arduino-0018-linux-x64

arduino-0018-linux-x64/examples/Sensors/Knock/Knock.pde

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+/* Knock Sensor
+  
+   This sketch reads a piezo element to detect a knocking sound. 
+   It reads an analog pin and compares the result to a set threshold. 
+   If the result is greater than the threshold, it writes
+   "knock" to the serial port, and toggles the LED on pin 13.
+  
+   The circuit:
+	* + connection of the piezo attached to analog in 0
+	* - connection of the piezo attached to ground
+	* 1-megohm resistor attached from analog in 0 to ground
+
+   http://www.arduino.cc/en/Tutorial/Knock
+   
+   created 25 Mar 2007
+   by David Cuartielles <http://www.0j0.org>
+   modified 30 Jun 2009
+   by Tom Igoe
+
+ */
+ 
+
+// these constants won't change:
+const int ledPin = 13;      // led connected to digital pin 13
+const int knockSensor = 0;  // the piezo is connected to analog pin 0
+const int threshold = 100;  // threshold value to decide when the detected sound is a knock or not
+
+
+// these variables will change:
+int sensorReading = 0;      // variable to store the value read from the sensor pin
+int ledState = LOW;         // variable used to store the last LED status, to toggle the light
+
+void setup() {
+ pinMode(ledPin, OUTPUT); // declare the ledPin as as OUTPUT
+ Serial.begin(9600);       // use the serial port
+}
+
+void loop() {
+  // read the sensor and store it in the variable sensorReading:
+  sensorReading = analogRead(knockSensor);    
+  
+  // if the sensor reading is greater than the threshold:
+  if (sensorReading >= threshold) {
+    // toggle the status of the ledPin:
+    ledState = !ledState;   
+    // update the LED pin itself:        
+    digitalWrite(ledPin, ledState);
+    // send the string "Knock!" back to the computer, followed by newline
+    Serial.println("Knock!");         
+  }
+  delay(100);  // delay to avoid overloading the serial port buffer
+}
+