Re: [Linuxptp-users] grandmaster with an H/P 3805A GPS disciplined osc

[Richard C. <ric...@gm...>]

On Wed, Aug 21, 2013 at 07:47:54AM +0200, Richard Cochran wrote:
> On Tue, Aug 20, 2013 at 02:00:05PM -0700, David Gravereaux wrote:
> > I was wondering if I use NTPd for controlling the GPS radio with its
> > built-in driver for it along with the PPS signal on the comport as the
> > DCD line
> > <http://support.ntp.org/bin/view/Support/Z3801AReceiverModifications>,
> > would this share the same counter for PTP?
> 
> This setup will synchronize the Linux system time to the external
> Z3801A box using a PPS signal. You could use ptp4l with software time
> stamping and the 'free_running' option to serve this time to your
> network.

But you have an Intel i210, right?

So it would be even better to feed the PPS from the Z3801A into one of
the i210's SDP pins. (Be careful with the signal conditioning, SDP is
CMOS directly to the chip.)

I posted a igb patch on netdev to enable the SDP functions. This was
not accepted into mainline (I'll have to make minor changes first),
but it does work. You can patch your kernel with it.

Then you can use the i210's external time stamps of the PPS to
discipline the i210's clock. You will have to write some code, but
you can re-use phc2sys and the testptp program, as they have most of
what you need.

The PPS will give you the phase offset from the full second, and you
can read the time and date from the serial port.

Good luck,
Richard