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Subject: | Re: LabView interface to EPICS |
From: | Dirk Zimoch <[email protected]> |
To: | [email protected] |
Date: | Fri, 20 Sep 2013 13:48:08 +0200 |
Hi Emmanuel,I have tried EPICS on cRIO but I am not satisfied with it. I do not like that neither alarms nor time stamps are forwarded to EPICS. LabView and EPICS communicate through a shared memory region which contains only values and is processed by both sides with independent cycle rates.
So when your EPICS record is scanned ".1 second", you get a new timestamp every 100 msec. But that does not mean that LabView has updated the value in the meantime. Not even dream of "I/O Intr" processing whenever LabView writes a new value.
Worse is that alarms are not handled. I looked into the LabView EPICS VI and found that in fact if it gets an error input, it skips writing into the shared memory! That means if something goes wrong on the LabView side (e.g broken hardware) EPICS happily reads the last good value and updates its timestamps. In my opinion the worst way you can deal with faults.
I reported these problems to NI a long time ago. But since they seen not able to do anything about this, I cancelled all NI related projects.
Dirk On 19.09.2013 22:26, Emmanuel Mayssat wrote:
All, While investigating high-level framework for EPICS, I came across the following page http://digital.ni.com/public.nsf/allkb/BEF3C387D96E1A0C86257A3600508278 Is any one using LabView with EPICS? What are the benefit of such a setup? What are the drawbacks? Regards, -- Emmanuel