ESP32 + DC Motor L298N: Controlling Speed and Direction

1. Introduction

The L298N is the most popular DC motor driver for beginners, since it packs in two H-bridges, handles up to 2A per channel, 5V-35V motor voltage, and has an onboard 5V regulator. An H-bridge lets you reverse the current through a DC motor (changing rotation direction) and PWM-modulate it to change the average speed.

This project uses the L298N's Motor A channel: two digital pins (IN1/IN2) set the rotation direction, the ENA pin receives a PWM signal that sets the speed, with an automatic speed-ramp demo and manual control over Serial.

2. Components Needed

3. Wiring Diagram

GPIO16/17/18 aren't part of the boot-strapping pin group, so they're safe to use as outputs right from ESP32 boot.

4. Sample Code

/*
 * ESP32 + DC Motor L298N - Dieu khien toc do va chieu quay
 * Board: ESP32 DevKit V4 (board_esp32_devkitc)
 * Module: L298N - DC Motor Driver Dual (mod_l298n_motor), dung kenh A
 *
 * Wiring:
 *   L298N VCC (logic 5V) -> ESP32 5V (VIN)
 *   L298N GND            -> ESP32 GND (chung GND voi nguon dong co)
 *   L298N IN1            -> ESP32 GPIO16
 *   L298N IN2            -> ESP32 GPIO17
 *   L298N ENA (PWM toc do)-> ESP32 GPIO18
 *   L298N VS (motor 5V-35V) -> Nguon dong co rieng (PIN/adapter), KHONG lay tu ESP32
 *   L298N OUT1/OUT2       -> 2 day dong co DC (khong noi ve ESP32)
 *
 * An toan phan cung (checklist dong co):
 *  - L298N chiu toi da 2A/kenh - dong co DC nho (<=1A) an toan; dong co lon hon
 *    phai kiem tra dong stall trong datasheet truoc khi dau.
 *  - GND logic (ESP32) va GND motor (VS) BAT BUOC noi chung - neu khong PWM/IN
 *    se khong co muc tham chieu dung, dieu khien loi/nhieu.
 *  - L298N co diode bao ve flyback tich hop san trong IC driver (khong can diode
 *    ngoai rieng cho dong co DC chuan, khac voi relay/solenoid dung cuon day tro).
 *  - Khong cap 12V/VS truc tiep vao bat ky chan GPIO ESP32 (chi 3.3V logic).
 */

static const int IN1_PIN = 16;
static const int IN2_PIN = 17;
static const int ENA_PIN = 18;

static const int PWM_CHANNEL = 0;
static const int PWM_FREQ_HZ = 1000;
static const int PWM_RESOLUTION_BITS = 8; // 0-255

int currentSpeed = 0;      // 0-255
bool currentForward = true;

void setMotor(bool forward, int speed) {
  speed = constrain(speed, 0, 255);
  digitalWrite(IN1_PIN, forward ? HIGH : LOW);
  digitalWrite(IN2_PIN, forward ? LOW : HIGH);
  ledcWrite(PWM_CHANNEL, speed);
  currentForward = forward;
  currentSpeed = speed;
}

void stopMotor() {
  digitalWrite(IN1_PIN, LOW);
  digitalWrite(IN2_PIN, LOW);
  ledcWrite(PWM_CHANNEL, 0);
  currentSpeed = 0;
}

void setup() {
  Serial.begin(115200);
  delay(300);
  Serial.println();
  Serial.println("=== ESP32 + L298N DC Motor boot OK ===");

  pinMode(IN1_PIN, OUTPUT);
  pinMode(IN2_PIN, OUTPUT);

  ledcAttach(ENA_PIN, PWM_FREQ_HZ, PWM_RESOLUTION_BITS);
  // Note: Arduino-ESP32 core 3.x dung ledcAttach(pin, freq, resolution) va
  // ledcWrite(pin, duty) truc tiep tren so pin (khong can channel rieng nua
  // trong core moi, nhung giu bien PWM_CHANNEL de tuong thich code doc).

