I also use TinyGPS++, though a version I've modified for the MSP430 and 
other processors - I've also made it "const correct" and added conditional 
compilation so that a reduced size version can be built if you don't need 
the maths stuff (that drags in a whole bunch of libraries that may waste a 
load of space). I did provide my modified version back to Mikal at Sundial 
plus some comments about handling negative heights (below sea level) etc. - 
some of that has made it into the latest version.

I ignore the RTC when GPS is available but use the NMEA $GPRMC sentences to 
discipline the RTC. When I've no GPS for a while, I switch to the RTC, e.g. 
when the network is down and my NWTS is not seeing NTP or the GPS puck just 
loses its fix.

Nick

On Wednesday, 29 September 2021 at 17:34:27 UTC+1 nixiebunny wrote:

> My latest scope clock uses a DS3232 RTC chip for general timekeeping. This 
> chip only keeps time to the nearest second, as far as the user-readable 
> registers are concerned. 
> I also have a USB port that can read the time from a GlobalSat GPS puck. 
> This reports the time once a second through the Arduino TinyGPS library, 
> with the age of the time in milliseconds (typically 250). This should let 
> me compensate for the read delay by setting the tick (50/60Hz) counter in 
> my local time variables.
> What do any of you time nuts do about displaying the time accurately, and 
> making the RTC be reasonably accurate compared to the GPS? 
> Do you discipline the RTC with GPS? Do you just ignore the RTC when GPS is 
> available? Set the RTC occasionally?
>
>

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