main.c

#include <avr/io.h>

#include <util/delay.h>

/*#define PB0 0

#define PB1 1

#define PB2 2

#define PB3 3*/

/*Prototypes*/

void step1(void);

void step2(void);

void step3(void);

void step4(void);

int main(void)

{

  DDRB |= (1<<PB0) | (1<<PB1) | (1<<PB2) | (1<<PB3);

   while(1)

   {

    step1();

      _delay_ms(50);

    step2();

    _delay_ms(50);

    step3();

    _delay_ms(50);

    step4();

    _delay_ms(50);

  }

  return 0;

}

void step1()

{

  /*1100*/

  PORTB |=  (1<<PB0);      

  PORTB |=  (1<<PB1);

  PORTB &=~ (1<<PB2);   

  PORTB &=~ (1<<PB3);    

}

void step2()

{

  /*0110*/

  PORTB &=~ (1<<PB0);      

  PORTB |=  (1<<PB1);    

  PORTB |=  (1<<PB2);   

  PORTB &=~ (1<<PB3);  

} 

void step3()

{

  /*0011*/

  PORTB &=~ (1<<PB0);      

  PORTB &=~ (1<<PB1);    

  PORTB |=  (1<<PB2);   

  PORTB |=  (1<<PB3); 

}

void step4()

{

  /*1001*/

  PORTB |=  (1<<PB0);      

  PORTB &=~ (1<<PB1);    

  PORTB &=~ (1<<PB2);   

  PORTB |=  (1<<PB3); 

}