On 2013-08-14, Mark C. Stephens <[email protected]> wrote: > Good on you David and welcome back to 2013. > I do hope that some official changes are made to refclock_nmea to catch this > receiver bug and process it accordingly. > There are a lot of folks stranded in 1993. > > --marki > > -----Original Message----- > From: [email protected] > [mailto:[email protected]] On Behalf Of > David Malone > Sent: Wednesday, 14 August 2013 5:30 AM > To: [email protected] > Subject: Re: Start of new GPS 1024 week epoch > > Magnus Danielson <[email protected]> writes: > >>Remember that any Sunday, it is likely that a GPS reciever have slipped >>a multiple of 1024 weeks. NTP drivers should be able to recognice it >>and compensate for it, as it is a re-occuring bug in many recievers. > >>This issue have been discussed over and over again at time-nuts.
Surely if the receiver is delivering the wrong date, it is the receiver manufacturer that needs to make the changes, not ntp, including sending you a new receiver if necessary. Warrenty limits notwithstanding, this fails that "fitness for purpose" test, and you could hardly have detected it when you bought it. > > It seems my ancient GPSclock 200 has recently slipped back to December 1993 > too. Resetting it hasn't helped and I doubt I will be able to do a firmware > update, so I've made a hack to refclock_nmea.c (version ntp-4.2.6p5), by > replacing: > > reftime.l_ui += caltontp(&date); > > with > > reftime.l_ui += caltontp(&date); > while (reftime.l_i + 512*7*86400 < rd_timestamp.l_i) > reftime.l_i += 1024*7*86400; > > I'm trying to adjust the timestamp given by NMEA might be slow by some > multiple of 1024 weeks, and so tries to adjust it so that it is reasonably > close to the system time associated with the read of the NMEA data. I'm not > sure if I've got the code exactly bang-on, but it has got ntp running with > the unit again. Except of course if the rd_timestamp.l_i is way out (that is why one would want to use a gps clock to fix it-- eg on bootup with the Raspberry Pi say), > > David. > > _______________________________________________ > questions mailing list > [email protected] > http://lists.ntp.org/listinfo/questions _______________________________________________ questions mailing list [email protected] http://lists.ntp.org/listinfo/questions
