// Define the pins for red and green LEDs
#define RLED 21
#define GLED 22

// Declare hardware timer pointers
hw_timer_t *My_timer1 = NULL;
hw_timer_t *My_timer2 = NULL;

// Declare timer status flags
boolean timer1_status = false;
boolean timer2_status = false;

// My_timer1 interrupt function - toggles red LED state
void IRAM_ATTR blink1(){
  digitalWrite(RLED, !digitalRead(RLED));
}

// My_timer2 interrupt function - toggles green LED state
void IRAM_ATTR blink2(){
  digitalWrite(GLED, !digitalRead(GLED));
}

void setup() {
  // Set the LED pins as output
  pinMode(RLED, OUTPUT);
  pinMode(GLED, OUTPUT);

  // Initialize the timers, prescaler = 80, count up
  My_timer1 = timerBegin(1000000);
  My_timer2 = timerBegin(1000000);

  // Attach interrupt functions to the timers
  timerAttachInterrupt(My_timer1, &blink1);
  timerAttachInterrupt(My_timer2, &blink2);

  // Set the timer alarms and disable them
  timerAlarm(My_timer1, 250000, true, 0); // 250ms
  timerStop(My_timer1);
  timerAlarm(My_timer2, 125000, true, 0); // 125ms
  timerStop(My_timer2);

  // Begin serial communication for user interaction
  Serial.begin(9600);
  Serial.println(F("Please select an LED: "));
}

void loop() {
  // Check if any character available for reading from the serial port
  if (Serial.available()) {
    char c = Serial.read();

    // If the received character is 'r' or 'R', toggle red LED
    if (c == 'r' || c == 'R') {
      timer1_status = !timer1_status;
      if (timer1_status)
        timerStart(My_timer1);
      else {
        timerStop(My_timer1);
        digitalWrite(RLED, LOW);  // Ensure LED is off
      }
    }
    // If the received character is 'g' or 'G', toggle green LED
    else if (c == 'g' || c == 'G') {
      timer2_status = !timer2_status;
      if (timer2_status)
        timerStart(My_timer2);
      else {
        timerStop(My_timer2);
        digitalWrite(GLED, LOW);  // Ensure LED is off
      }
    }
    // If the received character is neither 'r'/'R' nor 'g'/'G', return an error
    else {
      Serial.println(F("Error, please select a valid LED."));
    }
    Serial.println(F("Please select an LED: "));
  }
  delay(50);  // delay in between reads for stability
}