Cut and paste the following into a file called LED_Demo.c

    /* Blinker Demo */

    #include <avr/io.h>     /* Defines pins, ports, etc */
    #define F_CPU 8000000UL         /* Sets up the chip speed for delay.h */
    #include <util/delay.h>     /* Functions to waste time */

    #define LED  PB0        /* Defines pin PB0 for the LED.  I
                     often include a bunch of the circuit
                     info in the code this way, which
                     makes porting the code to another
                     chip easier and reminds you of how to
                     hook it up. */

    void main(void){

      DDRB = _BV(LED);            /* Data Direction Register B:
                           writing a one to the bit
                           enables output.  More on the
                           _BV() macro in the next
                           lesson. */

      while(1){         /* the main loop, from which we never return */

        PORTB = _BV(LED);       /* Turn on the LED bit/pin in PORTB */
        _delay_ms(400);     /* wait */

        PORTB = 0;             /* Turn off everything(!) on PORTB */
       _delay_ms(400);      /* wait */

      }
    }

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