> Does anyone have any experience in using an A to D input with a ladder
> resistor array of 8 resistors and 8 switches to allow for the 8
> switches to be used without taking up more than 1 I/O into the
> processor?
>
> If the resistors are all 1k in value then the input voltage will
> correspond to whichever button is pressed?  Is this a practical route
> to explore?

I have never done this, but it sounds like it should work.  Note that the
switches are connected in a priority arrangement.  Multiple simultaneous
key presses will appear like a single key press of the highest priority
key.  If this isn't a problem, then you're probably fine.

You will also want to do some filtering and detection of settling of the
A/D value before assuming a key is pressed.  Since the ladder produces a
single voltage, it will slew thru legitimate states before settling on the
proper voltage for the key pressed.


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