[time-nuts] Re: Suggestions solicited for Pi/GPSDO ntp server

[David Taylor via time-nuts]

On 26/05/2022 17:44, Lee Reynolds via time-nuts wrote:

Hi, Lords of Time!

(Been a lurker for many years, just know too little to add but am always
fascinated by your discussions. It almost reads like theological
discursions at some points, it gets into such fine and abstruse points!)

I think it's about time to retire my old former cell site GPSDO.

Technology has improved and I'm thinking of setting up a Raspberry Pi
based ntp server for the local devices. (I also have some spare Pi's, so...)

Does anyone have any suggestions for a good solid Pi/GPSDO setup and
code for such a purpose? Something like Leo's device but, of course,
much cheaper?

Any suggestions would be greatly appreciated.

TIA,

    Lee


Lee,

What accuracy are you wanting for your "local devices"?  A Windows box NTP 
server could give you hundreds of microseconds, a Raspberry Pi tens of 
microseconds.  With the RPi you could have several local GPS/PPS/NTP servers 
perhaps located in different parts of the building.


Hal has given some good advice.  I particularly sympathise with the "out of 
date" part, where Linux OS changes almost on the basis of (it sometime seems) 
"if it works, break it!".  I've built a few of the Raspberry Pi NTP servers, 
and in practice the Ethernet being over USB isn't an issue, but if you can get 
a Pi 4 that would reduce that problem.


But the Pi4 isn't so easily obtainable right now, and it generates rather more 
heat, so the stability of the CPU clock isn't as good as on earlier RPi models. 
 Ambient temperature can be a problem, so try to keep the RPi out of direct 
sunshine, preferably in a cupboard away from any heating.  All to keep the CPU 
clock stable!  No need for a display, it can all be built from the command line 
over SSH.


Ask if you have further questions.

David
--
SatSignal Software - Quality software for you
Web: https://www.satsignal.eu
Email: david-tay...@blueyonder.co.uk
Twitter: @gm8arv
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[time-nuts] Re: Suggestions solicited for Pi/GPSDO ntp server

[Hal Murray via time-nuts]

> I think it's about time to retire my old former cell site GPSDO.
> Technology has improved and I'm thinking of setting up a Raspberry Pi based
> ntp server for the local devices. (I also have some spare Pi's, so...)

> Does anyone have any suggestions for a good solid Pi/GPSDO setup and code for
> such a purpose? Something like Leo's device but, of course, much cheaper? 

How nutty of a NTP server do you want?

How much of a Linux hacker are you?  Do you need a detailed step-by-step guide 
or are rough hints good enough?

There are several varieties of GPS HAT available.  Ballpark $50.  I think most 
of them come with good setup directions.

There are several/many web pages describing how to set things up.  This is the 
classic.

The Raspberry Pi as a Stratum-1 NTP Server
  https://www.satsignal.eu/ntp/Raspberry-Pi-NTP.html

Google for >Raspberry Pi GPS NTP setup< will find many others.

-

That's GPS, no DO.  If you have a GPSDO that you like you will have to convert 
to 3V logic and wire it up: RX, TX, PPS.

--

Pis up to 3 have their Ethernet connected over USB so there is 125 
microseconds of fuzz on the timing.  You would have to put your time-nut hat 
on to notice that.  The Ethernet on the Pi 4 has a direct connection.

The Pi 3 and Pi 4 come with BlueTooth on the serial port.  You have to disable 
that or setup another serial port.

You can use either chrony or ntpsec.  You can use GPSD, or go direct with most 
GPS devices.

Pi IO pins are 3V only.

Linux changes.  Some of the setup descriptions may be old enough to be out of 
date.

There are also minor differences between distros.


-- 
These are my opinions.  I hate spam.


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