[sdiy] mcu project with too few I/O lines :(

[BrightBoy]

> i'm doing a microcontroller project here with an optrex graphical
> display (128x64), rotary encoder, led matrix (16 leds), and key
> matrix (16 keys). of course there is also the midi and in system
> programming connectors. unfortunately my microcontroller (atmega8)
> does not have a lot of i/o lines available, and I'm left clueless
> how to interface all that stuff to it. The display has an 8bit
> data bus + a few i/o lines for reading, writing, etc. for the
> led matrix, i'd like brightness control for each led (PWM?).

Bert,

I have an article which explains how you can use a single tri-state
output to control two LED's.  The only drawback is that they BOTH 
cannot be ON at the same time.  It's either one or the
other ON or both OFF.

If that's a useful arrangement, let me know and I'll dig up the
article.  It either came from EDN or Electronic Design magazine.

Cheers,

Jeff R. Dec