//https://forum.arduino.cc/t/ds18b20-sdcard-data-logger-with-rtc/1274999
//========Set the time for the RealTimeClock (RTC) with Set_RTC_Time.ino first==========
//For the RTC and the SD-Card-Connector
#include <SD.h>
#include <SPI.h>
#include "DS3231.h"
//For the DS18B20
#include <OneWire.h>
#include <DallasTemperature.h>
File myFile;
DS3231  rtc(SDA, SCL);
int pinCS = 53; // Pin 10 on Arduino Uno
//=====DS18B20======
// Data wire from the DS18B20 is plugged into pin 3 on the Arduino
#define ONE_WIRE_BUS 3
// Setup a OneWire instance to communicate with any OneWire devices
OneWire oneWire(ONE_WIRE_BUS);
// Pass OneWire reference to Dallas Temperature
DallasTemperature sensors(&oneWire);
//-------------------------------------------------------------
void setup() {
  Serial.begin(9600);
  pinMode(pinCS, OUTPUT);
  if (SD.begin())  {    // SD Card Initialization
    Serial.println("SD card is ready to use.");
  } 
  else  {
    Serial.println("SD card initialization failed");
    return;
  }
  rtc.begin();
  //=======DS18B20=======
  pinMode(ONE_WIRE_BUS, OUTPUT);
  sensors.begin(); //Start up the library
}
//---------------------------------------------------------------
void loop() {
  Serial.print(rtc.getDateStr());
  Serial.print(",");
  Serial.print(rtc.getTimeStr());
  Serial.print(",");
  //======DS18B20=========
  sensors.requestTemperatures(); //Call sensor to request the Temperature
  Serial.println(String(sensors.getTempCByIndex(0)) + "°C"); //Output the values on the monitor
  myFile = SD.open("test_ds.txt", FILE_WRITE);
  if (myFile) {
    myFile.print(rtc.getDateStr());
    myFile.print(",");
    myFile.print(rtc.getTimeStr());
    myFile.print(",");
    sensors.requestTemperatures(); //Call sensor to request the Temperature
    myFile.println(String(sensors.getTempCByIndex(0)) + "°C"); //Save the values on the SD-Card
    myFile.close(); // close the file
  }
  // if the file didn't open, print an error:
  else {
    Serial.println("error opening txt-file");
  }
  delay(3000);  //Wait for 3 sec
  readSD();
}
//----------------------------------------------------------
void readSD() {
  myFile = SD.open("test_ds.txt", O_READ);    //If no exist, create file
  if (myFile) {
    Serial.println("test_ds.txt listing");
    while (myFile.available()) {
      Serial.write(myFile.read());
    }
    myFile.close();
  }
  else {
    Serial.println("error opening test_ds.txt");
  }
}