Raspberry Pi 4

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08 Jul 2019 18:36 #138884 by Hakan
Replied by Hakan on topic Raspberry Pi 4
After some torture


I guess that's it then.
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13 Jul 2019 14:03 #139255 by andypugh
Replied by andypugh on topic Raspberry Pi 4
People have achieved better than that with the Pi3. so I think that there may be room for improvement.

Try here; github.com/guysoft/RealtimePi

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13 Jul 2019 15:13 - 13 Jul 2019 15:30 #139257 by Hakan
Replied by Hakan on topic Raspberry Pi 4
I am all for improvements. Checked the link. We both use the RaspberryPi kernel patched with the official Preempt RT patches. The link uses CustomPi, I used standard raspbian. My immediate thought is that there should not be much of a difference.

One thing I know is that the sd-card I used during these tests was amazingly slow. I will retest early next week with a much faster sdcard, perhaps that slowed things down. Apart from that I can just say I was hoping for a better result and I am willing to test good leads.
Last edit: 13 Jul 2019 15:30 by Hakan.

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14 Jul 2019 11:04 #139302 by wicki
Replied by wicki on topic Raspberry Pi 4
Here is a little q&d-howto to install a rt-patch :

erste.de/raspi4-RT-kernel-howto.html

I will also document the needed steps for compiling the linCNC-source on
the RP4 the next days.

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14 Jul 2019 11:27 #139305 by andypugh
Replied by andypugh on topic Raspberry Pi 4

andypugh wrote: Try here; github.com/guysoft/RealtimePi


OK, as far as I can see the images there do not boot the 4 into a realtime kernel, so are no help at all.

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14 Jul 2019 13:59 #139313 by tommylight
Replied by tommylight on topic Raspberry Pi 4
What does uname -a say ?
Have some RPI 3B and i did download that last night but did not have time to test yet.

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14 Jul 2019 14:27 #139314 by wicki
Replied by wicki on topic Raspberry Pi 4
compile, latency-test and start of lincnc 2.9 on a PI4 :

erste.de/raspi4-RT-kernel-howto.html#compile_linCNC_on_Raspi4
The following user(s) said Thank You: tommylight

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15 Jul 2019 09:24 #139391 by wicki
Replied by wicki on topic Raspberry Pi 4
one axis test: lincnc 2.9 on RPI4 with
Linux raspberrypi 4.19.50-rt22-v7l+ #2 SMP PREEMPT RT Sat Jul 13
09:21:03 BST 2019 armv7l GNU/Linux

a stable 5kHz step/dir signal is generated.
as a quad-signal 10kHz should be possible.

further tests in a 4-axis system will follow.

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15 Jul 2019 10:11 #139398 by andypugh
Replied by andypugh on topic Raspberry Pi 4
Hakan / wicki can you add some details here:
github.com/guysoft/RealtimePi/issues/17#issuecomment-511322405
guysoft makes the RealtimePi images, and TiejunChina does the "official" rpi-4.19-y-rt style builds.
But it seems that neither of them own a Pi4 for testing with.

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15 Jul 2019 16:57 #139467 by Hakan
Replied by Hakan on topic Raspberry Pi 4
I tested today again with a new sd card. Well it was better but didn't really solve anything.

If I run latency-histogram for under 1 minute I get similar looking graph like wicki's.
The previous graph I posted ran for 1.5 hour with me surfing and 7? glxgears.

I can't see there is a real difference otherwise. I used the 4.19.57 kernel with the RT-patches for 4.19.50, but it shouldn't matter, the RT-patches don't change that much and the patching was clean with just a few line offsets. wicki used 4.19.50 for kernel and rt-patches. There is a difference of course.

wicki what does the latency-histogram look after, say, 10 minutes?

And does it work running linuxcnc, that is of ocurse the interesting question.
wicki, if you are busy testing I think I'll wait for your results.

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