#define WAIT 100
#define SWITCH_PIN 13
void setup() {
  pinMode(10, OUTPUT);
  pinMode(SWITCH_PIN, INPUT_PULLUP);
  Serial.begin(9600);  
}

void loop() {
  digitalWrite(10, HIGH);
  delay(WAIT);
  digitalWrite(10, LOW);
  delay(WAIT);
  Serial.println(digitalRead(SWITCH_PIN));
  delay(100);
}