#define LED 12    //LED Digital pin
#define SLIDE 13  // Potentiometer Digital pin
#define PERIOD 100  //PWM Period in us

volatile int pwm_value = 0;   //Duty Cycle Time
hw_timer_t *My_timer = NULL;

void IRAM_ATTR onTimer(){
  bool led_status = digitalRead(LED);

  if(led_status && pwm_value!=PERIOD){
    digitalWrite(LED,!led_status);
    timerWrite(My_timer, pwm_value);
  
  }
  else if(!led_status && pwm_value!=0){
    digitalWrite(LED,!led_status);
    timerWrite(My_timer, PERIOD-pwm_value);
  }

  Serial.println("Hello, ESP32!");
}

void setup() {
  //Serial.begin(115200);
  pinMode(LED, OUTPUT);
  pinMode(SLIDE, INPUT);
  
  //Timer initializer
  My_timer = timerBegin(0, 80, true);
  //0: hw timer number (ESP32 has 3hw timers available)
  //80: time divider. ESP32 clk 80MHz so we set every tick to 1 us
  //true: counter shoud increment

  //Attach Interrupt
  timerAttachInterrupt(My_timer, &onTimer, true);
  timerAlarmWrite(My_timer, PERIOD, true);
  //PERIOD: number of microseconds after which the interrupt should occur
  //true: timer counter will reload after interrupt

  timerAlarmEnable(My_timer); //Enable
}

void loop() {
  pwm_value= map(analogRead(SLIDE), 0, 4095, 0, PERIOD);
  //Serial.println(analogRead(SLIDE));
}