[time-nuts] Raspberry Pi tweaks and custom kernel, was RE: PPS for NTP Server - How Close Is "Good Enough"?

Chris Caudle chris at chriscaudle.org
Mon Jun 15 10:15:09 EDT 2015

On Mon, June 15, 2015 1:23 am, David J Taylor wrote:
> I don't think either system is good enough as a "microsecond" level
server, but either is fine for "tenth millisecond" level.

The BeagleBone Black has the advantage that you can run one of the timers
from an external input, so you can use the 10MHz from your GPSDO to drive
the timer (takes care of temperature variations of the system clock), and
have the timer captured based on the PPS input (eliminates interrupt
latency as a factor in capturing the timer).
With that setup you should be able to get into the high nanoseconds
stability range.  For transfer to other systems the BBB Ethernet supports
PTP, so you should be able to get just under microsecond level
synchronization between systems on the same LAN.

Here is someone working on connecting a NavSpark GPS to a BBB.  I don't
think I have seen his name on the 'Nuts list, but I don't recall for sure.

Chris Caudle

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