command to home Y axis

Is there a command-line way to home only the y axis? I'm configuring proximity switches and would like to repeat homing. The manual mentions axis-remote but I don't see the available commands.

AXIS Help->Quick reference says the Home key will 'Send active joint home'. This does work for X and Z for me but nothing for Y. I'm using the master branch with KINEMATICS = trivkins coordinates=XYYZ.

I haven't found a way to do that - it seems the homing sequence is fairly "canned", without a lot of flexibility until it is homed. While you're fiddling with the prox switches, you could set HOME for Z and X to be just barely backed off their own switches, then when you go to repeat the homing sequence to tweak Y, the X and Z will zip through their sequence in a couple of seconds, with the gantry homing starting just after that.

I

The LinuxCNC master branch (2.8~pre) includes a simulation
config for a gantry with two joints (motors) driving a
single axis (coordinate letter).

The configuration is available from the Configuration
Selector as:
No special hardware is needed (it's a simulation).

You can experiment with this axis-gui-based config to show
both 'Home All' and individual joint homing (and unhoming):
Note that when joints are synchronized (using negative
HOME_SEQUENCE numbers), the synchronized joints
are always homed together (not individually). Synchronized
joints cannot be jogged prior to homing but the corresponding
axis coordinate can be jogged after homing of course.

Using the trivkins specifier kinstype=both helps to clarify
the distinctions of joints and axis letters in this sim config.

Important notes for configuring machines with nontrivial kinematics
(including gantries with two motors for a single coordinate)
are at:

linuxcnc.org/docs/devel/html/getting-sta...dating-linuxcnc.html

and especially:
linuxcnc.org/docs/devel/html/getting-sta..._axes_specifications


More information on the trivkins kinematics module are in the man
page ($ man trivkins) or at:

linuxcnc.org/docs/devel/html/man/man9/trivkins.9.html


Excerpts from configs/sim/axis/gantry.ini:

I tested configs/sim/axis/gantry.ini. To home only Y I can switch to joint mode, then select joint 1, then home. After homing it reverts back to World mode automatically where I can jog Y. After jogging Y, the key sequence to home Y again is then:
$, 1, Home, Enter

I will update my config similar to this.

The setting "kinstype= both" will give you options to jog in individual joint mode - but I don't think it's going to serve your purposes.

Homing is the process by which two coordinated joints are recognized as an axis - so there is no "Y axis" until homing of the two joints that comprise the Y axis is complete. You will be able to move the right and left sides of your ganty one at a time - but this can totally mess things up, racking, bending and possibly breaking your gantry. Until a coordinated homing cycle is complete you will remain in Joint Mode - only after successfully homing will the controller combine the two joints and switch to World Mode, where your axes earn their letter names.

Just be careful out there!

You will be able to move the right and left sides of your
ganty one at a time

Incorrect.
As mentioned earlier:

Synchronized joints cannot be jogged prior to homing but
the corresponding axis coordinate can be jogged after homing of
course.

This behavior is documented in the section on HOME_SEQUENCE (3.10):
in the chapter on 'Homing Configuration'. Excerpt:

Joint mode jogging of joints having a negative HOME_SEQUENCE
is disallowed. In common gantry applications, such jogging can lead
to misalignment (racking). Note that conventional jogging in
world coordinates is always available once a machine is homed.

Ref: linuxcnc.org/docs/devel/html/config/ini-homing.html
linuxcnc.org/docs/devel/html/config/ini-....html#_home_sequence

Some machines with complex kinematics require a calibration
procedure to jog joints prior to homing but the homing final
moves must be synchronized. This can be accomplished by changing
the HOME_SEQUENCE settings temporarily but provisions must be
made to inhibit homing under these conditions. The inifile
HOME_SEQUENCE items can be altered between runs or one can use a
different inifile for the calibration procedures. A method using
hal logic for doing this within a running system is described in
'3.14. Inhibiting Homing' in the referenced docs Homing
Configuration chapter.

Ref: linuxcnc.org/docs/devel/html/config/ini-...l#_inhibiting_homing

That must have disappeared from a later release of 2.8pre - since the version I started on allowed the right and left to move independently. I did it quite a bit during early setup. I have since both upgraded and stopped using kinstype= both, so I didn't notice the change. Sorry for the disinformation!

release of 2.8pre

There are *no* releases of the master branch (2.8~pre).
Changes are made on an ongoing basis and may occasionally
break things or alter behavior.

Users building from git can monitor commits from
the command line ('$ git fetch' for instance); users
using deb packages from the buildbot may need to
monitor commit messages as the buildbot makes debs
when new commits are made.

Developers try to maintain the 'Updating' docs when
signficant behaviors are changed:

linuxcnc.org/docs/devel/html/getting-sta...dating-linuxcnc.html

However, the best information about the state of the master branch
is attained by monitoring the commit messages made with
each commit.

Ref: github.com/LinuxCNC/linuxcnc/commits/master

Users need to understand the potential instabilities and
the risk inherent in any software particularly a code
with ongoing development.

I set up my config like the example gantry except it's XYYZ.

I find I can home Y through the menu (in either World mode or Joint mode) Machine->Homing->Home Joint 1 (Sequence -1 SYNC)
or Home Joint 2 (Sequence -1 SYNC)

The Home shortcut key, however, does not work in World mode. If pressed, there is a message in the terminal "home_joint <y> Use joint mode for homing".

To use the 'Home' key in world mode, you will need to return to joint mode first.
In the axis gui, you can toggle between world and joint mode with the '$' key.