void step(int dir) {
  if(dir == 1) {
    i++;
	if(i>3) i = 0;
	} else {
		i--;
	if(i<0) i=3; 
	}
	switch(i) { // podanie napięcia na odpowienia uzwojenie – wykonanie kroku 
      case 0:
		digitalWrite(PWMA, LOW);
      	digitalWrite(DIRB, LOW);
      	digitalWrite(PWMB, HIGH);
	break; 
      case 1:
		digitalWrite(PWMB, LOW);
      	digitalWrite(DIRA, LOW);
      	digitalWrite(PWMA, HIGH);
	break;
      case 2:
		digitalWrite(PWMA, LOW);
      	digitalWrite(DIRB, HIGH);
      	digitalWrite(PWMB, HIGH);
	break;
      case 3:
		digitalWrite(PWMB, LOW);
      	digitalWrite(DIRA, HIGH);
      	digitalWrite(PWMA, HIGH);
	break; 
    }
}