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Examples > Communication

Dimmer

Demonstrates the sending data from the computer to the Arduino board, in this case to control the brightness of an LED. The data is sent in individual bytes, each of which ranges from 0 to 255. Arduino reads these bytes and uses them to set the brightness of the LED.

Circuit

An LED connected to pin 9 (with appropriate resistor).

Code

int ledPin = 9;

void setup()
{
  // begin the serial communication
  Serial.begin(9600);
  pinMode(ledPin, OUTPUT);
}

void loop()
{
  byte val;

  // check if data has been sent from the computer
  if (Serial.available()) {
    // read the most recent byte (which will be from 0 to 255)
    val = Serial.read();
    // set the brightness of the LED
    analogWrite(ledPin, val);
  }
}

Processing Code

// Dimmer - sends bytes over a serial port
// by David A. Mellis

import processing.serial.*;

Serial port;

void setup()
{
  size(256, 150);

  println("Available serial ports:");
  println(Serial.list());

  // Uses the first port in this list (number 0).  Change this to
  // select the port corresponding to your Arduino board.  The last
  // parameter (e.g. 9600) is the speed of the communication.  It
  // has to correspond to the value passed to Serial.begin() in your
  // Arduino sketch.
  port = new Serial(this, Serial.list()[0], 9600);  

  // If you know the name of the port used by the Arduino board, you
  // can specify it directly like this.
  //port = new Serial(this, "COM1", 9600);
}

void draw()
{
  // draw a gradient from black to white
  for (int i = 0; i < 256; i++) {
    stroke(i);
    line(i, 0, i, 150);
  }

  // write the current X-position of the mouse to the serial port as
  // a single byte
  port.write(mouseX);
}