Code for controlling brightness of LED using ESP32 ADC and PWM.

ESP32-ADC-LED-PWM-Control.ino

#define ADCPIN A0
const int LEDPin = 16;  /* GPIO16 */

uint16_t dutyCycle;

const int PWMFreq = 5000;
const int PWMChannel = 0;
const int PWMResolution = 12;
const int MAX_DUTY_CYCLE = (int)(pow(2, PWMResolution) - 1);

//const int ADC_RESOLUTION = 4095;


void setup()
{  
  /* Initialize PWM Channels with Frequency and Resolution */
  ledcSetup(PWMChannel, PWMFreq, PWMResolution);
  
  /* Attach the LED PWM Channel to the GPIO Pin */
  ledcAttachPin(LEDPin, PWMChannel);
  
  
}
void loop()
{
  /* Read Analog Input from three ADC Inputs */
  dutyCycle = analogRead(ADCPIN);
  /* Map ADC Output to maximum possible dutycycle */
  //redDutyCycle = map(redDutyCycle, 0, ADC_RESOLUTION, 0, RED_MAX_DUTY_CYCLE);
  
  /* Set PWM Output of Channel with desired dutycycle */ 
  ledcWrite(PWMChannel, dutyCycle);

  delay(10);
}