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

From: Eric S. Raymond
Subject: Re: [gpsd-users] GPS reporting wrong time to SHM
Date: Fri, 7 Sep 2012 08:23:15 -0400
User-agent: Mutt/1.5.21 (2010-09-15)

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
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>
                <a href="";>Eric S. Raymond</a>

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