On Sun, 4 May 2025, Nicklas SB Karlsson wrote:
Date: Sun, 04 May 2025 13:39:48 +0200
From: Nicklas SB Karlsson <n...@nksb.eu>
Reply-To: "Enhanced Machine Controller (EMC)"
<emc-users@lists.sourceforge.net>
To: emc-users@lists.sourceforge.net
Subject: Re: [Emc-users] Connect index pulse?
It is an ordinary very common encoder have with a zero output. It does not
have any index-enable net just an output. All
encoders I have seen with an index output have been like this so therefore
assume it is a very common problem how to connect these and simple solution
available.
I could of course create an index net or write a component with an IO output
that write value only then edge is
detected. Then it will be possible to connect this to joint index-enable as
both are IO.
Nicklas Karlsson
LinuxCNC assumes that the encoder counter hardware has index support.
By support I mean the hardware can detect the index signal and either
clear the count or better, capture the count at index for later processing.
This processing is the following:
If index-enable is false, the hardware ignores the index signal. If
index-enable is set true (by LinuxCNC) the hardware is primed to detect the
index signal. When index enable is true and an index signal is detected, two
things are done, the encoder position presented to LinuxCNC is zeroed (this is
optional, Theres a LinuxCNC INI constant to change this expectation) and
index-enable is set false. This falling edge of index-enable is used by
LinuxCNC to detect the index occurance.
Also LinuxCNCs software encoder component has this index support built
in.
The reason for this is that the index pulse can be very short relative
to the servo thread period so will be missed at higher speeds unless
captured in hardware. The clearing of the position is done for a similar
reason: so the position of index occurance is captured in hardware so
thats is not a velocity dependent position error because of software
sampling of the count at the servo thread rate.
You could make a simple index component to create a (tri-state) index-enable
pin from a software read index signal. It could also do the position
zerowing if desired, but it would not work except at quite
low speeds or low resolution. That is, it might work for homing
but not for spindle synched motion.
s??n 2025-05-04 klockan 10:26 +0100 skrev andy pugh:
On Sun, 4 May 2025 at 09:26, Nicklas SB Karlsson <n...@nksb.eu> wrote:
>
> Any simple solution to connect index pulse from encoder to joint index-enable?
Are you sure you want to do that? Why?
Typically the system sets the whole index-enable net, then when the
index pulse is seen it is taken low by the encoder counter, that
signals to the rest of the net that the index has been seen,
Are you trying to home to index without an encoder counter?
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Peter Wallace
Mesa Electronics
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