[time-nuts] GPS module recommendation for Pi timing

[Hal Murray]

Thanks.

kb8tq at n1k.org said:
> One of the ways a GPS module “freaks out” is to slip by one code cycle
> (which is just slightly over 1 ms). If you have a surveyed location, some
> firmware will reject the solution and at least you will be in holdover.

If it slips, how long does it stay slipped?

I have plenty of old GPS units.  I'm a bit surprised I haven't noticed 
something like that.  Maybe I'm not looking hard enough and/or in the right 
place.

> In a case where the *only* thing you can trust is the GPS, filtering isn’t
> going to do much good. 

You also have the CPU crystal.  It's not good for long term stability, but 
shouldn't have any troubles holding to a ms over several seconds.



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