Easy Bluetooth Controlled Scrolling Text




French engineer in robotics. I love Arduino projects / coding / guitar / various electronics. Oh,...

Intro: Easy Bluetooth Controlled Scrolling Text

Hi all,

In this Instructable, I'll show you how to create a simple scrolling text, using led matrix modules. These modules are cheap and easy to use. And, to make this project more fun, a bluetooth feature was added : you will be able to send a message to the system using a mobile phone !

I'll show you how to wire the system with an arduino card, how the program works, and how to use the device with a smart-phone. If you don't want to use the bluetooth feature, just check the last step to see how to do the same with the arduino serial port.

Follow these simple steps to get a nice gadget !!

Any comments for help, tips, and ideas are welcome !

10k views ! Many thanks !!

Step 1: Stuff Needed

Ok, to create this, you will need :

  • an arduino card, with 3v3 logic levels : here, an arduino Nano. You can also use an UNO, but you will have to add a level converter.
  • a HC06 bluetooth serial module. Search for "arduino bluetooth serial module" on the web. You will be able to find it easily.
  • one or more led matrix modules. You can find them on the web, check "MAX7219 led matrix modules". You can find them ready to sue, or as a kit "ready for soldering".
  • breadboard wire, and a breadboard.
  • Usb cable for the arduino card.
  • (optional) rubbers
  • (optional) power supply for the arduino card.

Step 2: Note on the Matrix Modules

Again, these modules are cheap, and easy to find. The great thing about these is that you can wire them in series (8 max), all the boring hardware aspects are handled by the library and the MAX7219 chip.

The problem is that you can't directly put them side by side, because of the connectors. You can put them side by side vertically, but the wiring is complicated. (The wires are under the modules...)

The solution is to put them head to tail, like the final picture. You will say "it will not work, as the rows and columns are toggled". Yes, but don't worry, my program handles this, and flip the pixels every two modules, to get a perfect rendering !

My tip : use small rubbers to keep them in contact. Of course, for a nice finishing, you can fix them on a piece of wood, or similar.

Step 3: How It Works

Ok, the program is quite simple :

  • the arduino starts. A sample message is displayed on the led matrices.
  • if nothing happens on the bluetooth module, the stored message stays on the screens.
  • meanwhile, the arduino program check the serial port (where the bluetooth module is connected). If nothing is on the buffer, the same message keeps "turning".
  • if some data is available on the virtual serial port, the message is downloaded, and replaces the previous message.

The bluetooth modules acts as a serial client. All the boring connecting/security aspects are handled by the module. In fact, the bluetooth module is connected by two TX/RX signals, and acts as a serial port, just like a computer. A bluetooth client terminal on the phone handles the connection, and allow the user to send and receive text.

Step 4: Wiring the Led Matrices

Ok, the wiring is simple :

The "input" pins are on the left side of the module, when the MAX7219 chip is on the left.

  • VCC : on the 5v pin of the arduino. Use the breadboard as you will need more 5v pins.
  • GND : Gnd port of the arduino. Again, use the breadboard.
  • DIN : pin 12 of the arduino (It's the "Data In" signal of the SPI link)
  • CS : pin 10 (the "chip select" signal)
  • CLK : pin 11 (the clock signal)

You can put up to 8 modules in series. In my case, I've got 5 of them.

Put the modules head to tail, make sure the input pins of the first module are on the top (check the pictures). Wire them in series, like the pictures. My tip : wire the modules before putting the rubbers, to avoid errors in the wiring.

Use small rubbers to keep the modules together.

Step 5: Wiring the Bluetooth Module

Ok, the bluetooth module is also easy to wire :

  • Vcc : 5v pin of the arduino
  • GND : ground pin
  • Tx : arduino pin 8
  • Rx : arduino pin 9

Watch out, the module only handles 3v3 logical levels on TX and RX pins. Don't connect them on a 5v pin ! Use a level converter instead.

When on, a led on the module should blink. In fact, the led blinks when the module starts, then stays ON when the module is connected with the phone. Great for debugging !

My wiring is quite ugly... due to a lack of wires, I had to do something not very good with the breadboard... sorry...!

Step 6: The Program

Ok, the program is attached on this step.

You will need the "Led Control" libraries to compile the sketch. Informations are here.

You can download the libs here (there is a button "download zip" on the right):

Remember, you have to unzip them in the "libraries" folder of the main arduino folder. Make sure the folder name is "LedControl". Make sure that the .H and .CPP files are directly inside.

  • Connect the arduino nano to the computer.
  • In the arduino IDE, make sure that the correct board is selected (The nano in my case).
  • In the program, change the line 40, and put the number of matrices used. 5, in my case. You can use up to 8 modules.
  • On the line 48, you can adjust the speed of the text. Put a bigger value if you want to reduce the speed.(It's the delay in ms between a "step" on the screens)
  • Compile and upload the program. The modules will blink randomly during the upload process. It's normal !

