#include <avr/io.h>
#include <util/delay.h>

// LED is on pin 1
#define LED      PB1
#define DELAY_MS 1000

int main ()
{
  uint8_t high = 0;
  uint16_t ms = 0;

  // Setup LED pin for output in port B's direction register
  DDRB |= (1 << LED);

  // Set LED pin HIGH
  PORTB |= (1 << LED);

  while (1) {

    if (high) {
      // Set LED pin HIGH
      PORTB |= (1 << LED);
    } else {
      // Set LED pin LOW
      PORTB &= ~(1 << LED);
    }

    high = !high;

    // Delay for 1 second
    for (ms = DELAY_MS; ms > 0; ms -= 10) {
      _delay_ms(10);
    }
  }

  return 0;
}