[time-nuts] PPS for NTP Server - How Close Is "Good Enough"?

Hal Murray hmurray at megapathdsl.net
Wed Jun 10 05:00:29 EDT 2015

eds_equipment at verizon.net said:
> OK, here is the actual question. Do you think it is OK to consider a  pulse
> which arise 250 ns early to be close enough? And no, I am not  forgetting
> about that 3 ns, there is about 3 ns of delay added by the  output
> circuitry. 

If you want to earn your time-nut merit badge, you have to measure it.

The Ethernet on the Raspberry Pi is on the USB bus.  That adds about a 1/2 ms 
of jitter.

If you are using ntpd, there is a fudge factor that lets you correct for any 
offset.  (and another one that lets you use the other edge, but I think the 
Pi doesn't capture it)

These are my opinions.  I hate spam.

More information about the time-nuts mailing list