/* * Lab 1 - Task 4: External Interrupts & Timer Events
 * Objective: Use a button interrupt to change the timer blink rate.
 */

const int buttonPin = 4;           // Button connected to GPIO 4 (Pull-up)
const int ledPin = 2;              // LED connected to GPIO 2

hw_timer_t * timer = NULL;         // Timer pointer
volatile bool ledState = false;    // State of the LED
volatile bool fastBlink = false;   // Flag to track blink mode

// 1. Timer Interrupt Service Routine (ISR)
void IRAM_ATTR onTimer() {
  ledState = !ledState;            // Toggle LED state
  digitalWrite(ledPin, ledState);
}

// 2. External GPIO Interrupt Service Routine (ISR)
void IRAM_ATTR onButtonPress() {
  fastBlink = !fastBlink;          // Toggle the blink mode flag
  
  if (fastBlink) {
    // Set timer to trigger every 200,000 microseconds (0.2 seconds = Fast)
    timerAlarm(timer, 200000, true, 0);
  } else {
    // Set timer to trigger every 1,000,000 microseconds (1 second = Normal)
    timerAlarm(timer, 1000000, true, 0);
  }
}

void setup() {
  Serial.begin(115200);
  pinMode(ledPin, OUTPUT);
  pinMode(buttonPin, INPUT);       // Using external pull-up resistor

  // Initialize the Hardware Timer (1 MHz frequency)
  timer = timerBegin(1000000);
  timerAttachInterrupt(timer, &onTimer);
  timerAlarm(timer, 1000000, true, 0); // Start with 1 second alarm

  // Initialize External Interrupt on the Button Pin
  // digitalPinToInterrupt() ensures the correct mapping for the ESP32
  // FALLING edge triggers the interrupt when voltage goes from HIGH (3.3V) to LOW (GND)
  attachInterrupt(digitalPinToInterrupt(buttonPin), onButtonPress, FALLING);
  
  Serial.println("Task 4 Ready: Press button to change blink rate.");
}

void loop() {
  // Main loop remains empty. Everything is handled by interrupts!
}