[ntp:questions] Using a uC based embedded device as SNTP server
Richard B. Gilbert
rgilbert88 at comcast.net
Fri Feb 17 01:16:11 UTC 2012
On 2/16/2012 4:52 AM, Thorsten Mühlfelder wrote:
> I've already posted these questions 8 months ago without answers, but
> now the problem came to my mind again. Sorry for double post.
> I'm using a Atmel uC embedded device as SNTP server. The code is
> working so far, but I wonder what the correct settings are for:
> * stratum
If your Atmel uC gets its time from an atomic clock directly, it is
Stratum 1. If Atmel uC gets time from a stratum 1 server it is a
stratum 2 clock and so on. Each hop adds a little more garbage to the mix.
> * precision
Precision describes how finely you can "slice" time. This has little or
nothing to do with accuracy.
> * root dispersion
> * reference identifier
> * reference timestamp
> The embedded device has a battery buffered hardware RTC, that is
> capable of 1 second resolution. The used oscillator though has a
> frequency tolerance of 20 ppm.
> On startup the device tries to get the time from a pre-configured NTP
> server once.
> In my understanding my server is a stratum 1 with reference identifier
> LOCL. Also I chose reference timestamp as last time correction by
> SNTP. Is this correct?
> I also wonder about the precision an root dispersion settings, as the
> RTC only has a resolution of 1 second.
> Thanks for any help, I'd like to set it up the right way.
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