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

[Roman Sowa]

Couple of days ago I posted an idea of using chain of HC597
and HC 595 as unlimited I/O expander using only 4 pins of
uC. They are serial shifters, one is for input, other for output.
So with one serial communication you can control 1000's ;-)
of i/o. As for PWM LED - you can simply apply PWM to
OE inputs of those chips.

If you want more detail, let me know.

Roman

----- Original Message ----- 
From: Bert Schiettecatte <bert.schiettecatte at esat.kuleuven.ac.be>
To: <synth-diy at dropmix.xs4all.nl>
Sent: Friday, May 23, 2003 8:23 PM
Subject: [sdiy] mcu project with too few I/O lines :(


> hi all,
> 
> 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?). 
> 
> I thought about using a key encoder and maybe an LED driver but 
> those ICs are pretty expensive (7$ for a key encoder, that's more 
> than a microcontroller!). does anyone have some advice here and 
> how to interface this stuff without buying tons of additional ICs 
> which cost a lot of $$$?
> 
> thanks,
> bert