Experimental Physics and
Industrial Control System

Benjamin Franksen via Core-talk <[email protected]> · Tue, 4 Dec 2018 17:57:15 +0100

Am 22.11.18 um 17:00 schrieb Ralph Lange:
> On Thu, 22 Nov 2018 at 16:13, Benjamin Franksen via Core-talk <
> [email protected]> wrote:
> 
>> Am 19.11.18 um 18:29 schrieb Johnson, Andrew N. via Core-talk:
>>> The CA protocol's channel name length is not limited by the size of the
>>> NAME field in the IOC.
>>
>> I am aware of that. Sorry for not expressing myself clearly.
>>
>>> Ben, what limitations are you trying to solve, and how do you know that
>>> they actually exist?
>>
>> Basically, the limit of 40 bytes on the DBR_STRING data type. Which in
>> turn implies a limit on the length of things you can put into link
>> field.
>>
> 
> I don't quite understand.
> Link fields have much wider limits: pushed to 128 then 256 chars in 3.15;
> unlimited in 7.0
> Setting those fields through CA is possible using the "long string" mode,
> i.e. by writing an array of char to the PV which gets a "$" suffix.
> 
> ralph@debian-testing:~$ caput -S ai.INP$
> this_is_an_extremely_long_string_that_still_can_be_written
> Old : ai.INP$
> New : ai.INP$ this_is_an_extremely_long_string_that_still_can_be_written
> NPP NMS
> 
> So: which use case is not solved by the currently available mechanisms?

Hm. I did not realize that this is possible now. Looks like there is no
longer any need for what I proposed. Good to know (and thanks for
everybody's patient explanations).

Cheers
Ben

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System