Hi Calibrating your GPS pulse ambiguity is one of the all time great reasons to get a WWVB based wall clock !!!
Bob > On Jun 6, 2017, at 8:38 PM, Graham / KE9H <ke9h.gra...@gmail.com> wrote: > > Ben: > > Be careful. > > Most GPS receivers send out the serial message after the tick, that tells > you what the time of the tick was. > > Read the manual. > > If you want to drive a clock display with a GPS, you pretty much have to > have an independent time system that advances on the tick, then validate it > when the serial message shows up. > > --- Graham / KE9H > > == > > On Tue, Jun 6, 2017 at 6:46 PM, Ben Hall <kd5...@gmail.com> wrote: > >> Good evening all, >> >> There is a saying: "a man with one watch knows the time, a man with two is >> never sure." Clearly, this man wasn't a timenut and didn't have GPS. ;) >> >> I've been working on the Arduino code for the TruePosition boards that >> quite a few of us have bought from the e-place. >> >> It's my first real foray into both Arduino and the C language. (About a >> million years ago I was reasonably competent with FORTRAN...the 1977 >> version...) It's mostly working - I can receive and display pretty much >> everything that comes out of the unit minus a few parameters. I can >> display it all on three pages on a 4 line by 20 character I2C display. >> Currently, the pages are selected by grounding out one of two pins, or >> having nothing grounded. Eventually, I'm going to change this so that it >> changes display pages when a button is pressed. I don't have lat/long >> display yet, nor can I handle doing a survey, but those are coming. >> >> My code probably would make a real programmer vomit, but hey, it works. :) >> >> Back to the man with multiple watches. I was having a very frustrating >> issue with my TruePosition and Arduino code being one second behind my >> other sources of time. I went round and round, trying to figure out why >> the TruePosition thru the Arduino was a second slow. In the end, it turns >> out that it wasn't slow...it was correct...but that my other sources of >> time have errors. >> >> I finally proved this to myself by firing up an old Trimble Lassen LP GPS >> board unit equipped with a 1PPS tick light and serial output...and it was >> clear that it matched the TruePosition after correcting for the fact that >> my TruePosition / Arduino code only updates the display when 1PPS is >> asserted high...but that the Lassen LP displays the serial message before >> it becomes valid at the next 1PPS tick. >> >> I was slightly embarrassed...I should have known that the other sources of >> time all had sources of error beyond my control. I should have trusted the >> TruePosition as being the purest, least complicated, and the path I knew >> the most about between GPS and my eyeballs. >> >> So for a while...the statement was true. With my multiple sources of >> time...I really didn't know the time. But it was also untrue, as when I >> got agreement between two very "pure" sources of time, I knew everything >> else was wrong. ;) >> >> I'm getting to the point that once I've got the button logic working, I'll >> send out my source to anyone who wants to take a look at it or use it. I >> will stipulate one condition - you can't make too much fun of how poorly >> programmed it is. ;) >> >> thanks much and 73, >> ben, kd5byb >> _______________________________________________ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to https://www.febo.com/cgi-bin/m >> ailman/listinfo/time-nuts >> and follow the instructions there. >> > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.