Per Hedeland wrote: > In article <[EMAIL PROTECTED]> "David J > Taylor" > <[EMAIL PROTECTED]> > writes: >> Harlan Stenn wrote: >>>>>> In article <[EMAIL PROTECTED]>, >>>>>> "David J Taylor" >>>>>> <[EMAIL PROTECTED]> >>>>>> writes: >>> >>> John> 5) [Make sure] you have "options PPS_SYNC" in your kernel >>> config >>> >>> David> 5 - I have not done that explicity. How could I check that, >>> and David> change it if required? It's been 10+ years since I ran >>> UNIX. >>> >>> Assuming an x86 box, put the following in >>> /usr/src/sys/i386/conf/PPS: >> [] >> [] >> >> Many thanks, Harlan. I'll look into this, although I am a little >> disappointed to find that less than 24 hours after starting with >> FreeBSD I'm having to recompile the kernel! > > Well, using PPS_SYNC shouldn't be *required* to use the PPS signal on > FreeBSD - what it does is make the kernel discipline the local clock > directly from the PPS signal, but FreeBSD also supports the PPSAPI, to > let ntpd collect the timestamps from the PPS signal. It should be > possible to use this via the ATOM driver. I haven't personally > verified any of this though (hence the "should"s) - and I guess > PPS_SYNC may give better results, but it could be interesting to try > both variants. > > --Per Hedeland > [EMAIL PROTECTED]
Per, thanks for that. I think I understand what you are saying (although I may not next week!): - you need to recompile the kernel if you want the PPS signal to discipline the local clock directly - there is an alternative programming interface, the PPSAPI, which FreeBSD supports, but this API is not used by the NEMA driver. (Why not?) - you may be able to use the PPSAPI if you install the ATOM driver as well as the NMEA driver. I wonder which the preferred approach is, and which would give the better results? I'm trying to put together a small Web page on this, so I may quote your words (if that's OK). Thanks, David _______________________________________________ questions mailing list [email protected] https://lists.ntp.isc.org/mailman/listinfo/questions
