int const button = 12,
step = 7,
a1 = 5,
a2 = 4,
b1 = 3,
b2 = 2;

// Global Variables
bool tt [4][4] = {  /* Truth table - 4rows, 4columns - 2b,2a,1a,1b*/ 
  {0,1,1,0},
  {1,0,1,0},
  {1,0,0,1},
  {0,1,0,1}
};
int speed = 750;
int past_step = -1;


// User defined functions
void motor(int s){
  if(s>0){ // +ve num
    for(int i=0; i<s; i++){
      if(past_step = 3){
        past_step = -1;
      }
      past_step++;
      digitalWrite(b2, tt[past_step][0]);
      digitalWrite(a2, tt[past_step][1]);
      digitalWrite(a1, tt[past_step][2]);
      digitalWrite(b1, tt[past_step][3]);
      delay(750);
      Serial.println(i);
    }
    
  }
  else{ // -ve num
    for(int i=0; i<s; i++){
      if(past_step = 0){
        past_step = 4;
      }
      past_step--;
      digitalWrite(b2, tt[past_step][0]);
      digitalWrite(a2, tt[past_step][1]);
      digitalWrite(a1, tt[past_step][2]);
      digitalWrite(b1, tt[past_step][3]);
      delay(750);
      Serial.println(s);
    }
  }
}

void setup() {
  Serial.begin(9600);
  Serial.println("Hello World");
  pinMode(button, INPUT_PULLUP);
  pinMode(step, OUTPUT);
  pinMode(a1, OUTPUT);
  pinMode(a2, OUTPUT);
  pinMode(b1, OUTPUT);
  pinMode(b2, OUTPUT);
}

void loop() {
  // Taking input from user
  while(!Serial.available());
  String input = Serial.readString();
  int num = input.toInt();
  // Rotating the motor 
  motor(num);
  

}




/*
for(int i=0; i<4; i++){
    digitalWrite(b2, tt[i][0]);
    digitalWrite(a2, tt[i][1]);
    digitalWrite(a1, tt[i][2]);
    digitalWrite(b1, tt[i][3]);
    delay(speed);
  }
*/