Re: [chrony-users] Newbie Help Needed

[Stuart Maclean <stuart@xxxxxxxxxxxxxxxxxx>]

Hi again,

after reading your C code more thoroughly, I realized I am still not
understanding it all..

> In a pseudocode the program would do something like this:
> 
> 	gettimeofday(&sample.tv);
> 	sample.offset = sample.tv - CSAC; // or negative value of that?
> 	sample.pulse = 0;
> 	sample.leap = 0;
> 	sample.magic = SOCK_MAGIC;

Your term 'CSAC' above, does that mean the 'seconds since epoch' string
that came over serial from the CSAC, converted to an int?  If yes,
doesn't the exact time at which I do the gettimeofday then matter??

And I am wary of your comment.  Would I want sample.tv - CSAC, or the
reverse?  If you are confused by this, then I certainly am ;)

>  
> 	sample.tv_sec = pps_timestamp.tv_sec;
> 	sample.tv_usec = pps_timestamp.tv_nsec / 1000;
> 	sample.offset = pps_timestamp.tv_nsec / 1e9;
> 	sample.pulse = 1;
> 	sample.leap = 0;
> 	sample.magic = SOCK_MAGIC;

Does 'pps_timestamp' above mean the Linux system time value I grabbed,
using the kernel api call do_gettimeofday(), in the interrupt handler
attached to the PPS event?

Finally, is there any requirement on how OFTEN I must get PPS events and
CSAC time strings?  Will it all fail if I 'miss' or discard say a PPS?

Regards

Stuart


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