Experimental Physics and
Industrial Control System

Hi Scott,

If you want to get the underlying 0,1,   use caget -n isfishy   (type caget -h for on-line help).

As your records have no DTYP field set, they use the "Soft Channel" device support. In that case no conversions between raw values and engineering values happen. The RVAL field is not used by the record.

HTH - rolf -

P.S.: You are using very old EPICS documentation. Which release are you working with?

As a follow-up: Given that VAL is a string in this case, how can we retrieve the underlying boolean value of 0 or 1?

Thanks!

Scott

---

From: Tech-talk <tech-talk-bounces at aps.anl.gov> on behalf of Feister, Scott via Tech-talk <tech-talk at aps.anl.gov>
Sent: Wednesday, August 11, 2021 11:54 AM
To: tech-talk at aps.anl.gov <tech-talk at aps.anl.gov>
Subject: Simple binary input question about RVAL?

 

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Hi EPICS users,

 

This is a very basic question regarding getting started with binary inputs, and the purpose of RVAL. (As an aside, perhaps we should anyone provide an example for a binary input (bi) similar to the “temperature:water” (ai) example from the Getting Started guide under “Test EPICS”, at:

https://docs.epics-controls.org/projects/how-tos/en/latest/getting-started/installation.html#test-epics

 

My students and I have been struggling to get a simple binary input working, though I think we’ve got it now. We first tried expanding, in the above Getting Started tutorial, the “test.db” script with:

 

test.db:

“””

record(ai, "temperature:water")

{

    field(DESC, "Water temperature in the fish tank")

}

record(bi, "isfishy")

{

    field(DESC, "True if the fish tank has fish inside.")

}

“””

 

However, “caget isfishy” shows a blank value, and “caput isfishy 0” does not seem to change anything. This perplexed us for a while.

 

Looking into it further in the user docs, we landed at documentation for the binary input record: https://epics.anl.gov/EpicsDocumentation/AppDevManuals/RecordRef/Recordref-11.html

 

Then, we tried modifying ZNAM and ONAM such as

test.db:

“””

record(bi, "isfishy")

{

    field(DESC, "True if the fish tank has fish inside.")

    field(ZNAM, "False")

    field(ONAM, "True")

}

“””

 

And now we can do “caput isfishy 1” and all “caget isfishy” prints with “True”, as does “caget isfishy.VAL”. However, I noticed that “caget isfishy.RVAL” still gives 0. So here’s my question: Is this zero in RVAL expected even though the Boolean is now True, and why? Thanks!

 

Scott

References:

Simple binary input question about RVAL? Feister, Scott via Tech-talk

Re: Simple binary input question about RVAL? Feister, Scott via Tech-talk

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