On Fri, 10 Apr 2020, Leonardo Marsaglia wrote:
Date: Fri, 10 Apr 2020 19:01:51 -0300
From: Leonardo Marsaglia <ldmarsag...@gmail.com>
Reply-To: "Enhanced Machine Controller (EMC)"
<emc-users@lists.sourceforge.net>
To: "Enhanced Machine Controller (EMC)" <emc-users@lists.sourceforge.net>
Subject: Re: [Emc-users] Home use index problem (In step + dir mode)
Do you have a home switch and is it working?
If you want to home to index only you must set HOME_SEARCH_VELOCITY to 0
The home switch is working perfectly. I'm pushing it by hand because I'm
only testing in the desk but it works. If I only use home switch for homing
it works perfectly. The problem starts when I try to use the index pulse.
If you have homing setup for home switch + index, motions index-enable output
should be set high when the home switch is tripped
If I set HOME_SEARCH_VELOCITY to 0 and try to home using index only, the
joint.0.index-enable pin turns to TRUE and when the motor trips the index
pulse it stops but I get the following error message and the homing aborts.
Always in the same position of the motor, so the index is detected.
The following error is expected unfortunately since motion expects the position
to have been zeroed on index detection, but the stepgen position is not affected
by the encoder index
Do the servos have a emulated encopder output (you mentioned a Z signal, is
that from the drive?)
Yes the drive has the encoder output pins for the A, /A, B, /B, Z and /Z
signals. I'm only using the Z and /Z signals because I thought I could home
with index independently of the feedback I was using.
No, index handling is intimately entangled with the position feedback.
This is because index detection effectively zeros the position feedback
at the instant of index detection so its is precise regardless of the detection
speed. As I mentioned, there is firmware to support index detection with the
stepgen hardware, but it is not currently supported by the hostmot2 driver
Also as you might expect, the stepgen index input pin is not an encoder input
rather, its part of the stepgen.
You can use homing with index if you use the drives encoder output
for feedback, but this is a bit more work and more difficult
to tune
Peter Wallace
Mesa Electronics
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