//Debounce

/* Each time the input pin goes from LOW to high (e.g. because of a push-button press),
   the output pin is toggled from LOW to HIGH or HIGH to LOW. There's a minimum delay
   between toggles to debounce the circuit (i.e to ignore noise)

   The Circuit:
   LED attached from PIN 8 to ground through 220 ohm resistor.
   Push button attached to pin 2 from +5V
   10K resistor attached to pin 2 from ground
*/

//Constants won't change. They're used here to set pin numbers:
const int buttonPin = 2; //The number of the pushbutton pin.
const int ledPin = 8; //The number of the LED pin.

//Variables will change:
int ledState = HIGH; //The current state of the output pin.
int buttonState; //The current reading from the input pin.
int lastButtonState = LOW; // The previous reading from the input pin.

//The following variables are unsigned longs because the time, measured in
//milliseconds, will quickly become a bigger number than can be stored in an int.
unsigned long lastDebounceTime = 0; //The last time the output pin was toggled.
unsigned long debounceDelay = 50; //The debounce time; increase if the output flickers

void setup()
{
  Serial.begin(115200);
  Serial.println("ready..");
  pinMode(ledPin, OUTPUT); //Initialize the LED pin as an output.

  pinMode(buttonPin, INPUT); //Initialize the pushbutton pin as an input.

  digitalWrite(ledPin, ledState); //Set initial LED state
}

void loop()
{
  int reading = digitalRead(buttonPin); //Read the state of the switch into a local variable:

  //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 (reading != lastButtonState)
  {
    lastDebounceTime = millis(); //Reset the debouncing timer
  }

  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 (reading != buttonState) //If the button state has changed:
    {
      buttonState = reading;

      if (buttonState == HIGH) //Only toggle the LED if the new button state is high
      {
        ledState = !ledState;
      }
    }
  }

  digitalWrite(ledPin, ledState); //Set the LED:

  lastButtonState = reading; //Save the reading. Next time through the loop, it'll be the lastButtonState:
}