[Pool] High Offset / Jitter

Alby alby at empire.org
Tue Mar 1 19:11:48 UTC 2011



Courtney:

 You are my heroine today. :) Looks like I gotta get crack'n on
upgrading debian to squeeze and 2.6.37  :)



On Tue, March 1, 2011 2:06 pm, Courtney Bane wrote:
>
> The kernel driver for using the serial DCD pin as a PPS source didn't
> actually hit the mainline kernel until 2.6.34 (I think); it was the PPS
> framework that went in in 2.6.32. Additionally, it didn't get enabled in
> Debian until 2.6.37, which is currently only in unstable (hopefully it'll
>  hit testing next week). Ubuntu has it enabled in the 2.6.35 kernel in
> 10.10 (aka Maverick).
>
>
> However, even with a kernel supporting PPS, you'll still need to rebuild
> NTP, since Debian's version doesn't have PPS support enabled. It should
> just be a matter of dropping the timepps.h header file in
> /usr/local/include, and rebuilding the package. The instructions linked
> to before also cover rebuilding ldattach; if you're running Squeeze (the
> newest stable version, released last month) or newer, you don't need to
> do that.
>
> My home time server is running Debian Squeeze, with the latest 2.6.37
> kernel pulled in from unstable. The only thing I've compiled myself was
> NTP. For configuring the serial port, I created an
> /etc/udev/rules.d/09-pps.rules file (pasted below); it sets up a /dev/gps0
>  symlink to the appropriate serial port, enables PPS and low-latency on
> the serial port, and creates a /dev/gpspps0 symlink to the PPS device.
> I've
> also pasted the relevant output from "ntpq -p" to show that it's working.
>
>
> /etc/udev/rules.d/09-pps.rules:
> KERNEL=="ttyS1", SYMLINK+="gps0"
> KERNEL=="ttyS1", RUN+="/bin/setserial -v /dev/%k low_latency"
> KERNEL=="ttyS1", RUN+="/usr/sbin/ldattach pps /dev/%k"
> KERNEL=="pps0", OWNER="root", GROUP="tty", MODE="0660", SYMLINK+="gpspps0"
>
>
>
> $ ntpq -p
> remote    refid  st t when poll reach   delay   offset  jitter
> ===================================================================
> oGPS_NMEA(0)   .GPS.   0 l    5   16  377    0.000    0.001   0.002
>
> --
> Courtney Bane
> "He that would make his own liberty secure, must guard even his enemy
> from oppression; for if he violates this duty, he establishes a precedent
> that will reach to himself."  -- Thomas Paine
>
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> pool mailing list pool at lists.ntp.org http://lists.ntp.org/listinfo/pool
>
>




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