[ntp:questions] pps coming in, not received by ntpd

unruh unruh at invalid.ca
Tue Jul 2 19:18:28 UTC 2013


On 2013-07-02, David Taylor <david-taylor at blueyonder.co.uk.invalid> wrote:
> On 02/07/2013 15:18, unruh wrote:
> []
>> To timestamp the pps, you have to have some module (ie kernel level)
>> timestamp process. shmpps, gpsd, the kernel pps, write your own,....
>
> Thanks for the information, Bill.  My only additional comment is that 
> the code to timestamp the PPS /can/ be in user-mode, although 
> kernel-mode is preferable.  Additional Linux modules are /not/ required.

?? To timestamp the interrupt, you need kernel land. Ie, you need a
module. Now you can use one of the modules others have written or you
can write your own. But userland cannot get any sort of accuracy trying
to figure out when and if a hardware line has been pulled up or not.
I do not know what you mean by your last sentence. If you mean you are
happy with the modules that are supplied by others, fine. It is possible
that your own module might be faster than the supplied ones, in which
case you might want to use them.If you mean modules are not needed then
I beg to differ.
 



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