// Learning Processing
  // Daniel Shiffman
  // http://www.learningprocessing.com
  
  // Example 19-9: Handshaking
  
  import processing.serial.*;
  
  int val = 0; // To store data from serial port, used to color background  
  Serial port; // The serial port object  
  
  void setup() {
    size(200,200);
  
    // In case you want to see the list of available ports
    // println(Serial.list());
  
    // Using the first available port (might be different on your computer)  
    port = new Serial(this, Serial.list()[0], 9600);
  
    // Request values from the hardware device
    // The byte 65 tells the serial device that we want to receive data.
    port.write(65); 
  
  }
  
  void draw() {
    // The serial data is used to color the background.   
    background(val); 
  }
  
  // Called whenever there is something available to read   
  void serialEvent(Serial port)  {   
    // Read the data   
    val = port.read();   
    // For debugging   
    // println( "Raw Input:  " + input);   
  
    // After we receive a byte, we reply asking for the next one. 
    port.write(65);      
  }