Debian Wheezy increased my Latency

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13 Jan 2015 17:38 #54965 by franstrein
Hello LinuxCNC experts,

I am trying to convert my Deckel FP1 milling machine to CNC, and making lots of progress.
I am using a home-built controller with Toshiba THB6064AH Chopper and LinuxCNC as controller.
And gmoccapy as the UI, with a Faytech 19" touchscreen (just installed this weekend), a very good combination!

Question:
During my last software install, I used the Debian Wheezy LinuxCNC 2.6 ISO install image, expecting an easier install path instead of installing first the Ubuntu LTS version with LinuxCNC 2.5.

However the big problem with the Debian Wheezy install is that the Latency test increased from the 5000-10000 ns result to a ± 50.0000 ns result!
This was on exactly the same hardware configuration.

The same observation was also done in the post by Pop at linuxcnc.org/dapper/index.php/english/fo...uxcnc-26-with-wheezy last month.

Should I worry about these increased Latency Test results?
For the moment I reverted back the Ubuntu LTS version and upgraded that to 2.6.5.

Thanks for your help,
Frans

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13 Jan 2015 19:04 #54969 by ArcEye

This was on exactly the same hardware configuration.


What computer are you running on?
Are you using a video card or on-board graphics?

On some of my older computers I found Debian a bit 'heavier' and had increased latency figures.
This was down to the load from the graphics and adding a small cheap AGP card cured it completely

regards

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14 Jan 2015 00:30 #54980 by andypugh

franstrein wrote: I am trying to convert my Deckel FP1 milling machine to CNC, and making lots of progress.
I am using a home-built controller with Toshiba THB6064AH Chopper and LinuxCNC as controller.


To wander off-topic, how is that going? I would have expected the FP1 to be a bit heavy for stepper motors to move, especially the table.

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14 Jan 2015 01:20 #54983 by franstrein
Andy,

Indeed a bit off-topic. :)
The conversion is going very well. I started with small, old, "free", steppers (about 1.5Nm each) and reduction belts for all axis, using the available transmissions and trapezium spindles.
That all worked well, except sometimes for the Z-axis (which had a double reduction belt). I replaced the stepper for Z last week with a larger, 2.5Nm, and that works as well (except for very slow helical feeds). Need to test that further...

I posted my first attempt (about 1 year ago) on youtube at

using Mach3 at that time
I will make a new movie with my current setup asap.

Let me know in case you want more construction details.

Frans

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14 Jan 2015 01:45 - 14 Jan 2015 01:46 #54984 by andypugh

franstrein wrote: Let me know in case you want more construction details.


I was just wondering, because I used 750W servos on my (smaller) milling machine and the Z isn't very fast.
Last edit: 14 Jan 2015 01:46 by andypugh.

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21 Feb 2015 05:39 #56170 by franstrein
ArcEye,

Thanks for your answer and observation.
The on-board graphics card was indeed likely causing the large latency.
I changed to a old AGP Video card, and most times the latency is way back below 10,000 ns again.

Now I only need to install the software and configuration changes back into the Debian Wheezy version..

For a latest youtube movie of my setup, see


Thanks,
Frans

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