Any PIC with an external Interrupt will do this job.
Don't sample, let the INT pin (With an Interupt service routine) do the job!

  *
  |  __O    Thomas C. Sefranek   WA1RHP@ARRL.NET
  |_-\<,_   Amateur Radio Operator: WA1RHP
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> -----Original Message-----
> From: pic microcontroller discussion list
> [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Ted Larson
> Sent: Friday, April 18, 2003 7:26 PM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: [PIC]:Optical Encoder and PICs
>
>
> I am also interested in this problem....although I have a
> slightly different
> problem. I am a newbie to PICS, and I am attempting to design a PIC circut
> for reading a shaft encoder attached to a motor, and that has a
> really fine
> grain.  I don't have a data sheet on the encoder....but when hooked up to
> the scope, I am getting a 28 microsecond pulse width, with the
> motor turning
> at the highest RPM for my application.  If I don't want to miss
> any pulses,
> I need to be sampling at a rate of about 36khz (36,000 pulses per second).
> I have two motors I would like to monitor with one PIC.  What I would like
> to do, is have the PIC pull in the shaft data, and keep track of it, and
> then deliver it over a serial line when asked for the totals.
> What would be
> the best PIC for doing this?  I want to make sure my clocking is
> fast enough
> that there is no chance of missing a pulse.
>
> Thanks,
>
> - Ted
>
>
> -----Original Message-----
> From: cdb [mailto:bodgy1@OPTUSNET.COM.AU]
> Sent: Thursday, April 17, 2003 9:10 PM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: [PIC]:Optical Encoder and PICs
>
>
> On Thu, 17 Apr 2003 08:01:48 -0400, Mccauley, Daniel H wrote:
>  was wondering if anyone had experience of using an optical encoder
> (A and
> B inputs for quadrature mode) on a PIC microcontroller.
> I'd like to use the A and B output of the optical encoder and tied
> into
> PortB and have each pulse (either on A or B) trigger an interrupt.
>
> I don't with an optical version, but here is some code in 'C' that
> you can play around with. See also another incarnation elsewhere in
> last weeks archives, where I had a counting problem with my original
>  code.
>
> //EncoderA_pin on PORTA: 1. B_pin on PORTA: 0
> //This checks for the sequence 10->11 for CW pulses and 11->01 for
> CCW.
> void getenc()
> {
>
>         if (!bRA0)              //enc_B is low
>                 old_enc_state=1;        //make flag high
>
>         //we get here if both enc_B is now high and      old assumed state
> was
> high
>         if ((bRA0) && (old_enc_state))
>                 {
>                         if (bRA1)               //If enc_A is now high we
> have gone from 10->11 in
> pulses
>                                 {
>                                         enc_state=1;
>                                         old_enc_state=0;
> flag now low
> so that we have to wait for the
> next 11 to come around
>                                 }
>                                 if((!bRA1) && (old_enc_state))
>                                         {
>                                                 enc_state=-1;
>                                                 old_enc_state=0;
>                                         }
>
>         }
> else
>         {
>                 enc_state=0; //here if there was no change in encoder
> position
>         }
> }
>
> Colin
> --
> cdb, bodgy1@optusnet.com.au on 18.04.2003
>
> I have always been a few Dendrites short of an Axon and believe me it
> shows.
>
> Light travels faster than sound. That's why some people appear bright
> until they speak!
>
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