Blog post: http://www.slickstreamer.info/2013/10/led-stripe-music-visualiser-spotify.html

IkeaDioderLed.ino

#define REDPIN 3
#define GREENPIN 5
#define BLUEPIN 6

char payload[5] = "100";


unsigned long timeLastCommand;


void setup () 
{
  Serial.begin(57600);
  pinMode(REDPIN, OUTPUT);
  pinMode(GREENPIN, OUTPUT);
  pinMode(BLUEPIN, OUTPUT);
}

byte inByte = 0;
char code[4]; 
int bytesread = 0;
void loop () 
{
    handleIncomingData();     

   if( (millis() - timeLastCommand) > 60000){
     setColor(0,0,0);
   } 
}

void handleIncomingData(){
  
  if (Serial.available() > 0) {
       
         inByte = Serial.read();
         //Serial.println(inByte);
         if(inByte == 4){
            bytesread = 0;
            while(bytesread<4) {              
              if( Serial.available() > 0) { 
                  inByte = Serial.read(); 
                  if((inByte == 10)||(inByte == 13)) { 
                    break;                       
                  } 
                  code[bytesread] = inByte;  
                  //Serial.print('r');
                  //Serial.println(bytesread);              
                  bytesread++;                   
                } 
            } 
            if(bytesread == 3) { 
              setColor(code[0],code[1],code[2]);   
              Serial.flush();   
            } 
            bytesread = 0;
            timeLastCommand = millis();
     }
   }
}

void setColor(int r, int g, int b){
  
  analogWrite(REDPIN, r);
  analogWrite(GREENPIN, g);
  analogWrite(BLUEPIN, b); 
}