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Examples > Communication

Physical Pixel

An example of using the Arduino board to receive data from the computer. In this case, the Arduino boards turns on an LED when it receives the character 'H', and turns off the LED when it receives the character 'L'.

The data can be sent from the Arduino serial monitor, or another program like Processing (see code below), Flash (via a serial-net proxy), PD, or Max/MSP.

Circuit

An LED on pin 13.

click the image to enlarge

image developed using Fritzing. For more circuit examples, see the Fritzing project page

Schematic

click the image to enlarge

Code

 /*
   Physical Pixel
  
  An example of using the Arduino board to receive data from the 
  computer.  In this case, the Arduino boards turns on an LED when
  it receives the character 'H', and turns off the LED when it
  receives the character 'L'.
  
  The data can be sent from the Arduino serial monitor, or another
  program like Processing (see code below), Flash (via a serial-net
  proxy), PD, or Max/MSP.
  
  The circuit:
  * LED connected from digital pin 13 to ground
  
  created 2006
  by David A. Mellis
  modified 14 Apr 2009
  by Tom Igoe and Scott Fitzgerald
  
  http://www.arduino.cc/en/Tutorial/PhysicalPixel
  */

 const int ledPin = 13; // the pin that the LED is attached to
 int incomingByte;      // a variable to read incoming serial data into

 void setup() {
   // initialize serial communication:
   Serial.begin(9600);
   // initialize the LED pin as an output:
   pinMode(ledPin, OUTPUT);
 }

 void loop() {
   // see if there's incoming serial data:
   if (Serial.available() > 0) {
     // read the oldest byte in the serial buffer:
     incomingByte = Serial.read();
     // if it's a capital H (ASCII 72), turn on the LED:
     if (incomingByte == 'H') {
       digitalWrite(ledPin, HIGH);
     } 
     // if it's an L (ASCII 76) turn off the LED:
     if (incomingByte == 'L') {
       digitalWrite(ledPin, LOW);
     }
   }
 }

Processing Code

// mouseover serial 

// Demonstrates how to send data to the Arduino I/O board, in order to 
// turn ON a light if the mouse is over a square and turn it off 
// if the mouse is not. 

// created 2003-4
// based on examples by Casey Reas and Hernando Barragan
// modified 18 Jan 2009
// by Tom Igoe


import processing.serial.*; 

float boxX;
float boxY;
int boxSize = 20;
boolean mouseOverBox = false;

Serial port; 

void setup()  {
  size(200, 200);
  boxX = width/2.0;
  boxY = height/2.0;
  rectMode(RADIUS); 

  // List all the available serial ports in the output pane. 
  // You will need to choose the port that the Arduino 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 Arduino board is connected to (in this case #0) 
  // Make sure to open the port at the same speed Arduino is using (9600bps) 
  port = new Serial(this, Serial.list()[0], 9600); 

}

void draw() 
{ 
  background(0);

  // Test if the cursor is over the box 
  if (mouseX > boxX-boxSize && mouseX < boxX+boxSize && 
    mouseY > boxY-boxSize && mouseY < boxY+boxSize) {
    mouseOverBox = true;  
    // draw a line around the box and change its color:
    stroke(255); 
    fill(153);
    // send an 'H' to indicate mouse is over square:
    port.write('H');       
  } 
  else {
    // return the box to it's inactive state:
    stroke(153);
    fill(153);
    // send an 'L' to turn the LED off: 
    port.write('L');      
    mouseOverBox = false;
  }

  // Draw the box
  rect(boxX, boxY, boxSize, boxSize);
}

Output

As you mouse over the center square, the LED on pin 13 should turn on and off. The Processing applet looks like this:

Max patch

The Max/MSP patch looks like the image below. The text of the patch is linked behind the image. Copy it and paste it into a new patch window.