Implementation of interrupt driven binary switch

The difference between the interrupt driven binary switch example and
the normal binary switch example is the following:
* Interrupt example does not use debouncer because it rely on loop()
iterating over time (but it sleeps between iterations)
* Interrupt example is more power conservative because it sleeps as soon
as it has sent updated data and no activity happens on the pin
* Interrupt example is limited to only two IO pins for the sensor, due
to limitations in the Arduino HW. The example uses the preprocessor to
ensure that this is not misconfigured or sleep function can not be
expected to behave as intended.

libraries/MySensors/examples/BinarySwitchSensorInt/BinarySwitchSensorInt.ino

@@ -0,0 +1,60 @@
+// Interrupt driven binary switch example 
+// Author: Patrick 'Anticimex' Fallberg
+// Connect button or door/window reed switch between 
+// digitial I/O pin 3 (BUTTON_PIN below) and GND.
+// This example is designed to fit Arduino Nano/Pro Mini
+
+#include <MySensor.h>
+#include <SPI.h>
+
+#define CHILD_ID 3
+#define BUTTON_PIN 3  // Arduino Digital I/O pin for button/reed switch
+
+#if (BUTTON_PIN < 2 || BUTTON_PIN > 3)
+#error BUTTON_PIN must be either 2 or 3 for interrupts to work
+#endif
+
+MySensor gw;
+
+// Change to V_LIGHT if you use S_LIGHT in presentation below
+MyMessage msg(CHILD_ID,V_TRIPPED);
+
+void setup()  
+{  
+  gw.begin();
+
+  // Setup the button
+  pinMode(BUTTON_PIN,INPUT);
+  // Activate internal pull-up
+  digitalWrite(BUTTON_PIN,HIGH);
+  
+  // Send the sketch version information to the gateway and Controller
+  gw.sendSketchInfo("Binary Sensor", "1.0");
+
+  // Register binary input sensor to gw (they will be created as child devices)
+  // You can use S_DOOR, S_MOTION or S_LIGHT here depending on your usage. 
+  // If S_LIGHT is used, remember to update variable type you send in. See "msg" above.
+  gw.present(CHILD_ID, S_DOOR);  
+}
+
+// Loop will iterate on changes on the BUTTON_PIN
+void loop() 
+{
+  uint8_t value;
+  static uint8_t sentValue=2;
+
+  // Short delay to allow button to properly settle
+  gw.sleep(5);
+  
+  value = digitalRead(BUTTON_PIN);
+  
+  if (value != sentValue) {
+     // Value has changed from last transmission, send the updated value
+     gw.send(msg.set(value==HIGH ? 1 : 0));
+     sentValue = value;
+  }
+
+  // Sleep until something happens with the sensor
+  gw.sleep(BUTTON_PIN-2, CHANGE, 0);
+} 
+