RGB_moodlight.c

// 2009 Kenneth Finnegan
// kennethfinnegan.blogspot.com

// Pins. Must be PWM pins.
#define REDLED  9
#define BLUELED  10
#define GREENLED  11
// Can't be higher than 255
#define MAXBRIGHT  200

// s[tate] t[arget] colors
byte s[3] = {0}, t[3] = {0};

void setup() {
  // Make the random MORE RANDOM!
  randomSeed(analogRead(0));
  
  // Initialization wiring check
  // You should see RED, BLUE, then GREEN.
  // If you don't, then you ballsed something up.
  analogWrite(REDLED, MAXBRIGHT);
  delay(1000);
  analogWrite(REDLED, 0);
  analogWrite(BLUELED, MAXBRIGHT);
  delay(1000);
  analogWrite(BLUELED, 0);
  analogWrite(GREENLED, MAXBRIGHT);
  delay(1000);
  analogWrite(GREENLED, 0);
}

void loop() {
  byte i, offset;
  
  // Select the next target color
  // Start from a random one of the three colors to prevent
  // the cycle from being red biased.
  offset = random(3);
  t[offset] = random(MAXBRIGHT);
  t[(offset+1)%3] = random(MAXBRIGHT - t[offset]);
  t[(offset+2)%3] = MAXBRIGHT - t[offset] - t[(offset+1)%3];
  
  // Slowly drift to the new target color 1 at a time until
  // it has been reached
  while(s[0]!=t[0] || s[1]!=t[1] || s[2] != t[2]) {
    for (i = 0; i<3; i++) {
      if (s[i] > t[i]) {
        s[i] = s[i] - 1;
      } else if (s[i] < t[i]) {
        s[i] = s[i] + 1;
      }
      analogWrite(REDLED, s[0]);
      analogWrite(BLUELED, s[1]);
      analogWrite(GREENLED, s[2]);
      delay(10);
    }
  }
  analogWrite(REDLED, s[0]);
  analogWrite(BLUELED, s[1]);
  analogWrite(GREENLED, s[2]);
  // Let the viewer enjoy the new color before
  // selecting the next target color.
  delay(2000);
}