Re: NTP with a Serial PPS

Hi to all,
at first i want to thank you everyone for the rapid reply and for labour supply.
So I want give you some answers in order to make you understand well
my configuration/actual scenario on my environment.

Jason Rabel wrote:
I don't think you really need to use the "disable" lines in the compiling,
having the extra clocks doesn't hurt anything. In addition to the SHM driver
you probably need the PPS/ATOM driver too which isn't in your compile
string...

I don't have recompiled my kernel (2.6.18) with other modules.
I have only downloaded the last version of ntp software and installed it.
The shmpps is the only software that I'm using , so I don't know if
changing only the "configure parameters" in the ntp installation it
will change something.
The shmpps driver seems work but it seems that ntp software ignores
the existence of the SHM source.

Hal Murray wrote:

The SHM driver is only useful if you have a helper program running
outside ntpd which writes to the SHared Memory segment.

Does anything other than gpsd write info to the SHM segment?

I don't thinks that in my pc is running other "helper program" outside ntpd.



The (atomized) NMEA driver is the correct one to use with the GPS-18LVC.

I've lost track of PPS support in Linux. The NMEA driver uses
the PPS signal if the kernal supports grabbing the timestamp.

I think gpsd does it without special kernel support. (I haven't
tried it.) If so, it's probably better than the NEMA driver
without kernel support.

In my pc is not installed gpsd. I suppose it is a daemon ...
If I have understood well, this daemon will suplly the requirement of
a "kernel support", so it could be better for me instead of
reconfigure and recompile the kernel.

Chris Adams wrote:

I use shmpps from http://time.qnan.org/ on Linux; it works fine for me.

Perfect. Can you see in the "ntpq -p" output a line similar to :

*SHM(0) .PPS. 0 l 13 16 377 0.000 -0.015 0.004

If no, what it mean for you "it works fine for me".
If yes, whitch SW tools are installed on your pc? Is your environment
similar to mine?
MY ENVIRONMENT IS:
PC LINUX with kernel 2.6.18 + ntp last version sw + shmpps SW

In my previous mail you can find also my ntp.conf file content.


Thanks to all community,
Best Regards
Elio Giugliano.
.

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