PICs AD inputs: what do I need to add for the diagram to work?

[William At MyBlueRoom]

Attached is a input stage selector for a Elk MM-443 **broken link removed**

I'd like to use a similar setup on a PIC *that's what the Elk uses too, Do I simply need a resistor or should I clamp the inputs too?

 

[Nigel Goodwin]

The PIC already clamps them - but that's no good for this situation, because it needs to read analogue inputs!.

The answer is simple though, a potential divider - and the series resistor will act with the internal diodes as a clamp as well (assuming too much voltage is applied).

 

[William At MyBlueRoom]

I figured out why I was confused, they use a +12V pullup and I want to use +5. Hmmm. Here's the simulator circuit.