Re: [chrony-users] Chrony gets out of sync regularly

Config: Host sync'd to nearby stratum 1s. Jitter ~35 usec. gpsd 3.23

gpspipe, gpspipe -R and ntpshmmon running simultaneously for several hours

gpspipe -T '%s' --usec -r | sed 's|,.*||'

Min Max

(sec) (sec)
.132419 .168017 GPGBS
.132332 .167903 GPGGA
.132393 .167985 GPGSA
.389284 .549959 GPGSV
.132364 .167938 GPRMC
.132263 .167829 GPZDA

gpspipe shows that the data is sent in binary mode.

I'll send some other details off-list.

>>> Why do you need the SHM 0? You can use SHM 1 or SOCK.

Some cookbooks (e.g., https://support.ntp.org/bin/view/Support/ConfiguringSHMRefclocks ) use both SHM 0 and SHM 1

On Wed, Mar 2, 2022 at 3:34 AM Miroslav Lichvar <mlichvar@xxxxxxxxxx> wrote:

On Tue, Mar 01, 2022 at 03:09:27PM -0600, Steven Sommars wrote:
> I understand the jumps to be gpsd-related. I see identical behavior on
> one of my RPi4+ublox GPS units.
> NMEA sentence timing remains consistent. As an optimization some gpsd
> versions move the GPS into ublox binary mode for the serial data stream.
> The ublox serial binary mode timing is not consistent. The gpsd folks
> apparently believe that the arrival time of serial data is untrustworthy
> and should not be used.

Can you try the following command and compare the output when the
offset jumps?

# gpspipe -T '%s' --usec -r | sed 's|,.*||'

For example, with gpsd 3.23.1 and a ublox unit I have here I get:

1646208470.067774: $GPZDA
1646208470.067792: $GPGGA
1646208470.067806: $GPRMC
1646208470.067811: $GPGSA
1646208470.067814: $GPGBS
1646208470.082703: $GPGSV
1646208470.082721: $GPGSV
1646208470.082726: $GPGSV

The timing of the messages in my case is stable to about 20
milliseconds. In the "super-raw" (gpspipe -R) output I can see it's
using the binary protocol.

--
Miroslav Lichvar

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