// ESP32 Timer
//
// This is just a test and it seems to work.
//
// Documentation:
//   https://espressif-docs.readthedocs-hosted.com/projects/arduino-esp32/en/latest/api/timer.html#arduino-esp32-timer-api
//

int ledPin = 5;
hw_timer_t * timer = NULL;

// Note: "volatile" is not required here.
volatile bool ledOn = false;

void ARDUINO_ISR_ATTR onTimer()
{
  digitalWrite(ledPin, ledOn ? LOW : HIGH);
  ledOn = !ledOn;
}

void setup() 
{
  Serial.begin(115200);

  pinMode(ledPin, OUTPUT);

  // The parameter of timerBegin is the resolution
  // of the timer (the base clock in Hz).
  // Start with a value of 1MHz.
  // I don't know the limits, but 1kHz does not work.
  timer = timerBegin(1000000);

  // Connect to the ISR.
  timerAttachInterrupt(timer, &onTimer);

  // Set the divider to twice per second.
  // Is that a software divider ?
  timerAlarm(timer, 500000, true, 0);

  // At this point, the timer is already started.
  // Calling "timerStart(timer);" again causes
  // a warning.
}

void loop() 
{
  delay(10);
}