#include <Wire.h>
#include <Arduino.h>

#define I2C_PERIFERAL_ADRESS 8 // address on the I2C network

#define LDR_PIN 0 

const long A = 1000;     //Resistance on darkness on KΩ
const int B = 27;        //Resistance on light (10 Lux) on KΩ
const int Rc = 10;       //Calibracion  resistance on KΩ

unsigned int ilum, rawValue;
void setup() {
  //set up pins
  pinMode(LDR_PIN,INPUT);

  //Set up I2C bus
  Wire.begin(I2C_PERIFERAL_ADDRESS);
  Wire.onRequest(onRequest);
}
//Function that read the average sensor reading
int readSensor(int samples = 10){
  long value = 0;
  for(int i=0; i<samples; ++i){
    value += analogRead(LDR_PIN);
    delay(10);
  }
  return value/samples;
}
void loop() {
  rawValue = readSensor(100);
  ilum = ((long)rawvalue*A*10)/((long)B*Rc*(1024-rawvalue)); // make the transformation from raw value to lumens
}

void onRequest(){
  //Send the current light value
  Wire.write(highByte(ilum));
  Wire.write(lowByte(ilum));
}