sergio masci wrote:
> On Mon, 24 May 2010, Russell McMahon wrote:
>
>
>   
> 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
>   
Bad idea. You have multiple USB devices.
To use same socket you need a hub. More expense.
It's trivial to have say HW TTL USART between the PICs and one with USB.
but one PIC with shift registers or switches or buffers is best unless a 
space issue.
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