int inA1 = PA0; // input 1 of the stepper
int inA2 = PA1; // input 2 of the stepper
int inB1 = PA3; // input 3 of the stepper
int inB2 = PA4; // input 4 of the stepper

int stepDelay = 25; // Delay between steps in milliseconds

void setup() {                
  pinMode(inA1, OUTPUT);     
  pinMode(inA2, OUTPUT);     
  pinMode(inB1, OUTPUT);     
  pinMode(inB2, OUTPUT);     
}

void step1() {
  digitalWrite(inA1, LOW);   
  digitalWrite(inA2, HIGH);   
  digitalWrite(inB1, HIGH);   
  digitalWrite(inB2, LOW);   
  delay(stepDelay);
  
}
void step2() {
  digitalWrite(inA1, LOW);   
  digitalWrite(inA2, HIGH);   
  digitalWrite(inB1, LOW);   
  digitalWrite(inB2, HIGH);   
  delay(stepDelay);
}
void step3() {
  digitalWrite(inA1, HIGH);   
  digitalWrite(inA2, LOW);   
  digitalWrite(inB1, LOW);   
  digitalWrite(inB2, HIGH);   
  delay(stepDelay);
}
void step4() {
  digitalWrite(inA1, HIGH);   
  digitalWrite(inA2, LOW);   
  digitalWrite(inB1, HIGH);   
  digitalWrite(inB2, LOW);   
  delay(stepDelay);
}
void stopMotor() {
  digitalWrite(inA1, LOW);   
  digitalWrite(inA2, LOW);   
  digitalWrite(inB1, LOW);   
  digitalWrite(inB2, LOW);   
}

// the loop routine runs over and over again forever:
void loop() {
  for (int i=0; i<=11; i++){ 
    step1(); 
    step2();
    step3();
    step4();
  }
  stopMotor();
  delay(2000);
  
  for (int i=0; i<=11; i++){
    step3();
    step2();
    step1();
    step4(); 
  }
  
  stopMotor();
  delay(2000);
}