatio) / 360;
const float wheelRPM = 3;
const long stopDuration = 400;
bool stepperMoving = false;
long steps = 12800;

unsigned long lastStepperMoveTime = 0;

// FreeRTOS Task Handle
TaskHandle_t StepperTaskHandle = NULL;

void setup() {
  Serial.begin(9600);
  pinMode(stepPin, OUTPUT);
  pinMode(dirPin, OUTPUT);
  pinMode(enablePin, OUTPUT);

  // Set direction and enable stepper motor
  digitalWrite(dirPin, HIGH);
  digitalWrite(enablePin, LOW); // LOW to enable

  // Create a task for stepper control on core 0
  xTaskCreatePinnedToCore(
    stepperControl,
    "StepperControlTask",
    10000,
    NULL,
    1,
    &StepperTaskHandle,
    0
  );
}

void loop() {
  // Placeholder for your logic to set `stepperMoving` and `steps`
  // For demonstration, we will just move the stepper every 10 seconds
  if (millis() - lastStepperMoveTime > 10000) {
    stepperMoving = true;
    steps = 12800; // Example steps
    lastStepperMoveTime = millis();
  }
}

void moveStepper(long steps) {
  digitalWrite(enablePin, LOW); // Enable stepper motor
  for (long i = 0; i < steps; i++) {
    digitalWrite(stepPin, HIGH);
    delayMicroseconds(156); // Adjust delay as needed
    digitalWrite(stepPin, LOW);
    delayMicroseconds(156);

    if (i % 1000 == 0) {
      vTaskDelay(1); // Yield to other tasks
    }
  }
  digitalWrite(enablePin, HIGH); // Disable stepper motor
}

void stepperControl(void * parameter) {
  for (;;) {
    if (stepperMoving) {
      moveStepper(steps);
      stepperMoving = false; // Stop the stepper after moving the required steps
    } else {
      vTaskDelay(1); // Yield to other tasks
    }
  }
}

Let’s discuss on the code now,

Define Pin Numbers and Stepper Settings

We start by defining the pin numbers and stepper motor settings.

#define stepPin 16
#define dirPin 17
#define enablePin 18

const int stepsPerRevolution = 1600;
const int gearRatio = 80;
const int stepsPerDegree = (stepsPerRevolution * gearRatio) / 360;
const float wheelRPM = 3;
const long stopDuration = 400;
bool stepperMoving = false;
long steps = 12800;

unsigned long lastStepperMoveTime = 0;

TaskHandle_t StepperTaskHandle = NULL;

Setup Function

In the ‘setup’ function, we initialize the serial communication and configure the GPIO pins. We also create a FreeRTOS task to handle stepper motor control on core 0.

void setup() {
  Serial.begin(9600);
  pinMode(stepPin, OUTPUT);
  pinMode(dirPin, OUTPUT);
  pinMode(enablePin, OUTPUT);

  digitalWrite(dirPin, HIGH);
  digitalWrite(enablePin, LOW);

  xTaskCreatePinnedToCore(
    stepperControl,
    "StepperControlTask",
    10000,
    NULL,
    1,
    &StepperTaskHandle,
    0
  );
}

Main Loop

In the ‘loop’ function, we can place the logic to control when the stepper motor should move. For demonstration purposes, we will move the stepper motor every 10 seconds.

In this loop, you can add the logic for the other functionalities.

void loop() {
  if (millis() - lastStepperMoveTime > 10000) {
    stepperMoving = true;
    steps = 12800;
    lastStepperMoveTime = millis();
  }
}

Move Stepper Function

The ‘moveStepper’ function handles the actual movement of the stepper motor. It ensures smooth operation by inserting delays. The delay will be responsible for the speed of the motor.

void moveStepper(long steps) {
  digitalWrite(enablePin, LOW);
  for (long i = 0; i < steps; i++) {
    digitalWrite(stepPin, HIGH);
    delayMicroseconds(156);
    digitalWrite(stepPin, LOW);
    delayMicroseconds(156);

    if (i % 1000 == 0) {
      vTaskDelay(1);
    }
  }
  digitalWrite(enablePin, HIGH);
}

Step 5: Stepper Control Task

The ‘stepperControl’ function runs as a FreeRTOS task on core 0. It continuously checks if the stepper motor needs to move and calls the ‘moveStepper’ function accordingly.

void stepperControl(void * parameter) {
  for (;;) {
    if (stepperMoving) {
      moveStepper(steps);
      stepperMoving = false;
    } else {
      vTaskDelay(1);
    }
  }
}

Conclusion

By utilizing FreeRTOS tasks and the dual-core architecture of the ESP32, we can achieve smooth and reliable stepper motor control. This approach ensures that the motor movements are not interrupted by other tasks, leading to precise and accurate positioning.

With this setup, you can expand the functionality of your project by adding more complex logic and operations on the second core, making full use of the ESP32’s capabilities.

Feel free to customize the code to fit your specific application needs.

Contact us for any consultations or projects related to any Stepper.

Email: udara@protonest.co

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