> I've been thinking.......instead of using each AN as a separate input, by
> using one bi-directional opto-link to a satellite PIC it would be possible
> to
> send commands to it to control a MUX that could select from many
> analogue sources with eg a 4051. That satellite PIC then does the AD
> and bit bangs the result to the host PIC via the other opto. Which may be
> an answer to Bob's question ;
>
> > Be careful. Do you have to have each analog input isolated from the
> > others, or just all the analogs isolated from the rest of the world, but
> > sharing common circuitry among themselves?

Why use a 4051. Why not just use the built in analog mux on the satellite
PIC. ie:

    biggerpic < smallerpic + 4051

I guess your answer to my question is: "it is ok for the analog channels to
have common circuitry".

Bob Ammerman
RAm Systems

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