Is it possible to multiplex the scanning of 4 push-button switches on
the same 4 'data' lines as an LCD module is using ?

I've sort of thought along the lines of having all of the switches
commoned at one side and then having an OPen -collector arrangement to
short the switches to ground at read time.

The drawback with this arrangement is that when the switches are NOT
being read and one or more switches are closed, data lines will be
shorted together. Adding diodes seemed like an obvious step forward but
the 0.7V drop takes them to the top end of the TTL logic '0' level.

Anyone got any suggestions please ?

Also I am looking at using a standard 16x2 LCD with these switches to
allow menu selection and configuration settings - has anyone done
anything that allows the PIC to communicate with a host processor (in
this case it is ACORN podule bus) to download menu choices, selections
etc. I am trying to reduce the amount of processing done by the host so
that the PIC can deal with most of the menu control if poss........

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| Mark Birks                       |
| Hardware Section Leader          |
| OmniBus Systems, Stanford House, |
| Stanford-on-Soar,                |
| Loughborough, Leicestershire. UK.|
|                                  |
| Tel/Fax: +44 (0)990 004300/333   |
| E-Mail: markb@omnibus.co.uk      |
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