-------
ARDUINO
-------

int analogPin = 3;     // potentiometer wiper (middle terminal) connected to analog pin 3
                       // outside leads to ground and +5V
int val = 0;           // variable to store the value read
#define INTERVAL 100  // interval between readings, in milliseconds

void setup()
{
  Serial.begin(9600);          //  setup serial
}

void loop()
{
  val = analogRead(analogPin);    // read the input pin
  Serial.println(val);             // debug value
  delay(INTERVAL);
}

----------
PROCESSING
----------

//modified from tom igoe http://itp.nyu.edu/physcomp/Labs/SerialDuplex

import processing.serial.*;     // import the Processing serial library
Serial myPort;                  // The serial port
int sensor;

void setup() {
  //println(Serial.list());  // List all the available serial ports
  myPort = new Serial(this, Serial.list()[0], 9600);
  myPort.bufferUntil('\n');   // read bytes into a buffer until you get a linefeed (ASCII 10)
  size(800,300);

  smooth();
  noStroke();
  fill(90,30,50,155);
}

void draw() {
    background(0);
    ellipse (width/2,height/2,sensor,200);
}

void serialEvent(Serial myPort) { 
  String myString = myPort.readStringUntil('\n'); // read the serial buffer
  if (myString != null) {  // if you got any bytes other than the linefeed
    myString = trim(myString);
    sensor = int(myString);//convert the section into integer
    print("stretch level = " + sensor + "\t"); // print out the value
    println(); // add a linefeed after all the sensor values are printed 
  }
}