Need help incorporating debounce into state-of-change code

Hey everyone,

I'm pretty new to arduino (actually programming altogether) so please excuse my "nubeness". I'm trying to put together a marketing demo for my company in which a stepper motor turns one way until a limit switch is triggered, then turn another way until another go switch is triggered. I'm using the StateChangeDetection example which works fine, but my limit switches have around a 50 millisecond bounce when triggered. I've downloaded the debounce library but haven't been able to properly incorporate it into the StateChangeDetection code. Can anybody help shed some light on this issues? any help would be greatly appreciated.

/* 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.


// 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); }



  // compare the buttonState to its previous state

if (buttonState != lastButtonState) {
    // if the state has changed, increment the counter

Change it to

  // compare the buttonState to its previous state
  static unsigned long lastStateChangeTime = 0;
  if (buttonState != lastButtonState && millis() - lastStateChangeTime > 50) {
    lastStateChangeTime = millis();
    // if the state has changed, increment the counter

This will ignore any state changes that happen within 50 milliseconds of the previously acted-on state change.

This worked great, thanks.