Переключение (Debounce)

/* 
  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 13 to ground
  * pushbutton attached from pin 2 to +5V
  * 10K resistor attached from pin 2 to ground
  
  * Note: On most Arduino boards, there is already an LED on the board
  connected to pin 13, so you don't need any extra components for this example.
  
  
  created 21 November 2006
  by David A. Mellis
  modified 3 Jul 2009
  by Limor Fried
  
  
  http://www.arduino.cc/en/Tutorial/Debounce
  */

 // 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 =  13;      // 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 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 toggled
 long debounceDelay = 50;    // the debounce time; increase if the output flickers

 void setup() {
   pinMode(buttonPin, INPUT);
   pinMode(ledPin, OUTPUT);
 }

 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:
     buttonState = reading;
   }

   // set the LED using the state of the button:
   digitalWrite(ledPin, buttonState);

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