arduino-0017-linux-x64

arduino-0017-linux-x64/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).  
+ 
+ The circuit:
+ * LED attached from pin 13 to ground
+ * pushbutton attached from pin 2 to +5V
+ * 10K resistor attached from pin 2 to ground
+ 
+ * Note: On most Arduino boards, there is already an LED on the board
+ connected to pin 13, so you don't need any extra components for this example.
+ 
+ 
+ created 21 November 2006
+ by David A. Mellis
+ modified 3 Jul 2009
+ by Limor Fried
+ 
+ 
+ http://www.arduino.cc/en/Tutorial/Debounce
+ */
+
+// constants won't change. They're used here to 
+// set pin numbers:
+const int buttonPin = 2;     // the number of the pushbutton pin
+const int ledPin =  13;      // the number of the LED pin
+
+// Variables will change:
+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 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 = 50;    // the debounce time; increase if the output flickers
+
+void setup() {
+  pinMode(buttonPin, INPUT);
+  pinMode(ledPin, OUTPUT);
+}
+
+void loop() {
+  // 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 the switch changed, due to noise or pressing:
+  if (reading != lastButtonState) {
+    // reset the debouncing timer
+    lastDebounceTime = millis();
+  } 
+  
+  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;
+  }
+  
+  // 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;
+}
+