Re: [chrony-users] Setting up Chrony with PPS

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On Fri, Feb 19, 2016 at 07:25:40AM -0800, Deven Hickingbotham wrote:
> Okay, this makes sense as I had to recompile ntp to get it working with PPS.
> 1. Where do I find timepps.h?  If I have to download it, where should it be
> placed?

On Debian it should be in the pps-tools package. The file should be
in /usr/include or /usr/include/sys.

> 2. Does timepps.h just have to be present or do I have to change it so it
> looks for GPIO 4?

Just present.

> 3. What would be the correct way to configure chrony.conf to recognize PPS?

In the chrony configuration file you would have something like:

refclock PPS /dev/pps0 lock NMEA
refclock SHM 0 offset 0.5 delay 0.2 refid NMEA noselect

When chronyd has some NTP sources, you may want to tweak the offset
value of the SHM refclock so the measured offset as reported in
"chronyc sourcestats" is close to zero and the PPS signal can be
locked to it properly.

> 4. Other than stopping the chrony service before installing v2.3, are there
> any other steps that should be taken before updating?

Not really. But the update process itself will depend on whether you
want to replace the packaged version or install the new version to
/usr/local. You may need to modify /etc/init.d/chrony so it starts the
right binary. The cleanest solution would be to rebuild the Debian
package with the new version.

Miroslav Lichvar

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