Knock Sensor using Piezo Element

An analog read example using a piezo element out of the SparkFun Inventor's Kit with a MSP-
EXP430F5529LP....

/* 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 pin 23 (P6.0)
 - connection of the piezo attached to ground
 1-megohm resistor attached from pin 23 (P6.0) to GND
   http://www.arduino.cc/en/Tutorial/Knock
  
   created 25 Mar 20070
   by David Cuartielles <http://www.0j0.org>
   modified 30 Aug 2011
   by Tom Igoe
   modified 4 Feb 2013
   by Frank Milburn for MSP-EXP430F5529LP
   This example code is in the public domain.
 */

// these constants won't change:
const int ledPin = RED_LED;                  // connected the red LED on the LaunchPad
const int knockSensor = P6_0;                // the pin the piezo is connected to
const int threshold = 20;                    // threshold value to decide when the detected sound is a knock or not
                                             // NOTE: You may need to vary this depending on your sensor
// 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);                        // initiate the serial connection and let the user know we've started
  Serial.println("Starting to listen.... ");
}
void loop()
{ 
  sensorReading = analogRead(knockSensor);   // read the sensor and store it in the variable sensorReading:
   
  if (sensorReading >= threshold)            // if the sensor reading is greater than the threshold:
  {   
    ledState = !ledState;                    // toggle the status of the ledPin:           
    digitalWrite(ledPin, ledState);          // and update the LED pin itself:
    Serial.print("Knock! Reading was:");     // let the user know there was a knock and how loud it was
    Serial.println(sensorReading);      
  }
  delay(30);                                 // delay to avoid overloading the serial port buffer
                                             // vary this delay if multiple knocks or no knocks are detected
}