// Declarations
void ledBlinkFunction();

// LED connected to digital pin 17
const int LED_PIN = 17;

unsigned int blinkLed;

// Interface function to blink the yellow LED
void blinkTheLED() {
  blinkLed++;
}

void setup_timer_interrupt()
{

  // initialize digital led-pin as an output.
  pinMode(LED_PIN, OUTPUT);

  blinkLed = 0;

  //set timer1 interrupt at 10Hz
  TCCR1A = 0;// set entire TCCR1A register to 0
  TCCR1B = 0;// same for TCCR1B
  TCNT1  = 0;//initialize counter value to 0
  // set compare match register for 1hz increments
  
  //  OCR1A = 40. This results is 16MHz / 8 / 40 = 20 uS between interrupts
  OCR1A = 40;

  // turn on CTC mode
  TCCR1B |= (1 << WGM12);

  // Set CS12:CS10 to 010 = /8 prescaler
  TCCR1B |= (1 << CS11);  
 
  // enable timer compare interrupt
  TIMSK1 |= (1 << OCIE1A);
}

enum {
  MODE_INACTIVE,
  MODE_ON,
  MODE_OFF,
  MODE_SWITCH,   // Just have been off
};

// 10uS timer interrupt function
ISR(TIMER1_COMPA_vect,ISR_NOBLOCK) {
  
  static unsigned int ledCnt=10000;
  
  rxInterrupt();
  
  if( (--ledCnt) == 0 ) {
    ledCnt = 10000;
    ledBlinkFunction();
  }
}  

// 10Hz (100mS) timer interrupt function
void ledBlinkFunction() {

  static unsigned long timer = 0;
  static int mode = MODE_INACTIVE;

  switch( mode ) {

  case   MODE_INACTIVE:
    if( blinkLed > 0 ) {
      blinkLed--;
      mode = MODE_ON;
      timer = 1;
      digitalWrite(LED_PIN, LOW);   // turn the LED on (HIGH is the voltage level)
    }
    break;

  case MODE_ON:
    timer--;
    if( timer == 0 ) {
      mode = MODE_OFF;
      digitalWrite(LED_PIN, HIGH);    // turn the LED off by making the voltage LOW
      timer = 1;
    }
    break;

  case MODE_OFF:
    timer--;
    if( timer == 0 ) {
      mode = MODE_INACTIVE;
      digitalWrite(LED_PIN, HIGH);    // turn the LED off by making the voltage LOW
      break;

    }
  }
}