//Celsius to Fahrenheit conversion
double Fahrenheit(double celsius)
{return 1.8 * celsius + 32;}

//int Celcius2Fahrenheit(int celcius)
//{return (celsius * 18 + 5)/10 + 32;}
 
//Celsius to Kelvin conversion
double Kelvin(double celsius)
{return celsius + 273.15;}
 
// dewPoint function NOAA
// reference: http://wahiduddin.net/calc/density_algorithms.htm 
double dewPoint(double celsius, double humidity)
{
       double RATIO = 373.15 / (273.15 + celsius);  // RATIO was originally named A0, possibly confusing in Arduino context
        double SUM = -7.90298 * (RATIO - 1);
        SUM += 5.02808 * log10(RATIO);
        SUM += -1.3816e-7 * (pow(10, (11.344 * (1 - 1/RATIO ))) - 1) ;
        SUM += 8.1328e-3 * (pow(10, (-3.49149 * (RATIO - 1))) - 1) ;
        SUM += log10(1013.246);
        double VP = pow(10, SUM - 3) * humidity;
        double T = log(VP/0.61078);   // temp var
        return (241.88 * T) / (17.558 - T);
}

// delta max = 0.6544 wrt dewPoint()
// 5x faster than dewPoint()
// reference: http://en.wikipedia.org/wiki/Dew_point
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; }

#include <dht11.h>
dht11 DHT11;
#define DHT11PIN 2 
#include <OneWire.h>
#include <DallasTemperature.h>
// Data wire is plugged into port 2 on the Arduino
#define ONE_WIRE_BUS 10

OneWire oneWire(ONE_WIRE_BUS);
DallasTemperature sensors(&oneWire);


#include <Adafruit_GFX.h>
#include <Adafruit_PCD8544.h>

// pin 7 - Serial clock out (SCLK)
// pin 6 - Serial data out (DIN)
// pin 5 - Data/Command select (D/C)
// pin 4 - LCD chip select (CS)
// pin 3 - LCD reset (RST)
Adafruit_PCD8544 display = Adafruit_PCD8544(7, 6, 5, 4, 3);
#define Backlight_Pin 9
 
 void setup()
{
Serial.begin(9600);
Serial.println("DHT11 DS18B20 temperature");
Serial.print("DHT11 LIBRARY VERSION: ");
Serial.println(DHT11LIB_VERSION);
Serial.println();

// DS18B20
sensors.begin(); 
// Nokia 5110 display
display.begin();
// you can change the contrast around to adapt the display
// for the best viewing!
display.setContrast(50);
pinMode(Backlight_Pin, OUTPUT);

pinMode(0, INPUT);
Serial.print("Backlight ");
Serial.println(analogRead(0));

display.clearDisplay();
display.setTextSize(1);
display.setTextColor(BLACK);
display.setCursor(0,0);
display.println("Ready");
display.display();
}
 
float dht11_temperature = 0;
float dht11_humidity = 0;
float ds18b20_temperature = 0;
 
#define TEMP_SIZE LCDWIDTH
float temp[TEMP_SIZE] = {0.0};
int temp_pos = 0; // position in circular buffer above
 
void loop()
 {
Serial.println("\n");

int chk = DHT11.read(DHT11PIN);

Serial.print("DHT11 Read sensor: ");
switch (chk)
{
    case DHTLIB_OK: 
                Serial.println("OK"); 
                break;
    case DHTLIB_ERROR_CHECKSUM: 
                Serial.println("Checksum error"); 
              break;
   case DHTLIB_ERROR_TIMEOUT: 
                Serial.println("Time out error"); 
               break;
  default: 
               Serial.println("Unknown error"); 
                break;
 }

   dht11_humidity = (float)DHT11.humidity;
   Serial.print("Humidity (%): ");
   Serial.println(dht11_humidity, 2);
 
   dht11_temperature = (float)DHT11.temperature;
   Serial.print("Temperature (oC): ");
   Serial.println(dht11_temperature, 2);
 
   Serial.print("Temperature (oF): ");
   Serial.println(Fahrenheit(DHT11.temperature), 2);
 
   Serial.print("Temperature (K): ");
   Serial.println(Kelvin(DHT11.temperature), 2);
 
   Serial.print("Dew Point (oC): ");
   Serial.println(dewPoint(DHT11.temperature, DHT11.humidity));
 
   Serial.print("Dew PointFast (oC): ");
   Serial.println(dewPointFast(DHT11.temperature, DHT11.humidity));
 
 
   Serial.print("DS18B20 Requesting temperatures...");
   sensors.requestTemperatures(); // Send the command to get temperatures
   Serial.println("DONE");
 
   sensors.requestTemperatures(); // Send the command to get temperatures
   Serial.print("Temperature for the device 1 (index 0) is: ");
   ds18b20_temperature = sensors.getTempCByIndex(0);
   Serial.println(ds18b20_temperature);  
 
   temp[temp_pos] = ds18b20_temperature;
 
   display.clearDisplay();
   display.setCursor(0,0);
   display.print(dht11_temperature, 0);
   display.print("C ");
   display.print(dht11_humidity, 0);
   display.print("% ");
   display.print(ds18b20_temperature, 1);
   display.print("C");
 
  float min = temp[0], max = temp[0];
   
  for(int i = 0; i < TEMP_SIZE; i++) {
//    Serial.print(temp[i]);
//    Serial.print(" ");
    if (temp[i] < min && temp[i] > 0) min = temp[i];
    if (temp[i] > max) max = temp[i];
   }
  Serial.println();
  
  Serial.print("temperature range ");
  Serial.print(min);
  Serial.print("-");
  Serial.println(max);

  // draw right to left so most recent value is on the right
  for(int x = TEMP_SIZE - 1; x >= 0; x--) {
   int pos = ( x + temp_pos + 1 ) % TEMP_SIZE;
     if ( temp[pos] > 0 ) {
       int y = ( ( temp[pos] - min ) / ( max - min ) ) * ( LCDHEIGHT - 10 );
      display.drawLine(x, LCDHEIGHT - y, x, LCDHEIGHT, BLACK);
//      display.drawPixel(x,y + 10, BLACK);
//      Serial.print(temp[pos],2);
//      Serial.print(" ");
    }
  }
   Serial.println(); 
// refresh LCD
display.display();

// pulse display backlight
int backlight = 0;

float old_temp = temp[(temp_pos + TEMP_SIZE - 1) % TEMP_SIZE];
if ( ds18b20_temperature < old_temp ) {
backlight = 32;
  } else if ( ds18b20_temperature > old_temp ) {
   backlight = 255;
  }
  analogWrite(Backlight_Pin, backlight); 
 delay(2000);

  if ( ++temp_pos > TEMP_SIZE ) temp_pos = 0;
 
}