Easy Bluetooth Controlled Scrolling Text

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About: French engineer in robotics. I love Arduino projects / coding / guitar / various electronics. Oh, I like cooking also ! PS : English is not my main language, please inform me in case of grammar mistakes ! ...

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 !!

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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 !!

13 People Made This Project!

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212 Discussions

None
Vtronics

4 months ago

Hello
Your project works fine but i have one question on it.
Why the massage gets erased when ever the power is off or Reset the arduino .The problem is that when ever the massage is send using Bluetooth the last send massage gets erased and when ever the power is on the display show the initial condition of the code but i wont the last massage which i have send to be get displayed and when ever i send the massage it should be changed.
And is there any command to over come this problem , if yes then in code at which part that command is to be written
please help me in this

1 reply
None
EduardoS64

Question 7 months ago on Step 9

Hi Yoruk, is it possible to send a message from voice instead of texting? Can it use the normal text messaging from any Android phone to display on the matrix? And one more question: Can i use a Mega with level a shifter instead of Nano?
Thanks

3 answers
None
YorukEduardoS64

Reply 6 months ago

Speech recognition does requires a lot of computing power... A micro-controler is just not powerful enough. Didn't know is a raspberry pi can do that... Maybe ?

"Can it use the normal text messaging from any Android phone to display on the matrix?" yes, if you use a sms receptor module. It does requires a SIM card.

"Can i use a Mega with level a shifter instead of Nano?" Yes !

None
EduardoS64Yoruk

Reply 6 months ago

Thanks Yoruk, I know speech recognition needs computing power but that already exists in the Android OS and i thought it could be used to send messages to the Arduino. So if i use a SMS receptor would that be possible? Is there a specific SMS receptor you would recommend? Could you elaborate on that? Thanks for replying.

None
Sam-Kun

Question 1 year ago

Hi there, this problem keeps popping up in the code im not sure what to do

Sketch uses 5922 bytes (19%) of program storage space. Maximum is 30720 bytes.
Global variables use 1885 bytes (92%) of dynamic memory, leaving 163 bytes for local variables. Maximum is 2048 bytes.
Low memory available, stability problems may occur.

13 answers
None
KarthikV30Sam-Kun

Answer 8 months ago

Hi Sam kun how u get rid of low memory problem

None
YorukSam-Kun

Reply 1 year ago

What is your Arduino board model ?

None
Sam-KunSam-Kun

Reply 11 months ago

the latest version and now there is a problem uploading the code to the board

None
Sam-KunSam-Kun

Reply 11 months ago

this is the components ive put together and im not too clear on where to change the "writeCol" as i am just only picking up this language and still barely learning the basics of it

hah.jpeg
None
YorukSam-Kun

Reply 11 months ago

Please check the other comments, someone already made the transformation if I remember correctly !

None
Sam-KunYoruk

Reply 11 months ago

Thx for the tip, i adapted his code to the original one it now goes sideways but the words are inverse the words go to the center of modules 2 and 3 and come out of 1 and 4 and blinks slowly rather than move smoothly


