Experimental Physics and
Industrial Control System

"Johnson, Andrew N. via Core-talk" <[email protected]> · Tue, 4 Dec 2018 19:06:00 +0000

Hi Ben,

It would be nice if the sequencer could support long strings. I haven't
tried to see what's possible at the moment, and I'm not suggesting you
should try to change the definition of the string type because that
would break existing programs, but maybe adding a new type or an option
to allow strings to be longer than 40 might be a possibility...

- Andrew

On 12/4/18 10:57 AM, Benjamin Franksen via Core-talk wrote:
> 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
>

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Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System