Arduino Two-Way Bluetooth Communication Tutorial

Welcome to another Arduino Tutorial! Today we are going to learn how to use Bluetooth to exchange data between two Arduino boards! As a demonstration project, we are going to build a simple weather station. There is a lot to cover so let’s get started!

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Today’s project is this. An Arduino Nano is measuring the temperature and the humidity using the DHT22 sensor. This board sends the data from the sensor to another Arduino Nano board, which displays the data from the sensor on a small screen, and sends back a message that the data was received OK. When the first Arduino board receives the OK message the LED lights up. As you can see we have established a bi-directional communication channel, and the two Arduino boards can exchange data! To achieve that we use a low-cost Bluetooth module, the HC-05! The range we can achieve is excellent; we can easily get about 10 meters of range even with walls between the modules! It is a perfect solution for indoor use and very easy to implement! Let’s now see how to build this project.

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WHERE TO BUY
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Arduino Nano: http://educ8s.tv/part/ArduinoNano

HC - 05 Bluetooth: http://educ8s.tv/part/HC05

DHT22 Sensor: http://educ8s.tv/part/DHT22

1.8" Color TFT: http://educ8s.tv/part/7735

Resistors: http://educ8s.tv/part/Resistors

Large Breadboard: http://educ8s.tv/part/LargeBreadboard

Jumper Wires: http://educ8s.tv/part/JumperWires

Wires: http://educ8s.tv/part/Wires

Devastator Robot: http://educ8s.tv/part/DevastatorRobot

Full disclosure: All of the links above are affiliate links. I get a small percentage of each sale they generate. Thank you for your support!

The HC-05 Bluetooth module is a very low-cost Bluetooth module for Arduino. It costs around 3$.

We are going to use two modules in this project, so one of them must be set in Master Mode and the other one to Slave mode to achieve bidirectional communication. That’s what we are going to do now. First of all we have to connect the module to an Arduino. We need to connect five wires. Please follow this schematic diagram. The Rx and Tx pins of the module use 3.3V logic levels, so we use a simple voltage divider at the Rx pin of the module and we do not connect it directly to the Arduino board. Also, note that the Rx pin of the module goes to the Rx Pin of the Arduino and the Tx Pin of the module goes to the Tx pin of the Arduino. Now we are ready to power up the Arduino. Before plugging in the USB cable, press the button on the Bluetooth module to enter the command mode. If the LEDs on the module start flashing slowly, that means that we have entered the command mode successfully.

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LIBRARIES
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Easy Transfer: https://github.com/madsci1016/Arduino-EasyTransfer

 DHT22: https://github.com/adafruit/DHT-sensor-library

 Adafruit GFX: https://github.com/adafruit/Adafruit-GFX-Library

 Adafruit ST7735: https://github.com/adafruit/Adafruit-ST7735-Library

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CODE & SCHEMATICS
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