Heres the code,

// Easy bluetooth controlled scrolling text
// by Yoruk for Instructable
// 26 02 15 : first code
// 03 03 15 : buffer updating
// 04 03 15 : faster version, both buffers
// 05 03 15 : cleaning and help
/*
WIRING :
pin 12 - DataIn of the first led matrix module
pin 11 - CLK of the first led matrix module
pin 10 - CS of the first led matrix module
pin 9 : RX pin of the bluetooth module
pin 8 : TX pin of the bluetooth module
5V : 5v of the matrix module, 5v of the bluetooth module
GND : the two GND signals of the matrix modules and the bluetooth module
WARNING : Use a 3v3 arduino card (nano...) or a level converter !!!
Wire the matrix modules in serie. See the Instructable steps.
*/
//Librairie for the LEDs matrix
#include "LedControl.h"
// virtual serial lib, used with bluetooth
#include <SoftwareSerial.h>
//How many matrixes we have ?
int MatrixNumber =4;
//virtual serial port bluetooth configuration
SoftwareSerial BT(8, 9); //pin 8 : virtual RX pin 9 : virtual TX
// the delay between each screen display (ms)
int SpeedDelay = 1;
//total string lenght. The first message is 25 characters long (including spaces)
int LongueurChaine=25;
char incomingByte; //incoming data from the BT link
// the two pixels arrays
char Buffer[200]; //contient tout les pixels de TOUTE LA PHRASE
char Buffer_inverse[200]; //contient tout les pixels de TOUTE LA PHRASE, mais symetrises pour affichage sur ecran inverses
// the message array
char Phrase[50];
//here we set up the led matrix
LedControl lc=LedControl(12,11,10,MatrixNumber);
// character lib
int fontDefinitions[480] = {
0x00,0x00,0x00,0x00,0x00,/*space*/ // is 32 in ASCII
0x00,0xF6,0xF6,0x00,0x00,/*!*/
0x00,0xE0,0x00,0xE0,0x00,/*"*/
0x28,0xFE,0x28,0xFE,0x28,/*#*/
0x00,0x64,0xD6,0x54,0x08,/*$*/
0xC2,0xCC,0x10,0x26,0xC6,/*%*/
0x4C,0xB2,0x92,0x6C,0x0A,/*&*/
0x00,0x00,0xE0,0x00,0x00,/*'*/
0x00,0x38,0x44,0x82,0x00,/*(*/
0x00,0x82,0x44,0x38,0x00,/*)*/
0x88,0x50,0xF8,0x50,0x88,/***/
0x08,0x08,0x3E,0x08,0x08,/*+*/
0x00,0x00,0x05,0x06,0x00,/*,*/
0x08,0x08,0x08,0x08,0x08,/*-*/
0x00,0x00,0x06,0x06,0x00,/*.*/
0x02,0x0C,0x10,0x60,0x80,/*/*/
0x7C,0x8A,0x92,0xA2,0x7C,/*0*/
0x00,0x42,0xFE,0x02,0x00,/*1*/
0x42,0x86,0x8A,0x92,0x62,/*2*/
0x44,0x82,0x92,0x92,0x6C,/*3*/
0x10,0x30,0x50,0xFE,0x10,/*4*/
0xE4,0xA2,0xA2,0xA2,0x9C,/*5*/
0x3C,0x52,0x92,0x92,0x0C,/*6*/
0x80,0x86,0x98,0xE0,0x80,/*7*/
0x6C,0x92,0x92,0x92,0x6C,/*8*/
0x60,0x92,0x92,0x94,0x78,/*9*/
0x00,0x00,0x36,0x36,0x00,/*:*/
0x00,0x00,0x35,0x36,0x00,/*;*/
0x10,0x28,0x44,0x82,0x00,/*<*/
0x28,0x28,0x28,0x28,0x28,/*=*/
0x00,0x82,0x44,0x28,0x10,/*>*/
0x40,0x80,0x8A,0x90,0x60,/*?*/
0x7C,0x82,0xBA,0xBA,0x62,/*@*/
0x3E,0x48,0x88,0x48,0x3E,/*A*/
0xFE,0x92,0x92,0x92,0x6C,/*B*/
0x7C,0x82,0x82,0x82,0x44,/*C*/
0xFE,0x82,0x82,0x82,0x7C,/*D*/
0xFE,0x92,0x92,0x92,0x82,/*E*/
0xFE,0x90,0x90,0x90,0x80,/*F*/
0x7C,0x82,0x82,0x8A,0x4E,/*G*/
0xFE,0x10,0x10,0x10,0xFE,/*H*/
0x82,0x82,0xFE,0x82,0x82,/*I*/
0x84,0x82,0xFC,0x80,0x80,/*J*/
0xFE,0x10,0x28,0x44,0x82,/*K*/
0xFE,0x02,0x02,0x02,0x02,/*L*/
0xFE,0x40,0x20,0x40,0xFE,/*M*/
0xFE,0x60,0x10,0x0C,0xFE,/*N*/
0x7C,0x82,0x82,0x82,0x7C,/*O*/
0xFE,0x90,0x90,0x90,0x60,/*P*/
0x7C,0x82,0x82,0x86,0x7E,/*Q*/
0xFE,0x90,0x98,0x94,0x62,/*R*/
0x64,0x92,0x92,0x92,0x4C,/*S*/
0x80,0x80,0xFE,0x80,0x80,/*T*/
0xFC,0x02,0x02,0x02,0xFC,/*U*/
0xF8,0x04,0x02,0x04,0xF8,/*V*/
0xFC,0x02,0x0C,0x02,0xFC,/*W*/
0xC6,0x28,0x10,0x28,0xC6,/*X*/
0xC0,0x20,0x1E,0x20,0xC0,/*Y*/
0x86,0x8A,0x92,0xA2,0xC2,/*Z*/
0x00,0x00,0xFE,0x82,0x00,/*[*/
0x00,0x00,0x00,0x00,0x00,/*this should be / */
0x80,0x60,0x10,0x0C,0x02,/*]*/
0x20,0x40,0x80,0x40,0x20,/*^*/
0x01,0x01,0x01,0x01,0x01,/*_*/
0x80,0x40,0x20,0x00,0x00,/*`*/
0x04,0x2A,0x2A,0x2A,0x1E,/*a*/
0xFE,0x12,0x22,0x22,0x1C,/*b*/
0x1C,0x22,0x22,0x22,0x14,/*c*/
