On Fri, Jul 22, 2011 at 2:30 PM, Javier Herrero <jherr...@hvsistemas.es> wrote: > I've found a plot of the ntp-synthesized GPS output compared with the > UTC-aligned GPS from a Thunderbolt. The generated PPS output was 1us wide, > and it is represented in infinite persistence to get an idea of the jitter. > The offset was around 50us, and the jitter around 8us, so not very bad (it > was at least one order of magnitude better than my requirements, so I did > not bother to optimize it further). > > The ntp source was a M12-based ntp server (a blackfin running uClinux, not a > Soekris :) ). > > Driving the PPS output to a serial port from the ntp is not as trivial as > you think. This PPS output is from an "oscillator" disciplined to the system > clock - really a stearable divider from the system clock (it is an embedded
The software PPS on the serial port that i suggested would be an intermediate step. What you measured was the output of what I called a NTPDXO decided down. I think we are talking about the same kind of design. I guessed that the jitter on the final PPS would be 1000x worse than from a GPS and your 8uS measurement is spot on that. The M12 has a handful of nS error Chris Albertson Redondo Beach, California _______________________________________________ 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.