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[questions] Re: GPS+PPS vs NTP server, why a huge offset ?



On 16/06/2022 10:00, Thiebaud HUMBERT wrote:
To do the inversion, I just changed the "Pulse Mode" parameter to "Falling edge" from "Rising edge".
The offset induced by the "pulse length" has disappeared.
But there is still an offset of around 10.3ms, which I think is induced by USB as explained in this article about other chipsets (https://lists.freebsd.org/pipermail/freebsd-usb/2019- August/016078.html)

Yes, Thiebaud, USB is not good enough for PPS signals!

See if your motherboard has a true serial port - perhaps just as a header but not a back connector. If not, just set the offset of the PPS to ~10.3 milliseconds (10.3 - IIRC the offsets are in milliseconds but please check). Plus or minus 10.3, try it and see! Not perfect, but better than nothing.

You might find better results using that GPS/PPS with a Raspberry Pi as a stratum-1 server and offering that as a server on your LAN.

Cheers,
David
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Cheers,
David
Web: http://www.satsignal.eu
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