[time-nuts] Beaglebone NTP server

Simon Marsh subscriptions at burble.com
Thu Dec 11 04:24:52 EST 2014

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.
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 

I took a more brute force approach and clocked the BBB from a more 
stable reference.



On 10/12/2014 23:56, Paul wrote:
> On Wed, Dec 10, 2014 at 4:58 PM, Brian Lloyd <brian at lloyd.aero> 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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