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Re: [gpsd-dev] RC for DRIFT message

From: Greg Troxel
Subject: Re: [gpsd-dev] RC for DRIFT message
Date: Sun, 22 Feb 2015 18:00:19 -0500
User-agent: Gnus/5.130006 (Ma Gnus v0.6) Emacs/24.4 (berkeley-unix)

address@hidden (Eric S. Raymond) writes:

> I think top of the agenda for the next cycle is the additional report
> that Gary and Hal want for time service.  This, as I understand it,
> should do for in-band time reporting what the PPS message does for
> PPS - that is, report the offset between in-band GPS time and the
> system clock.
> Almost everything about this feature is easy to specify.  We can call
> it DRIFT or CLOCKDRIFT and it can have the same members PPS does -
> second and nanosecond parts for real (GPS) and CPU clock time.

"drift" implies frequency error.   This is a phase error, or an offset.
So call it "clockoffset" or something. 

> * When the first I/O from the report burst for a second is received.
> * When the report burst for a second is done and the other reports
>  are omitted.
> Which do you guys actually want? I would favor the second - it fits
> into the existing logic better - but either will be relatively easy.

I don't think it matters, as long as it's close enough to when it was
measured to not cause trouble.    The output should contain

  system clock at time of meaurements
  gps time - system clock (at above time)

more or less.

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