Rasp Pi at +/- 1 us from GPS
hmurray at megapathdsl.net
Sun Nov 26 20:13:16 UTC 2017
You don't need the RTC. You can get the initial time over the net.
> - (if I understand properly) pps-client takes a pair of GPIO pins and
> calibrates latency, so its PPS adjustment is more accurate.
I've thought of doing something like
sleep until a bit after a second ticks
turn on GPIO
And catching things on a scope that is also watching a PPS.
> I hope to be able to install NTPsec:
> - as a time server
> - leaving system time alone
I think it should do what you want if you set it up with only a localclock.
(no normal servers)
> I don't know how to measure if pps-client is doing what it says it is...
On Linux, can generate graphs and such by watching /sys/class/pps/pps0/assert
(on non Linux, you will have to work a bit harder, but you can get the same
data using the PPS API)
Here is a python hack to monitor 60 Hz from the line. You can tweak it to
grab every sample.
You can also monitor things using ntpd. Of course, that will include the
noise from the other system and the USB Ethernet. Turn on rawstats. Add
"server foo noselect". It will collect data, but not use it for timing.
That will log info from each client-server pair. (That's when the logging
system is the client. You can do the same on the other end. They should
These are my opinions. I hate spam.
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