You should see the welcome message on the led display...

Step 7: On the Phone

Ok, you will have to setup a bluetooth terminal client on your mobile phone.

On the android store, you can find them for free. For this project, I'll use "Bluetooth SPP", but any similar app should work. Just search for "bluetooth serial" or "bluetooth terminal" on the app store.

  • Turn on the bluetooth on the phone.
  • Use the phone utility to find and locate bluetooth emitters.
  • The emitter name is "HC-06". Select Connect. The password is 1234.
  • Launch the Bluetooth SPP app. Hit the menu button on your phone, select Connect. Select the HC06 module.
  • In the operating mode screen, select Real-time mode.
  • The phone will work, then says that the connection is ok.
  • Check the bluetooth module, the led should stay ON (no more blinking)

When running again the app, you can use a "Restore last connection" feature to get the connection with the module. Works great !

The app you use may be different, of course.

Step 8: Send a Message !

  • Ok, so make sure that the phone is correctly connected to the module.
  • Push the reset pin of the arduino.(Optional, but show the initial message)
  • Check the phone, you should see "Hi ! I'm waiting for a message. Type it and press SEND."
  • Type any message you want, then click on Send.
  • The select message should be now on the led display !

Congrats, you make it work !

Step 9: Final Words

Ok, this project is great, because it's based on a very simple modules, and the result is quite useful. You may want to use this as a general-purpose message display... You can finish this project by making an enclosure to hide the wires and make something beautiful...

If you don't want to use the bluetooth, just use the program given here. Use the arduino serial monitor (or other terminal program) to send a message.

I hope my steps are clear... If you need more explanations, just ask !!

Thanks for reading !!

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163 Discussions


Answer 7 weeks ago

Yes ! You just have to use another power supply... (Like a mobile phone charger).

It should works the same way !


Question 4 months ago

after changing in code"//How many matrixes we have ?

int MatrixNumber =9;"

message loop run on 8 matrix but on 9 it play separately....

2 more answers

Answer 3 months ago

Thank you Yoruk


Answer 4 months ago

You can't use more than 8 modules in series, it's a limit of the MAX7219.

If you want to use more that 8 modules, you will have to use an other SPI port. You can share some signals (clock...) with the existing one ! But it's a lot of modifications in the code...

vishruta patil

Question 5 months ago

Yes, We have tried space after Hello word. But still the problem continues.

When we use 4 matrix then it starts scrolling from beginning of first matrix but if we used 6 matrix then it scrolls from middle of second matrix.

1 more answer
Yorukvishruta patil

Answer 5 months ago

Strange... Please let me a couple of days to check this.

vishruta patil

Question 5 months ago

Yes...The loop is working properly. But we have no idea about array initialization...

1 more answer
Yorukvishruta patil

Answer 5 months ago

You mean, the loop starts with the right "H" ?

Have you tried to add spaces after the "Hello" word ?

vishruta patil

Question 5 months ago


Thanks for the project.....

we have tried the same project . We are using 6 matrix. But their is a little problem that when we send any message it starts scrolling from middle of second matrix instead of start of first matrix.......Will you please give us solution?

Thank you...!

1 more answer
Yorukvishruta patil

Answer 5 months ago

But is the loop working correctly ?

Looks like a problem during the array initialisation...


Question 5 months ago


Thanks for the project.

I have a little problem with sending messages. Wiring is ok, connection between smartphone and HC06 working and i have the message : 'Hi ! I'm waiting for a message...' on the led matrix.

But, when i send a message, nothing happen. I've tried with PIC32BTN, Bluetooth SPP Manager and BluetoothTerminal HC06. Connection ok but that's all.

What can be the problem ?

3 more answers

Answer 5 months ago

The problem is that the arduino didn't get anything from the bluetooth module. Have you double-checked the wiring between the bluetooth module and the arduino ? You have to wire TX on RX (not TX-TX and RX-RX !!).

And you have to use the virtual serial port, not the hardware one.

Let me know...


Answer 5 months ago

I had connected RX and TX on the D8 and D9 port while it was enough to use the RX and TX ports of the arduino ...
My bad. Everything is working now. Thanks


Answer 5 months ago

Great news !


Question 8 months ago

hi sir... i have 5 modules of 8*8 matrix...i have uploaded the code but these are not working properly...

all the LED's glow at same time and the required message is not being displayed....

1 more answer

Answer 8 months ago

Hmmm.... It clearly looks like there is a problem in the wiring. The whole modules can blink if thay don't receive the good data, ie if the data wires are not well connected.

Can you show me a picture of your wiring ?

You can also try less modules to start, one or two only, just to check.


8 months ago

if HC-05 module is compatible in this project?


Question 8 months ago on Introduction

sir ,can i ask if HC-05 module is compatible to this?


1 year ago

What should I change in the code if I want to put them side by side?