Re: PPS fix determination vs. cgps?

[Steve Bourland]

Yo Gary!
  I suck, sorry I never finished off this thread...it's been a frustrating 
experience...

On Fri, 22 Jan 2021, gpsd-users-request@nongnu.org wrote:

>   2. Re: PPS fix determination vs. cgps? (Gary E. Miller)
> ------------------------------
>
> Message: 2
> Date: Fri, 22 Jan 2021 09:56:42 -0800
> From: "Gary E. Miller" <gem@rellim.com>
> Subject: Re: PPS fix determination vs. cgps?
>
> > > Looks like you are sending GPRMC, GPGSA and GPGSV every cycle.  That
> > > is not normal.  The Garmin, and most other receivers, do not compute
> > > GSV every fix, so sending it every fix is a waste.  Maybe that is
> > > confusing the cycle ender.
> > >
> > > BTW, what is your serial port speed? 
> >
> > 4800 baud....happy to see if I can speed that up if the Garmin will
> > do it...but feel like years ago I looked into it and in NMEA mode,
> > 4800 is the max output speed?  Will investigate.
>
> The Garmin 18 will do up to 19,200.  The 5Hz will got to 38,400.
>
> 4,800 is marginal, especially when sky view is output every second.
>
> gpsctl can change the speed for you, but it is a bit finicky.

I tried to get gpsctl to change the speed, but on this particular unit, it 
would always override my garmin driver selection when it saw the NMEA 
coming out and fail to send any commands.  In the mean time, I have 
another Garmin 18 that started acting flaky on me, so I have succumb to 
your very sage original advice...and am working on retiring them.  Your 
post today with this link:
http://www.leobodnar.com/shop/index.php?main_page=product_info&cPath=107&products_id=301
triggered my memory that I hadn't let you know that I have broken down and 
ordered two of these:
http://www.leobodnar.com/shop/index.php?main_page=product_info&products_id=272
to keep my offline network on time and my machines synced.  Assuming these 
guys work well, I intend to get some at least one more down the road to 
make sure there are no issues with selection (enough sources).

> You can use -x, with effort.  force the driver with -t.  Odd that the
> device was not detected as a Garmin.

I thought about going into the code to try and override the override of 
the detection loop, but realized that would really just postpone the 
inevitable failure of the devices...they've been working for well over a 
decade, so I feel they've done their duty.

> We never finish anything here, just steps forward.

As always, truly appreciate the steps forward you keep making, and I still 
have some Garmins lying around, so if you want me to help testing future 
code and future Ubuntu releases, more than happy to help as best I can.

> Or, spend $10 on a modern GPS.  The Garmin 18 are ancient.  Barley
> functional my modern standards.

Well, I'm spending a bit more to get the full time server included.  I'll 
look at picking up some cheap units over the next few months for testing 
if it's helpful to you.  If you have units you'd prefer me to look for, 
feel free to ping me and let me know!
                                        Thanks,
                                          Steve