/* Port Toggle - PortB - BT 3/12/14                           */
/* The following program just  keeps toggling pin 0 of port B */
/*                                                            */

#include <avr/io.h>                                //standard Atmel16 include

#define sbi(x,y) x |= _BV(y)                      //set bit - using bitwise OR operator 
#define cbi(x,y) x &= ~(_BV(y))                   //clear bit - using bitwise AND operator
#define tbi(x,y) x ^= _BV(y)                      //toggle bit - using bitwise XOR operator
#define is_high(x,y) (x & _BV(y) == _BV(y))       //check if the y'th bit of register 'x' is high ... test if its AND with 1 is 1

/* _BV(a) is a macro which returns the value corresponding to 2 to the power 'a'. Thus _BV(PX3) would be 0x08 or 0b00001000 */

int main(void)
{
    DDRB=0xff;                                   //PORTB as OUTPUT
    PORTB=0x00;                                  //All pins of PORTB LOW

    unsigned int i;
    while(1==1)                                  //Infinite loop
    {
        for(i=0;i<65535;i++);                    //delay - yes, it's cheesy but it works
        for(i=0;i<65535;i++);                    //delay
        tbi(PORTB,PB0);                          //here the toggling takes place
    }
}