Arduino - Bluetooth LED Matrix

In this tutorial, we will learn how to control an LED matrix display using a smartphone via Bluetooth or BLE by using Arduino. We will have the option to choose between two different modules, HC-05 for Classic Bluetooth (Bluetooth 2.0) and HM-10 for Bluetooth Low Engery (BLE, Bluetooth 4.0). The tutorial will provide step-by-step instructions for both modules. To send messages from the smartphone to the LED matrix display, we will use the Bluetooth Serial Monitor App, which can be found at Bluetooth Serial Monitor App. Once the message is received by Arduino, it will be displayed on the LED matrix display.

Hardware Required

1	×	Arduino UNO or Genuino UNO
1	×	USB 2.0 cable type A/B
1	×	HC-05 Bluetooth Module
1	×	(Alternative) HM-10 BLE Module
1	×	LED matrix display
1	×	Breadboard
1	×	Jumper Wires
1	×	(Optional) 9V Power Adapter for Arduino
1	×	(Recommended) Screw Terminal Block Shield for Arduino Uno
1	×	(Optional) Transparent Acrylic Enclosure For Arduino Uno

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DIYables Sensor Kit 30 types, 69 units

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About LED matrix display and Bluetooth Module

Before starting this tutorial, it is recommended that you have a basic understanding of LED matrix displays and Bluetooth modules, including their pinouts, how they work, and how to program them. If you are not familiar with these topics, please review the following tutorials for more information:

Wiring Diagram

To control the LED matrix display using Classic Bluetooth, you need to use the HC-05 Bluetooth module and connect it to Arduino according to the below wiring diagram:

This image is created using Fritzing. Click to enlarge image

To control the LED matrix display using BLE, you need to use the HM-10 Bluetooth module and connect it to Arduino according to the below wiring diagram:

Arduino LED matrix display BLE Wiring Diagram

This image is created using Fritzing. Click to enlarge image

Arduino Code - controls LED matrix display via Bluetooth/BLE

The code below will work for both the HC-10 Bluetooth module and the HM-10 BLE module

/* * Created by ArduinoGetStarted.com * * This example code is in the public domain * * Tutorial page: https://arduinogetstarted.com/tutorials/arduino-bluetooth-led-matrix */ #include <MD_Parola.h> #include <MD_MAX72xx.h> #define HARDWARE_TYPE MD_MAX72XX::FC16_HW #define MAX_DEVICES 4 // 4 blocks #define CS_PIN 9 // create an instance of the MD_Parola class MD_Parola ledMatrix = MD_Parola(HARDWARE_TYPE, CS_PIN, MAX_DEVICES); String text; void setup() { Serial.begin(9600); ledMatrix.begin(); // initialize the object ledMatrix.setIntensity(0); // set the brightness of the LED matrix display (from 0 to 15) ledMatrix.displayClear(); // clear LED matrix display text.reserve(30); } void loop() { if (Serial.available()) { // if there is data comming text = Serial.readStringUntil('\n'); // read string until meet newline character ledMatrix.displayClear(); // clear led matrix display ledMatrix.displayScroll(text.c_str(), PA_CENTER, PA_SCROLL_LEFT, 100); Serial.print("LED Matrix displayed: "); // reports action to smartphone app Serial.println(text); } if (ledMatrix.displayAnimate()) { ledMatrix.displayReset(); } }

Quick Steps

To control an LED matrix display using Bluetooth or BLE:

Navigate to the Libraries icon on the left bar of the Arduino IDE.
Search “MD_Parola”, then find the MD_Parola library
Click Install button.

You will be asked to install the MD_MAX72XX library for dependency. Click Install All button.

Install the Bluetooth Serial Monitor App on your smartphone.
Copy the provided code and open it with the Arduino IDE. Upload the code to your Arduino. If you are unable to upload the code, try disconnecting the TX and RX pins from the Bluetooth module, uploading the code, and then reconnecting the RX/TX pins again.
Open the Bluetooth Serial Monitor App on your smartphone.
Select the Classic Bluetooth or BLE option, depending on the module you are using.

Pair the Bluetooth App with the HC-05 Bluetooth module or the HM-10 BLE module.

Type a message, for example “HELLO” and click the Send button to send it to the Arduino.

Observe the message displayed on the LED matrix display and on the Bluetooth App.
Verify the result on the Android App.

If you found the Bluetooth Serial Monitor app to be helpful, please consider leaving a 5-star rating on the Play Store. Your feedback is greatly appreciated! Thank you!

Video Tutorial

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Function References

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