Driving an RGB LED — SIK Circuit 3

/*
SparkFun Inventor's Kit
Example sketch 03 — RGB LED

Make an RGB LED display a rainbow of colors!

Hardware connections:
  RGB LED pins (from flattened edge): RED, COMMON, GREEN, BLUE
  RED -> 330 ohm resistor -> Pin 9
  COMMON -> GND
  GREEN -> 330 ohm resistor -> Pin 10
  BLUE -> 330 ohm resistor -> Pin 11

This code is completely free for any use.
*/

const int RED_PIN = 9;
const int GREEN_PIN = 10;
const int BLUE_PIN = 11;

int DISPLAY_TIME = 10;  // milliseconds

void setup()
{
  pinMode(RED_PIN, OUTPUT);
  pinMode(GREEN_PIN, OUTPUT);
  pinMode(BLUE_PIN, OUTPUT);
}

void loop()
{
  mainColors();
  showSpectrum();
}

void mainColors()
{
  // Off
  digitalWrite(RED_PIN, LOW);
  digitalWrite(GREEN_PIN, LOW);
  digitalWrite(BLUE_PIN, LOW);
  delay(1000);

  // Red
  digitalWrite(RED_PIN, HIGH);
  digitalWrite(GREEN_PIN, LOW);
  digitalWrite(BLUE_PIN, LOW);
  delay(1000);

  // Green
  digitalWrite(RED_PIN, LOW);
  digitalWrite(GREEN_PIN, HIGH);
  digitalWrite(BLUE_PIN, LOW);
  delay(1000);

  // Blue
  digitalWrite(RED_PIN, LOW);
  digitalWrite(GREEN_PIN, LOW);
  digitalWrite(BLUE_PIN, HIGH);
  delay(1000);

  // Yellow (red + green)
  digitalWrite(RED_PIN, HIGH);
  digitalWrite(GREEN_PIN, HIGH);
  digitalWrite(BLUE_PIN, LOW);
  delay(1000);

  // Cyan (green + blue)
  digitalWrite(RED_PIN, LOW);
  digitalWrite(GREEN_PIN, HIGH);
  digitalWrite(BLUE_PIN, HIGH);
  delay(1000);

  // Purple (red + blue)
  digitalWrite(RED_PIN, HIGH);
  digitalWrite(GREEN_PIN, LOW);
  digitalWrite(BLUE_PIN, HIGH);
  delay(1000);

  // White (all on)
  digitalWrite(RED_PIN, HIGH);
  digitalWrite(GREEN_PIN, HIGH);
  digitalWrite(BLUE_PIN, HIGH);
  delay(1000);
}

void showSpectrum()
{
  int x;
  for (x = 0; x < 768; x++)
  {
    showRGB(x);
    delay(DISPLAY_TIME);
  }
}

void showRGB(int color)
{
  int redIntensity;
  int greenIntensity;
  int blueIntensity;

  if (color <= 255)
  {
    redIntensity = 255 - color;
    greenIntensity = color;
    blueIntensity = 0;
  }
  else if (color <= 511)
  {
    redIntensity = 0;
    greenIntensity = 255 - (color - 256);
    blueIntensity = (color - 256);
  }
  else
  {
    redIntensity = (color - 512);
    greenIntensity = 0;
    blueIntensity = 255 - (color - 512);
  }

  analogWrite(RED_PIN, redIntensity);
  analogWrite(GREEN_PIN, greenIntensity);
  analogWrite(BLUE_PIN, blueIntensity);
}