/*
 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 PC0, PC1, and PC2
 * SD card attached to SPI bus as follows:
 ** MOSI/CMD - PB3
 ** MISO/DAT0 - PB4
 ** CLK - PB5
 ** CD/DAT3 - PD4
         
 */

#include <SD.h>
#define chipSelect  4

void setup()
{
  Serial.begin(9600);
  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(10, 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.");
}

int count;

void loop()
{

  // make a string for assembling the data to log:
  String dataString = "$LOG";
  delay(100);
  dataString += String(count); // print number of measurement
  dataString += ",";


  // read three sensors and append to the string:
  for (int analogPin = 0; analogPin < 3; analogPin++) {
    int sensor = analogRead(analogPin);
    dataString += String(sensor);
    if (analogPin < 2) {
      dataString += ","; 
    }
  }

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