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

//MOSI 11
//MISO 12
//SCK  13

File dataFile;

const int chipSelect = 10;
const int sensorPin = A0;
void setup() {

  Serial.begin(9600);

  while(!SD.begin(chipSelect)){
    Serial.print("Error initializing SD card, retrying");
    delay(250);
    for (int i=1;i<4;i++){
      Serial.print(".");
      delay(250);
    }
    Serial.println("");
  }
  Serial.println("SD card initialized");

  if (SD.exists("temp.csv")){
    SD.remove("temp.csv");
    Serial.println("temp.csv already exists, removing...");
  }

  dataFile = SD.open("temp.csv", FILE_WRITE);
  if (dataFile){
    Serial.println("Succesfully opened test.txt");
    dataFile.close();
  } else {
    Serial.println("Error opening test.txt");
  }
}

void loop() {
  // put your main code here, to run repeatedly:
  int sensorVal = analogRead(sensorPin);
  float voltage = (sensorVal/1024.0) * 5.0;
  float temperature = (voltage - 0.5) * 100;
  dataFile = SD.open("temp.csv", FILE_WRITE);
  dataFile.print(millis());
  dataFile.print(",");
  dataFile.println(temperature);
  dataFile.close();
  Serial.println(temperature);
  delay(1000);
}