Improvements in debounce from Limor

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

@@ -17,8 +17,8 @@
  
  created 21 November 2006
  by David A. Mellis
- modified 17 Jun 2009
- by Tom Igoe
+ modified 3 Jul 2009
+ by Limor Fried
  
  
  http://www.arduino.cc/en/Tutorial/Debounce
@@ -34,10 +34,10 @@ 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 follow variables are long's because the time, measured in miliseconds,
+// 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 = 200;   // the debounce time, increase if the output flickers
+long debounceDelay = 50;    // the debounce time; increase if the output flickers
 
 void setup() {
   pinMode(buttonPin, INPUT);
@@ -45,29 +45,29 @@ void setup() {
 }
 
 void loop() {
-  buttonState = digitalRead(buttonPin);
+  // 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 ((buttonState == HIGH) && 
-    (lastButtonState == LOW) && 
-    (millis() - lastDebounceTime) > debounceDelay) {
-    // toggle the output
-    if (ledState == HIGH) {
-      ledState = LOW;
-    } else {
-      ledState = HIGH;
-    }
-    // ... and store the time of the last button press
-    // in a variable:
+
+  // If the switch changed, due to noise or pressing:
+  if (reading != lastButtonState) {
+    // reset the debouncing timer
     lastDebounceTime = millis();
   } 
   
-  // set the LED using the ledState variable:
-  digitalWrite(ledPin, ledState);
+  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;
+  }
   
-  // save the buttonState.  Next time through the loop,
+  // 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 = buttonState;
+  lastButtonState = reading;
 }