Use gps for clock correction

Russell Sears sears at cs.berkeley.edu
Thu Aug 14 19:29:54 CEST 2008


Bastian Muck wrote:
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> GPS would be perfect for updating time, cause the time sent is more 
> exact then the times, you can get by any other way. What about ntpd, can 
> it handle gps-data?
> 

Yes, with some work:

http://time.qnan.org/

Does the FR have access to the PPS signal from the GPS chip?  That might 
get it down to tens of microseconds of clock jitter.  :)  It looks like 
gpsd should work as well.  Plus, ntp can fall back on NTP over 
GPRS/wifi/usb if it's been a while since the last GPS connection.  It 
can also set the hardware clock skew so it drifts fewer minutes per day 
when there's no network or sky.

I wonder how hard it would be to add GSM time broadcast support to NTP...

-Rusty

> Stefan Schmidt schrieb:
> | Hello.
> |
> | On Thu, 2008-08-14 at 23:48, Matt wrote:
> |> Isn't time available via GSM broadcasts?
> |
> | Sometimes. There is a standard for it, but not all operators have it 
> enabled for
> | it. AFAIK no german provider has it for example.
> |
> | If anyone have a provider which has this feature enabled and like to 
> develop a
> | patch just let us know.
> |
> | regards
> | Stefan Schmidt
> |
> | -------------------------
> |
> | _______________________________________________
> | Openmoko community mailing list
> | community at lists.openmoko.org
> | http://lists.openmoko.org/mailman/listinfo/community
> 
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