On Mon, 24 May 2010, Russell McMahon wrote:

> I started off suggesting the serial system mainly because I have used
> it and found it useful. I was by no mans sold on it and "lots of
> ports" sounds easy. But having argued the point I feel the SR scheme
> is simpler to do, conceptually simpler and easier to code than the two
> processor system. Do it all in one processor and it would be
> different.

Hmm, now there's a thought! Build a small unit that looks after N lines 
and talks to the PC via USB. If you can get N down to 45, build two 
identical units with different USB addresses, get them to look after their 
own block of lines and let the PC sort out the rest. You could even reduce 
N to a much (DIP PIC) friendlier number and use more units. I don't know 
much about USB, how easy would it be to have several PICs sharing one USB 
socket? Of course all this is assuming that the project is just a one off.

Anyway I still prefer the "wide" shift register solution.

Regards
Sergio Masci
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