//Libraries
#include "DHT.h";
#include <LiquidCrystal_I2C.h>
//for DS18B20
#include <OneWire.h>
#include <DallasTemperature.h>

//Constants
#define DHTPIN 2     // what pin we're connected to
#define DHTTYPE DHT22   // DHT 22  (AM2302)
#define LCD_I2CADDR 0x27   

DHT dht(DHTPIN, DHTTYPE); //// Initialize DHT sensor for normal 16mhz Arduino
LiquidCrystal_I2C lcd(LCD_I2CADDR,20,4);

OneWire oneWire(3);  // Pin 3 DS18B20 data pin
DallasTemperature sensor(&oneWire);

// Creat a new characters shape of the degree symbol
byte degree[8] = {B00110,
                  B01001,
                  B01001,
                  B00110,
                  B00000,
                  B00000,
                  B00000,
                  B00000}; 
void setup()
{
  dht.begin();
  sensor.begin();  // DS18B20
  lcd.init();
  lcd.createChar(0,degree);
  lcd.backlight();
}

void loop()
{
  delay(2000);
  lcd.clear();
  lcd.setCursor(0,0);
  lcd.print("Temperature:");

  // get temperature and humidity from DHT22
  float humidity = dht.readHumidity();
  //float temperature = dht.readTemperature();

  // un-commend if using DS18B20 toget temperature
  sensor.requestTemperatures();
  float temperature = sensor.getTempCByIndex(0);
  
  // Display temperature on 2nd line
  lcd.setCursor(0, 1);
  lcd.print(temperature, 1);     // set one decimal
  lcd.print(char(0));
  lcd.print("C");
  lcd.setCursor(11, 1);
    // convert the Celsius to Fahrenheit
  float tempF = temperature * 9 / 5 + 32;
  lcd.print(tempF);
  lcd.print(char(0));
  lcd.print("F");
  // Display Humidity on 3rd line
  lcd.setCursor(0,2);
  lcd.print("Humidity: ");
  lcd.setCursor(11, 2);
  lcd.print(humidity, 1);
  lcd.print("%");
  // Dsiplay Dew Point on 4th line
  lcd.setCursor(0,3);
  lcd.print("Dew Point: ");
  lcd.setCursor(11, 3);
  lcd.print(dewPointFast(temperature,humidity), 1);
  lcd.print(char(0));
  lcd.print("C");
}/* --(end main loop )-- */

// function from http://arduino-info.wikispaces.com/PROJECT-Temp-Humidity-Display
double dewPointFast(double celsius, double humidity)
{
        double a = 17.271;
        double b = 237.7;
        double temp = (a * celsius) / (b + celsius) + log(humidity/100);
        double Td = (b * temp) / (a - temp);
        return Td;
}