/* Color sensor

A RGB LED has three LEDs inside one package.  By varying 
the intensity of each LED you can mix these primary
colors and generate a wide range of different hues and 
saturation.

The intensity of a LED is controlled by turning it off and
on at a variable duty cycle using the analogOutput property
of the digital output pins.

A photoresistor is a device whose resistance varies with 
the intensity of the light falling on it.  As the light
gets stronger the resistance decreases.  Thus you can measure
the amount of light falling on the photoresistor.

If the illumination on a surface is of a particular color,
then the photoresistor can be used to sense how well that
color is reflected or absorbed by the surface.  And thus
we can detect the color.

*/

int SensorPin = 0;
int RedPin = 11;
int GreenPin = 10;
int BluePin = 9;

/* The senseColor function sets the LED to a particular
mix of red, green, and blue, and then senses the intensity
of the light falling on the photoresistor.  The sampleDelay
parameter is the number of milliseconds to wait after turning
on the LED before sensing the intensity.  It takes a while
for the photoresistor to react, so a delay of 1 second is 
appropriate.  

So that the value returned by this function increases as
a function of increasing intensity, we subtract the voltage
read from the sensor from 1024.

NOTE: this function also displays the values read on the
serial monitor using the printMeasurement procedure.

*/

int senseColor(
  int redOut, int greenOut, int blueOut, int sampleDelay) 
{
  int intensity;
  
  // illuminate the surface with three colors
  
  analogWrite(RedPin, redOut);
  analogWrite(GreenPin, greenOut);
  analogWrite(BluePin, blueOut);
  
  // wait for the sensor to respond
  delay(sampleDelay);
  
  // return the intensity.  A lower level means a brighter
  // illumination, so rescale
  
  intensity = 1024 - analogRead(SensorPin);
  
  printMeasurement(redOut, greenOut, blueOut, intensity);
  
  return intensity;
}

/* The printMeasurement procedure uses the serial monitor
to print the red, green, blue values set for the LED and
the measured intensity.
*/

void printMeasurement(int red, int green, int blue, 
int intensity) {
  Serial.print("RGB LED input values: ");
  Serial.print(red, DEC);
  Serial.print(", ");
  Serial.print(green, DEC);
  Serial.print(", ");
  Serial.print(blue, DEC);
  Serial.print(". Intensity: ");
  Serial.println(intensity, DEC);
  }

void setup() {
    pinMode(RedPin, OUTPUT);
    pinMode(GreenPin, OUTPUT);
    pinMode(BluePin, OUTPUT);
    
    Serial.begin(9600);
}

void loop() {
  int redIn;
  int greenIn;
  int blueIn;
  int blackIn;

  int sampleDelay = 1000;
  
  redIn = senseColor(255, 0, 0, sampleDelay);
  greenIn = senseColor(0, 255, 0, sampleDelay);
  blueIn = senseColor(0, 0, 255, sampleDelay);

  blackIn = senseColor(0, 0, 0, sampleDelay);

  Serial.println(" ");
  delay(2000);
}