AVR Microcontroller Hello World (LED Blink) http://youtu.be/smsW95zcFfE

gistfile1.cpp

#define F_CPU 1000000 //1MHz
#include <avr/io.h>
#include <util/delay.h>

int main(void)
{
  DDRC |= (1<<DDC5); // set LED pin PC5 to output

    while(1)
    {
        PORTC |= (1<<PORTC5); // drive PC5 high
        _delay_ms(500); // delay 500 ms
        PORTC &= ~(1<<PORTC5); // drive PC5 low
        _delay_ms(500); // delay 500 ms
    }
}