[time-nuts] Syncing Tom's PICDivs to 1PPS

Scott Stobbe scott.j.stobbe at gmail.com
Thu Jul 21 10:05:15 EDT 2016

I think you will have to decided if you want both your xo (presumably 10
MHz) and PPS to be phase aligned to UTC. No matter which way you go you
will have propagation delay across a clock divider. If you just want your
PPS to be on phase, you can steer your xo.

On Thu, Jul 21, 2016 at 12:11 AM, Bob Stewart <bob at evoria.net> wrote:

> For my next GPSDO board revision, I would like to include one of Tom's
> PICDiv devices to give a much better 1PPS out than the Ublox receivers are
> capable of.  This means that it has to be started (or slewed to be) exactly
> on time.  So I was wondering if anyone had experimented in controlling the
> startup of one of these PICDivs to make them in sync, and if you'd be
> willing to share your solution before I start digging into it.  I haven't
> yet looked at the source code for any of these devices, but it's my
> understanding that this feature isn't provided, and is deemed to be
> difficult due to the input divider making for a large steering step.  Even
> a suggestion as to which of the chips would be the best candidate would be
> much appreciated.  I'm looking for a method that's deterministic, rather
> than starving the PICDiv of clock cycles and waiting for the 1PPS to match
> a conveniently correct 1PPS from the Ublox.
> Bob - AE6RV
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