Another option is to use the PortB interrupt on change capability.
Attach both A and B to PortB pins that trigger the interrupt on change
and you'll have a full four interrupts per period.

If you want to just use the external interrupt pin and still get four
interrupts per period, use an XOR gate to combine A and B, and when you
get an interrupt toggle the interrupt trigger from rising to falling or
falling to rising.

-Adam

Mccauley, Daniel H wrote:

>Am I safe to assume that the typical PIC implemented optical encoder scheme
>is to have the INPUT A of
>the optical encoder connected to RB0 (Ext INTERRUPT) of the PIC and INPUT B
>of the encoder connected to another pin
>such as RB1?  So that when RB0 detects a rising edge, the interrupt routine
>would then check to see if INPUT B is high
>or low to determine direction?
>
>Is this standard or do they use routines that trigger off both INPUT A and
>INPUT B for double resolution??? Or possible they would only do this if they
>needed twice the resolution?
>
>Thanks!
>
>D
>
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