LinuxCNC + Orange Pi (allwincnc)

Please try a latency test with 1mS servo thread only and post the results if possible. I am getting 200uS jitter on a 1mS servo only on my board with the RT kernel from H3CNC.

To run desktop browsers you need more than 1GB of RAM. Another issue - H3 is too slow (1.4 GHz) for the big apps. Use it just for CNC user interface and console apps.

Jitter about 200us is normal for the H3 and Armbian Buster.

latency histogram --nobase --servo 1000000
4 glxgears
after 947 seconds
-283 +249 latency
and again with 2000000 ( 2mS servo only )
i see
263 222 at 500seconds

but:
latency doesnt matter (as much) if arisc handles the time critical processes.
I think the latency is interesting but not crucial.

I have a limited perspective due to my needs,
and may easily fail to see needs of others.

So, here's 2 questions of interest:
Is there someplace to put 'isolcpus=1,2,3 idle=poll" ?
Is there any benefit to moving OS from SD to eMMC ?

tomp

tjtr33 wrote:

Is there someplace to put 'isolcpus=1,2,3 idle=poll" ?

Already answered here forum.linuxcnc.org/38-general-linuxcnc-q...c-pwm-success#207612 :)

MX_Master wrote:

Hi, TomP.

`isolcpus ...` can be added to the armbianEnv.txt or directly to the boot.cmd/scr inside setenv bootargs "... here ..."

tjtr33 wrote:

Is there any benefit to moving OS from SD to eMMC ?

disk IO speed x 4

I have been thinking of a simple way to connect pololu drivers to the orange pi

So what I used is a Arduino cnc shield V4

Unfortunately it only supports 12 volt.
Since I am using an old laptop power supply which is 19 volt. So 12 volt is not an option. I figured out that the limit is the onboard regulator for the arduino. So I removed it. Capacitors are 47V. But now I need 5v for the Pololu 8825 drivers. Can I take that from the 5 volt pin of the orange pi?

Creative25 wrote:

Can I take that from the 5 volt pin of the orange pi?

yes

Thx MXMaster
I edited boot.cmd
and then did
sudo mkimage -C none -A arm -T script -d /boot/boot.cmd /boot/boot.scr
then rebooted
now latency-histrogram --nobase --servo 1000000
has values cut in half ( compared to before editing boot.cmd)
after 1/2 hour with 4 glxgears
i have -153 and +138 uS latency

I did not move OS from SD to eMMC yet,
I will let the latency test cook overnight
thx TomP

Hi Bari Hi MXMaster

I ran latency-histogram on the opi+2e armbian buster xfce
withadded to command.tct and compiled
params ofand 4 glxgears
and got (after more than 13 hours)
base -44.5 +46.8
servo -115.9 +121.7

the editing for isolcpus and idle definitely help

it does slow down the axis gui, but acceptable
( if you "lower your expectations" TM SNL )

todo:
Add the ntp 'fix' from samco
Move the os from sd to emmc
Drive these closed loop stepperd LC57H380+LCDA357H
www.alibaba.com/product-detail/3-Phase-n...-2N_62339788859.html
Build and study the app 'tuna' for tuning rt environments

Regards
tomp

Tom,

I have similar jitter here. I also tried with isolcpus=2,3 and =3 and GUI performance was snappier and the jitter stayed about the same.

There is noticeable improvement when GPU hardware accel is used with the Rpi4. At some point I'll have to see how much better it behaves on the Opi's with hardware accel.

I'll try the =3 asap
here's a pretty crappy video
( pink and squeezed samll, so bigify and turn on CC )
now i will set up these servo-steppers
tomp

i just uploaded it it YT so may have a delay for public approval