#include <SPI.h>
#include <SD.h>
#include "DHT.h"

#define DHTTYPE DHT22

// On the Ethernet Shield, CS is pin 4. Note that even if it's not
// used as the CS pin, the hardware CS pin (10 on most Arduino boards,
// 53 on the Mega) must be left as an output or the SD library
// functions will not work.
const int chipSelect = 10;

const int write_led = 7;



#define DHTPIN 2     // what digital pin we're connected to
DHT dht(DHTPIN, DHTTYPE);

void setup()
{
 // Open serial communications and wait for port to open:
  Serial.begin(9600);
   while (!Serial) {
    ; // wait for serial port to connect. Needed for Leonardo only
  }

  Serial.print("Initializing SD card...");
  // make sure that the default chip select pin is set to
  // output, even if you don't use it:
  pinMode(chipSelect, OUTPUT);
  
  // see if the card is present and can be initialized:
  if (!SD.begin(chipSelect)) {
    Serial.println("Card failed, or not present");
    // don't do anything more:
    return;
  }
  Serial.println("card initialized.");

  dht.begin();

  pinMode(write_led, OUTPUT);
}

void loop()
{
  // make a string for assembling the data to log:
  String dataString = "";

  // Reading temperature or humidity takes about 250 milliseconds!
  // Sensor readings may also be up to 2 seconds 'old' (its a very slow sensor)
  float h = dht.readHumidity();
  // Read temperature as Celsius (the default)
  float t = dht.readTemperature();
  // Read temperature as Fahrenheit (isFahrenheit = true)
  float f = dht.readTemperature(true);

  // Check if any reads failed and exit early (to try again).
  if (isnan(h) || isnan(t) || isnan(f)) {
    Serial.println("Failed to read from DHT sensor!");
    return;
  }

  dataString += String(h);
  dataString += ",";
  dataString += String(t);

  // open the file. note that only one file can be open at a time,
  // so you have to close this one before opening another.
  File dataFile = SD.open("datalog.txt", FILE_WRITE);

   

  // if the file is available, write to it:
  if (dataFile) {
    dataFile.println(dataString);
    digitalWrite(write_led, HIGH);

    dataFile.close();
    // print to the serial port too:
    Serial.println(dataString);
    delay(100); 
  }  
  // if the file isn't open, pop up an error:
  else {
    Serial.println("error opening datalog.txt");
  } 

  digitalWrite(write_led, LOW);
  delay(1000);
}