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

#define ONE_WIRE_BUS 2   // yellow DATA wire on D2

OneWire oneWire(ONE_WIRE_BUS);          // 1-Wire bus on D2
DallasTemperature sensors(&oneWire);   // DS18B20 driver on that bus

void setup() {
  Serial.begin(9600);
  sensors.begin();                      // search the bus for probes
  Serial.print("Probes found: ");
  Serial.println(sensors.getDeviceCount());
}

void loop() {
  sensors.requestTemperatures();             // start a conversion on every probe
  float tempC = sensors.getTempCByIndex(0);  // read the first probe

  if (tempC == DEVICE_DISCONNECTED_C) {      // -127 means no reply
    Serial.println("Error: probe not found - check wiring and pull-up");
  } else {
    Serial.print("Temperature: ");
    Serial.print(tempC);
    Serial.println(" C");
  }
  delay(1000);
}

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

#define ONE_WIRE_BUS 2          // all yellow DATA wires on D2
const float ALARM_C = 30.0;     // LED turns on above this temperature

OneWire oneWire(ONE_WIRE_BUS);
DallasTemperature sensors(&oneWire);
DeviceAddress addr;             // 8-byte address buffer
uint8_t count = 0;

void printAddress(DeviceAddress a) {
  for (uint8_t i = 0; i < 8; i++) {
    if (a[i] < 16) Serial.print("0");
    Serial.print(a[i], HEX);
  }
}

void setup() {
  Serial.begin(9600);
  pinMode(LED_BUILTIN, OUTPUT);
  sensors.begin();
  count = sensors.getDeviceCount();
  Serial.print("Probes found: ");
  Serial.println(count);

  for (uint8_t i = 0; i < count; i++) {
    if (sensors.getAddress(addr, i)) {
      sensors.setResolution(addr, 12);  // 0.0625 C steps
      Serial.print("Probe ");
      Serial.print(i);
      Serial.print(" address: ");
      printAddress(addr);
      Serial.println();
    }
  }
}

void loop() {
  sensors.requestTemperatures();   // all probes convert at the same time
  bool alarm = false;

  for (uint8_t i = 0; i < count; i++) {
    if (!sensors.getAddress(addr, i)) continue;
    float t = sensors.getTempC(addr);
    Serial.print("Probe ");
    Serial.print(i);
    Serial.print(": ");
    if (t == DEVICE_DISCONNECTED_C) {
      Serial.println("not responding");
      continue;
    }
    Serial.print(t);
    Serial.println(" C");
    if (t > ALARM_C) alarm = true;
  }

  digitalWrite(LED_BUILTIN, alarm ? HIGH : LOW);
  Serial.println("---");
  delay(2000);
}