[time-nuts] How to get PPS from ublox mini-PCI GPS to APU2 SoC serial port for ntpd

Attila Kinali attila at kinali.ch
Tue Aug 16 15:36:03 EDT 2016

On Mon, 15 Aug 2016 16:57:27 -0400
Paul <tic-toc at bodosom.net> wrote:

> Finally, these boxes are intended to be routers (hence the three network
> interfaces) not time-servers and unless you're irrevocably wedded to the
> miniPCIe in APU2 route there are probably better choices for time servers.

I disagree here. With the APU and its IRQ system you get already to
sub-us PPS time stamping (probably in the 10ns-100ns range).
This is way than good enough for a NTP server. It should be even good
enough for an PTP system, if normal network switches are used.

The advantage of the APU is that you have a standard PC, which simplifies
the use of software considerably. Of course, with an embedded system
you can get the PPS timestamping down to <10ns precision. But at an
several times larger software complexity, which you also have to build
yourself to a large extend.

Unless time-nuts levels of precision/accuracy are required, an APU
is good enough and an easy solution. If you go for time-nuts levels,
then I would question the use of ethernet long before I question
the hardware platform.

			Attila Kinali
Malek's Law:
        Any simple idea will be worded in the most complicated way.

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