Picture of Wearable Message Board

I had several 8x8 LED matrices with a MAX7219 driver board lying around for a clock/message board project i'm working on.  I'm heading to RobotFest in MD this weekend with my kid and thought it'd be fun to make a wearable message board to clip on my backpack since I had the parts lying around.


Time to build: 4-6 hrs
Cost: $20-$30 depending on parts and how much stuff you have laying around and if you want to make it bluetooth enabled.

I am using a bluetooth module I have for another robotics project that was very simple to integrate, and I wanted to build my first stand-alone  ATmega328 project instead of doing everything on an arduino all the time.
This project is fairly simple and inexpensive.  The "MAX7219 8x8 LED matrix kit" boards can be found on ebay for as low as $2.70 with free shipping, ATmega's with the arduino bootloader are about $4, the capacitors and oscillators are only a 10-50 cents per part if you buy a bunch at a time.  The bluetooth module is more expensive but i am using a much more expensive model than what is really required for the project.  You can do the same thing with a cheaper version that is only around $8.  Or leave out the bluetooth all together and just run a pre-set series of animations or text.

(estimated costs in USD)
1 x ATmega328P-PU ($4)
1 x 28 Pin DIP IC Socket ($0.20)
1 x 16Mhz Crystal Oscillator ($0.50)
2 x 22 pF capacitors ($0.20)
1 x Bluetooth Module ($8-30)
1 x 8x8 MAX7219 LED Matrix board kit ($3)
1 x 3AA Battery Holder ($2.50)
3 x AA batteries ($3)
1 x piece of breadboard ($2.50)
Total: $24 -  $46

Various header pins (male and female), hookup wire, solder, some kind of enclosure, Arduino for programming the ATmega328

Soldering iron, dremel for enclosure


MaxK210 months ago


So i modified your code a little bit for my own application. But how can i send bitmaps to a second matrix? Id really like to see it work so i can make 8x16 animations.

also here is a cool little animation.:

void spaceinvader() {

int wait =300;



Greetings most15,

Your instructions on instructables was a good one as I'm new to arduino.

I did stumble on the code though after downloading the necessary and including #include <Adafruit_HEX.h>

#include <Max72xxPanel.h>

and try to verify Snake in the Arduino 1.0.5 sketch window it stopped @

Max72xxPanel matrix = Maxx722xxPanel (pinCS, numberofHorizontalDisplays, numberofVerticalDisplays);

The error window shows 'Max72xxPanel' does not name a type also

inside window shows snake:9 error 'Max72xxPanel' does not name type

snake.for: In function 'void setup'():

snake:20: error: 'matrix' was not declared in scope

snake.pre: In function 'void loop()':

snake:47 error: 'matrix' was not declared in this scope

If you can decipher this please help, I am using Max7219 matrixes.

Kind regards


bluesthue (author)  JDBUILDER20131 year ago

it looks like you have a typo on the line where you're initializing the panel. your code says max722xxpanel(...). should be max72xx instead.

corrected the typos but still no joy,still getting error message of the matrix not being declared in void seup. Don't want to give up on this one because it's a real cool gadget if working...........Any ideas could it be something missing from downloading the Max72xxPanel.h zip file?

bluesthue (author)  JDBUILDER20131 year ago

you ALSO need the adafruit gfx library. and make sure your libraries are in the right location. I think I'm the arduino ide under settings you can specify a folder to use, or put them in the default libraries location. http://www.arduino.cc/en/Hacking/Libraries

bluesthue (author)  bluesthue1 year ago

if you can padte your full code in here I can take a look. or copy and paste this code http://matthewroy.com/WearableMessageBoard/WearableMSGv1.ino

Thanks for speedy reply I will scrutinize my coding more closely when I next fire up my sketch and let you know if it repaired the issue


Sorry correction on your name mroy15