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

// convert from loop cycles to msecs
#define _delay_ms(x) _delay_loop_2((x)*(F_CPU/4000))

/*
  void delay_ms(unsigned int t) 

  _delay_loop_2() can only take a 16-bit argument.  This routine 
    repeatedly calls _delay_loop_2() in order to get the desired busy
    wait length.  Note that there is some overhead in the loop that is
    not counted in the delay (so the delay is actually just a little longer)

  This code is also specific to the 1 MHz clock

*/

void delay_ms(unsigned int t) {
  unsigned int nloops = (unsigned short) (t >> 8);
  unsigned int i;

  for(i = 0; i < nloops; ++i) {
    _delay_ms(256);
  };
  i = t & 0xFF;
  if(i > 0) {
    _delay_ms(i);
  };
  
};

int main (void)
{

	/* Set PORTB (LEDs) to all outputs */
	DDRB = 0xFF;
	
	while(1) {
	  PORTB = PORTB ^ 0x1;  // Toggle bit 0
	  delay_ms(500);
	  PORTB = PORTB ^ 0x2;  // Toggel bit 1
	  delay_ms(250);
	  PORTB = PORTB ^ 0x2;  // Toggel bit 1
	  delay_ms(250);
	};
	return (0);
}