Code to supplement the "Interfacing Arduino from Processing" Tutorial

Arduino_Example_1.ino

/*
 * Interfacing Arduino from Processing
 * Example 1 Arduino Sketch
 * 
 * The Arduino listens for any data on the serial buffer.
 * If any data is received it is stored in a char-variable.
 * If the received value is 'H' then the led is turned on and
 * if the received value is 'L' then the LED is turned off.
 * No action is taken for other values.
 *
 * Abhik Pal
 */
 
// LED connected to pin 13
const int ledPin = 13;

void setup()
{
  // set the led as output
  pinMode(ledPin, OUTPUT);
  
  // begin serial communication with a baud rate of 9600
  Serial.begin(9600);
}

void loop()
{
  // check for any available data on the serial port
  if (Serial.available())
  {
    // store received value as a char
    char inputValue = Serial.read();
    
    // if the received value is 'H' turn on the LED
    if(inputValue == 'H')
    {
      digitalWrite(ledPin, HIGH);
    }
    // if the received value is 'L' turn off the led
    else if(inputValue == 'L')
    {
      digitalWrite(ledPin, LOW);
    }
    else
    {
      // else do nothing
    }
  }
  else
  {
    // do nothing
  }
  
  // a small delay to keep things sane
  delay(10);
}

Arduino_Example_2.ino

/*
 * Interfacing Arduino from Processing
 * Example 2 Arduino Sketch
 * 
 * Analog values are first read from the pot-meter
 * connected on Analog Pin 0 (aka pin 14) and stored in
 * a variable. The value is then sent over the serial port
 * to a processing sketch running on a computer, where
 * the received value can be used to draw visuals, or do
 * other stuff.
 *
 * Abhik Pal
 */
 
// potmeter connected on pin 14 i.e Analog 0 (A0)
const int potPin = 14; 

void setup()
{
  // declaring potPin as INPUT is not nessasary as Analog 
  // pins are pre-configured to receive inputs.
  
  // begin serial communication with a baud rate of 9600
  Serial.begin(9600);
}

void loop()
{
  // read pot meter value
  int potReading = analogRead(potPin);
  
  // Send  the value via the serial port
  Serial.println(potReading);
  
  // add a delay to control amount of data sent and
  // prevent insanely weird results
  delay(100);
}

Processing_Example_1.pde

/*
 * Interfacing Arduino from Procesisng
 * Example 1 Processing Sketch
 *
 * The code sends a 'H' to the ardunino via the Serial port
 * if the mouse coordinates are inside the button and the 
 * left mouse button is pressed.
 * If either of the two conditions are not met then a 'L' is
 * sent.
 * The sent values are then interpreted by the Arduino to
 * switch on/off the led connected on pin 13 
 *
 * Abhik Pal
 */

// import the processing serial library
import processing.serial.*;

// create an instance of the Serial object
Serial arduinoPort;

void setup()
{
  // setting up the basic interface attributes
  size(400, 400);
  background(20);
  noStroke();
  fill(100);

  // set up the serial port
  // change "COM5" to the port your arduino is connected
  arduinoPort = new Serial(this, "COM5", 9600);
}

void draw() {
  
  // draw a rectangle to act as our button
  rect(150, 150, 100, 100);
  
  // check if the mouse pointer is over our button
  if((mouseX > 150) && (mouseX < 250) && (mouseY > 150) && (mouseY < 250))
  {
    // change fill color to give visual feedback
    fill(220);
    
    // check if the mouse button is presses
    // i.e. detect a click
    if(mousePressed == true)
    {
      // send 'H' to light up the LED on the arduino
      arduinoPort.write('H');  
    }
    else
    {
      // else do nothing
    }
  }
  else
  {
    // use default fill
    fill(110);
    
    // send 'L' to turn off the LED
   arduinoPort.write('L'); 
  }
}  

Processing_Example_2.pde

/*
 * Interfacing Arduino from Procesisng
 * Example 2 Processing Sketch
 *
 * The sensor readings sent from the Arduino are
 * converted to int data type and stored in a variable
 * The variable is then used to draw a simple bar on the
 * window. The height of the bar is dependent on the
 * value received i.e. it changes when we rotate the
 * pot-meter.
 *
 * Abhik Pal
 */


// import the processing serial library
import processing.serial.*;

// create an instance of the Serial object
Serial arduinoPort;

// this variable will store the height of the 
// bar.
float barHeight = 0;

void setup()
{
  // setting up the basic interface attributes
  size(600, 150);
  background(20);
  noStroke();
  fill(220);

  // set up the serial port
  // change "COM5" to the port your arduino is connected
  arduinoPort = new Serial(this, "COM5", 9600);
  
  // serialEvent will be triggred when a
  // '\n' (newline) character is received.
  // As we have used Serial.println(); to send our data
  // from the Arduino a '\n' character will be found at the end
  // of our desired value i.e. the pot-meter reading
  arduinoPort.bufferUntil('\n');
  
}

void draw()
{
  // clear the screen so that new changes can be
  // observed
  background(20);
  // drawing our  bar  
  rect(25, 25, barHeight, 100);
}


// Triggreed whenever the character defined in 
// arduinoPort.bufferUntil(); is received
void serialEvent(Serial arduinoPort)
{
  // store the raw input received from the arduino
  // as string.
  // the readStringUntil() method makes sure that
  // only the values upto '\n' charcter are stored
  String rawInput = arduinoPort.readStringUntil('\n');
  
  // convert the string to an int
  // the trim() function is used to remove any spaces
  // from the string
  int rawVal = int(trim(rawInput));
  
  // map the received values from a range of 0 to 1023
  // to a smaller range of 0 to 550; our maximum and minimum
  // bar heights.
  barHeight = map(rawVal, 0, 1023, 0, 550);
}