I am currently undertaking a project where I am attempting to build a bluetooth thermometer using an arduino. I have the temperature sensor working and returning temperature readings via a usb connection to the serial monitor in the Arduino IDE using the following code.

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

Timer t;

// Data wire is plugged into pin 10 on the Arduino
#define ONE_WIRE_BUS 10

// Setup a oneWire instance to communicate with any OneWire devices
OneWire oneWire(ONE_WIRE_BUS);

DallasTemperature sensors(&oneWire);

DeviceAddress insideThermometer = { 0x28, 0x94, 0xE2, 0xDF, 0x02, 0x00, 0x00, 0xFE };

void setup(void)
  // start serial port
  // Start up the library
  // set the resolution to 10 bit (good enough?)
  sensors.setResolution(insideThermometer, 10);
  int tickEvent = t.every(3000,doTempReading);


void loop()

void printTemperature(DeviceAddress deviceAddress)
  float tempC = sensors.getTempC(deviceAddress);
  if (tempC == -127.00) {
    Serial.print("Error getting temperature");
  } else {
    Serial.print("C: ");

void doTempReading()
  Serial.print("Getting temperatures...\n\r");

  Serial.print("Inside temperature is: ");

I now want to try and transmit the readings via a bluetooth connection using the HC 05 module to a raspberry pi which will record the data.

I have done a lot of research and tried several different techniques and can't understand how to go about it.

What mode does the HC 05 need to be in? (Command AT/slave/data/etc.) How should it be wired (I have found several different methods using various resistors and capacitors and unsure which to follow). How should I pair it with the Raspberry pi?

Thanks in advance for any help.

  • 1
    have you tried searching "Arduino HC05" in google? – dhimaspw Feb 22 '17 at 8:25

I know this is old but to help out newcomers:

Here's a place you can begin https://create.arduino.cc/projecthub/millerman4487/view-serial-monitor-over-bluetooth-fbb0e5

The wiring depends on which arduino board you are using and the model of your HC-05 BT module. mine uses 4 pins VCC (5v) GND (ground) TX --> TX and RX --> RX

You should be able to google the wiring for your module, and connect to the raspberry pi after you install bluetooth on raspberry pi

sudo apt-get install bluetooth bluez blueman

sudo reboot

Navigate to new bluetooth interface in menu bar through

  • preferences
  • bluetooth

Add new device, turn arduino on with BT module plugged in and make sure your HC-05 module is blinking red, and you should see a pair connection named HC-05 on raspberry pi. Password is 1234

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