// constants won't change. They're used here to// set pin numbers:const int buttonPin = 2; // the number of the pushbutton pinconst int ledPin = 13; // the number of the LED pin// Variables will change:int ledState = HIGH; // the current state of the output pinint buttonState; // the current reading from the input pinint lastButtonState = LOW; // the previous reading from the input pin// the following variables are long's because the time, measured in miliseconds,// will quickly become a bigger number than can be stored in an int.long lastDebounceTime = 0; // the last time the output pin was toggledlong debounceDelay = 50; // the debounce time; increase if the output flickersvoid setup() { pinMode(buttonPin, INPUT); pinMode(ledPin, OUTPUT); // set initial LED state digitalWrite(ledPin, ledState);}void loop() { // read the state of the switch into a local variable: int reading = digitalRead(buttonPin); // check to see if you just pressed the button // (i.e. the input went from LOW to HIGH), and you've waited // long enough since the last press to ignore any noise: // If the switch changed, due to noise or pressing: if (reading != lastButtonState) { // reset the debouncing timer lastDebounceTime = millis(); } if ((millis() - lastDebounceTime) > debounceDelay) { // whatever the reading is at, it's been there for longer // than the debounce delay, so take it as the actual current state: // if the button state has changed: if (reading != buttonState) { buttonState = reading; // only toggle the LED if the new button state is HIGH if (buttonState == HIGH) { ledState = !ledState; } } } // set the LED: digitalWrite(ledPin, ledState); // save the reading. Next time through the loop, // it'll be the lastButtonState: lastButtonState = reading;}