Lab2 Submission - LED diffuser

Submitted by wendy.xue on Sat, 02/09/2013 - 23:13



I created a new function called myRepeatedKeyProcessCommand() that reads a series of repeated key strokes and calculates the correct level of brightness of the three LEDs. The expected key inputs are limited to the letter of r, g and b. The function counts the number of repeated r, g and b in the input. Each key stroke is  10% of the full brightness of the corresponding LED. For example, rrr is 30% of the full brightness 255. The maximum number of key inputs are set to 30, since ideally each key should be repeated maximum 10 times. If a key is repeated more than 10 times, the brightness is set to 100%, i.e 255. 

The formula used to calculate the brightness is: # of key repeated * 0.1 * 255

The  function checks if keys other than r, g, b are used as input and display error messages to the user. 

The diffuser consists of two parts. The inner layer is a large cotton ball and the outer layer is a cube cover made of white paper. The cotton ball was placed on the LEDs and then covered by the paper cover.  

Components Used

- 1 red LED

- 1 blue LED

- 1 green LED

- 3 220  Ω Resistors

- 1 Arduino Uno

- cotton ball and cube paper cover as diffuser




 * 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>
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
int redValue = 127;
int greenValue = 127;
int blueValue = 127;
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 'r245' or 'b3'  
  //Uncomment the following line to read commands of the form 'rrrb'
  //processRepeatKeyCommands(serInString, 100);
  //Or write your own function...
  //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 + 10) % 255;
      analogWrite(redPin, redValue);
      Serial.print("setting color r to ");
    //If the character is g (green)...
    } else if (colorCode == 'g') {
      greenValue = (greenValue + 10) % 255;
      analogWrite(greenPin, greenValue);
      Serial.print("setting color g to ");
    //If the character is b (blue)...
    } else if (colorCode == 'b') {
      blueValue = (blueValue + 10) % 255;
      analogWrite(bluePin, blueValue);
      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...
//change the value of the red, green, or blue LED according to the command received.
//for example, r240 sets the red LED to the value 240 (out of 255)
void processNumericalCommands(char *strArray) {
  //read in the first character in the string
  colorCode = serInString[0];
  //if the first character is r (red), g (green) or b (blue), do the following...
  if( colorCode == 'r' || colorCode == 'g' || colorCode == 'b' ) {
    //convert the string to an integer
    //(start at the second character, or the beginning of the string '+1')
    colorVal = atoi(serInString+1);
    Serial.print("setting color ");
    Serial.print(" to ");
    if(colorCode == 'r') 
      analogWrite(redPin, colorVal);
    else if(colorCode == 'g')
      analogWrite(greenPin, colorVal);
    else if(colorCode == 'b')
      analogWrite(bluePin, colorVal);
//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;
void myProcessRepeatKeyCommands(char *strArray, int maxLength){
  int i=0;
  int redCount =0;
  int greenCount =0;
  int blueCount =0;
  int redVal = 0;
  int blueVal = 0;
  int greenVal = 0;
  if( serInString[0] !='\0'){
  //read all the serial input characters and count number of repeated red, blue and green key strokes
  while(i<maxLength && serInString[i] != '\0'){
    colorCode = serInString[i];
    if(colorCode =='r'){
      redCount ++;
    else if(colorCode == 'g'){
      greenCount ++;
    else if(colorCode == 'b'){
      blueCount ++;
      Serial.print("Wrong color code, use r, g, b.");
  Serial.print("redcount ");
  Serial.print("greenCount ");
  Serial.print("blueCount ");
  //percentage is incremental of 10%
  //maximum key stroke for each color therefore is only 10 for 100%
  //reset to 100% if key stroke goes over maximum
  if(redCount >10){
    redCount =10;
  if(blueCount >10){
    blueCount =10;
  if(greenCount >10){
    greenCount =10;
    redVal = (int)(redCount*0.1*255);
    analogWrite(redPin, redVal);
    Serial.print("Setting red to ");
    blueVal = (int)(blueCount*0.1*255);
    analogWrite(bluePin, blueVal);
    Serial.print("Setting blue to ");
    greenVal = (int)(greenCount*0.1*255);
    analogWrite(greenPin, greenVal);
    Serial.print("Setting green to ");
cotton ball as the inner layer of the diffuser
diffuser outer cover
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