int val;         // variable to receive data from the serial port
int ledpin = 48;  // Wiring board LED

void setup() 
{
  pinMode(ledpin, OUTPUT);  // pin 48 (on-board LED) as OUTPUT
  Serial.begin(9600);       // start serial communication at 9600bps
}

void loop() {
  if( Serial.available() )         // if data is available to read
  {
    val = Serial.read();           // read it and store it in 'val'
    if( val == 'H' )               // if 'H' was received
    {
      digitalWrite(ledpin, HIGH);  // turn ON the LED
    } 
    else if( val == 'L' ) { 
      digitalWrite(ledpin, LOW);   // otherwise turn it OFF
    }
  }
  delay(100);                      // wait 100ms for next reading
}

/* Processing code for this example

 // mouseover serial
 // by BARRAGAN <http://barraganstudio.com>
 
 // Demonstrates how to send data to the Wiring I/O board, in order to
 // turn ON a light if the mouse is over a rectangle and turn it off
 // if the mouse is not.
 
 // created 13 May 2004
 // revised 6 November 2009
 
 import processing.serial.*;
 
 Serial port;
 boolean firstTime = true;
 
 void setup() 
 {
   size(200, 200);
   noStroke();
   // List all the available serial ports in the output pane.
   // You will need to choose the port that the Wiring board is 
   // connected to from this list. The first port in the list is
   // port #0 and the third port in the list is port #2.
   println(Serial.list());
   
   // Open the port that the Wiring board is connected to (in this case #1)
   // Make sure to open the port at the same speed Wiring is using (9600bps)
   port = new Serial(this, Serial.list()[1], 9600);  
 }
 
 // function to test if mouse is over square
 boolean mouseOverRect()
 {
   return ((mouseX >= 50)&&(mouseX <= 150)&&(mouseY >= 50)&(mouseY <= 150));
 }
 
 void draw() 
 {
   // Wait 3 seconds for the Wiring board to start 
   if(firstTime) {
     delay(3000);
     firstTime = false;
   }
   
   background(#222222);
   if(mouseOverRect())      // if mouse is over square
   {
     fill(#BBBBB0);         // change color
     port.write('H');       // send an 'H' to indicate mouse is over square
   } else {
     fill(#666660);         // change color
     port.write('L');       // send an 'L' otherwise
   }
   rect(50, 50, 100, 100);  // draw square
 }
 
 */