rs_blinker.ino does not work on Elegoo Mega 2560 R3

[joshuasv]

The code provided in the rs-blinker.ino does not work on my Elegoo Mega 2560 R3. It did not switch the LED. After a bit of tweaking I got it working, code below.

Question. Do you see any faults on this code that may not yield the intended results?

#define LED_PIN 2 // Pin number for the onboard LED (Arduino Uno)

const unsigned long long freq = 50; // So I can see it

void setup() {
  pinMode(LED_PIN, OUTPUT); // Set the LED pin as output

  // Configure Timer1
  cli(); // Disable global interrupts
  
  TCCR1A = 0; // Set Timer1 to Normal mode (no PWM)
  TCCR1B = 0; // Clear Timer1 control register B
  
  // Set compare match register for 1Hz (1-second interval)
  // OCR1A = 15624; // (16 MHz / (1024 * 1Hz)) - 1
  OCR1A = (F_CPU) / (1024 * freq) - 1; 

  
  // Set prescaler to 1024 and enable CTC mode
  TCCR1B |= (1 << WGM12); // Configure for CTC mode
  TCCR1B |= (1 << CS12) | (1 << CS10); // Set prescaler to 1024

  // Enable Timer1 compare interrupt
  TIMSK1 |= (1 << OCIE1A);

  sei(); // Enable global interrupts
}

// Interrupt Service Routine for Timer1 Compare Match A
ISR(TIMER1_COMPA_vect) {
  digitalWrite(LED_PIN, !digitalRead(LED_PIN)); // Toggle LED
}

void loop() {}