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RE: Using non-PPS receiver for ntpd? (Stein, Josh)
From: |
Stein, Josh |
Subject: |
RE: Using non-PPS receiver for ntpd? (Stein, Josh) |
Date: |
Wed, 9 Jun 2021 15:31:13 +0000 |
Hi Steve,
Due to reasons outside of my control at this time, I have to use the receiver
I already have. In the future, I will look into a different receiver (and
probably be a bit overwhelmed at the sheer number of units out there on the
net).
I am not particularly tied to ntpd; I chose it because it appeared to be the
one used in most of the examples.
--J
-----Original Message-----
From: gpsd-users <gpsd-users-bounces+josh=anl.gov@nongnu.org> On Behalf Of
Steve Bourland
Sent: Wednesday, June 9, 2021 10:10 AM
To: gpsd-users@nongnu.org
Subject: Re: Using non-PPS receiver for ntpd? (Stein, Josh)
Yo Josh!
On Wed, 9 Jun 2021, gpsd-users-request@nongnu.org wrote:
> Today's Topics:
>
> 5. Using non-PPS receiver for ntpd? (Stein, Josh)
> ------------------------------
>
> Message: 5
> Date: Wed, 9 Jun 2021 14:00:27 +0000
> From: "Stein, Josh" <josh@anl.gov>
> Subject: Using non-PPS receiver for ntpd?
>
>
> Hello everyone,
>
> I currently only have access to a USB GPS receiver connected to an
> rPi which does not supply PPS data. Despite the lack of PPS accuracy,
> I would like to use this receiver as a clock source to the ntp daemon
> running on that Pi. This Pi in turn will serve time to the other
> devices on my setup giving me a relative synchronization of their
> clocks. In this particular instance, I can tolerate some pretty
> egregious jitter - on the order of tens of seconds.
In my experience, the USB time on some ancient receivers could keep time within
a second of "real" time.
> My first question is fundamental - given the discussion in the guide
> here (https://gpsd.gitlab.io/gpsd/gpsd-time-service-howto.html), is it
> even feasible to use a non PPS receiver in this role?
My gut response is yes, but if Gary or David (Taylor) come along and advise
against it, they know MUCH better than I do.
I fully expect Gary to ask why you don't spend the <$30 to get a GPS with PPS,
a question I would also pose. Is this a question of you can't bring a new GPS
into the environment?
I assume you're in the same situation I am, a network that has no Internet
connection. Given that, and that the Pi will only have this one source, I
believe chrony may handle that situation better, but again, my memory on this
is rusty.
Best of luck!
Steve