#include <Wire.h>
#include <LiquidCrystal_I2C.h>
#include <DHT.h>
#include "RTClib.h"

#define LDR_PIN 2

// LDR Characteristics
const float GAMMA = 0.7;
const float RL10 = 50;

LiquidCrystal_I2C mylcd(0x27,20,4);
DHT dht2(2, 22);

RTC_DS1307 rtc;

void setup(){
  pinMode(LDR_PIN, INPUT);
  mylcd.init();
  mylcd.backlight();
   dht2.begin();
    if (! rtc.begin()) {
    Serial.println("Couldn't find RTC");
    Serial.flush();
    abort();
  }
}

void loop(){
   DateTime now = rtc.now();

  mylcd.clear();
  mylcd.setCursor(1-1, 1-1);
  mylcd.print(String("TEM:") + String(dht2.readTemperature()) + String(char(0xdf)) + String("C"));
  mylcd.setCursor(1-1, 2-1);
  mylcd.print(String("HUM:") + String(dht2.readHumidity()) + String("%"));
  mylcd.setCursor(1-1, 3-1);
  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));
  mylcd.print(String("BRGHT:") + String(lux) + String("lux"));
  mylcd.setCursor(1-1, 4-1);
  // 在LCD屏幕上显示)时间
  mylcd.print("TIME:");
  mylcd.print(formatDigits(now.hour()));
  mylcd.print(":");
  mylcd.print(formatDigits(now.minute()));
    mylcd.print(":");
  mylcd.print(formatDigits(now.second()));
  delay(1000);

}

// 格式化时间，将一位数转换为两位数，例如将9转换为09
String formatDigits(int digits) {
  if (digits < 10) {
    return "0" + String(digits);
  } else {
    return String(digits);
  }
}