ESP32 PWM using Arduino IDE

What is PWM?

Imagine

ESP32 PWM

Image(pin diagram),
specifications of PWM

Method 1: analogWrite()

void analogWrite(pin, dutyCycle),

Method 2: LEDC Driver

ledcAttach()

bool ledcAttach(uint8_t pin, uint32_t freq, uint8_t resolution);

ledcWrite()

bool ledcWrite(uint8_t pin, uint32_t duty);

Example 1: Fading LED – analogWrite()

We will increase and decrease the LED brightness over time. We will use the analogWrite() function to control the brightness of the LED.

Code

const int ledPin = 2;

void setup() {
  pinMode(ledPin, OUTPUT);
}

void loop() {
  // Increasing LED brightness
  for(int val=0; val<=255; val++)
  {
    analogWrite(ledPin, val); 
    delay(1);
  }

  // Decreasing LED brightness
  for(int val=255; val>=0; val--)
  {
    analogWrite(ledPin, val);
    delay(1);
  }
}

Explanation

Start by defining the LED pin. In this example, we will be using an onboard LED attached to GPIO 2.

const int ledPin = 2;

Configure the LED pin as an OUTPUT pin.

pinMode(ledPin, OUTPUT);

Vary the duty cycle using a for loop. Notice how we use the first for loop to increase the duty cycle from 0 to 255 and then the second for loop to decrease the duty cycle from 255 to 0. You can change the delays to make the LED fade quickly or slowly.

// Increasing LED brightness
for(int val=0; val<=255; val++)
  {
    analogWrite(ledPin, val); 
    delay(1);
  }

// Decreasing LED brightness
  for(int val=255; val>=0; val--)
  {
    analogWrite(ledPin, val);
    delay(1);
  }

Use the analogWrite() function to set the duty cycle.

analogWrite(ledPin, val);

Output

Example 2: Fading LED – ledcWrite()

We will increase and decrease the LED brightness over time. We will use the ledcWrite() function to control the brightness of the LED.

Code

const int ledPin          = 2;
const uint32_t frequency  = 1000;
const uint8_t resolution  = 8;
uint32_t maxDutyCycle     = (1 << resolution) - 1;

void setup() {
  ledcAttach(ledPin, frequency, resolution);
}

void loop() {
  // Increasing LED brightness
  for (uint32_t duty = 0; duty <= maxDutyCycle; duty++) {
    ledcWrite(ledPin, duty);
    delay(1);
  }

  // Decreasing LED brightness
  for (int32_t duty = maxDutyCycle; duty >= 0; duty--) {
    ledcWrite(ledPin, duty);
    delay(1);
  }
}

Output

Explanation

Start by defining the LED pin, we will be using the built-in LED at GPIO. Set desired frequency and resolution.

const int ledPin          = 2;
const uint32_t frequency  = 1000;
const uint8_t resolution  = 8;

For iteration, calculate the maxDutyCycle by the following method. The code line performs the following action:
maxDutyCycle = 2^reolution – 1

uint32_t maxDutyCycle = (1 << resolution) - 1;

Attach the LED pin to the LEDC driver, with a given frequency, resolution, and channel using the ledcAttach() function.

ledcAttach(ledPin, frequency, resolution);

Vary the duty cycle using a for loop. Notice how we use the first for loop to increase the duty cycle from 0 to maxDutyCycle (255) and then the second for loop to decrease the duty cycle from maxDutyCycle (255) to 0. You can change the delays to make the LED fade quickly or slowly.

// Increasing LED brightness
  for (uint32_t duty = 0; duty <= maxDutyCycle; duty++) {
    ledcWrite(ledPin, duty);
    delay(1);
  }

  // Decreasing LED brightness
  for (int32_t duty = maxDutyCycle; duty >= 0; duty--) {
    ledcWrite(ledPin, duty);
    delay(1);
  }

Use the ledcWrite() function to set the duty cycle.

ledcWrite(ledPin, duty);