Re: [gpsd-dev] More on Venus PPS off by a second

[Gary E. Miller]

Yo Hal!

On Mon, 01 Feb 2016 17:23:35 -0800
Hal Murray <address@hidden> wrote:

> It's working now.  I don't know if I did anything (like restart gpsd
> or ntpd) to tickle the switch.

Fingers crossed.

> At the same time that the PPS timing shifted from 1 second off to
> good, the serial shifted from off b 600 ms to off by 250 ms.  They
> are off in the same direction as the PPS is off when it is off by a
> second.

Odd.

> After 15 minutes, the serial shifted back to 600 ms off and the PPS
> stayed good.

Yeah, as the satellite geometry changes the time to compute the fix
changes and taht adds variable delay to the start of the next fix output.

> Is gpsmon a good way to get data when chasing this sort of problem?

Not as much data as a -D 7, but a fair overview.

> Visually, gpsmon pauses for a bit after the GPVTG.  There is a tiny
> pause after the PPS line.  The timing seemed the same yesterday when
> it was off by a second.

Yeah, that is expected, and good.  That means the GPS can output all the
current second's data before the next PPS comes.  When the serial line
is too slow, the output backs up, and things fall apart.

RGDS
GARY
---------------------------------------------------------------------------
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
        address@hidden  Tel:+1 541 382 8588

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