Fix Debounce example to work as described

This alters the debounce example code to toggle the LED rather than just use
the button state to set the LED state.

Fixes #293

Author: miek

build/shared/examples/02.Digital/Debounce/Debounce.ino

@@ -19,6 +19,8 @@
  by David A. Mellis
  modified 30 Aug 2011
  by Limor Fried
+ modified 28 Dec 2012
+ by Mike Walters
  
 This example code is in the public domain.
  
@@ -43,6 +45,9 @@ long debounceDelay = 50;    // the debounce time; increase if the output flicker
 void setup() {
   pinMode(buttonPin, INPUT);
   pinMode(ledPin, OUTPUT);
+
+  // set initial LED state
+  digitalWrite(ledPin, ledState);
 }
 
 void loop() {
@@ -62,12 +67,21 @@ void loop() {
   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;
+
+    // if the button state has changed:
+    if (reading != buttonState) {
+      buttonState = reading;
+
+      // only toggle the LED if the new button state is HIGH
+      if (buttonState == HIGH) {
+        ledState = !ledState;
+
+        // set the LED:
+        digitalWrite(ledPin, ledState);
+      }
+    }
   }
 
-  // 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;