On 2012-05-25, Chris Albertson <[email protected]> wrote: > On Fri, May 25, 2012 at 12:29 AM, Terje Mathisen <"terje.mathisen at > tmsw.no"@ntp.org> wrote: > >> Chris Albertson wrote: >> >>> Next how to get the PPS to be at the top of the second. Two methods >>> >>> 1) don't bother. Linux PPS will log the time of both the GPS's PPS >>> and the Rb PPS. Read the log file to determine the offset. This give >>> offset with uSec precision. To get better you need a hardware time >>> interval counter. I happen to have a few of those and can read >>> sub-nanoseconds but this is gross overkill. Microseconds are good >>> enough for NTP...... >>> >> >> Much simpler would be to use a fudge command to specify the current phase >> offset between the Rb and GPS PPS signals, i.e. if the Db happened to start >> out 367 ms off, just let ntpd know that these pulses are supposed to have >> such an offset. >> >> > Yes, correct the "fudge" method is what I was getting at in #1 above. I > assumed that every on here would know to use the measured difference in a > "fudge" but the key is measuring the offset. Get that from the log file. > or a TIC if you have one. > > But there is a problem in the even with the best Rb the offset will drift > over time.
Yes. but slowly (probably about 1 sec per millenium or less) > > > > Chris Albertson > Redondo Beach, California _______________________________________________ questions mailing list [email protected] http://lists.ntp.org/listinfo/questions
