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List:       gpsd-users
Subject:    Re: [Gpsd-users] NovAtel OEM-V3 & gpsd --> 1PPS problem & NMEA
From:       "Gary E. Miller" <gem () rellim ! com>
Date:       2011-08-25 15:20:02
Message-ID: alpine.LNX.1.00.1108250816320.11898 () catbert ! rellim ! com
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Yo Wouter!

On Thu, 25 Aug 2011, Wouter Pelgrum wrote:

> I'm trying to use gpsd to synchronize my data collection computer to UTC

Should be no problem.

> GPSD is receiving the 1PPS but doesn't accept it:
>
> gpsd: GPS on /dev/ttyS0 is offline (0.000297 sec since data)
> gpsd: PPS cycle: 999923, duration: 998948 @ 1314283636.990037
> gpsd: PPS cycle: 999925, duration: 977 @ 1314283636.991014
> gpsd: PPS pulse rejected

Yep, that is what it is supposed to do.  Notice that you only have 2
cycles after turning on the GPS?  The GPS needs WAY more time than that
to get a good lock.

You need to run gpsd with the -n flag so that the GPS is kept running
all the time.  And you need to get a newer version of gpsd, yours looks
old.

> My guess is that GPSD doesn't like a 1ms pulse...

Nope.  Your trace shows gpsd read the pulse just fine.

>  - Is this the case? What are the requirements of the 1PPS pulse for GPSD?

Pretty much anything you can throw at a serial port will work.

> Another question:
> - What NMEA messages are needed to have GPSD working correctly with NTP?
> GPGGA, GPZDA ?

You do not even need NMEA, you just need a complete time, date and year.

RGDS
GARY
- ---------------------------------------------------------------------------
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97701
	gem@rellim.com  Tel:+1(541)382-8588

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