0x1C,0x22,0x22,0x12,0xFE,/*d*/
0x1C,0x2A,0x2A,0x2A,0x18,/*e*/
0x10,0x7E,0x90,0x80,0x40,/*f*/
0x18,0x25,0x25,0x25,0x1E,/*g*/
0xFE,0x10,0x10,0x10,0x0E,/*h*/
0x00,0x12,0x5E,0x02,0x00,/*i*/
0x02,0x01,0x01,0x11,0x5E,/*j*/
0xFE,0x08,0x08,0x14,0x22,/*k*/
0x00,0x82,0xFE,0x02,0x00,/*l*/
0x3E,0x20,0x1C,0x20,0x1E,/*m*/
0x3E,0x20,0x20,0x20,0x1E,/*n*/
0x1C,0x22,0x22,0x22,0x1C,/*o*/
0x3F,0x24,0x24,0x24,0x18,/*p*/
0x18,0x24,0x24,0x3F,0x01,/*q*/
0x3E,0x10,0x20,0x20,0x10,/*r*/
0x12,0x2A,0x2A,0x2A,0x04,/*s*/
0x00,0x10,0x3C,0x12,0x04,/*t*/
0x3C,0x02,0x02,0x02,0x3E,/*u*/
0x30,0x0C,0x02,0x0C,0x30,/*v*/
0x38,0x06,0x18,0x06,0x38,/*w*/
0x22,0x14,0x08,0x14,0x22,/*x*/
0x38,0x05,0x05,0x05,0x3E,/*y*/
0x22,0x26,0x2A,0x32,0x22,/*z*/
0x00,0x10,0x6C,0x82,0x82,/*{*/
0x00,0x00,0xFF,0x00,0x00,/*|*/
0x04,0x02,0xFF,0x02,0x04,/*|, arrow*/
0x82,0x82,0x6C,0x10,0x00,/*}*/
0x08,0x10,0x18,0x08,0x10/*~*/
};
void setup() {
//matrix modules init
for(int adresse=0;adresse<MatrixNumber;adresse++) {
/*The MAX72XX is in power-saving mode on startup*/
lc.shutdown(adresse,false);
/* Set the brightness to a medium values */
lc.setIntensity(adresse,4);
/* and clear the display */
lc.clearDisplay(adresse);
}
// BufferBuilding("Hi ! Sent me a message...", 25); //first message on the led screen
BufferBuilding("Testing", 10); //first message on the led screen
Serial.begin(9600); //we also set the normal serial link, for debug
BT.begin(9600); // bluetooth initialisation
//we sent a message on the phone to tell the user that he can do someting...
BT.println("Hi ! I'm waiting for a message. Type it and press SEND.");
}
void loop() {
DrawText( LongueurChaine); //draw the message, in a loop
//or, if we get something on the virtual bluetooth port...
if (BT.available() > 0) {
LongueurChaine = BT.available(); //incoming string lenght
for (int i = 0; i < LongueurChaine; i++) {
// read the incoming byte:
incomingByte = BT.read();
Phrase[i] = incomingByte; ///store the character into the string array
}
//debug features, to check :
Serial.print("Display: ");
Serial.println(Phrase);
Serial.print("Length : ");
Serial.println(LongueurChaine);
//buffers cleaning, to store the new message
for(int k = 0; k < 200; k++) {
Buffer[k]=0;
Buffer_inverse[k]=0;
}
//we create the new buffers, so the new message will be drawn when leaving the sub
BufferBuilding(Phrase, LongueurChaine);
}
}
void BufferBuilding(char * stringToDisplay, byte stringLength)
{
int i =0;
//loop on every characters (on the string)
for(int k = 0; k < stringLength; k++) {
//here we call the characters library
int caract= k;
Buffer[i+0] = fontDefinitions[((stringToDisplay[caract] - 32) * 5) + 0];
Buffer[i+1] = fontDefinitions[((stringToDisplay[caract] - 32) * 5) + 1];
Buffer[i+2] = fontDefinitions[((stringToDisplay[caract] - 32) * 5) + 2];
Buffer[i+3] = fontDefinitions[((stringToDisplay[caract] - 32) * 5) + 3];
Buffer[i+4] = fontDefinitions[((stringToDisplay[caract] - 32) * 5) + 4];
Buffer[i+5] = B00000000; //one blank column of leds between two characters
i=i+6;
}
// here, we create a second buffer, to display the message on the switched matrixes
for(int k = 0; k < stringLength*6; k++) {
for(int i = 0; i < 8; i++) {
bitWrite( Buffer_inverse[k] ,i, bitRead(Buffer[k] ,7-i) ) ;
}
}
}
void DrawText( byte stringLength) {
for(int k = 0; k < stringLength*6; k++) {
delay(SpeedDelay);
//delay(10000);
//k is the column
//buffer drawing
for (int m = 0; m < MatrixNumber; m++) { //loop on the matrix
if (m % 2 == 0) //check is the module is upside-down or not...
{
//here, the matrix is flipped upside-down
for (int i = 0; i < 8; i++) { //loop on the columns
lc.setColumn(m,7-i,Buffer[i+k+8*m]);
}
}
else
{
//classical
for (int i = 0; i < 8; i++) { //loop on the columns
lc.setColumn(m,i,Buffer_inverse[i+k+8*m]);
}
}
}
}
}

