Read Temperature of DS18b20 with ESP32

temperature.cpp

#include "Arduino.h"
#include <DallasTemperature.h>
// Data wire is plugged into pin 21 on the ESP32
#define ONE_WIRE_BUS 21
// Setup a oneWire instance to communicate with any OneWire devices (not just Maxim/Dallas temperature ICs)
OneWire oneWire(ONE_WIRE_BUS);
// Pass our oneWire reference to Dallas Temperature.
DallasTemperature DS18B20(&oneWire);
char temperatureCString[6];
float tempC = 0.0;

void setup()
{
    Serial.begin(115200);
    delay(500);
    // initialize LED digital pin as an output.
    Serial.write("\r\nStarte OneWireBus");
    dtostrf(tempC, 2, 2, temperatureCString);
    DS18B20.begin();
    int n = 0;
    do
    {
        DS18B20.requestTemperatures();
        tempC = DS18B20.getTempCByIndex(0);
        delay(500);
        Serial.print(".");
        n++;
    } while (tempC == -127 && n < 20);
    dtostrf(tempC, 2, 2, temperatureCString);
    Serial.println("\r\nTemperatur ist " + String(temperatureCString));
}

void loop()
{
}