>I am considering building a small LED matrix sign, probably
>using 12 stackable 8x8 LED matrix blocks (approx 2"x2").  This
>would produce a display surface of 8 rows each 96 wide - enough
>for 16 chars of 5x8 with one space between.  (One use would be
>a Caller ID I could read at night with my glasses off :-)
>
>How is this generally done?  If I did 8 way multiplexing, with

Zhahai,

I am currently using a Maxim MAX7219 chip to drive five seven-gegment LED
displays in my project.  The 7219 handles the scanning for up to eight
displays. It interfaces to the uP via a three-wire serial interface, and
you can daisy-chain several of them by connecting DATA OUT of one to the
DATA IN pin of the next one.

These parts are designed for seven-segment displays, but could easily
handle the type of work you're describing.  Just spend a few minutes with
the data sheet.  I don't know what the price of these babies are, but I
think it's about $7.00US each, which may be a bit high.  On the other hand,
each chip handles 64 individual LEDs and has features like brightness
control built in, and external parts count is really low-- one resistor!!!


The part is PERFECT for my project, and has made life considerable easier
for me.  Whether or not it's right for you is something only you can
decide, but I thought I'd let you know it was out there.

-Matt


  "DOS Computers manufactured by companies such as IBM, Compaq, Tandy, and
millions of others are by far the most popular, with about 70 million
machines in use wordwide. Macintosh fans, on the other hand, may note that
cockroaches are far more numerous than humans, and that numbers alone do
not denote a higher life form."