How to test realtime in Classic Ladder

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12 Aug 2013 22:46 #37589 by nichis
I would like to demonstrate that realtime is working on a classic ladder project. Which kind of test could I do? I imagine I have to allocate a thread with a fast period before and with a very slow period after for seeing the difference; but is this a good way?

I have already done a program with a cosine signal (amplitude 2) generated using siggen and linking it to a classic ladder variable, if signal is <1 increment a counter, but i don't note difference between fast and slow thread..
Which kind of example could I create?

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13 Aug 2013 01:36 #37596 by cmorley
Do you have a scope? Scope the output pins and see it the wave form is correct.
What do you want to know about the fast and slow threads? which one is more on time?

I assume you know about the latency test but want to actually measure true output.

I haven't ever done this nor can recommend the best way, but it seems if you test the output independently from the computer, you will get the best idea.

Hopefully Peter from Mesa will chime in - I think he actually suggested this once and may have done it.

Chris M

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14 Aug 2013 20:22 #37665 by nichis

What do you want to know about the fast and slow threads? which one is more on time?

Yes, but now I think I was wrong, because fast or slow it is always realtime, instead i want to see the difference between realtime classic ladder and no-realtime..

The problem is that I can't use hal commands without realtime so I can't test classic ladder programs that use siggen or something similar without realtime, is right?
However if I do (for example) a program that uses TimerOn block I think it could be a way for seeing differences

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14 Aug 2013 21:41 #37666 by PCW
You can use hal without realtime (see the sim configs)
I've never tried using classic ladder without realtime
but other than not having any real I/O (well modbus might work)
I dont see offhand why it would not work

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14 Aug 2013 22:06 - 14 Aug 2013 22:07 #37671 by nichis

You can use hal without realtime (see the sim configs)



How? I don't find sim configs
Last edit: 14 Aug 2013 22:07 by nichis.

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14 Aug 2013 23:07 #37673 by PCW
You can either install a simulator only linuxcnc version, or if you have the linuxcnc sources
and dev environment setup, rebuild/reconfigure for simulator


wiki.linuxcnc.org/cgi-bin/wiki.pl?Instal...ng_LinuxCNC_realtime
(see section 2.10)

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