pending motions in MDI mode not updated?
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Sebastian Kuzminsky
2017-02-10 16:05:59 UTC
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I'm working on a specialized UI which computes appropriate G-Codes first
and passes them to LinuxCNC for execution finally. Using the MDI mode
worked quiet nice for the task, used v2.5.3 so far.
With the recent v2.7.8 (and git master/HEAD), I noticed that the
remaining number of pending motions in EMC_TRAJ_STAT.queue is not
reduced anymore during the operation. When sending MDI commands, it
increases ok, but keeps the initial number of motions until it is
completely done. Unfortunately, this prevents progress tracking.
Perhaps a different issue, but at the same time the IDs of subsequent
motions are not updated, but always == 0. They get reset to 0 in
emcmotCommandHandler(), for example just above the tpAddLine() call (it
is done 4x at other places as well).
I'm not sure if this is desired behaviour, a bug or if I'm doing
something wrong, for example should I use something else than MDI mode
for the task?
If it's a bug, I prepared a tiny quick fix which solves both issues for
me, but it might not be appropriate, incomplete and cause unintended
side-effects. Perhaps, someone with a thorough understanding of the
inner mechanism knows how to fix this properly.
Thanks for any hints!
Hi Ingo! That sounds like an interesting project.

What you describe about the motion queue and the motion id definitely
sounds like regression. There was a big change to the trajectory
planner in 2.7. Can you test the final 2.6 release and see if that one
is ok? I bet it is. This would help us focus our debugging effort.

src/emc/motion and src/emc/tp are the Motion controller controller and
the Trajectory Planner (which is part of Motion). Motion is quite far
removed from the Interpreter, which is where MDI lives.

The architecture diagram here tries to explain it:

The block labeled "EMCMOT" is Motion, and the block labeled EMCTASK is
Task, which includes the Interpreter. (Sorry about the scaling of that
image, if it doesn't fit in your browser you can scroll left and right
to see the sides...)

It sounds like maybe you care about MDI queue depth rather than
trajectory planner queue depth, if so look at Task and the
queuedMDIcommands stat struct member.
Sebastian Kuzminsky