[ntp:questions] Thunderbolt at NTP ref clock.

Thomas Laus lausts at acm.org
Wed Jul 31 15:13:43 UTC 2013


On 2013-07-31, unruh <unruh at invalid.ca> wrote:
>> 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. 
>
There used to be a price listed, I think cost was around $40.  

> 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).
>
The pulse width wasn't adjustable.  It was was just on the ragged edge
of what the Soekris UART DCD was able to see for pps kernel
discipline.  It occasonally missed a pulse and that caused some
problems for ntp because it had the time solution from the serial
port data, but not the pps timestamp that matched.

Tom 

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