[time-nuts] Re: Small NTP appliance

[folkert]

> > I have one general question. I don't believe that an internal crystal in the
> > microcontroller will have the accuracy or precision required to have better
> > than a few milliseconds of accuracy (whereas NTP likes to live in the
> > microsecond realm), though I very well could be wrong on that one.
> 
> Accuracy is not a problem.  You can measure that and correct for it.
> 
> Most modern kernels have a side door used by ntpd to adjust the clock 
> frequency.  Typical values are few 10s of PPM and it's easy to measure down 
> 0.001 PPM or better.  The NTP world calls that drift.  If you have a PC or 
> Raspberry Pi running Linux or *BSD and ntpd you can find the drift.

Hmmm, I believe Eamonn is going to use a microcontroller. They usually
don't run linux or something like that.

In a distant past I tried replacing the clock-crystal of an arduino with
an OXCO. That was not succesful but that was because I realised I would
have to make changes to e.g. the bootloader and such so that things
would still have correct bitrate on the serial pins. Hmmm, maybe if I
just had put code on it that would simply output something over the
serial pins on a known baudrate, I could've checked if it indeed worked
at the electronics-part.