Re: [chrony-users] Refclock Integration Advice

[Joe Smith <joe.smith@xxxxxxxxxxxxxxxxxxx>]

I don't know if this helps at all but I did once encounter a situation where we switched from using an Adafruit GPS breakout board to using a Trimble chip. Things stopped working properly and we ultimately found (using a digital oscilloscope) that the default width of the PPS pulse coming from the Trimble chip was too narrow for the SBC to detect. The Trimble chip has a mechanism to adjust the width of the pulse and once that was done it worked like a champ. Not sure if this fits your situation but maybe something to look into? We were using a Beaglebone Black as our SBC, running Ubuntu. I don't recall the specific Trimble chip that was used as it wasn't my design and I was just called in to troubleshoot.

On Mon, Nov 23, 2020 at 10:04 AM Miroslav Lichvar <mlichvar@xxxxxxxxxx> wrote:

On Mon, Nov 23, 2020 at 02:56:58PM +0000, Chang, Benjamin wrote:
> So it does seem like the PPS isn't updating my timestamps.
> However, ppswatch does receive updated timestamps? See attached.
>
> What could be causing my PPS to "register" but not update timestamps? That seems counterintuitive to the system (granted I am a rookie in all this).

Maybe it's registering reliably only one edge of the pulse? Compare
the assert and clear events with:

while sleep 1; do cat /sys/class/pps/pps2/{assert,clear}; done

--
Miroslav Lichvar


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