Re: Long String support in phoebus

["Nonn, Patrick via Tech-talk" <tech-talk at aps.anl.gov>]

Hi Andrew,

thanks for that. I tested the <pv_name>.$ syntax in phoebus, and it works there, as well.

Regards,

Patrick

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From: "Johnson, Andrew N." <anj at anl.gov>
To: "Johnson, Andrew N." <anj at anl.gov>
Cc: "Patrick Nonn" <patrick.nonn at desy.de>, "tech-talk" <tech-talk at aps.anl.gov>
Sent: Monday, 13 July, 2020 18:51:34
Subject: Re: Long String support in phoebus

Sorry I worded that reply badly, the field modifier of course comes after the (optional) field name. You can only omit the dot when you’re addressing the VAL field with no modifiers.

And of course CA clients should normally treat a channel name as an opaque string, since only the specific server knows how to parse it properly. Non-IOC servers using the PCAS or some other server library can use totally different syntax and semantics for names.

- Andrew

On Jul 13, 2020, at 11:25 AM, Johnson, Andrew N. via Tech-talk <tech-talk at aps.anl.gov> wrote:

Hi Patrick,

On Jul 13, 2020, at 4:08 AM, Nonn, Patrick via Tech-talk <tech-talk at aps.anl.gov> wrote:

I would like to clarify, that you have to address the VAL field of a PV specifically and add a $ to that. "caput -S <pv_name>$" will not work. (Because caput addresses <pv_name>$.VAL, that way.) The same is true for CSS, incl. phoebus. I'm mentioning that, because I actually found some old tech-talk entry before I started this thread, where it was also mentioned that you have to add a $ to the pv name, which did not work for that reason.

You can omit the VAL field name, but you must still include the dot which marks the end of the record name and tells the name lookup code that whatever follows is a field modifier. If there’s no field name after that modifier will apply to the default field (which is VAL at the moment but might not always be with new record types in future releases of EPICS). Thus “caget -S <pv_name>.$” will work for the lsi and lso record types.

- Andrew

Let me summarize, what to do, if your lso/lsi won't hold more than 40 characters:

- check the field SIZV, it defaults to 41 (=40 characters)
- check the environment variables EPICS_CA_MAX_ARRAY_BYTES and EPICS_CA_AUTO_ARRAY_BYTES
 For more information, check: https://epics.anl.gov/base/R3-16/1-docs/RELEASE_NOTES.html
- for caput/caget: make sure you use the -S option
- for caput/caget and CSS: Address the pv as <pv_name>.VAL$
- for CSS, incl. Phoebus: check the "max_array_bytes"-setting
- for CSS Phoebus: make sure to set the format property to "String"

Have I forgotten something?

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Complexity comes for free, simplicity you have to work for.

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Complexity comes for free, simplicity you have to work for.