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Re: [gpsd-dev] Meaning of negative PPS offset?
From: |
Gary E. Miller |
Subject: |
Re: [gpsd-dev] Meaning of negative PPS offset? |
Date: |
Tue, 26 Aug 2014 13:21:53 -0700 |
Yo Greg!
On Tue, 26 Aug 2014 15:52:46 -0400
Greg Troxel <address@hidden> wrote:
>
> "Gary E. Miller" <address@hidden> writes:
>
> >> which is I think what you are saying. So the bug is that in
> >> cases we are saying.
> >>
> >> n - N = -40ms
> >
> > Which makes no sense. The NMEA at time X never preceeds the PPS
> > for time X.
>
> As I understand it, this discussion is happening because of a device
> which is sending NMEA in advance of the PPS edge.
I finally got that far back in my email. The GR-601W, which has a known
kernel driver glitch. It should be special cased as it is kernel driver
specific. No other known USB device, of any driver, support PPS.
> >> Or perhaps even to only capture PPS when it's within 200 ms
> >> of the system clock.
> >
> > Which fails for older and slower GPS.
>
> I meant system clock, not NMEA.
So did I.
> So it would work when the device was
> synced via NTP coarsely.
Which was removed as a contraint with the latest patches.
> (I didn't quote most of your message, because I basically am in
> agreement with it - I knew my example times were not really quite
> right, but that they weren't critical to the point.)
Fair enough, except similar constants have been tried in the code
and failed, so best to be explicit they are WAGs.
> So the real issue is to find out if this device that seems to have
> premature NMEA really does do that.
GR-601W, which I have right here.
RGDS
GARY
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Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97701
address@hidden Tel:+1(541)382-8588
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- [gpsd-dev] Meaning of negative PPS offset?, Eric S. Raymond, 2014/08/26
- Re: [gpsd-dev] Meaning of negative PPS offset?, Greg Troxel, 2014/08/26
- Re: [gpsd-dev] Meaning of negative PPS offset?, Miroslav Lichvar, 2014/08/26
- Re: [gpsd-dev] Meaning of negative PPS offset?, Eric S. Raymond, 2014/08/26
- Re: [gpsd-dev] Meaning of negative PPS offset?, Eric S. Raymond, 2014/08/26
- Re: [gpsd-dev] Meaning of negative PPS offset?, Gary E. Miller, 2014/08/26
- Re: [gpsd-dev] Meaning of negative PPS offset?, Eric S. Raymond, 2014/08/26
Re: [gpsd-dev] Meaning of negative PPS offset?, Gary E. Miller, 2014/08/26
Re: [gpsd-dev] Meaning of negative PPS offset?, Hal Murray, 2014/08/26
Re: [gpsd-dev] Meaning of negative PPS offset?, Miroslav Lichvar, 2014/08/27