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

Rob nomail at example.com
Tue Jul 2 19:36:36 UTC 2013

unruh <unruh at invalid.ca> wrote:
> 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.

You may think that, but gpsd does it that way and it works surprisingly

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