[ntp:questions] Re: Please demistify the SHM driver

Jerome Oufella oufella at SPAMBLOCKchez.com
Wed Sep 17 19:48:50 UTC 2003


Thanks everyone for your help, these instructions allowed me to write a 
working SHM driver interface to my GPS clock. It seems working actually, 
NTP.

# On the host where the GPS clock is attached :
localhost:~$ ntpq -p
remote      refid      st t   when poll reach  delay   offset  jitter
=========================================================================
LOCAL(1)   LOCAL(1)    9  l   42   64   377    0.000    0.000   0.008
*SHM(1)    SHM(1)      10 l   20   64   377    0.000   -2.813   4.625

# And on a remote host ntp-syncing on the previous one :
remhost:~$ ntpq -p
remote       refid      st t  when poll reach   delay   offset  jitter
==========================================================================
  LOCAL(1)    LOCAL(1)   9  l  34   64   377     0.000   0.000   0.015
*lift-puurai SHM(1)     11 u  22   32   377     16.467  0.313   1.255

Regards,
Jerome.



Jerome Oufella wrote:
> Hi everyone,
>     I'm writing an handler for a proprietary kind of GPS clock, using 
> RS232 signals and the SHM driver.
> The NTP documentation describes the structure of the memory segment, and 
> says that :
> 
> "[...] (clockTimeStampSec, clockTimeStampUSec,
>         receiveTimeStampSec,  receiveTimeStampUSec,
>         leap, precision) are passed to ntp
> [...]"
> 
> What value(s) should I set, while my GPS clock only sends me the 
> following values :
>  - Day
>  - Month
>  - Year
>  - Hour (local time)
>  - Minutes
>  - Seconds
> Once every minute. I use them to build a UNIX time_t. Should it be 
> stored in clockTimeStampSec or receiveTimeStampSec ?
> What about leap & precision ?
> 
> Thanks in advance.
> 
> Jerome.
> 




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