1 #include <avr/io.h>

     2 #include <util/delay.h>

     3 

     4 #define false       0

     5 #define true        1

     6 

     7 #define SBI(port, bit) do { port |= (1 << (bit)); } while (0)

     8 #define CBI(port, bit) do { port &= ~(1 << (bit)); } while (0)

     9 

    10 int main (void)

    11 {

    12     // LED

    13     SBI(DDRB, DDB5);

    14 

    15     while (true) {

    16         // flip

    17         PORTB ^= (1 << PORTB5);

    18         

    19         // busyloop

    20         _delay_ms(1000);

    21     }

    22 }