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*/ 
  {1,0,1,0},
  {1,0,0,1},
  {0,1,0,1},
  {0,1,1,0}
};
int speed = 1000;

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

void loop() {
  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);
  }
}