[time-nuts] GPS for Nixie Clock

Gary E. Miller gem at rellim.com
Wed Jul 13 17:01:47 EDT 2016

Yo Mark!

On Wed, 13 Jul 2016 19:17:54 +0000
Mark Sims <holrum at hotmail.com> wrote:

> Most
> receivers with binary messages take around 1000 lines,  but they
> usually support more features.

gpsd GPS drivers in C run from 432 to 1843 LOC.  And likely a number of
features are missing, but few that anyone misses.

> Parsing the GPSD JSON formatted
> messages is quite a bit more complex than NMEA if you want to do it
> "properly".

If you grab the gpsd JSON feed, and you have a decnet JSON parsing 
library then the parser should be short.

The cgps client does it in 847 lines including curses ouput, and parses
a lot of odd stuff.

That said, the NTPsec driver in C for gpsd JSON is almost 2200 lines.
But that is not a shining example of code...

You only need to write one parser for gpsd JSON.  If you try to do NMEA
directly you will find a ton of variants.  Likely all you would need is to 
connect and then parse the PPS sentence (TOFF):  That looks like this:

{"class":"TOFF","device":"GPS0","real_sec":1428001514, "real_nsec":1000000,"clock_sec":1428001513,"clock_nsec":999999999}

Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
	gem at rellim.com  Tel:+1 541 382 8588
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