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8ac3da2 Aug 3, 2016
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* 1 Button Shield - Debounce Toggle LED
* Press the pushbutton to toggle the LED
* Pushbuttons often generate spurious open/close transitions when pressed, due to mechanical and physical issues.
* This example demonstrates how to debounce an input, which means checking twice in a short period of time to make sure the pushbutton is definitely pressed.
* 1 Button Shield pushbutton connects pin D3 to GND
const int buttonPin = D3;
const int ledPin = BUILTIN_LED;
// the current state of the LED and button
int ledState = LOW;
int buttonState = LOW;
// the current and previous readings from the input pin
int thisButtonState = LOW;
int lastButtonState = LOW;
// time is measured in milliseconds and will quickly exceed limitations of an integer, so we use a long for these two
unsigned long lastDebounceTime = 0; // the time the button state last switched
unsigned long debounceDelay = 50; // the state must remain the same for this many millis to register the button press
void setup() {
pinMode(buttonPin, INPUT);
pinMode(ledPin, OUTPUT);
// set initial LED state
digitalWrite(ledPin, ledState);
void loop() {
// the buttonPin is read multiple times and the value must remain the same for debounceDelay millis to toggle the LED
// read button state, HIGH when pressed, LOW when not
thisButtonState = digitalRead(buttonPin);
// if the current state does not match the previous state
// the button was just pressed/released, or is transition noise
if (thisButtonState != lastButtonState) {
// reset the timer
lastDebounceTime = millis();
// once delay millis have elapsed, if the state remains the same, register the press
if ((millis() - lastDebounceTime) > debounceDelay) {
// if the button state has changed
if (thisButtonState != buttonState) {
buttonState = thisButtonState;
// only toggle the LED if the buttonState has switched from LOW to HIGH
if (buttonState == HIGH) {
ledState = !ledState;
// toggle the LED
digitalWrite(ledPin, ledState);
// persist for next loop iteration
lastButtonState = thisButtonState;