Re: [gpsd-users] GPS reporting wrong time to SHM

[Alexander Carver]

On 9/7/2012 05:23, Eric S. Raymond wrote:
> Alexander Carver <address@hidden>:
> > > I think the safest thing to do would be to document this as a known SiRF.
> > > firmware bug.  Can you identify the SiRF firmware version from the log?
> >
> > Yes, the receiver identifies the software as:
> >
> > Version 2.3.2-GSW2-2.05.024-C1Prod1.1
>
> Does this new FAQ entry match your experience?
>
> <h1 id="timelag2">Why is my GPS time off by exactly one second?</h1>
>
> <p>This can happen if (a) there has been a recent <a
> href="ftp://maia.usno.navy.mil/ser7/tai-utc.dat";>leap-second
> adjustment</a>, (b) you have a version of GPSD that was built before
> the adjustment, and (c) your GPS doesn't ship the current leap-second
> offset in a form GPSD can see.  If this happens, GPSD will fall back
> to a compiled-in default that is off by one</p>
>
> <p>Some SiRFs have a particularly insidious version of this.  They are
> supposed to ship a MID52 sentence (which GPSD knows how to interpret)
> containing the current leap-second offset.  But there is at least one
> firmware revision that ships a damaged version of MID52 with a garbled
> start sequence or a zero length field.  This GPSD cannot handle.</p>
>
> <p>The bad revision is 2.3.2-GSW2-2.05.024-C1Prod1.1; there may be
> others.  Suspect this if you have persistent off-by-one errors. If you
> are able to identify other bad firmeare versions, please let us
> know about it.</p>

That's pretty much it.

Out of curiosity, where in the code does gpsd pick up the messages from 
the serial port prior to sending it along to the giant switch switch 
statement in the SiRF driver?  I might tinker with the message collector 
and see if I can snag a broken MID 52.