Help needed with a Sparkfun LED Matrix - Dual

Forum 2005-2010 (read only) Hardware Interfacing
1

Hi,

I've bought one of these 8 X 8 matrixes: LED Matrix - Dual Color - Small - COM-00681 - SparkFun Electronics

I'm using the code here Arduino Playground - DirectDriveLEDMatrix as a starting point, but I can't seem to control the matrix in a meaningful way.

I can't figure out how to determine the correct setup for the row and col arrays. The data sheet for the Matrix differs from other tutorials, each col has 2 pin numbers instead of one, e.g col pin no 1 is connected to 5,20. Whereas in the tutorial col pin no 1 is connected to 13. How should the code be setup to reflect this? Are the dual values used to address different colours?

Problem 2, this matrix has 12 pins on each side, not 8, can this be connected to an Arduino with 16 inputs ?

Also I've seen some references to using the MAX7219 to control matrixes, is this necessary?

Any help would be greatly appreciated!

2

The Playground article is for single color matrix. Yours is a 2 color matrix.
There are not enough pins on the Arduino to directly drive both colors. You have two main choices:

  1. Use the Playground article to drive only one color of the matrix - just to see it work.
  2. Use some kind of multiplexing technique. With this you again have several choices but the 2 most common are:

A. Use 74HC595 chips for multiplexing
B. Use 2 MAX7219 chips - each driving a color.

I drove that same RG matrix with the 2 MAX7219 chips.
http://www.arduino.cc/playground/Main/MultiplexMAX72xx
(Note the pin numbers in the article are for the Medium RG matrix - the small has different pin #'s.

The 595 approach is cheaper (unless get free samples of the MAX7219/21) and a bit more complex to wire. You will find examples for that approach on the forum.

3

Thanks for the info, I found this useful article which helped me http://oomlout.com/8X8M/8X8M-Guide.pdf, using their wiring setup I was able to turn on all the LEDs.

4

So now I'm trying to get text to scroll like in this example http://www.oomlout.co.uk/8-x-8-bicolour-led-matrix-p-233.html

I am getting a scrolling effect of sorts but all the LEDs are staying "on", so I can't make out any text

I have the exact setup as in the tutorial except I am using 300 Ohm resistors, not 1k ones, would this make a difference?

Thanks!

5

So I tried with 1k resistors but the LEDs still stay on, can anyone think of what I could be missing?