  stopMotor();
  Serial.println("Lenh Serial: 'F<0-255>' chay tien, 'R<0-255>' chay lui, 'S' dung.");
  Serial.println("{\"status\":\"ready\"}");
}

void handleSerialCommand() {
  if (!Serial.available()) return;
  char cmd = Serial.read();
  if (cmd == 'S' || cmd == 's') {
    stopMotor();
    Serial.println("{\"cmd\":\"stop\"}");
    return;
  }
  if (cmd == 'F' || cmd == 'f' || cmd == 'R' || cmd == 'r') {
    int val = Serial.parseInt();
    setMotor(cmd == 'F' || cmd == 'f', val);
    Serial.printf("{\"cmd\":\"%s\",\"speed\":%d}\n", (cmd == 'F' || cmd == 'f') ? "forward" : "reverse", currentSpeed);
  }
  while (Serial.available() && Serial.peek() != '\n') Serial.read();
  if (Serial.available()) Serial.read();
}

void demoRamp() {
  // Demo tu dong: tang toc tien -> giam -> tang toc lui -> giam -> dung, lap lai
  static unsigned long lastStepMs = 0;
  static int demoPhase = 0; // 0 ramp up fwd, 1 ramp down fwd, 2 ramp up rev, 3 ramp down rev
  const unsigned long STEP_MS = 40;

  if (millis() - lastStepMs < STEP_MS) return;
  lastStepMs = millis();

  switch (demoPhase) {
    case 0:
      setMotor(true, currentSpeed + 5);
      if (currentSpeed >= 255) demoPhase = 1;
      break;
    case 1:
      setMotor(true, currentSpeed - 5);
      if (currentSpeed <= 0) demoPhase = 2;
      break;
    case 2:
      setMotor(false, currentSpeed + 5);
      if (currentSpeed >= 255) demoPhase = 3;
      break;
    case 3:
      setMotor(false, currentSpeed - 5);
      if (currentSpeed <= 0) demoPhase = 0;
      break;
  }
}

void loop() {
  handleSerialCommand();
  demoRamp();

  static unsigned long lastTelemetryMs = 0;
  if (millis() - lastTelemetryMs >= 1000) {
    lastTelemetryMs = millis();
    Serial.printf("{\"direction\":\"%s\",\"speed\":%d}\n", currentForward ? "forward" : "reverse", currentSpeed);
  }
}

5. Code Walkthrough

Arduino-ESP32 core 3.x uses the new PWM API: ledcAttach(pin, freq, resolution) attaches a 1kHz/8-bit PWM signal directly to GPIO18, then ledcWrite(pin, duty) writes a 0-255 duty cycle. The setMotor(forward, speed) function

sets IN1/IN2 to opposite states to choose direction (HIGH/LOW or LOW/HIGH — if both are the same level, the motor brakes or free-spins depending on the circuit's exact behavior),

then writes the PWM value to ENA to set the speed. demoRamp() runs a 4-phase cycle: ramp up forward → ramp down forward → ramp up reverse → ramp down reverse, each step 40ms apart to simulate smooth acceleration. Serial commands like F<speed>/R<speed>/S allow manual control alongside the demo.

6. Hardware Safety Notes

• The L298N handles up to 2A per channel continuously — safe with a DC motor rated under 1A; a higher-power motor needs its stall current checked in the datasheet first (the current when the motor is fully jammed, which can be 5-10x the rated current).

• The logic GND (ESP32/VCC side) and the power GND (VS/motor supply side) must share a common point — otherwise the IN1/IN2/ENA signal levels lose their reference, and the driver misbehaves or doesn't respond.

• The L298N has built-in flyback protection diodes inside the IC for standard DC motor windings — no separate diodes needed like when using a relay/solenoid.

• Never feed the VS voltage (6-12V or higher) into any ESP32 GPIO pin — ESP32 GPIOs only tolerate 3.3V, and doing so will instantly destroy the chip.

• The VS supply should be physically separate (its own battery/adapter) from the ESP32's power — sharing one weak supply can cause voltage sag and reset the ESP32 when the motor starts.

7. Common Issues

8. Summary

This guide covered using the L298N to control a DC motor's speed (PWM via ENA) and direction (IN1/IN2) on ESP32, along with key safety notes about a shared GND and separating the power supply.

This is the foundation for 2-wheel/4-wheel robot car projects, mini conveyor belts, or any application needing bidirectional DC motor control, in the Motor Control category.