[time-nuts] NTP and Oncore UT+

Bob Camp lists at rtty.us
Sat Apr 19 18:17:28 EDT 2014


If you have a serial “thing” hooked to the GPS, pulling the sawtooth data out of it is not very hard. They all have some sort of repeating message that contains time / date / sawtooth information. 


On Apr 19, 2014, at 4:58 PM, Bob Stewart <bob at evoria.net> wrote:

> I've done as much as I can do with my little Adafruit, so I guess it's time to move to a timing receiver.  I already have a UT+, so I might as well make use of it.  My thought was to use the NTP refclock driver and probably take the sawtooth from SHMEM with a simple "C" program to pass to my GPSDO.  The reference pages indicate that a PPS interface is "required".  Do I need to wire up the PPS just to get access to the sawtooth value, or can I just hook up serial access to the UT+ and use NTP as an interface to the UT+?  I have no experience with setting up a refclock driver, so any help would be appreciated.  Using NTP certainly looks a lot easier than figuring out why this UT+ doesn't always like to talk on the serial port and writing custom code to do the bits I want.  The PPS from the UT+ will, of course, be connected to my GPSDO board.
> From the manual:
> "The driver requires a standard PPS interface for the 
> pulse-per-second output from the receiver. The serial data stream alone 
> does not provide precision time stamps (0-50msec variance, according to 
> the manual), whereas the PPS output is precise down to 50 nsec (1 sigma) for the VP/UT models and 25 nsec for the M12 Timing. If you do not have the PPS signal available, then you should probably be using the NMEA 
> driver rather than the Oncore driver."
> Bob - AE6RV
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