[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.


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