refclock 28 gone wacky on me

Fri Jun 10 02:04:14 UTC 2016

Yo Mike!

Back on list since I think I see a real problem here.

On Thu, 9 Jun 2016 21:41:32 -0400
Mike <bellyacres at gmail.com> wrote:

> On 06/09/2016 09:26 PM, Gary E. Miller wrote:
> > Yo Mike!
> >
> > On Thu, 9 Jun 2016 21:22:29 -0400
> > Mike <bellyacres at gmail.com> wrote:
> >  
> >> On 06/09/2016 09:03 PM, Gary E. Miller wrote:
> >> Hmm.  And do you see two timestamps a second or just one?
> >>
> >> How about you just send me 10 sconds of output?  
> If I'm reading this output right I see two timestamps each second.
> GPGGA and GPRMC
> 
> root at rpi-ticker:/home/mike# cat /dev/gpsd0
> $GPGGA,013525.940,4053.2374,N,08231.2681,W,1,05,1.7,409.2,M,-33.9,M,,0000*6E
> $GPGSA,A,3,25,19,05,02,12,,,,,,,,3.2,1.7,2.7*3B
> $GPGSV,3,1,12,02,72,009,22,05,57,208,30,12,42,237,25,25,36,285,22*71
> $GPGSV,3,2,12,06,34,071,05,19,26,127,21,29,23,312,19,09,19,053,*77
> $GPGSV,3,3,12,20,12,223,19,23,03,031,,17,02,131,,13,00,167,*75
> $GPRMC,013525.940,A,4053.2374,N,08231.2681,W,000.0,231.7,100616,,,A*73
> $GPVTG,231.7,T,,M,000.0,N,000.0,K,A*0A
> $GPGGA,013526.940,4053.2374,N,08231.2681,W,1,05,1.7,409.2,M,-33.9,M,,0000*6D
> $GPGSA,A,3,25,19,05,02,12,,,,,,,,3.2,1.7,2.7*3B
> $GPGSV,3,1,12,02,72,009,22,05,57,208,30,12,42,237,25,25,36,285,22*71
> $GPGSV,3,2,12,06,34,071,05,19,26,127,21,29,23,312,19,09,19,053,*77
> $GPGSV,3,3,12,20,12,223,20,23,03,031,,17,02,131,,13,00,167,*7F
> $GPRMC,013526.940,A,4053.2374,N,08231.2681,W,000.0,231.7,100616,,,A*70
> $GPVTG,231.7,T,,M,000.0,N,000.0,K,A*0A
> $GPGGA,013527.940,4053.2374,N,08231.2681,W,1,06,1.3,409.2,M,-33.9,M,,0000*6B
> $GPGSA,A,3,25,19,05,02,06,12,,,,,,,2.9,1.3,2.6*32
> $GPGSV,3,1,12,02,72,009,22,05,57,208,30,12,42,237,25,25,36,285,22*71
> $GPGSV,3,2,12,06,34,071,10,19,26,127,21,29,23,312,19,09,19,053,*73
> $GPGSV,3,3,12,20,12,223,20,23,03,031,,17,02,131,,13,00,167,*7F
> $GPRMC,013527.940,A,4053.2374,N,08231.2681,W,000.0,231.7,100616,,,A*71
> $GPVTG,231.7,T,,M,000.0,N,000.0,K,A*0A
> $GPGGA,013528.940,4053.2374,N,08231.2681,W,1,05,1.7,409.2,M,-33.9,M,,0000*63
> $GPGSA,A,3,25,19,05,02,12,,,,,,,,3.2,1.7,2.7*3B
> $GPGSV,3,1,12,02,72,009,22,05,57,208,30,12,42,237,25,25,36,285,22*71
> $GPGSV,3,2,12,06,34,071,09,19,26,127,20,29,23,312,19,09,19,053,*7A
> $GPGSV,3,3,12,20,12,223,20,23,03,031,,17,02,131,,13,00,167,*7F
> $GPRMC,013528.940,A,4053.2374,N,08231.2681,W,000.0,231.7,100616,,,A*7E
> $GPVTG,231.7,T,,M,000.0,N,000.0,K,A*0A
> $GPGGA,013529.940,4053.2374,N,08231.2681,W,1,05,1.7,409.2,M,-33.9,M,,0000*62
> $GPGSA,A,3,25,19,05,02,12,,,,,,,,3.2,1.7,2.7*3B
> $GPGSV,3,1,12,02,72,009,22,05,57,208,30,12,42,237,25,25,36,285,22*71
> $GPGSV,3,2,12,06,34,071,08,19,26,127,21,29,23,312,19,09,19,053,*7A
> $GPGSV,3,3,12,20,12,223,21,23,03,031,,17,02,131,,13,00,167,*7E
