[time-nuts] Logging and correlating NMEA messages with TICC timestamp

Forrest Christian (List Account) lists at packetflux.com
Mon Jun 24 05:51:52 UTC 2019


I have a couple of GPS receivers I'm experimenting with that I've been
using a TICC to gather timestamps of the 1PPS output to ascertain
their relative quality.

In the process of doing this, I've discovered that some of the 1PPS
outputs are not as stable as I'd like them to be.  For instance, the
one currently on my bench emits stuff like this every once in a while:

330364.902989667231 chA
330365.582893064933 chA
330365.584094826326 chA
330365.902989679840 chA

Note the 2 inserted pulses between the two correct ones.

I'd like to be able to look at a log of the GPS NMEA output at the
appropriate time for this and other events to determine if they
correspond to some sort of GPS event.    In addition, I'd like to
gather the phase correction data (aka quantization error) from the GPS
(and which is spit out in a NMEA sentence as well) in a way that is
correlated to the TICC timestamp it goes with.

I know I can hack together something in python or similar to open both
ports and log them together using a common timestamp.  But this also
seems like something which is probably being done regularly in time
labs around the globe so there's likely some tool to do this that I'm
unaware of.

So I guess I'm asking what everyone else is using to gather both
timestamp data and NMEA data in a correlated way....

Thanks for any input.

-- 
- Forrest




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