#include <LiquidCrystal_I2C.h>
LiquidCrystal_I2C lcd(0x27, 16, 2);

#define LDR_PIN 2
const float GAMMA = 0.7;
const float RL10 = 50;

int STARTg = 8;
int RESETr = 9;
int sw_status = 0;

void setup() 
{
  Serial.begin(115200);
  pinMode(LDR_PIN, INPUT);
  pinMode(10, OUTPUT);  
  lcd.init();
  lcd.backlight();
}
void loop() {
  if (digitalRead(STARTg)==1)
  {
  sw_status = 1;
  delay(100);
  Serial.println("STARTg");
  }
  else if (digitalRead(RESETr)==1)
  {
  sw_status = 2;
  delay(100);
  Serial.println("Stop");
  }
  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));
if(sw_status == 1)
{
  lcd.setCursor(0, 0);
  lcd.print("--Room : ");
  if (lUX < 300) {
  lcd.print("Dark --");
  digitalWrite(10, HIGH);
  } else {
  lcd.print("light--");
  digitalWrite(10, LOW);
  }
  lcd.setCursor(2, 1);
  lcd.print("LUX = ");
  lcd.print(lUX);
  lcd.print("          ");
  delay(100);
}
else if (sw_status == 2 )
{
lcd.clear();
digitalWrite(10, LOW);
delay(100);
}
}