On 11/12/2014 04:15, Chris Albertson wrote:
Those sub 1 u-second numbers are very good. They argue for using the BBB as an NTP server but I wonder if it really is the best. I think the numbers that matter are measures of the close on the computers who use your BBB as a server. In other words the goal is to synchronize a set of computers. Can The little BBB push accurate time out to a set of user computers and keep then in sync better then some other NTP server platform?
The BBB scores over the Pi here in having real hardware ethernet instead of USB ethernet.
Better, the BBB has hardware support for IEEE1588 timestamping so you can ditch NTP and distribute time using the BBB as a PTP grandmaster. The software is mature, but unfortunately a kernel rebuild is required to enable the appropriate drivers.
The attached graph shows an overnight test using two BBBs connected via a normal (i.e. non-IEEE1588) gigabit switch. The offset graphed is as reported by PTP on the slave, the black line is a moving 100 point average and the scale is in ns. The stddev offset over the period is about 260ns.
Cheers Simon _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
