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Re: [gpsd-dev] RC for DRIFT message
From: |
Eric S. Raymond |
Subject: |
Re: [gpsd-dev] RC for DRIFT message |
Date: |
Mon, 23 Feb 2015 00:12:02 -0500 |
User-agent: |
Mutt/1.5.23 (2014-03-12) |
Gary E. Miller <address@hidden>:
> Or call it TOS (for Top of Second) as some will just use it to
> frame cycles.
I like it.
> > The question is when it should be emitted. Plausible candidate times
> > are:
> >
> > * When the first I/O from the report burst for a second is received.
>
> That first I/O would need to contain a verifiably valid timme stamp.
>
> So a GPRMC would work as it tells us the time and that the fix
> is valid.
I have cycle detection logic, so after the first full cycle I can set
a flag at the end of the report-ender sentence. I have to do that
anyway to ship the JSON reports, which go out at that time.
That implies that when I *next* get I/O I can note the clock time, and
as soon as I have valid GPS time I can ship a TOS report. This is
actually going to happen at the same time the unit-0 ntpshm report is
shipped, I think.
> The message is time stamped so a little delay ( < 1 Sec) probably
> acceptable. The problem is knowing when you are really done without
> having already seen the next second.
Like I said, there's sentence-cycle detection. Solved problem.
> > Which do you guys actually want? I would favor the second - it fits
> > into the existing logic better - but either will be relatively easy.
>
> My gut feel is ASAP. Chronyd can slew the system clock more than 8%,
> so the longer a report sits unsent the harder it is to calculate what
> an offset relative to old system time means relative to present system
> time.
This can be done. It won't even be hard.
--
<a href="http://www.catb.org/~esr/">Eric S. Raymond</a>
- [gpsd-dev] RC for DRIFT message, Eric S. Raymond, 2015/02/22
- Re: [gpsd-dev] RC for DRIFT message, Gary E. Miller, 2015/02/22
- Re: [gpsd-dev] RC for DRIFT message,
Eric S. Raymond <=
- Re: [gpsd-dev] RC for DRIFT message, Hal Murray, 2015/02/22
- Re: [gpsd-dev] RC for DRIFT message, Eric S. Raymond, 2015/02/23
- Re: [gpsd-dev] RC for DRIFT message, Hal Murray, 2015/02/23
- Re: [gpsd-dev] RC for DRIFT message, Eric S. Raymond, 2015/02/23
- Re: [gpsd-dev] RC for DRIFT message, Hal Murray, 2015/02/24
- Re: [gpsd-dev] RC for DRIFT message, Eric S. Raymond, 2015/02/24
- Re: [gpsd-dev] RC for DRIFT message, Hal Murray, 2015/02/25
- Re: [gpsd-dev] RC for DRIFT message, Gary E. Miller, 2015/02/25
- Re: [gpsd-dev] RC for DRIFT message, Eric S. Raymond, 2015/02/26
- Re: [gpsd-dev] RC for DRIFT message, Gary E. Miller, 2015/02/23