/* * Lab 1 - Task 3: ESP32 Hardware Timer Interrupt
 * Objective: Blink a Yellow LED every 1 second using precise hardware timers.
 * Note: This code uses the updated ESP32 Arduino Core v3.x.x API.
 */

const int ledPin = 19;             // Yellow LED connected to GPIO 19
volatile bool ledState = false;    // Volatile variable for ISR

// Create a hardware timer pointer
hw_timer_t * timer = NULL;

// Interrupt Service Routine (ISR) function
// IRAM_ATTR ensures this function is loaded into RAM for fast execution
void IRAM_ATTR onTimer() {
  ledState = !ledState;            // Toggle the LED state
  digitalWrite(ledPin, ledState);  // Update the LED
}

void setup() {
  Serial.begin(115200);
  pinMode(ledPin, OUTPUT);

  Serial.println("Task 3 Ready: Starting Hardware Timer...");

  // 1. Initialize Timer
  // Set timer frequency to 1,000,000 Hz (1 MHz).
  // This means 1 timer tick = 1 microsecond.
  timer = timerBegin(1000000);

  // 2. Attach the ISR function to the timer
  timerAttachInterrupt(timer, &onTimer);

  // 3. Set the alarm
  // Parameters: timer pointer, alarm value (1,000,000 us = 1 second), auto-reload (true), reload count (0 = infinite)
  timerAlarm(timer, 1000000, true, 0);
}

void loop() {
  // The main loop is completely empty!
  // The ESP32 is toggling the LED entirely in the background using hardware interrupts.
}