[time-nuts] time sync from cellphone TO microcomputer

Esa Heikkinen tn1ajb at nic.fi
Sun Nov 22 04:08:50 EST 2015

Jim Lux kirjoitti:

> While this is trivial with a GPS receiver, we were thinking about a very 
> minimalist implementation, with a smart phone as the control interface.

Forget the smart phone - at least if it's un-rooted Android. I'm not 
sure how the default time sync is done, it's either by Google servers 
(which are famous of their non-standard way to handle leap seconds) or 
NITZ protocol from cellular network. Either way the time quality is very 
poor. It may be off even tens of seconds and usually it's off at least 
couple of seconds at most of the time.

You can have it synced by millisecond only by rooting it first and then 
installing some kind of NTP client or application. But it will be in 
sync only as long you keep the display on. I believe there's some kind 
of power saving methods wich cause the clock to go off-sync right after 
the display is turned off. This can be seen with NTP application easily.

So I prefer to use Raspberry Pi for example. You can create even Startum 
1 level NTP server with GPS receiver and Rpi. It works with same USB 
power supply than most smart phones and it can have WiFi if you want.



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