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| <== Date ==> | <== Thread ==> |
|---|
| Subject: | Re: Simple binary input question about RVAL? |
| From: | Rolf Keitel via Tech-talk <tech-talk at aps.anl.gov> |
| To: | "Feister, Scott" <scott.feister at csuci.edu>, tech-talk <tech-talk at aps.anl.gov> |
| Date: | Wed, 11 Aug 2021 12:40:40 -0700 |
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?CAUTION: This email originated from outside of CSUCI. Do not click links or open attachments unless you validate the sender and know the content is safe. Contact ITS if you have any concerns
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:
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