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Arduino/build/shared/dist/examples/Digital/Debounce/Debounce.pde

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/* 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).
*
* David A. Mellis
* 21 November 2006
*
* http://www.arduino.cc/en/Tutorial/Debounce
*/
int inPin = 7; // the number of the input pin
int outPin = 13; // the number of the output pin
int state = HIGH; // the current state of the output pin
int reading; // the current reading from the input pin
int previous = LOW; // the previous reading from the input pin
// the follow variables are long's because the time, measured in miliseconds,
// will quickly become a bigger number than can be stored in an int.
long time = 0; // the last time the output pin was toggled
long debounce = 200; // the debounce time, increase if the output flickers
void setup()
{
pinMode(inPin, INPUT);
pinMode(outPin, OUTPUT);
}
void loop()
{
reading = digitalRead(inPin);
// if we just pressed the button (i.e. the input went from LOW to HIGH),
// and we've waited long enough since the last press to ignore any noise...
if (reading == HIGH && previous == LOW && millis() - time > debounce) {
// ... invert the output
if (state == HIGH)
state = LOW;
else
state = HIGH;
// ... and remember when the last button press was
time = millis();
}
digitalWrite(outPin, state);
previous = reading;
}