ds18b20_test.ino

#include <Arduino.h>
#include <OneWire.h>
#include <DallasTemperature.h>

// Data wire is plugged into port D2 on NodeMCU
#define ONE_WIRE_BUS D2

// 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 sensors(&oneWire);

void setup(void)
{
  // start serial port
  Serial.begin(115200);
  delay (1000);
  Serial.println("Dallas Temperature Control Library - Async Demo");
  Serial.println("\nDemo shows the difference in length of the call\n\n");

  // Start up the library
  sensors.begin();

  uint8_t address[8];

  if (!sensors.getAddress (address, 0)) {
	  Serial.printf ("No device\n");
	  return;
  }
  sensors.setWaitForConversion (false);

}

void getTemp () {
	time_t start = millis ();

	sensors.requestTemperatures ();

	while (!sensors.isConversionComplete ()) {
		delay (1);
	}
	float temp = sensors.getTempCByIndex (0);
	time_t totalTime = millis () - start;

	if (temp == DEVICE_DISCONNECTED_C) {
		Serial.printf ("Error: Could not read temperature data\n");
	}
	else {
		Serial.printf ("Resolution is %d bit. Temp is %f. Measured in %d ms\n", sensors.getResolution (), temp, totalTime);
	}

}

void loop(void)
{ 
	sensors.setResolution (9);
	getTemp ();
	sensors.setResolution (10);
	getTemp ();
	sensors.setResolution (11);
	getTemp ();
	sensors.setResolution (12);
	getTemp ();
	delay (5000);
}