#include <LiquidCrystal.h>
#define photoresistance A0
#define THRESHOLD 100
#define PERIOD 15

const float GAMMA = 0.7;
const float RL10 = 50;
int analogValue = analogRead(A0);
float voltage = analogValue / 1024. * 5;
float resistance = 2000 * voltage / (1 - voltage / 5);
float lux = pow(RL10 * 1e3 * pow(10, GAMMA) / resistance, (1 / GAMMA));

const int rs = 12, en = 11, d4 = 5, d5 = 4, d6 = 3, d7 = 2;
LiquidCrystal lcd(rs, en, d4, d5, d6, d7);

bool etat_precedant;
bool etat_actuel;
void setup() 
{
    lcd.begin(16,2);
    //lcd.print(lux);
    //Serial.begin(9600);
}
void loop() 
{
  etat_actuel = get_ldr();
  if(!etat_actuel && etat_precedant)
  {
    print_byte(get_byte());
  }
  etat_precedant = etat_actuel;
}

bool get_ldr()
{
  int voltage = analogRead(resistance);
  return voltage > THRESHOLD ? true : false;
}

char get_byte()
{
  char ret = 0;
  delay(PERIOD*1.5);
  for(int i = 0; i < 8; i++)
  {
   ret = ret | get_ldr() << i;

   delay(PERIOD);
  }
  return ret;
}
void print_byte(char my_byte)
{
  char buff[2];
  sprintf(buff, "%c", my_byte);
  lcd.print(buff);
}