RaspberryPi 3: remote axis display?

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12 Feb 2020 07:42 - 12 Feb 2020 07:44 #157129 by twoflowers
I am just playing around with my RPi3B (not the+ version). Kernel rpi-4.19.y-rt. As with all RT-PREEMPT builds latency is depending on the relation of servothred to basethread, i.e. basethread 50000 gets a latency < 25000, while 65000 gets < 55000.

Now running linuxcnc on X11, I get

Unexpected realtime delay on task 0 with period 50000
This Message will only display once per session.
Run the Latency Test and resolve before continuing.
Unexpected realtime delay on task 0 with period 50000
This Message will only display once per session.
Run the Latency Test and resolve before continuing.

Shutting down and cleaning up LinuxCNC...
task: 2129 cycles, min=0.000049, max=0.034770, avg=0.010206, 0 latency excursions (> 10x expected cycle time of 0.010000s)
Note: Using POSIX realtime


But I still get a realtime error message on the display. ( Does anybody know what causes this message? )

Anyway, when I run the GUI remote over ssh -X ..., I do not get any trealtime error message - but the 3D preview is "a bit" sluggish.

So the question: Does anybody k now how to run axis on my local computer and make it control the romote axis (or linuxcnc) instance?
Last edit: 12 Feb 2020 07:44 by twoflowers.

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12 Feb 2020 07:50 #157132 by bbsr_5a
insert the DVD iso start from Your PC as live and try the machie from there
the error you get is as Ferror i think yoiu shoudt use a 100000 base in first place
even if the latency jumps to 200k it will give you a stepper setup at max 3m/min at 100steps/mm
We got crappy PC here and they run since long time on this setup dayly

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12 Feb 2020 08:43 #157140 by twoflowers
Nothing wrong whit th machine config, it works fine from PC :)

The realtime error occurs immediately after starting axis, even before the machine is turned on, but it does not occur over ssh. I think it's the GPU that causes trouble, so I'd like to run the axis GUI-part on my PC and the controlling part on the RPi.

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12 Feb 2020 10:01 #157147 by tommylight
RPI3 can not do latency low enough for a base thread. If not using direct GPIO, you should not need base thread.
Servo thread should be fine.

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12 Feb 2020 10:14 #157150 by twoflowers
Well, I use GPIO - that's the whole point of using the RPI3 anyway. And as said, without X11 on local display the RPi3 can handle a base thread of 50000. Anyway, this is not the (main) problem. That is still: can axis on my local PC be used to control axis on rpi? in docs indicate that it works, but miss thze importent part of "how".

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12 Feb 2020 10:37 #157152 by tommylight
www.google.com/search?biw=1056&bih=590&s...wsDC4Q4dUDCAo&uact=5
Beware that RPI3 has the ethernet port internally wired through a USB port so the latency/ delay is terrible .

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12 Feb 2020 17:44 #157201 by twoflowers
LOL .. probably lost in translation :) "axis-remote" is not what I want: I do not want to control a remote GUI from a local commandline. I want a local GUI to control the remote machine. Network latencies is not the problem, as only the GUI part is seperated over network.

To clearify: what kills latency on the RPi3 is opengl, not the usb-stuff.

I just came across "linuxcncrsh", but I still need a way to connect "some" gui -preferably axis - to it. Any idea?

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12 Feb 2020 19:56 #157211 by tommylight
In that case, Andy uses ssh i think, but i forgot the exact line he uses to connect. I did test that a while back and it did work on normal PC's, with all the latency of the network, but usable for a slow machine.

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26 Feb 2020 23:39 #158583 by andypugh
on your remote PC: ssh -Y This email address is being protected from spambots. You need JavaScript enabled to view it.

Then just start linuxCNC from the command line.

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27 Feb 2020 07:26 #158602 by twoflowers
Yes, this definitly works, but I also loose 3D acceleration in the preview window. What I would like to get working is a local axis instance with accelerated 3D preview on a non-realtime computer, that connects to a linuxcnc instance without OpenGL display on a RaspberryPi.

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