Jeff DeMaagd wrote:
>
> At 01:24 AM 12/11/01 +1100, Roman wrote:
>
> >Why use a chip? I have one circuit running
> >16 independent dip switches, a 7 seg. display
> >and 2 input/output pins on a 16F84 which only
> >has 13 IO pins, no other chips needed. Exactly
> >how many things do you need to connect??
> >-Roman
>
> Can you post a generalized schematic of this?
>
> I know tricks can be done but it seems aggravating to use them, but maybe
> you have something else going here.



Hi Jeff, I posted the circuit at:
http://centauri.ezy.net.au/~fastvid/pic_16sw.gif

No "tricks" needed other than one diode
for each switch. I used 1N4148 diodes at
less than 2c US each in the quantity we
bought for the product. Product is now obsolete
so I don't mind showing how we connected so
much to a small PIC. Much cheaper and probably
more reliable than adding another chip to
give more I/O ports.

The switches are individually addressable!
This is what the diodes do, so any number of
switches can be on at once, unlike some simple
matrix setups. It just scans the switches in
a 4x4 diode-ed matrix.
-Roman

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