LED Matrix Project

Forum 2005-2010 (read only) General Exhibition
1

Hey All,

Just though I would share my first Arduino project. It's an LED board using 4 Sparkfun RGB LED Matrices.

It shows time / temperature / weather and random patterns and a few retro 8 bit graphics like tetris and the pacman ghosts...

Wobbly video here:
http://blog.makezine.com/archive/2008/11/animated_timetemp_rgb_mat.html

Pics here:
Imgur

The arduino talks to the matrices using SPI and the core code is from the example libraries here (thanks for providing that guys!). It connects to the internet using an ethernet shield from Ladyada (Limor) to read data from a website I wrote for it.

Got loads of cool help from people on here and over at Sparkfun.

Currently working on getting it scrolling RSS feeds!

2

Nick,
Do you have any details on how you set all this up? I am really interested in building a project like this.

I am just starting out with using the Arduino (still waiting on UPS to deliver mine).

Thanks for any help.

John

3

Which LED matrix did you use? Does it have a serial interface?

4

Hey.

The matrices are from Sparkfun electronics. They are the RGB ones with the SPI backpack.

This makes it really easy to interface to arduino - just 4 wires per matrix.

There is demo code on the arduino site.

Cheers
Nick

5

Sparkfun is out of them right now, but I hope they get them in soon.

Since I am totally new to this, what are the four connections? Also does each matrix attach to the same pins or different pins?

Thanks,
-John

6

I ordered two from LEDsee, mid-December. Still haven't arrived in US. I know it takes a while from China but another vendor was faster. No good tracking of the package, either. Even if it's half the price of SparkFun, not sure it's worth it.

On the plus side, my rail of ten 74HC595s arrived from DigiKey so now I'm ready to play with the matrices when (if?) they do arrive. The only fault I have with DigiKey is the insane amount of packaging waste for hobby-sized orders. I already told SparkFun I was very impressed with their tiny USPS boxes by comparison.

7

John,

You need (apart from 5v and GND) for each matrix...

SPI clock
Data out (MOSI) - master out slave in
Data in (MISO) - master in slave out (i think you need this)
Chip select - enables the device ready to to read data in

on the demo sketch for arduino it tells you which pins are setup for which. Arduino Playground - RGBBackpack

So I wired as follows

Data out from the arduino goes to data in on the matrix
Data out from the matrix goes back to the arduino (though not sure if this is neccessary)
Clock goes to clock
Chip select goes to chip select

For my 4 matrices the clock, data out and data in are shared between all matrices - all the clock pins are wired together, all the data ins together and so on.

I then use 4 pins for the 4 enables and enable one matrix at a time..

I.e. Enable matrix one (enable pin high), send data. enable matrix 2, send data etc.

Basically does the example sketch 4 times, each time with a different enable pin high and a different set of data. That way by I can drive 4 matrices

I think you could also maybe wire them so that thay are chained together - Data out from one into data in of the next matrix and so on, the enable them all at once and send 4 chuks of data. This works as each matrix shifts out a bit of data to the next matrix every clock pulse. So 4 sets of data would get shifted along into all 4 matrices. This would be more efficient as you would only use up 1 pin on the arduino as you would enable all the matrices at the same time.

Hope this is some help

Nick

8

Yes. Thank you very much.

Now I just have to wait until Sparkfun makes some more available.

-John

9

Wow, this is a great project. Will definately look in to making one of these :slight_smile:
By the way, anybody looking for the RGB matrices, SparkFun just got in a new shipment :slight_smile: