On Wed, May 9, 2012 at 1:39 AM, Mike S <[email protected]> wrote: > On 5/8/2012 9:07 PM, Dave Hart wrote: >> >> 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 Soekris NET4501 has a high precision (125 ns?) hardware timer. The > elan-mmcr PPS driver was written by Poul Henning-Kemp (I think) to take > advantage of that. PPS starts the timer, then when the interrupt is handled, > does some math to remove the interrupt latency from the PPS timestamp. The > PPS signal also goes to the serial port DCD, which is what the Oncore works > with, so yes, PPS is available in two places.
The Oncore driver should use the system-provided PPSAPI with whichever device you point oncore.pps.0 to. Again I would focus on getting that configuration working, rather than trying to bodge something using the ATOM driver with one PPS device and Oncore with a different one, both handling the same signal. > The one difference I've noticed is that the regular (DCD) PPS does both > asserts and clears. The elan-mmcr only signals asserts. That works fine with > the Atom driver, but it seems the Oncore driver has a problem with it (just > guessing that may be the cause). The driver30.html page documenting the Oncore driver suggests otherwise. It says the PPS must capture assert timestamps, and if PPS offset is configured, must allow offsetting of the PPS from the top of second (assert offset). I assume your oncore configuration file isn't requesting offset of the PPS. In that case, its use of PPSAPI should be comparable to the ATOM driver's default -- using the assert edge as the on-time event at top of each second. Since this is apparently not working as well for you with the Oncore driver as with ATOM, I would like to understand if the Oncore driver has a defect that should be corrected. I'm not particularly interested in exploring workaround configurations involving enabling two PPS-providing drivers and trying to ignore the inferior PPS timestamps from one of them. Cheers, Dave Hart _______________________________________________ questions mailing list [email protected] http://lists.ntp.org/listinfo/questions
