Hi Max!  Thanks for the information, I was wondering if you had documented what 
you did to your Raspberry Pi so that it might be reproducible to someone like 
me (a newcomer time-nut and intermediate Linux user) ... you had said:

>>"Here is what I have been able to do with a Motorola Oncore UT+ that I got 
>>from Bob Stewart awhile back.  This is with a Raspberry PI 2 with a number of 
>>tweaks and a custom compiled kernel.  Nothing too drastic... plus the current 
>>Dev version of NTP compile on the Raspberry PI."

What tweaks?  What options have you compiled?  What are the gritty details of 
your setup?

>> "I'm getting better results letting ntpd discipline the clock over doing 
>> kernel discipline...
not surprising because the algorithms in the ntpd code are much more 
sophisticated than the Linux kernel pps code... ntpd discipline provides much 
lower jitter in my experience."

what setting is this and how might I go about experimenting with it?  Is that 
the "flag3" option in the "Generic NMEA GPS Receiver" documented here?  
https://www.eecis.udel.edu/~mills/ntp/html/drivers/driver20.html

<snip>

>>"Not too shabby for a killer deal on an Oncore UT+ for $5 from Bob!  I'm 
>>running the PPS out of the UT+ through a level converter to get the ~3.3v PPS 
>>output... the serial output on the UT+ is also going through a level 
>>converter direct into the Pi 2.  Using the oncore 127.127.30.0 ntpd driver 
>>and again, i'm not using hardpps kernel discipline."

I see word HARDPPS in the driver you mentioned 
(https://www.eecis.udel.edu/~mills/ntp/html/drivers/driver30.html ) but that 
documentation is a bit scarce... Could you fill me in on how you have it set 
up?  Is the PPSAPI also used for the "Generic NMEA GPS Receiver" (driver 20) or 
the PPS driver (driver 22)?

Thanks so much for your assistance!  Sorry if these questions have been posted 
before, but I am very curious about your setup as it nearly matches mine!

    -Randal "r3" of CubeCentral



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