ESP32 changing frequency instead of duty cycle

Question

Using this code on an ESP32 allows varying the duty cycle of the PWM with a fixed 5000 Hz frequency; it is working fine.

How do I vary the frequency and keep the duty cycle at a fixed value?

// the number of the LED pin
const int ledPin = 16;  // 16 corresponds to GPIO16

// setting PWM properties
const int freq = 5000;
const int ledChannel = 0;
const int resolution = 8;
 
void setup(){
  // configure LED PWM functionalitites
  ledcSetup(ledChannel, freq, resolution);
  
  // attach the channel to the GPIO to be controlled
  ledcAttachPin(ledPin, ledChannel);
}
 
void loop(){
  // increase the LED brightness
  for (int dutyCycle = 0; dutyCycle <= 255; dutyCycle++) {   
    // changing the LED brightness with PWM
    ledcWrite(ledChannel, dutyCycle);
    delay(15);
  }

  // decrease the LED brightness
  for (int dutyCycle = 255; dutyCycle >= 0; dutyCycle--) {
    // changing the LED brightness with PWM
    ledcWrite(ledChannel, dutyCycle);   
    delay(15);
  }
}

Answer 1

If you want to change the pwm frequency during runtime there is a function ledc_set_freq() for this purpose. I'm not sure if your duty cycle will remain valid, but I guess it does as long as the resolution does not change. You will have to try that on your own and eventually implement a compensation.