[time-nuts] beaglebone black, debian, NTP client

Attila Kinali attila at kinali.ch
Tue Jan 5 03:43:20 EST 2016


On Sat, 2 Jan 2016 11:47:09 -0000
"David J Taylor" <david-taylor at blueyonder.co.uk> wrote:

> I'm also using PPS with the BBB - you even commented on my Web page!
> 
>   http://www.satsignal.eu/ntp/BBB-vs-RPi.html

Yes, I know. But I didn't mention your webpage, because there is something
weird going on with your system. The jitter you are seeing is very high.
And it depends on the load of the OS that seems to have many unnecessary
processes running. Even if you don't use the timer unit, like Dan Drown
did, you shouldn't see a jitter higher than 2-4us on the PPS pin (that's
approximately half the interrupt latency of the BBB including kernel/software
induced latency). But yours goes up to +/-12us, ie is 6-12 times higher.


			Attila Kinali

-- 
It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
                 -- Miss Matheson, The Diamond Age, Neil Stephenson



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