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Re: [gpsd-users] Disable or restart PPS in gpsd?
From: |
Gary E. Miller |
Subject: |
Re: [gpsd-users] Disable or restart PPS in gpsd? |
Date: |
Wed, 3 Sep 2014 13:10:29 -0700 |
Yo Alexander!
On Wed, 03 Sep 2014 12:59:41 -0700
Alexander Carver <address@hidden> wrote:
> > Just do not expect any patches on such an old gpsd.
>
> Of course not. As I said I can compile a new version which is fine by
> me, I just can't go up on the kernel right now since a newer image is
> not available in the stable branch. I may at a later time investigate
> the backports which I understand may potentially be up to 3.14.
I do not think there is anything in newer kernels to affect this.
> > Sounds like you just want KPPS off in gpsd. So just compile it
> > without pps support.
>
> If I disable KPPS in gpsd will it still create the pps0 device or will
> it skip that part?
Creating pps0 is how KPPS works. No KPPS, then no pps0 from gpsd.
> If it skips that, how do I share the port with
> ldattach and gpsd?
gpsd never uses ldattach. Port sharing of a GPS is problematic as
autobaud and auto configure will get confused between two GPS clients.
Just have ntpd read the GPS by way of gpsd.
> > What sort of jitter difference are you seeing?
>
> Jitter using the PPS ATOM driver is nominally 6 microseconds. Jitter
> using SHM(1) from gpsd is up to 5 milliseconds. So about 1000 times
> worse. And this assumes that KPPS doesn't go belly up for some
> reason.
Something wrong with your setup then. No way gpsd adds 1000x jitter.
I routinely see around 1 microSec using gpsd and SHM(). Even better
with chronyd.
> Right now, SHM(0) isn't even reporting, gpsd is spewing KPPS errors,
> but ntpd's ATOM is happily ticking away with 1 microsecond jitter and
> less than 5 microseconds offset.
Likely because only one can use the port at a time.
> I used another one of my machines
> as a second preferred peer for seconds counting which is why ATOM is
> still running even though SHM(0) is dead. SHM(1) does not work at
> all if ntpd's ATOM is configured and when I only use SHM(0,1) with no
> ATOM, SHM(1) shows the bad jitter compared to ATOM's jitter.
You gotta pick ntpd or gpsd to run the GPS. You can't share and get
good timing.
RGDS
GARY
---------------------------------------------------------------------------
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97701
address@hidden Tel:+1(541)382-8588
- [gpsd-users] Disable or restart PPS in gpsd?, Alexander Carver, 2014/09/03
- Re: [gpsd-users] Disable or restart PPS in gpsd?, Gary E. Miller, 2014/09/03
- Re: [gpsd-users] Disable or restart PPS in gpsd?, Alexander Carver, 2014/09/03
- Re: [gpsd-users] Disable or restart PPS in gpsd?, Gary E. Miller, 2014/09/03
- Re: [gpsd-users] Disable or restart PPS in gpsd?, Alexander Carver, 2014/09/03
- Re: [gpsd-users] Disable or restart PPS in gpsd?,
Gary E. Miller <=
- Re: [gpsd-users] Disable or restart PPS in gpsd?, Alexander Carver, 2014/09/03
- Re: [gpsd-users] Disable or restart PPS in gpsd?, Gary E. Miller, 2014/09/04
- Re: [gpsd-users] Disable or restart PPS in gpsd?, Alexander Carver, 2014/09/04
- Re: [gpsd-users] Disable or restart PPS in gpsd?, Gary E. Miller, 2014/09/04
- Re: [gpsd-users] Disable or restart PPS in gpsd?, Alexander Carver, 2014/09/04
- Re: [gpsd-users] Disable or restart PPS in gpsd?, Gary E. Miller, 2014/09/04