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Re: [gpsd-dev] GPSd on FreeBSD

From: Gary E. Miller
Subject: Re: [gpsd-dev] GPSd on FreeBSD
Date: Tue, 10 Sep 2019 13:55:30 -0700

Yo Daniel!

On Tue, 10 Sep 2019 16:30:52 +0930
"O'Connor, Daniel" <address@hidden> wrote:

> >> Yes that is a red herring here, it should use time_pps_* on the
> >> dmtpps device node.  
> > 
> > If you understand the issue, then send a patch.  
> I understand what I want it to do, but I don't understand the
> internals of GPSd - I am trying to work it out but it's slow going.

Feel free to ask questions here.

> >>>> I'm unfamiliar with ppsapitest.  What does "ppscheck /dev/pps0"
> >>>> show?    
> >>> 
> >>> ppsapitest probably tests to the spec.  I'm assuming ppscheck is
> >>> from gpsd, and would test to what gpsd uses - of course quite
> >>> relevant here.    
> >> 
> >> Unfortunately as per my other email it doesn't build because it
> >> requires TIOMCIWAIT which FreeBSD doesn't have.  
> > 
> > Ah, yes, scons is not building due to no TIOMCIWAIT.  I thought that
> > had been fixed...  
> Looking at the ppscheck code it seems it only works with the
> TIOMCIWAIT ioctl so running it isn't useful for checking kernel PPS
> captures.

Yes, old news.  As the above snippet shows.

> > The FD of -2 is after the first failure.  The first failure is the
> > failure to open the device, which returned the error code of -2 in
> > place of an FD.  It does look like gpsd should not have continued
> > using the error return as an FD.  But the first failure was earlier
> > than you are looking.  
> There is no log message associated with the failure to open the
> device though.

Yes, there was, but I can't find that old log again.

> > Figure out what NTP is doing and let's see if we can get gpsd to do
> > similar on your distro.  
> NTP attempts to open /dev/gpspp0 and since it succeeds it uses that
> to get PPS info, it then opens /dev/gps0 and parse the NMEA.

Yes, at the simplesst level.  The devil is in the details.

> It would be good if I could pass gpsd my PPS source and it used it
> purely for PPS, however I don't know if that is possible (I think so
> though).

Just put it on the command line, as the doc shows:
        gpsd -n /dev/ttyS0 /dev/pps0

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

            Veritas liberabit vos. -- Quid est veritas?
    "If you can't measure it, you can't improve it." - Lord Kelvin

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