[LinuxPPS] PPS/ntpd fails on fresh startup

[Luca Bertagnolio]

Rodolfo,

On Tue, Oct 14, 2008 at 2:05 PM, Rodolfo Giometti <giometti at enneenne.com> wrote:
>> Looks like ntpd might have some initialization issues, maybe? BTW,
>> this happens with both a 4.2.4p4 and a 4.2.5p135 build.
>
> Yes. If I well remember some GPS antenna should be enabled for PPS
> signaling, maybe something there is wrong?

my Garmin GPS18LVC keeps PPS running the whole time, and I've configured it
so that the RMC sentence is the only one sent over the serial line.  The PPS
line is hardwired to an LED which keeps flashing roughly every second... :-D

I don't believe that the NMEA driver (20) does initialize the GPS
unless a "mode"
line is added to the configuration, and I don't have such line.

> Try to take a look into your NTPD GPS driver and try to understand
> where the IRQ or PPS are disabled.

I can try to read into refclock_nmea.c but what strikes me is the fact
that on the
very first run it doesn't work, while on the second and following it
*does* work.

Could it be something that it's done in the *deinitialization* phase
of ntpd that
"fixes" the situation?  Maybe Venu can give us a few more hints as he's worked
on the refclock_nmea.c code in the past, I see from the notes...

> Do you know if other people with your same GPS antenna have got
> similar problems?

nope.  I've only heard about happy users of the GPS18LVC, but maybe their
first instance of ntpd does not work either, but they bitch and moan a whole
less than I do... :-D

Ciao, Luca