/*** An introductory C program for AVR microcontrollers* Flashes a LED connected to PORTB of the device*//* These are avr-libc header files */#include<avr/interrupt.h>#include<util/delay.h>int main(void){ /* Initialise PortB, bit0 as output */ /* DDRB is the Data Direction Register for PortB */ DDRB = _BV(PB0); /* the main loop */ for(;;) { /* set PortB, bit0 */ /* this turns on the LED */ PORTB |= _BV(PB0); /* delay for 250 milliseconds */ /* _delay_ms() is a avr-libc function */ /* argument: number of milliseconds for delay */ _delay_ms(250); /* unset PortB, bit0 */ /* this turns off the LED */ PORTB &= ~_BV(PB0); /* delay again */ _delay_ms(250); } return 0; /* will never reach here! */}