put some diodes between outputs and keys to prevent blowing up outputs if
more than one key at a time is pressed (my kids would be great in testing
this)
the other possibility is to only switch one of them to output and keep the
others inputs.

Peter van Hoof
-------------
mailto:pvh@vertonet.com
http://go.to/pvh

> You may try something like this:
> use a 16F84 to read the keyboard, there are applications on the AN, let me
> see if I
> can find one...(2 min wait looking 4 it)...done, I couldn't find it, so:
>
> A0   A1   A2   A3   <---outputs sequenced (see below)
>  |    |    |    |
>  1----2----3----A-------B0 input
>  |    |    |    |
>  4----5----6----B-------B1 input    <----typical keypad
>  |    |    |    |
>  7----8----9----C-------B2 input
>  |    |    |    |
>  *----0----#----D-------B3 input
>
> you must add pulldown resistors on all tree B inputs