PWM

Example: Adjusting LED Brightness with PWM

Create a breathing light effect on the user LED of the Edge101 board by adjusting its brightness using PWM with a frequency of 5000Hz.

Hardware Preparation:

• ESP32 IoT Programmable Controller (SKU: DFR0886)×1

Sample Code:

// PWM channel configuration
#define PWM_CH        0    // Use PWM channel 0
#define PWM_FREQ      5000 // Set PWM frequency to 5kHz
#define PWM_RES       13   // 13-bit resolution (range 0-8191)
#define LED_PIN       15   // LED connection pin

// Breathing light control parameters
int brightness = 0;  // Current brightness value (0-255)
int fadeAmount = 5;  // Brightness change step

/**
 * Custom PWM output function
 * @param ch     PWM channel
 * @param val    Brightness value (0-255)
 * @param maxVal Maximum input value (default is 8-bit)
 */
void ledcAnalogWrite(uint8_t ch, uint32_t val, uint32_t maxVal = 255) {
  // Convert 8-bit brightness value to 13-bit duty cycle
  ledcWrite(ch, (8191 / maxVal) * min(val, maxVal));
}

void setup() {
  // Initialize PWM configuration
  ledcSetup(PWM_CH, PWM_FREQ, PWM_RES);  // Set PWM parameters
  ledcAttachPin(LED_PIN, PWM_CH);        // Bind pin to PWM channel
}

void loop() {
  // Output the current brightness value
  ledcAnalogWrite(PWM_CH, brightness);
  
  // Update brightness value (linear gradient)
  brightness += fadeAmount;
  
  // Reverse gradient direction when reaching brightness limits
  if (brightness <= 0 || brightness >= 255) {
    fadeAmount = -fadeAmount;
  }
  
  delay(30); // Control breathing light speed
}