// Ex. 5 - Configure timer block for signal generation
const int outputPin = 9;  // Pin connected to the output signal
const long frequency = 1000;  // Desired frequency in Hz (1 kHz)

void setup() {
  pinMode(outputPin, OUTPUT);

  // Calculate the Timer1 settings for the desired frequency
  long timerCompare = (16000000 / (2 * 1 * frequency)) - 1;  // 16 MHz clock, prescaler of 1

  // Configure Timer1
  TCCR1A = 0;  // Clear Timer1 control register A
  TCCR1B = 0;  // Clear Timer1 control register B
  TCNT1 = 0;   // Clear the Timer1 counter

  // Set the compare match register for the desired frequency
  OCR1A = timerCompare;

  // Set the CTC mode (Clear Timer on Compare Match)
  TCCR1B |= (1 << WGM12);

  // Set the prescaler to 1 and start the timer
  TCCR1B |= (1 << CS10);

  // Enable the output compare match A interrupt
  TIMSK1 |= (1 << OCIE1A);
}

void loop() {
  // Main loop does nothing, signal generation is handled by the ISR
}

// Interrupt Service Routine for Timer1 compare match
ISR(TIMER1_COMPA_vect) {
  // Toggle the output pin to generate the signal
  digitalWrite(outputPin, !digitalRead(outputPin));
}