[ntp:questions] Thunderbolt at NTP ref clock.

unruh unruh at invalid.ca
Wed Jul 31 14:36:47 UTC 2013


On 2013-07-31, Thomas Laus <lausts at acm.org> wrote:
> On 2013-07-30, E-Mail Sent to this address will be added to the BlackLists <Null at BlackList.Anitech-Systems.invalid> wrote:
>> Dave Baxter wrote:
>>> In reference to my other thread.
>>> "THunderbolt monitor/control on Win7 ?"
>>> Well, as that device seems happy in it's potential new home.
>>> I've been poking about the interweb looking for info as to getting the
>>> TB used as a reference clock for NTP.
>>> I found this page:-
>>> http://www.eecis.udel.edu/~mills/ntp/html/drivers/driver29.html
>>> That on the face of it, seems to tell me what I need.
>>> So, poking arround (no changes yet) my ntp.conf file, I "think" I need
>>> this:-
>>>
>>> # Trimble Thunderbolt on /dev/gps1 (first serial port)
>>> server 127.127.29.1 mode 2  minpoll 4 maxpoll 4   prefer
>>> fudge  127.127.29.1 time1 0.020
>>
> Years ago when I used a Thunderbolt to provide a local time reference
> on a Soekris system I found that the PPS pulse was a little too narrow
> to trigger the Soekris UART.  I had to use one of these:
>
> http://www.tapr.org/kits_fatpps.html

And in all those years they still have not figured out what the price
is? The web page says price is TBD. 

>
> To stretch the pulse for reliability.

What is the trimble pulse width? Are you sure it is not adjustable?
Remember that such a pulse stretcher adds latency. If you one want it to
10s of microseconds it is fine. If you are worried about ns it is not. 

(I guess if you are using a serial port you cannot care about better
than 10s of microseconds anyway).
>
>
> Tom
>
>



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