/* State change detection (edge detection) Often, you don't need to know the state of a digital input all the time, but you just need to know when the input changes from one state to another. For example, you want to know when a button goes from OFF to ON. This is called state change detection, or edge detection. This example shows how to detect when a button or button changes from off to on and on to off. The circuit: * pushbutton attached to pin 2 from +5V * 10K resistor attached to pin 2 from ground * LED attached from pin 13 to ground (or use the built-in LED on most Arduino boards) created 27 Sep 2005 modified 30 Aug 2011 by Tom Igoe This example code is in the public domain. http://arduino.cc/en/Tutorial/ButtonStateChange */ // this constant won't change: const int buttonPin = 2; // the pin that the pushbutton is attached to const int ledPin = 13; // the pin that the LED is attached to // Variables will change: int buttonPushCounter = 0; // counter for the number of button presses int buttonState = 0; // current state of the button int lastButtonState = 0; // previous state of the button void setup() { // initialize the button pin as a input: pinMode(buttonPin, INPUT); // initialize the LED as an output: pinMode(ledPin, OUTPUT); // initialize serial communication: Serial.begin(9600); } void loop() { // read the pushbutton input pin: buttonState = digitalRead(buttonPin); // compare the buttonState to its previous state if (buttonState != lastButtonState) { // if the state has changed, increment the counter if (buttonState == HIGH) { // if the current state is HIGH then the button // wend from off to on: buttonPushCounter++; Serial.println("on"); Serial.print("number of button pushes: "); Serial.println(buttonPushCounter); } else { // if the current state is LOW then the button // wend from on to off: Serial.println("off"); } } // save the current state as the last state, //for next time through the loop lastButtonState = buttonState; // turns on the LED every four button pushes by // checking the modulo of the button push counter. // the modulo function gives you the remainder of // the division of two numbers: if (buttonPushCounter % 4 == 0) { digitalWrite(ledPin, HIGH); } else { digitalWrite(ledPin, LOW); } }