#include

#define SETBIT(ADDRESS,BIT) (ADDRESS |= (1<<BIT))
#define CLEARBIT(ADDRESS,BIT) (ADDRESS &= ~(1<<BIT))
#define FLIPBIT(ADDRESS,BIT) (ADDRESS ^= (1<<BIT))
#define CHECKBIT(ADDRESS,BIT) (ADDRESS & (1<<BIT))
#define WRITEBIT(RADDRESS,RBIT,WADDRESS,WBIT) (CHECKBIT(RADDRESS,RBIT) ? SETBIT(WADDRESS,WBIT) : CLEARBIT(WADDRESS,WBIT))
volatile int i=1;
int main(void)
{
DDRB &= ~(1 << DDB0); // Clear the PB0 pin
// PB0 (PCINT0 pin) is now an input

PORTB |= (1 << PORTB0); // turn On the Pull-up
// PB0 is now an input with pull-up enabled
DDRD = 0xFF;
PORTD = 0xF9;

PCICR |= (1 << PCIE0); // set PCIE0 to enable PCMSK0 scan
PCMSK0 |= (1 << PCINT0); // set PCINT0 to trigger an interrupt on state change

sei(); // turn on interrupts

while(1)
{

if(i==0)
{
//i=0;
SETBIT(PORTD,0);
CLEARBIT(PORTD,1);
CLEARBIT(PORTD,2);
}
else
if(i==1)
{
SETBIT(PORTD,1);
CLEARBIT(PORTD,2);
CLEARBIT(PORTD,0);
}
else
{
SETBIT(PORTD,2);
CLEARBIT(PORTD,0);
CLEARBIT(PORTD,1);
}
}

}

ISR (PCINT0_vect)
{

/*if(PORTB & (1 << PB0))
{
i++;
if (i==3)
i=0;
}
else
{
i=i;
}*/
if(!CHECKBIT(PORTB,0))
{

i++;
if (i==3)
i=0;
}
else
{
i=i;

}

}
_________________________________________________
the switch is connected to PCINT0 (i.e. PortB0) and the led's are connected to PORTD0,1,2.
Since the switch press gives two interrupts (one high to low when pressed and other low to high when released ) the led's toggle by 2 instead of one.
I have used the for loop in the ISR but nothing seems to work
Kindly help

I come from PIC and I see some coincidences: INT0 for pin RB0 and PCINT0 for pin RB4-RB7.

Thanks to you I can understand the power of AVR interrupts.

Another article that would be interesting would be on other peripheral interrupts (ex timers and serial data). I find those interrupts to be much more interesting than external interrupts.