Adding a calibration example and moving knock into the sensors folder.

build/shared/dist/examples/Sensors/Knock/Knock.pde

@@ -0,0 +1,34 @@
+/* Knock Sensor
+ * by DojoDave <http://www.0j0.org>
+ *
+ * Program using a Piezo element as if it was a knock sensor.
+ *
+ * We have to basically listen to an analog pin and detect 
+ * if the signal goes over a certain threshold. It writes
+ * "knock" to the serial port if the Threshold is crossed,
+ * and toggles the LED on pin 13.
+ *
+ * http://www.arduino.cc/en/Tutorial/Knock
+ */
+
+int ledPin = 13;      // led connected to control pin 13
+int knockSensor = 0;  // the knock sensor will be plugged at analog pin 0
+byte val = 0;         // variable to store the value read from the sensor pin
+int statePin = LOW;   // variable used to store the last LED status, to toggle the light
+int THRESHOLD = 100;  // threshold value to decide when the detected sound is a knock or not
+
+void setup() {
+ pinMode(ledPin, OUTPUT); // declare the ledPin as as OUTPUT
+ Serial.begin(9600);       // use the serial port
+}
+
+void loop() {
+  val = analogRead(knockSensor);    // read the sensor and store it in the variable "val"
+  if (val >= THRESHOLD) {
+    statePin = !statePin;           // toggle the status of the ledPin (this trick doesn't use time cycles)
+    digitalWrite(ledPin, statePin); // turn the led on or off
+    Serial.println("Knock!");          // send the string "Knock!" back to the computer, followed by newline
+  }
+  delay(100);  // we have to make a delay to avoid overloading the serial port
+}
+