Just to echo that using the PRU cores is the wrong way to go, the BBB
has a multitude of hardware timers that will give better performance for
less hassle.
Having said that, by far the Number One thing to consider is controlling
the impact of temperature changes. If you sort that, the rest is icing
on the cake.
In order of complexity:
Out the box, using gpio-pps, the BBB is a good NTP server that will hold
its own against other SoC solutions.
Stick it in a box to control the temperature a bit and run Dan Drown's
gmtimer-pps, you'll get a great NTP server.
https://www.febo.com/pipermail/time-nuts/2014-December/089217.html
This is an easy, quick win that will give excellent results.
Add PTP and you should be able to sync time to other boxes at sub
microsecond levels.
But because we don't stop with 'just' great solutions ...
Dan has been looking at software compensation to control the temperature
impact.
https://www.febo.com/pipermail/time-nuts/2014-November/087745.html
I took a more brute force approach and clocked the BBB from a more
stable reference.
https://www.febo.com/pipermail/time-nuts/2014-November/088385.html
Cheers
Simon
On 10/12/2014 23:56, Paul wrote:
On Wed, Dec 10, 2014 at 4:58 PM, Brian Lloyd <[email protected]> wrote:
Well, I am hoping to get to the point where the path to using the BBB as an
NTP server using the PRU for more precise timing
Using a PRU seems like overkill if all you want from the BBB is NTP. The
standard pps-gpio should move the system clock precision below
system/network jitter (.5 to 1 microsecond). The next step is using a
timer (TIMER4) which should get you into .1 microsecond offsets.
Naturally if you're doing significant computing (heh) on the BBB you might
want to use a real time unit.
The current portion of this thread is part of the June-2013 hread started
by Gabs Ricalde about using TIMER4 for capture with 10MHz/1PPS input.
<https://www.febo.com/pipermail/time-nuts/2013-June/077430.html>
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