Maybe in the configuration below, a pull down resistor on RB
(10K-100K) will help having a controlled current flow through diode.
When NO will be closed, the falling edge may be sensed on RB.

On 5/16/07, Jim <jimf@webstudios.co.uk> wrote:
>
>
> Hi,
>
> I am using RB4-RB6 inputs to detect changes to a couple of Normally closed
> switches and raise an interrupt. This technique I have used successfully in
> the past, But I also have a number of Normally Open switches on RC0 - RC5
> that I want to trigger a RB interrupt too. What I am proposing is to add a
> 1N4148 diode pointing to the RB input from each of the RC switches in DDL
> style - Is this likely to work? What should I watch for?
>
>
>
>
>             +5v
>            --+--
>              |
>              |
>              \
>              / Pullup R
>              \
>              /
>              |
>              |            NO Switch
>  To Pic  ----+-----------O  O--------+
>  RC Input    |                       |
>              |                       |
>            ----                      |
>             \/                       |
>            ----                     ---
>              |                      GND
>              |
>   To Pic   --+
>   RB Input
>
>
> -Jim
>
>
>
>
>
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