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Quadrature-counting smartpins; is it possible to separately determine their state? — Parallax Forums

Quadrature-counting smartpins; is it possible to separately determine their state?

MicksterMickster Posts: 2,693
in Propeller 2

Ideally, I'd like to be able to detect them in the low-state to gate them with another low-going input but without having to use extra pins :|

Craig

Comments

  • cgraceycgracey Posts: 14,151
    edited 2022-12-16 07:08

    You could read the low-level states of the quadrature pins by setting the AAA input-selector bits of a nearby smart pin. Then the IN bit of the nearby smart pin would reflect the input state of the quadrature pin it points to.

  • MicksterMickster Posts: 2,693

    And the nearby smart pin wouldn't then be dedicated to this purpose, right? I only need to do this to set the home position of a servo motor after initial power-up.

  • evanhevanh Posts: 15,915
    edited 2022-12-16 08:22

    No problem at all. It's easy to switch between different pin modes with one instruction, WRPIN. A nearby pin input can be momentarily diverted to a neighbouring pin to check its level then immediately switched back to regular mode in a blink. The smartpin doing the incremental counting isn't impacted.

  • ManAtWorkManAtWork Posts: 2,176

    If you can be sure that the encoder is not moving at startup you can record the state of the A and B pins before you set up the smart pin quadrature counter mode. Then simply examine the lowest two bits of the counter. The pattern of the A and B pins repeats every 4 counts.

    Say, you startup in the A=0 and B=0 state with counter=0. Then A and B are simultanously 0 every time the two counter LSBs are low. If the counter starts at 0 while A=1 and B=1 then A and B will be low whenever the LSBs are equal to %10.

  • MicksterMickster Posts: 2,693

    Thanks guys, this is great stuff :+1:

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