Dave,
I've let the board collect ntp data for ~24 h and then using that data I was
able to adjust for the constantan drift. (I'm using the following client
http://doolittle.icarus.com/ntpclient/ that is based on xntpd), during the test
runs I also gather other statistics that will give you a fairly good idea of
how good your boards time is. If you follow their instructions I believe you
are able to get to 10 ms accuracy, my board seems to be able to get close to
that. I'm synchronizing two radars with 1000Hz prf hence I need sub millisecond
accuracy so they can point at the same volume. But then read Ian's comment and
it doesn't look promising for us?
Thank you all for your inputs, I appreciate them.
/Polly
--- In Ian Thompson <> wrote:
>
> Dave
>
> The principal factors are the OSes and their IP stacks. You can't depend
> on when NTP events are going to get handled if you are running a general
> purpose OS. You might improve the accuracy if you code your NTP servers
> and clients on an RTOS with a more deterministic IP stack.
> There are efforts to put PTP/IEEE-1588 handling into the Linux kernel.
> I'm not sure if this is to support specific PTP enabled hardware or to
> move the handling of PTP events to early in the stack.
>
> Ian T.
>
> On 08/25/2010 09:02 AM, Dave Cramer wrote:
> >
> >
> >
> >
> > On Wed, Aug 25, 2010 at 9:45 AM, Ian Thompson <
> > <>> wrote:
> >
> >
> >
> > It's not considered possible to synchronize to better than ±20 mS with
> > NTP,
> >
> >
> > What are the limiting factors here ? I will have all of my boards on
> > the same local network.
> >
> >
> >
> > hence the introduction of PTP [Precision Time Protocol or IEEE-1588] .
> > To get microsecond accuracy with PTP one needs an Ethernet MAC with
> > built in hardware support and a PTP master. I don't believe
> > Technologic
> > have any boards that include this as yet. I hope that they are
> > considering adding it!
> >
> > What exactly is required ?
> >
> > Dave
> >
>
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