[time-nuts] Re: Knowing when the PPS signal is locked to the satellite.

[Matthias Welwarsky]

On Mittwoch, 22. Juni 2022 14:59:29 CEST Dave via time-nuts wrote:
> I am using a NEO-6M to provide a PPS signal for an experiment but I need
> to know when it is locked or not.
> 
> Does anyone know if there is a way to find out from either the NMEA data
> stream or via the proprietary protocol ??

You can check e.g. the UBX-NAV-PVT message, if will tell you if the receiver 
has a valid UTC time and also the time uncertainty and what type of fix 
generated the nav solution. Or, UBX-NAV-TIMEUTC. Or, just UBX-NAV-STATUS. 

You can assume that as soon as a 3D or TIME fix is reported, the PPS is locked 
to GPS, or once the time uncertainty drops below a certain threshold.

Note that this is what an M8 receiver will provide. I don't have any manual 
for the M6 receivers at hand, so the actual messages might be different for a 
M6 which supports a different protocol version than the M8.

> At the moment I have it programmed to only provide a PPS signal when it
> is locked (or nothing if not) and monitor
> the PPS signal in the microprocessor, but it's not entirely satisfactory
> and I need a better mechanism.

That's not a bad mechanism actually. The PPS output is practically useless 
while the receiver is not locked to GPS.