two quadrature encoders, one 18f4431, is it possible?

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The topic is pretty straightforward, is it possible to read the count of two optical quadrature encoder with only one 18f4431? If yes how?
Thanks a lot to all of you

[John P]

I don't use that processor, but if it works the same as the 16F series PICs, you could bring all four input lines (two from each encoder) to pins of Port B, and use the interrupt-on-change feature. Obviously there would have to be some logic to determine which encoder changed, or if in fact both did. And a lot depends on how fast the encoders might be running. But in theory it seems workable.

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[RLScott]

[satishmunot]

Hi,
During my some project long before I was use AT89C52 MCU for tiny
application. In which I use AT16V8 for qurature encoder logic and source code from Microchip for 16v8 (application Note from MICROCHIP for SERVO MOTOR). I use TIMER 2 IN UPDOWN MODE for one motor intrface and INTERRUPT INT0 for CLK and one Port pin for DIRECTION.
and I write code for in ISR of INT0 for UPDOWN counting for other MOTOR.
I think u can use similar type of method.
regards
satish munot
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[Briany]

I think you can.

1 using the QEI function, and the other one using CCP1 and CCP2.

then I think you have to write the code for the CCP part.

[satishmunot]

hi
hello briany
how CCP1 and CCP2. will do up down counting when motor goes FWD/REV?
regards
satish
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HI

[Briany]

I've never tried it, but the idea's been in my head for a bit.

What I was thinking is:

since quad encoders rely on the phase diff to differentiate the direction, you can have signal A connected to CCP1 and signal B connected to CCP2. (both set to trigger at rising edge, or falling edge)

You then compare the two rising edge to see if they are first, 90 degree out of phase and which one is leading, then compare with previous history to find the frequency, then work out the speed.

It's a bit of calculation, and you need a small array to save the history. (namely to differentiate forward/rev from the history array - if previous phase difference > current phase difference, take current phase difference) and I think the challenging part is to keep the ISR for both CCP1 and 2 small to prevent missing a pulse.


I hope someone has a better idea, but I think mine will work.

[satishmunot]

hello briany
You mean one for up and other for down counting
regards
satish
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[Briany]