In article <[EMAIL PROTECTED]> Harlan Stenn
<[EMAIL PROTECTED]> writes:
>>>> In article <[EMAIL PROTECTED]>, [EMAIL PROTECTED] (Per
>Hedeland) writes:
>
>Per> I've never really seen the point of this - it saves a line in the
>Per> config file, but that's about it, and it seems to me that you get less
>Per> control and monitoring capabilities than when explicitly using ATOM
>Per> (actually it has been renamed to the more appropriate PPS, I'm just
>Per> behind the times...) to collect the PPS time stamps. As far as I know
>Per> you can't even tell that you're receiving any PPS pulses other than
>Per> implicitly by the low jitter.
>
>You can check out the status bits from the specific association using ntpq,
>and that does seem to be a bit lame.
Hm, I can't see that the NMEA driver does anything with status bits
depending on whether it receives PPS pulses or not - it basically boils
down to:
/*
* If the PPSAPI is working, rather use its timestamps.
* assume that the PPS occurs on the second so blow any msec
*/
if (nmea_pps(up, &rd_tmp) == 1) {
pp->lastrec = up->tstamp = rd_tmp;
pp->nsec = 0;
}
Care to elaborate?
>Per> Anyway, bottom line: You were probably already using the PPS signal
>Per> before you recompiled the kernel - you just couldn't tell.:-)
>
>From what I can tell, the answer is "perhaps". The association status bits
>would be the way to tell, and I agree that it would be better if the
>information was a bit easier to find.
Actually, there is another bit of info in David's "before" output:
precision: 1e-006 s
- and in the NMEA driver we find:
#define PRECISION (-9) /* precision assumed (about 2 ms) */
#define PPS_PRECISION (-20) /* precision assumed (about 1 us) */
- i.e., apparently it has set PPS_PRECISION. However checking the code
carefully reveals that it will do this if PPSAPI is available and the
initialization of it succeeds - which it of course will do regardless of
whether any pulses are actually received. (But since we know from the
"after" output that pulses are actually being received, I think the
answer is "yes"...)
--Per Hedeland
[EMAIL PROTECTED]
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