arduino-esp32/libraries/ESP32/examples/AnalogOut/LEDCSoftwareFade/LEDCSoftwareFade.ino

/*
 LEDC Software Fade

 This example shows how to software fade LED
 using the ledcWrite function.

 Code adapted from original Arduino Fade example:
 https://www.arduino.cc/en/Tutorial/Fade

 This example code is in the public domain.
 */

// use 12 bit precision for LEDC timer
#define LEDC_TIMER_12_BIT 12

// use 5000 Hz as a LEDC base frequency
#define LEDC_BASE_FREQ 5000

// fade LED PIN (replace with LED_BUILTIN constant for built-in LED)
#define LED_PIN 5

int brightness = 0;  // how bright the LED is
int fadeAmount = 5;  // how many points to fade the LED by

// Arduino like analogWrite
// value has to be between 0 and valueMax
void ledcAnalogWrite(uint8_t pin, uint32_t value, uint32_t valueMax = 255) {
  // calculate duty, 4095 from 2 ^ 12 - 1
  uint32_t duty = (4095 / valueMax) * min(value, valueMax);

  // write duty to LEDC
  ledcWrite(pin, duty);
}

void setup() {
  // Setup timer and attach timer to a led pin
  ledcAttach(LED_PIN, LEDC_BASE_FREQ, LEDC_TIMER_12_BIT);
}

void loop() {
  // set the brightness on LEDC channel 0
  ledcAnalogWrite(LED_PIN, brightness);

  // change the brightness for next time through the loop:
  brightness = brightness + fadeAmount;

  // reverse the direction of the fading at the ends of the fade:
  if (brightness <= 0 || brightness >= 255) {
    fadeAmount = -fadeAmount;
  }
  // wait for 30 milliseconds to see the dimming effect
  delay(30);
}