On Tue, May 8, 2012 at 10:57 PM, Mike S <[email protected]> wrote: > I've got a couple of Soekris NET4501s, with Moto M12+ GPS timing receivers. > They've been running pretty well with nanoBSD, using the special high > resolution elan-mmcr PPS driver. > > But, there doesn't seem to be any optimal refclock driver combination. (ntpd > 4.2.7p236) > > If I use the Atom refclock driven by elan-mmcr for PPS, and the Oncore > driver for TOD and PPS, the PPS sources seem to conflict. NTP appears to > alternate which PPS is used, causing quite a bit of jitter (Atom is very > stable, Oncore is subject to interrupt latencies). Not linking > /dev/oncore.pps.0 to /dev/cuau1 causes the Oncore driver to not work at all.
The Oncore driver is designed to require PPS to operate. > I've played with using "prefer" (prefer Oncore, prefer Atom, prefer both), > but that doesn't seem to make things any better. > > Using the Oncore driver alone would make sense, but to take advantage of the > accuracy provided by the elan-mmcr driver, I'd have to point > /dev/oncore.pps.0 to /dev/elan-mmcr. When I do that, the Oncore driver > doesn't work. I'm guessing that's because elan-mmcr only signals asserts, > and never clears, but maybe it's something else. > > Things get better with just the Atom driver and an external prefer peer, but > that means it can't be a stand-alone NTP server. I'm not familiar with the elan-mmcr driver. From your description it appears you have a single hardware PPS signal which is exposed to software via two different means (perhaps because it's connected to both a RS-232 input pin and another PPS input?). The obvious solution in that case is to point /dev/oncore.pps.0 to /dev/elan-mmcr as you tried. I would focus on debugging that configuration, with no separate PPS/ATOM driver configured. There may be a bug lurking in the Oncore driver your configuration exposes, or the problem may be with the elan-mmcr PPSAPI implementation. We don't have enough information yet. Cheers, Dave Hart _______________________________________________ questions mailing list [email protected] http://lists.ntp.org/listinfo/questions
