Hi They run an NCO (drop / add pulses) to generate the PPS off of the TCXO. The amount of adjustment is a function of the solution they derive from the GPS messages. In some cases they do a solution, and correct the *next* edge to that solution. In other chip sets the solution and the edge come out at the same time.
Bob On Mar 1, 2014, at 2:02 PM, John Seamons <j...@jks.com> wrote: > > On Mar 2, 2014, at 7:05 AM, Pete Lancashire <p...@petelancashire.com> wrote: > >> Idea. On the next go around for the board put the copper down and holes for >> a couple small daughter cards and any support logic needed to interface >> with the BBB. >> The the only additional cost would be limited to the daughter board I/O >> since my guess it would be SMT hence a bit hard to leave it unpopulated. > > Good idea. Also the Beagle spec allows for multiple, stacked interface boards > ('capes' they call them). So for a backwards compatible solution an > experimental GPSDO + backup power cape could be interposed between the Beagle > and 5370 board. I say experimental because I have no idea if any of the SDGPS > projects out there would be ultimately suitable for a DO. > > This brings up a question I have about how the PPS edge is actually derived > by a GPS receiver. Does it originally come from the NAV data stream and then > get corrected by the (fixed-mode) positioning solution to account for > transmission/system delays? I know about the issue of alignment with the > VCTCXO clock, but I'm talking about upstream of that. > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.