[time-nuts] WWVB Signal Generator

Andy Backus ANDREWBACKUS at msn.com
Thu Sep 6 13:17:34 EDT 2018


Instead of relying on the PPS to time the start of the simulated WWVB transmissions, I opted instead to rely on the Arduino timing functions and then refresh the data and the start every five minutes.  No WWVB clocks use the signal continuously; generally they all copy the signal once a day.


Also -- when the GlobalTop loses a fix it still puts out the RMC sentence, just without the lat and lon data.  And the PPS immediately stops.  I designed the parsing scheme to account for that.  How long that reporting would continue I don't know.


Andy Backus


________________________________
From: time-nuts <time-nuts-bounces at lists.febo.com> on behalf of Wayne Holder <wayne.holder at gmail.com>
Sent: Wednesday, September 5, 2018 5:49 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] WWVB Signal Generator

I was able to sort out my issue with the DST bits with the help of the
code Andy Backus recently published.  I believe my code should now be ready
for anyone who's curious to try out.  Complete details are available on the
following page:

  https://sites.google.com/site/wayneholder/controlling-time-2


This new code is a bit simpler than the ATTiny85-based code I published
before, as I've eliminated the use of interrupts and now use the GPS
module's PPS signal to control bit timing and simple calls to the millis()
function to control the timing of the bit modulation.  I still recommend
swapping the 16 MHz crystal for a 15.36 MHz one, but you should be able to
run the code on any ATMega328-based Arduino using a 16 MHz clock, although
with reduced range from the antenna to the clock.

Wayne

On Wed, Sep 5, 2018 at 8:48 AM Mark Sims <holrum at hotmail.com> wrote:

> If your receiver has it the $GPZDA  can be a better message to use.   They
> usually have better seconds resolution and some receivers give them some
> special love as to when they come out.  But, depending upon your code, this
> may not matter.  Also check to see if your chosen time message comes out
> before or after the 1PPS.
>
>
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