bombatuino/source/ConnectionChecker/ConnectionChecker.ino

const int buttonPin = 2;     // the number of the pushbutton pin
const int ledPin =  13;      // the number of the LED pin

void setup() {
  // initialize the LED pin as an output:
  pinMode(ledPin, OUTPUT);      
  // initialize the pushbutton pin as an input:
  pinMode(buttonPin, INPUT);
  digitalWrite(buttonPin, HIGH);  
}

void loop(){
  int buttonState = digitalRead(buttonPin);
  if (buttonState == LOW) {     
    digitalWrite(ledPin, HIGH);  
  } 
  else {
    digitalWrite(ledPin, LOW); 
  }
}