Custom homing - without back-off, keep in one direction

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21 Apr 2017 08:54 - 21 Apr 2017 09:00 #91758 by plmicia
plmicia created the topic: Custom homing - without back-off, keep in one direction
Dears,
I am retrofitting Brother TC-225 milling machine with LinuxCNC 2.7.8.
I would like to keep as much original behavior as possible, including homing sequence.
This milling machine is equipped with separate limit+, limit - and home switch.
Original homing is specific, without changing direction of the move. Home switch is someway "overpassed".

I will try to describe below original Brother homing process (in Liniux CNC nomenclature :-):
- search for home switch in "+" direction (@ home_search_vel). There is no back-off! after home switch trip
- final detection of switch home (@ home latch_vel), still in the same direction, home switch "overpassed" until release
- index pulse (@ home latch_vel), still in the same direction
Hope you understand what I mean :S .

Is it possible at all to interfere LCNC homing sequence so deep?

I am not sure why Brother engineers made such homing algorithm. Only backlash issues comes in to my mind...
Anyway, it is not a big deal to use homing sequence served by Linux, but I am jut curious if such modification is possible at all.
Last Edit: 21 Apr 2017 09:00 by plmicia.
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25 Apr 2017 13:51 #92057 by andypugh
andypugh replied the topic: Custom homing - without back-off, keep in one direction
All things are possible when you are talking about software, but it might be more trouble than you want to go to.

The home sequence code is here:
github.com/LinuxCNC/linuxcnc/blob/master...motion/homing.c#L362

You are interested in changing what happens at the end of HOME_SET_COARSE_POSITION and the states it goes to based on various velocities.
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