/*
 * LatchButton
 * This implements latching behavior on a pushbutton. 
 * The state of the input changes only when the pushbutton
 * has been pressed and then released. While simple in concept,
 * implementing a latch becomes complicated due to switch bounce.
 * This sketch modifies the provided sketch on the Arduino webpage found at 
 * http://www.arduino.cc/en/Tutorial/Debounce and modifies it for easier use 
 * in other code.
 */
 
 int buttonPin = 4;
 int currState;
 int prevState = LOW;
 long time = 0;
 int latchState = LOW;
void setup()                    
{
  setupLatch();
}

void loop()                     // run over and over again
{
  checkLatch();
}

void setupLatch(){
  Serial.begin(9600);
  pinMode(4, INPUT);
}

void checkLatch(){
  currState = digitalRead(buttonPin);
  if(currState ==HIGH &&prevState==LOW &&abs(millis()-time)>50){
    if(latchState == HIGH)
      latchState =LOW;
    else 
      latchState = HIGH;

    time = millis();
    Serial.println(latchState);
  }
  prevState = currState;
}