int sw = LOW;
int i = 0;

void setup() {
  Serial.begin(9600);
  pinMode(7, INPUT);

  pinMode(10, OUTPUT);
  pinMode(11, OUTPUT);
  pinMode(12, OUTPUT);
  pinMode(13, OUTPUT);
}

void loop() {
  if (digitalRead(7) == HIGH) {
    sw = !sw;
    i = (i + 1) % 16;
    
    digitalWrite(10, bitRead(i, 0));
    digitalWrite(11, bitRead(i, 1));
    digitalWrite(12, bitRead(i, 2));
    digitalWrite(13, bitRead(i, 3));

    Serial.println(i, BIN);
    
    delay(200);
    while (digitalRead(7) == HIGH);
  }
}