On Sun, 26 Jan 2014, Charles Steinkuehler wrote:
> Date: Sun, 26 Jan 2014 11:54:24 -0600
> From: Charles Steinkuehler <[email protected]>
> Reply-To: "Enhanced Machine Controller (EMC)"
> <[email protected]>
> To: EMC2-Users-List <[email protected]>
> Subject: [Emc-users] Encoder Index Support Survey
>
> I'm working on adding software encoder support to the BeagleBone PRU
> code. Counting up/down is easy, but I'm wondering how to deal with the
> index pulses. Both the Mesa VHDL code and the existing software encoder
> component have quite a variety of options, and I'm wondering if it is
> necessary to support them all (more options = longer code = lower
> operating frequency).
>
> If you use encoders on your machine, what options do you have set for
> the HAL component, and (if you know) what is the maximum pulse frequency
> for your machine?
>
> --
> Charles Steinkuehler
> [email protected]
>
>
I would simplify the index logic to this:
Always latch the current count on index (probably rising) edge
and provide the latched count to the driver. Have a (clearable) bit
that indicates the index was latched.
The rest can be handled in the driver
notes:
You really never want clear-on-index as this borks velocity
estimation.
Always latching the encoder on index provides a nice way to sanity check
the encoder counting (if abs (delta_latched_counts - counts/turn) >2 or so
>>> badd)
.
main things missing:
index polarity, AB gating of index, input filtering
Peter Wallace
Mesa Electronics
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