Hi Pretty much any generic GPS module will get you to 1 ms without a lot of effort. There is certainly no need for the M9F or M9T sort of parts. A typical module will deliver a pps signal that is better than 100 ns as far as timing.
How good you can do via serial on a Pi depends a bit on how loaded it is. “Microsecond" level performance is possible. I’d target low cost over performance in this case ….. Are you laying out a board for your gizmo? If so, there are a number of drop in solutions for not a whole lot of money. Bob > On Mar 13, 2020, at 10:06 AM, Brian Lloyd <br...@lloyd.aero> wrote: > > I have an application where I need to synchronize the internal TOD RTC in a > raspberry pi and need to pick a GPS module. We are building our own > hardware but still using the Pi so interconnection will be via GPIO/serial. > We won't try to use USB. > > This is not an NTP application. These units will be in the field and will > most likely not have Internet access. I need their clocks to be pretty > close. I am shooting for 1ms ... if possible. > > The new M9F and M9T modules from Ublox are a bit pricey. The M8T is a bit > more reasonable. OTOH I realize there are limits to how tightly I can > control the Pi's RTC and will run into diminishing returns, so even the M8T > might be overkill. > > Has anyone here figured out what the reasonable limit is for timing on a > Pi, and what makes sense for a timing module for an application like this? > > Thanks. > > -- > > > > Brian Lloyd > 706 Flightline > Spring Branch, TX 78070 > br...@lloyd.aero > +1.210.802-8FLY (1.210.802-8359) > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.