November 24, 2007
Reading for November 27th, are now posted. Enjoy!

October 2, 2007
To upload your thoughtless acts, create a new assignment page like any other lab. You'll see "Thoughtless Acts" listed as one of the assignment options.

May 24, 2008
This site has been archived and is no longer editable. Stay tuned for the next version, coming in the fall!

Revision of Color Mixer from Wed, 09/26/2007 - 23:35

Project Members: 
Elisa Oreglia


Diffusing and mixing the light emitted by the three LED, and controlling LED from the keyboard.
Components Used
RGB LED, one red one green one blue
Diffusor: a transparent box, covered with shredded pearly gift packaging material. The threads are transparent, with bright 'bits' glued at regular intervals. It's impossible to describe, really, but it diffused light pretty well.

Arduino Code

 * Serial RGB LED
 * ---------------
 * Serial commands control the brightness of R,G,B LEDs
 * Command structure is "<colorCode><colorVal>", where "colorCode" is
 * one of "r","g",or "b" and "colorVal" is a number 0 to 255.
 * E.g. "r0"   turns the red LED off. 
 *      "g127" turns the green LED to half brightness
 *      "b64"  turns the blue LED to 1/4 brightness
 * Alternate command structure is "<colorCode>*", where "colorCode" is
 * one of "r","g", or "b".
 * E.g. "r"    increases the red LED brightness by 10
 *      "rrr"  increases the red LED brightness by 30
 *      "ggb"  increases the green LED brightness by 20 and the blue by 10
 * Created 18 October 2006
 * copyleft 2006 Tod E. Kurt <
 * Adapted 5 September 2007
 * copylefter 2007 Ryan Aipperspach <>
//include support for manipulating strings.
//for a useful string comparison function, see the bottom of this file... stringsEqual()
#include <stdio.h>
#include <string.h>
#include <math.h>
char serInString[100];  // array that will hold the different bytes of the string. 100=100characters;
                        // -> you must state how long the array will be else it won't work properly
char colorCode;
int colorVal;
int redPin   = 9;   // Red LED,   connected to digital pin 9
int greenPin = 10;  // Green LED, connected to digital pin 10
int bluePin  = 11;  // Blue LED,  connected to digital pin 11
float redValue   = 0;
float greenValue = 0;
float blueValue  = 0;
void setup() {
  pinMode(redPin,   OUTPUT);   // sets the pins as output
  pinMode(greenPin, OUTPUT);  
  pinMode(bluePin,  OUTPUT);
  analogWrite(redPin,   redValue);   // set them all to mid brightness
  analogWrite(greenPin, greenValue);   // set them all to mid brightness
  analogWrite(bluePin,  blueValue);   // set them all to mid brightness
  Serial.println("enter color command (e.g. 'r43 or rrrrrrrrbbbb') :"); 
void loop () {
  //read the serial port and create a string out of what you read
  readSerialString(serInString, 100);
  //Uncomment the following line to read commands of the form 'rrrb'
  processRepeatKeyCommands(serInString, 100);
//Erase anything left in the serial string, preparing it for the
  //next loop
  resetSerialString(serInString, 100); 
delay(100);  // wait a bit, for serial data
void resetSerialString (char *strArray, int length) {
  for (int i = 0; i < length; i++) {
    strArray[i] = '\0';
//read a string from the serial and store it in an array
//you must supply the array variable
void readSerialString (char *strArray, int maxLength) {
  int i = 0;
if(!Serial.available()) {
  while (Serial.available() && i < maxLength) {
    strArray[i] =;
//go through the string, and increase the red value for each 'r',
//the green value for each 'g', and the blue value for each 'b'.
//For example "rrrg" increases red by 30 and green by 10.
void processRepeatKeyCommands(char *strArray, int maxLength) {
  int i = 0;
  //loop through the string (strArray)
  //i = the current position in the string
  //Stop when either (a) i reaches the end of the string or
  //                 (b) there is an empty character '\0' in the string
  while (i < maxLength && strArray[i] != '\0') {
    //Read in the character at position i in the string
    colorCode = serInString[i];
    //If the character is r (red)...
    if (colorCode == 'r') {
      //Increase the current red value by 10, and if you reach 255 go back to 0
      redValue = (redValue + 25.5);
      if (redValue >= 255) {redValue = 0;}
      analogWrite(redPin, ((int)redValue % 255));
      Serial.print("setting color r to ");
    //If the character is g (green)...
    } else if (colorCode == 'g') {
      greenValue = (greenValue + 25.5);
      if (greenValue >= 255) {greenValue = 0;}
      analogWrite(greenPin, ((int)greenValue % 255));
      Serial.print("setting color g to ");
    //If the character is b (blue)...
    } else if (colorCode == 'b') {
      blueValue = (blueValue + 25.5);
      if (blueValue >= 255) {blueValue = 0;}
      analogWrite(bluePin, ((int)blueValue % 255));
      Serial.print("setting color b to ");
    //Move on to the next character in the string
    //From here, the code continues executing from the "while" line above...
//compare two strings to see if they are equal
//compares the first 'numCharacters' characters of string1 and string2 to
//see if they are the same
//E.g. stringsEqual("hello","hello",5) => true
//     stringsEqual("hello","helaabbnn",3) => true
//     stringsEqual("hello","helaa",5) => false
boolean stringsEqual(char *string1, char *string2, int numCharacters) {
  if (strncmp(string1, string2, numCharacters) == 0) {
    return true;
  } else {
    return false;
See attached
Apparently Arduino has serious issues with Vista, that haven't been solved yet!


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