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

#define chipSelect 10
unsigned long time;

// the setup routine runs once when you press reset:
void setup() {
    // initialize serial communication at 9600 bits per second:
    Serial.begin(9600);

    Serial.print("Initializing SD card...");

    // 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.");
}

// the loop routine runs over and over again forever:
void loop() {
    // read the input on analog pin 0:
    int sensorValue0 = analogRead(A0);
    int sensorValue1 = analogRead(A1);
    int sensorValue2 = analogRead(A2);
    float voltage0 = sensorValue0 * 0.00488;
    float voltage1 = sensorValue1 * 0.00488;
    float voltage2 = sensorValue2 * 0.00488;

    // create datastring and SD card Logging
    String dataString = 
        String(time/1000) + "," + 
        String(voltage0) + "," +
        String(voltage1) + "," +
        String(voltage2);

    // 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("datafile.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);
    }
    // if the file isn't open, pop up an error:
     else {
        Serial.println("error opening datalog.txt");
    }

    time = millis();
    delay(1000);        // delay in between reads for stability
}