/*
  SD card datalogger
 
 This example shows how to log data from three analog sensors 
 to an SD card using the SD library.
 	
 The circuit:
 * analog sensors on analog ins 0, 1, and 2
 * SD card attached to SPI bus as follows:
 ** MOSI - pin 11
 ** MISO - pin 12
 ** CLK - pin 13
 ** CS - pin 4
 
 created  24 Nov 2010
 modified 9 Apr 2012
 by Tom Igoe
 
 This example code is in the public domain.
 	 
 */

#include <SD.h>

// 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.
//
// Chip Select pin is tied to pin 8 on the SparkFun SD Card Shield
const int chipSelect = 8;  

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.");
}

void loop()
{

  // open the file. note that only one file can be open at a time,
  // so you have to close this one before opening another.
  // this opens the file and appends to the end of file
  // if the file does not exist, this will create a new file.
  File dataFile = SD.open("datalog.txt", FILE_WRITE);

  // if the file is available, write to it:
  if (dataFile) 
  {  
    int timeStamp = millis();
    dataFile.print(timeStamp);
    dataFile.print(", ");
    Serial.print(timeStamp);
    Serial.print(", ");

    // read three sensors and append to the string:
    for (int analogPin = 0; analogPin < 3; analogPin++) 
    {
      int sensorVal = analogRead(analogPin);
      dataFile.print(sensorVal);
      Serial.print(sensorVal);
      if (analogPin < 2) 
      {
        dataString += ","; 
      }
    }
    dataFile.println();
    dataFile.close();
    Serial.println();
    // print to the serial port too:
  }  
  // if the file isn't open, pop up an error:
  else
  {
    Serial.println("error opening datalog.txt");
  } 
}