CODESYS - the IEC 61131-3 automation software

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PostPosted: Wed Dec 13, 2017 10:49 am 
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Joined: Mon Nov 09, 2015 10:59 am
Posts: 2
After a few days of running/powering on, I have started seeing the following exception occurring on one or two of the 11 Raspberry Pi's I am testing:

*EXCEPTION* [OmittedCycle watchdog] occurred: App=[Application], Task=[Task_HighSpeed] in the CmpIecTask component.

Attachment:
exception.jpg


I cannot find any reference to what "OmittedCycle watchdog" is. I have searched the Codesys help, fulltext search through the library manager checking any relevant library/components, Googled every combination I can think of and the only reference I can find to OmittedCycle is the following release notes:

Attachment:
2017-12-13 20_24_31-CODESYS.png


I log into the PLC and find it has stopped with that error. I do not have a screenshot of the Task Configuration monitor page but I will next time it occurs. Checking the Task Configuration monitor page shows the max cycle time for that task is well below the watchdog time set for it. Looking at the Task Configuration monitor in the attached screenshot, this currently running fine Pi's max cycle time did hit 3.3ms but is still running fine.

I have included screenshots of the current tasks configurations. Every few days (2 or 3) I will have a random Pi stop. Restarting the codesyscontrol runtime or a Reset Warm and a Start will get it going again.

Does anyone know where I can find more information on this exception?


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PostPosted: Fri Dec 15, 2017 11:05 pm 
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Joined: Mon Nov 09, 2015 10:59 am
Posts: 2
After some discussions with Edwin, this is one possible solution should you not need realtime:

/etc/CODESYSControl_User.cfg

[CmpSchedule]
ProcessorLoad.Enable=1
ProcessorLoad.Maximum=95
ProcessorLoad.Interval=5000
DisableOmittedCycleWatchdog=1


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PostPosted: Sun Dec 17, 2017 9:29 am 
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Joined: Mon Dec 13, 2010 3:02 pm
Posts: 43
Just to lit the fog a bit.

The high speed task is configured to 1ms. And the cycle time which has been shown in the monitor is much higher. This is what has been detected by the "omitted cycle watchdog".

The simple reason can be that you need an rt preempt patched kernel if you have such high timing constraints. If your timing requirements are more weak it might be enough to disable the task watchdog. AFAIK the omitted cycle is only detected when the task watchdog is enabled.

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