/**
 * ESP32 Timer Interrupt Demo
 * 
 * Blink LED with hardware timer interrupt.
 * 
 * Date: April 16, 2025
 * Author: Mike
 * License: 0BSD
 */

// Settings
static const uint16_t timer_divider = 80;         // clock ticks at 1 MHz now
static const uint64_t timer_max_count = 1000000;

// Pins (change this if your Arduino board does not have LED_BUILTIN defined)
static const int led_pin = LED_BUILTIN;

// Globals
static hw_timer_t* timer = NULL;

//*****************************************************************************
// Interrupt Service Routines (ISRs)

/**
* Use IRAM_ATTR qualifier to make sure the ISR resdie in the internal ram instead of
* flash so that it can be accessed faster.
*/
void IRAM_ATTR onTimer() {
  
  // Toggle lED.
  int pin_state = digitalRead(led_pin);
  digitalWrite(led_pin, !pin_state);
}

//*****************************************************************************
// Main (runs as its own task with priority 1 on core 1)

void setup() {

  // Pin configuration.
  pinMode(led_pin, OUTPUT);

  // Serial configuration.
  Serial.begin(115200);

  vTaskDelay(1000 / portTICK_PERIOD_MS);
  Serial.println("---ESP32 Timer Interrupt Demo---");

  // Create and start timer (frequency in Hz)
  timer = timerBegin(1000000);

  // Check if the timer configuration works.
  if (timer == NULL){
    Serial.println("ERROR: Timer configuration failed. ");
  }
  else{
    Serial.println("Timer configuration is successful. ");
  }

  // Provide ISR to timer (timer, function)
  // Attach interrupt to timer
  timerAttachInterrupt(timer, &onTimer);

  // Configure alarm value and autoreload of the timer. (timer, alarm_value, autoreload, reload_count)
  timerAlarm(timer, timer_max_count, true, 0);
}

void loop() {
  // Do nothing
}