#include <SD.h>

#define CS_PIN 10

File root;

const float BETA = 3950; // should match the Beta Coefficient of the thermistor

void setup() {
  Serial.begin(115200);

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

  if (!SD.begin(CS_PIN)) {
    Serial.println("Card initialization failed!");
    while (true);
  }
  

  Serial.println("initialization done.");

  
  //Serial.println("Files in the card:");
  root = SD.open("/");
  //printDirectory(root, 0);
  Serial.println("");

  //File writeFile = SD.open("temp.txt", FILE_WRITE);
  //writeFile.write("Writing temperature to SDcard.\n\n");
  //writeFile.close();
  

  /*
  // Example of reading file from the card:
  File textFile = SD.open("temp.txt");
  if (textFile) {
    Serial.print("temp.txt: ");
    while (textFile.available()) {
      Serial.write(textFile.read());
    }
    textFile.close();
  } else {
    Serial.println("error opening temperature.txt!");
  }
*/

}

void loop() {

  
  Serial.println();
  Serial.print("Measuring the temperature five times:\n");

  File writeFile = SD.open("temp.txt", FILE_WRITE);
  for (int i=1; i<6; i++) {
      
      Serial.print("Temperature ");
      Serial.print(i);
      Serial.print(" is ");
      int analogValue = analogRead(A0);
      float celsius = random(-10,10)*0.1 + 1 / (log(1 / (1023. / analogValue - 1)) / BETA + 1.0 / 298.15) - 273.15;
      //Serial.print("Temperature: ");
      Serial.print(celsius);
      Serial.println(" Celcius. Saved to the SDCard.");
      
      writeFile.write(celsius);
      delay(1000);
   }
  writeFile.close();
  
  Serial.println();
  Serial.println("Now reading the last 5 temperature values from the SDcard.");
  

  File textFile = SD.open("temp.txt");
  if (textFile) {
    Serial.print("Reading the SDcard: ");
    Serial.println();
    while (textFile.available()) {
      Serial.write(textFile.read());
    }
    textFile.close();
  } else {
    Serial.println("error opening temp.txt!");
  }

  Serial.println();
  delay(2000);

}
  
  
  


void printDirectory(File dir, int numTabs) {
  while (true) {

    File entry =  dir.openNextFile();
    if (! entry) {
      // no more files
      break;
    }
    for (uint8_t i = 0; i < numTabs; i++) {
      Serial.print('\t');
    }
    Serial.print(entry.name());
    if (entry.isDirectory()) {
      Serial.println("/");
      printDirectory(entry, numTabs + 1);
    } else {
      // files have sizes, directories do not
      Serial.print("\t\t");
      Serial.println(entry.size(), DEC);
    }
    entry.close();
  }
}