[ntp:questions] Second attempt at GPS-18 based NTP server

unruh unruh at invalid.ca
Thu Feb 2 17:07:55 UTC 2012

On 2012-02-02, Thomas Laus <lausts at acm.org> wrote:
> On 2012-02-02, Paul Duncan <pdu at noc.ac.uk> wrote:
>> So, I *think* that everything is okay, and it is using the PPS signal. 
>> There is one slight worry, which is what I see in /var/log/messages:
>> Feb  2 09:50:16 tock ntpd[1573]: refclock_nmea: time_pps_kcbind failed: 
>> Operation not supported
>> Please note, I have not done any recompiling of the kernel at this stage 
>> - just using the GENERIC kernel, because after reading the comments from 
>> Per Hederland in the System software customisation section of the above 
>> web page, it seemed unnecessary. Comments?
> I think that you will need to recompile uour kernel with the following
> option added.

In the latest linux kernels, the pps option is already included, if
selected by your distribution.
config PPS
config PPS_CLIENT_LDISC  (for serial DCD line support)
config PPS_CLIENT_PARPORT ( for parallel port support)

 I know that Mandriva supports only the parport as supplied-- why I have
no idea since almost everyone uses the serial port for PPS supply. 
But you can compile just the modules themselves if you want to, rather
than recompiling the whole kernel.

Eg, a make file with 
in it. 

Note that the parallel port support almost certainly does not work if
your parallel port is an add-in card with interrupt sharing support.

Here is my makefile to compile the serial module

 DEBFLAGS = -O2  #"-O" is needed to expand inlines

# call from kernel build system

obj-m   := pps-ldisc.o


KERNELDIR ?= /lib/modules/$(shell uname -r)/build
PWD       := $(shell pwd)



        rm -rf *.o *~ core .depend .*.cmd *.ko *.mod.c .tmp_versions

depend .depend dep:
        $(CC) $(EXTRA_CFLAGS) -M *.c > .depend

ifeq (.depend,$(wildcard .depend))
include .depend

> # Enable support for the kernel PLL to use an external PPS signal,
> # under supervision of [x]ntpd(8)
> # More info in ntpd documentation: http://www.eecis.udel.edu/~ntp
> options         PPS_SYNC
> Tom

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