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Re: [gpsd-users] PPS from kernel into gpsd

From: Tomalak Geret'kal
Subject: Re: [gpsd-users] PPS from kernel into gpsd
Date: Wed, 04 Apr 2012 21:43:25 +0100

Ah; I saw an example with .1 where the actual device path was given later with the 'pps' directive in /etc/ntp.conf. I've changed to .0 which must be closer.. many thanks for that.

The result hasn't changed actually but I'll look into it again after I get back to my desk and before I post back.

Cheers guys

PS also apologies for the top-post; just typing on this thing is hard enough!

Sent from my HTC

----- Reply message -----
From: "Alexander Carver" <address@hidden>
To: <address@hidden>
Subject: [gpsd-users] PPS from kernel into gpsd
Date: Wed, Apr 4, 2012 19:45

On 4/4/2012 11:27, Tomalak Geret'kal wrote:
> On 04/04/2012 19:05, Alexander Carver wrote:
>> On 4/4/2012 11:01, Tomalak Geret'kal wrote:
>>> [..]
>>> Now I want to use this PPS to steer ntpd in SHM(1), along with the
>>> NMEA-derived time that's already serving me well in SHM(0).
>>> According to [1], gpsd can use the RFC
>>> 2783 kernel PPS API "for extra accuracy". Can I use it as the sole
>>> source of PPS? How? Do I add /dev/pps0 to gpsd's device list? [..]
>> Skip gpsd and use ntpd's ATOM driver (refclock 22) to directly read in
>> /dev/pps0 into ntpd.
> Ah.. that appears to make much more sense.
> It appears not to be entirely working for me yet:
> # ntpq -p
> remote refid st t when poll reach delay offset jitter
> ==============================================================================
> *SHM(0) .SHM. 0 l 17 16 377 0.000 -6.959 74.995
> PPS(1) .PPS. 0 l - 16 0 0.000 0.000 0.008
> localhost .INIT. 16 l - 16 0 0.000 0.000 0.000
> But I suppose that's a question for another list now.

Looks like you're using the wrong PPS id number.  For /dev/pps0 your
ntpd config file should be  That peer status shows you're
using which causes ntpd to look for /dev/pps1 instead.

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