ESP32 PWM with example : dimming an LED

The ESP32 microcontroller offers a versatile and powerful feature set, making it ideal for numerous IoT applications. One of its standout features is the ability to generate PWM (Pulse Width Modulation) signals. PWM is commonly used for controlling motors, LEDs, displays, and other devices that require analog control through digital means. In this blog post, we will explore how to use PWM on the ESP32 to dim an LED.

Before you read this you also want to read the previous basic tutorials on how to use the ESP32 other features:

- ESP WROOM 32: LED Blink Tutorial

What is PWM?

PWM stands for Pulse Width Modulation. It is a technique used to simulate an analog output using digital means. By rapidly switching a digital signal on and off, PWM can effectively create a range of output levels. The ratio of the "on" time to the "off" time is known as the duty cycle, expressed as a percentage.

• 0% Duty Cycle: The signal is always off.
• 50% Duty Cycle: The signal is on half the time and off half the time.
• 100% Duty Cycle: The signal is always on.

By adjusting the duty cycle, we can control the brightness of an LED, the speed of a motor, or other analog properties of electronic devices. For examples of Fast PWM mode with Arduino see ATmega328P Fast PWM mode Programming Examples.

Setting Up PWM on ESP32

The ESP32 has 16 independent PWM channels, allowing you to control the duty cycle and frequency of the PWM signal. To dim an LED using PWM, follow these steps:

Components Needed:

• ESP32 development board
• LED
• Resistor (220 ohms)
• Breadboard and jumper wires

Circuit Diagram:

The following is the circuit diagram for applying PWM signal to the LED with ESP32 board.

1. Connect the anode (long leg) of the LED to GPIO 4 on the ESP32.
2. Connect the cathode (short leg) of the LED to one end of the 220-ohm resistor.
3. Connect the other end of the resistor to the ground (GND) pin on the ESP32.

Code Example:

Here’s a simple code example to demonstrate how to use PWM to dim an LED with the ESP32 using the Arduino IDE:

// Constants for PWM
const int ledPin = 4;    // GPIO where the LED is connected
const int pwmChannel = 0;
const int freq = 5000;   // PWM frequency
const int resolution = 8; // 8-bit resolution (0-255)

// Variables to store duty cycle
int dutyCycle = 0;

void setup() {
  // Configure the PWM channel
  ledcAttachChannel(ledPin, freq, resolution, pwmChannel);
}

void loop() {
  // Gradually increase the brightness
  for(dutyCycle = 0; dutyCycle <= 255; dutyCycle++){
    ledcWrite(pwmChannel, dutyCycle);
    delay(15);
  }
  
  // Gradually decrease the brightness
  for(dutyCycle = 255; dutyCycle >= 0; dutyCycle--){
    ledcWrite(pwmChannel, dutyCycle);
    delay(15);
  }
}

// Constants for PWM
const int ledPin = 4;    // GPIO where the LED is connected
const int pwmChannel = 0;
const int freq = 5000;   // PWM frequency
const int resolution = 8; // 8-bit resolution (0-255)

// Variables to store duty cycle
int dutyCycle = 0;