[ntp:questions] X2 assert and clear events (PPS) on LInux with sure GPS Board

unruh unruh at invalid.ca
Thu Jan 10 00:09:04 UTC 2013


On 2013-01-09, thelastromantic at live.fr <thelastromantic at live.fr> wrote:
> Hi,
>
> Thanks, it seems to work.
>
> So, i just need nanoseconds precision with this 1pps on my localhost,
> don't need NTP or other.

You will NOT get nanosecond precision. If that is your goal, give up
now. No computer can reach that. a)the time sources are not good enough
without corrections after the fact, and b) your computer cannot process
the pps signal fast enough to give you that precision. 

>
> I've have compiled succefully compiled my program with timepps.h,
> and i want to create a nanoseconds chronometer between each 1PPS.
> What function should i use from timepps.h code ?

You don't.

>
> Another solution : i've modeed ppstest, and i settimeofday to "0" each PPS,
> but the accuracy of settimeofday() seems to be bad, and i want just change the seconds to "0" on my local PC without change HH.MM and date. juste change the seconds to "0" for each PPS/seconds

That takes too long. And if your frequency is out by 1PPM ( and that is
a very good computer clock if its drift is only 1PPM)  your clock
will be out by 1000 ns by the time the next pulse occurs. 

Ie, you have set yourself and impossible task. 



>
> Sorry for my bad english



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