Re: DBT sentences

[Gary E. Miller]

Yo Владимир!

On Mon, 14 Jun 2021 22:46:09 +0300
Владимир Калачихин <v.kalachikhin@gmail.com> wrote:

> 14.06.2021 21:58, Gary E. Miller пишет:
> > What is command "?POOL;"?  
> 
> POLL of course, sorry.
> 
> > 
> > "POLL" returns the current state on that "DEVICE".  Since your
> > depth is only reported intermittently, most of the time POLL will
> > not return the depth.
> >   
> 
> "current state" must be the last existent value from timestamp, not 
> current.

Effectively the same thing.

> Else this behaviour makes POLL mode pointless.

I always thought so.  Never heard any suggestions, much less patches, to
do somthing "better".

> https://gpsd.gitlab.io/gpsd/gpsd_json.html#_poll speaks about caching 
> values -- it's reasonable.

Yes, cached for the current epoch.  As that link said:

    "Polling can lead to possibly surprising results when it is used
    on a device such as an NMEA GPS for which a complete fix has to be
    accumulated from several sentences."

And this is what you are seeing:

    "If you poll while those sentences are being emitted, the response
    will contain the last complete fix data and may be as much as one
    cycle time (typically 1 second) stale."

I see how that can be misleading.  It might be better said:

    "the current fix data do far in the cycle".


RGDS
GARY
---------------------------------------------------------------------------
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
        gem@rellim.com  Tel:+1 541 382 8588

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