None
YorukSam-Kun

Reply 11 months ago

Could you please show me a picture of the result ?

Are all the modules wired in series ?

None
Sam-KunYoruk

Reply 11 months ago

its suppose to say (I am Sam) but the word are scrolling in from the 2nd and 3rd module and scrolling out from the 1st and 4th module , i took the code u mentioned from the comments and just changed the variables from set.row to set.column from your original code and that is the result

arrow.jpeg
None
YorukSam-Kun

Reply 11 months ago

You are displaying a series of ">>>" ?
So you can't swap rows and columns if you want to read the text horizontally.

Please try this for the last function (let everything else unchanged) :


void DrawText( byte stringLength) {

for(int k = 0; k < stringLength*6; k++) {

delay(SpeedDelay);


//delay(10000);
//k is the column

//buffer drawing
for (int m = 0; m < MatrixNumber; m++) { //loop on the matrix

//here, the matrix is flipped upside-down
for (int i = 0; i < 8; i++) { //loop on the columns

lc.setRow(m,7-i,Buffer[i+k+8*m]);
}

}
}

}

and take a picture !

If it still doens't works, I'll have to see a picture of the BACK of your modules.

None
Sam-KunYoruk

Reply 11 months ago

There is a problem again the same problem of uploading the code has occurred again and i cant fix it almost all methods of fixing it has failed im not sure how to fix it now

None
Sam-KunSam-Kun

Reply 11 months ago

i manage to upload and this is the outcome,

for the picture on the left, all the characters are scrolling to the left in the same direction

the picture on the right, when i change it to (.setColumn) it scrolls to in a line and scrolls very slowly and moves bit by bit and the words are reverse


WhatsApp Image 2018-11-18 at 10.59.45 PM.jpegWhatsApp Image 2018-11-18 at 11.19.43 PM.jpegWhatsApp Image 2018-11-18 at 11.35.34 PM.jpeg
None
YorukSam-Kun

Reply 11 months ago

please replace the "lc.setColumn(m,7-i,Buffer[i+k+8*m]);" by "lc.setColumn(m,i,Buffer[i+k+8*m]);"