PPS and selection algorithm issues

[Hal Murray]

users at ntpsec.org said:
> *NMEA(0)     .GPS.        0 l    3   16  377   0.0000   0.2415 0.3372
> xPPS(0)      .PPS.        0 l    2   16  377   0.0000 -0.7080   0.0497 

The x says it isn't using the PPS driver.

> refclock nmea flag1 0 baud 9600 minpoll 4 time2 0.097
> refclock pps minpoll 4 flag2 0 time1 0.002 

Try adding a prefer to the nmea line.  THe PPS driver needs some place to 
get the seconds.  The prefer keyword is a hack to do that.

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If you want to get geeky, turning on flag3 for the PPS driver will move 
the PLL into the kernel.  That makes a significant difference.  I should 
make some pretty grapsh.

That isn't supported on the kernels shipped by most Linux distros -- it 
conflicts with power saving (or something like that).  If you want to 
build your own kernel, it needs:
  CONFIG_NTP_PPS=y
Or you can try FreeBSD.  The kernel they ship is ready to go.

-- 
These are my opinions.  I hate spam.