> $GPRMC,013529.940,A,4053.2374,N,08231.2681,W,000.0,231.7,100616,,,A*7F
> $GPVTG,231.7,T,,M,000.0,N,000.0,K,A*0A
> $GPGGA,013530.940,4053.2374,N,08231.2681,W,1,05,1.7,409.2,M,-33.9,M,,0000*6A
> $GPGSA,A,3,25,19,05,02,12,,,,,,,,3.2,1.7,2.7*3B
> $GPGSV,3,1,12,02,72,009,22,05,57,208,30,12,42,237,25,25,36,285,22*71
> $GPGSV,3,2,12,06,34,071,12,19,26,127,21,29,23,312,20,09,19,053,*7B
> $GPGSV,3,3,12,20,12,223,21,23,03,031,,17,02,131,,13,00,167,*7E
> $GPRMC,013530.940,A,4053.2374,N,08231.2681,W,000.0,231.7,100616,,,A*77
> $GPVTG,231.7,T,,M,000.0,N,000.0,K,A*0A
> $GPGGA,013531.940,4053.2374,N,08231.2681,W,1,05,1.7,409.2,M,-33.9,M,,0000*6B
> $GPGSA,A,3,25,19,05,02,12,,,,,,,,3.2,1.7,2.7*3B
> $GPGSV,3,1,12,02,72,009,22,05,57,208,30,12,42,237,25,25,36,285,22*71
> $GPGSV,3,2,12,06,34,071,11,19,26,127,20,29,23,312,20,09,19,053,00*79
> $GPGSV,3,3,12,20,12,223,21,23,03,031,,17,02,131,,13,00,167,*7E
> $GPRMC,013531.940,A,4053.2374,N,08231.2681,W,000.0,231.7,100616,,,A*76
> $GPVTG,231.7,T,,M,000.0,N,000.0,K,A*0A
> $GPGGA,013532.940,4053.2374,N,08231.2681,W,1,05,1.7,409.2,M,-33.9,M,,0000*68
> $GPGSA,A,3,25,19,05,02,12,,,,,,,,3.2,1.7,2.7*3B
> $GPGSV,3,1,12,02,72,009,22,05,57,208,30,12,42,237,25,25,36,285,22*71
> $GPGSV,3,2,12,06,34,071,09,19,26,127,20,29,23,312,19,09,19,053,00*7A
> $GPGSV,3,3,12,20,12,223,20,23,03,031,,17,02,131,,13,00,167,*7F
> $GPRMC,013532.940,A,4053.2374,N,08231.2681,W,000.0,231.7,100616,,,A*75
> $GPVTG,231.7,T,,M,000.0,N,000.0,K,A*0A
> $GPGGA,013533.940,4053.2374,N,08231.2681,W,1,05,1.7,409.2,M,-33.9,M,,0000*69
> $GPGSA,A,3,25,19,05,02,12,,,,,,,,3.2,1.7,2.7*3B
> $GPGSV,3,1,12,02,72,009,22,05,57,208,30,12,42,237,25,25,36,285,21*72
> $GPGSV,3,2,12,06,34,071,08,19,26,127,20,29,23,312,19,09,19,053,00*7B
> $GPGSV,3,3,12,20,12,223,20,23,03,031,,17,02,131,,13,00,167,*7F
> $GPRMC,013533.940,A,4053.2374,N,08231.2681,W,000.0,231.7,100616,,,A*74
> $GPVTG,231.7,T,,M,000.0,N,000.0,K,A*0A

Yes, one GPGGA and one GPRMC each second, but they are both for the
same fix, one fix per second, always ending in 0.940.

That is bad.

gpsd assumes that the fix data for each second starts to arrive just
after the beginning of the second.  But yours starts so close to the end
of the second that data will still be spilling into the next second, before
anything is computed.

Some of your lines are 78 chars long.  At 9600 each char takes 0.001
seconds.  78 chars is 0.078 seconds.  So even if the GPGGA is started
at exactly 0.940 into the second, the sentence can not be received, and
checksum checked, before the next second starts.  0.940 + 0.078 is 1.018
seconds.

gpsd may then pair the PPS with the wrong second.  Which is the sypmtom
you see.

Groan...  I'm gonna have to sleep on this one...

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