#define F_CPU 8000000UL
#include <avr/io.h>           /* Include AVR std. library file */
#include <util/delay.h>         /* Include inbuilt defined Delay header file */
#include <avr/interrupt.h>
static uint8_t mode = 0b00000000;

void int5_init(void)

{
   // Make sure you have connected a SW between PD1 (External Interrupt) and GND.
   cli();                 // Clear all the interrupts
   PORTE |= (1 << PE5);   // External SW PullUp
   DDRE &= ~(1 << PE5);   // External Interrupt Sensing Port(PE3) Input Port
   EICRB |= (1<<ISC50);   // External Interrupt 5, Falling Edge Asynchronously Interrupt
   EIMSK |= (1 << INT5);;   // External Interrupt 5 enable
   sei();

}


void Time_Delay(void)
{
	TCNT1 = 3906;					  //  TCNT1= for delay of 0.5 seconds
	TCCR1B |=  (1<<CS12)| (1<<CS10);     //  Scale down the timer frequency to 8MHz/1024
	while ((TIFR1 & (1<<TOV1))==0);  // wait for TF1 to roll over
	TCCR1B = 0;						    //  Stop Timer
	TIFR1 |=(1<<ICF1)|(1<<OCF1C)|(1<<OCF1B)|(1<<OCF1A)|(1<<TOV1);
}



int main()
{
  int5_init();                    // Initialization of INT5 Interrupt
  DDRB |= (1<< PB0);              // PORTB.0 will be used as an output.
  PORTB &= ~(1 << PB0);           // PORTB.0 pulled low
  while(1) {
  }

}

ISR (INT5_vect, ISR_NOBLOCK)
{
  // sei();
  // int5_init();
   mode = ~mode;
  if (mode == 0b00000000) {
    PORTB &= ~(1<<0);
  } else {
    while (mode != 0b00000000) {
      PORTB ^= (1<<0);
      Time_Delay();
    }
  } 
	EIMSK |= (1 << INT5);     // External Interrupt 5 enable
  
}