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

Bob Stewart bob at evoria.net
Thu Jul 21 00:11:08 EDT 2016

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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