Re: [gpsd-dev] Urgent: Need a fix for this weird GPSD behaviour...

[Gary E. Miller]

Yo address@hidden

On Tue, 21 Jul 2015 14:55:42 -0400
<address@hidden> wrote:

> Didn’t get any response to my last email…

Well, you tend to get what you pay for.

> As we drove along, we compared the values of our C++ code which uses
> libgpsmm.h with the values displayed using both CGPS and XGPS  on
> Raspbian Raspberry Pi B+. (All three applications were running at the
> same time on the same unit using the same GPS receiver.)

If cgps is showing you good results then clearly your program C++ code is bad

> It’s as if “read()” takes the values out of a FIFO that our code
> would not “unstack” fast enough.

Not much we can say without seeing your code.

> Again, I need to remind you that I installed GPSD following
> <http://www.instantsupportsite.com/self-help/raspberry-pi/raspberry-globalsat-353s4-install/>
> this tutorial and that following the step of editing the file
> “/lib/udev/gpsd.hotplug”,

We can only support our own RasPi howto.

A quick look at the page shows they fail to use the absolutely essential
'-n' option to gpsd.  I hope you added that already.

Unrelated to your problem, but the 353-s4 has pretty bad sensitivity, you
should instead use a SiRF 3 or ublox if you can.


> the dates that the GPS outputs through
> CGPS, XGPS and our own application is no longer 2015…. But 1995… !!!
> Don’t know if this could be connected to our issue.

You will not get a good fix until the date is good.  If you see 1995 then 
you have lost your ephmeris and almanac and you need to wait
30 minutes until it is reacquired.

> We had to make this editing of the file “/lib/udev/gpsd.hotplug”
> because without this, gpsd was starting as a service but it was
> failing at connecting to the socket...

I'm not sure why you feel you need the socket at all.

> We were forced to killall the
> gpsd process and restart it manually.

Yes, the RasPis daemon setup is known bad.

> Only then were the XGPS and
> CGPS applications able to work properly and the dates were the
> current 2015 ones. Now gpsd starts as a service at boot time but the
> date is 1995.

The RasPi service config for gpsd is known bad, dont use it.

Does your GPS have a battery in it?  Many RasPi GPS do not, thus they
lose the ephemeris and almanac on a power cycle.  Requiring up to 30 mins
to reacquire.

> See previous email below for a clear description of our code. (Note
> that we do not use the wait function provided by libgpsmm.h… we
> rather use a QTimer instance which is part of the QT UI lib we need
> to use for our application.)

Well, that would also be a problem. Don't try to rewrite the gpsd library 
until you know how it works.

RGDS
GARY
---------------------------------------------------------------------------
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
        address@hidden  Tel:+1(541)382-8588

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