> -----Original Message-----
> From: bari [mailto:bari00...@gmail.com]
> Sent: December-16-19 10:51 AM
> To: emc-users@lists.sourceforge.net
> Subject: Re: [Emc-users] Latency Warning Messages
>
> It depends on how you configure and run Linuxcnc with your intended
> hardware.
>
> In the .INI file there is a section EMCMOT
> http://linuxcnc.org/docs/2.6/html/config/ini_config.html#sub:EMCMOT-
> section
>
> The settings you place in BASE_PERIOD and SERVO_PERIOD set the length of
> each of these task periods for Linuxcnc.
>
> BASE_PERIOD = 50000 - the Base task period in nanoseconds.
>
> SERVO_PERIOD = 1000000 - This is the "Servo" task period in nanoseconds.
>
> If either thread run by the processor takes longer than the times in
> these settings you will see a latency message for it taking too long.
> This can be caused by things like trying to step too quickly (moving the
> motors faster) using the base period with a LPT port or by using too low
> a setting for the task periods to begin with based on your hardware and
> BIOS settings.
>
> How to choose your base period:
> http://wiki.linuxcnc.org/cgi-bin/wiki.pl?TweakingSoftwareStepGeneration
>
> The reason that you stopped having the latency messages when you
> changed
> from software stepping on the LPT port to hardware stepping on the MESA
> 7i92H is that you changed from using the Base Period (very short, fast)
> to the Servo Period (much slower) from the CPU's perspective. This
> allows you to use a PC with longer latency or higher jitter.
>
> On 12/16/19 12:03 PM, John Dammeyer wrote:
> > That's what I've found. When I run the test software to determine
> machine latency the on board video provides the smallest number. Any of
> the add on boards I tried all gave much worse numbers.
For example. The board in the machine at the moment generates a Servo Jitter
of 33217 and Base Jitter of 131983.
For the MESA and PP configuration I have:
BASE_PERIOD = 24000
SERVO_PERIOD = 1000000
If I understood the document link above correctly I should have set the base to
at least 132000 which would limit my step rate to about 3kHz. The video board
is a ow profile card that has a DVI connector out and can run to two VGA
monitors. Really just designed for desktop PC's that need multiple monitors to
display government forms or whatever. The Lenovo PC and card came from the
government surplus.
Now if I remove the video card and run the latency test for the on board video
I get a Servo Jitter of 351232 and Base Jitter of 418333.
Setting the .ini BASE_PERIOD to 420,000 results in no longer getting the
initial servo message. Of course now step rates are so severely restricted
that jog on the X axis results in an immediate following error.
I believe that the DC Servos are more forgiving if the step pulses are
occasionally held back since the internal step counter is compared against the
encoder counter and a following error fault by the motor only happens if it
reads more encoder counts than received on the step input. Probably why with
the video board installed and the initial error that I don't get faults.
And none of that is an issue with the MESA card.
John
> >
> > Also, if I understand how this works, if the fastest speed required for
> stepping is not to high then you won't get the messages. But if your step
> rates are up into 50kHz and higher then you get that warning once when you
> start up LinuxCNC.
> >
> > But I may have it all wrong. For my current testing I get that message
> when I use the parallel port but it doesn't appear to affect the step rates to
> the drives. I just dispose of the message. But that's because I don't care
> at
> the moment. I'll switch to the MESA once the testing and development is
> done.
> >
> > John
> >
> >> -----Original Message-----
> >> From: N [mailto:nicklas.karlsso...@gmail.com]
> >> Sent: December-16-19 9:38 AM
> >> To: Enhanced Machine Controller (EMC)
> >> Subject: Re: [Emc-users] Latency Warning Messages
> >>
> >>> I bought 3 different low profile video cards to try and get rid of that
> latency
> >> message. The ultimate and best solution was to buy the MESA 7i92H.
> Does
> >> away with the parallel port completely.
> >>> John Dammeyer
> >> The parrallel port cause latency messages?
> >>
> >>
> >> _______________________________________________
> >> Emc-users mailing list
> >> Emc-users@lists.sourceforge.net
> >> https://lists.sourceforge.net/lists/listinfo/emc-users
> >
> >
> > _______________________________________________
> > Emc-users mailing list
> > Emc-users@lists.sourceforge.net
> > https://lists.sourceforge.net/lists/listinfo/emc-users
>
>
>
> _______________________________________________
> Emc-users mailing list
> Emc-users@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/emc-users
_______________________________________________
Emc-users mailing list
Emc-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/emc-users
