[time-nuts] GPSDO with a RaspberryPi

Azelio Boriani azelio.boriani at screen.it
Fri Mar 1 08:38:15 EST 2013


OK, I'll try to rewrite and test that section.

On Fri, Mar 1, 2013 at 2:28 PM, Javier Serrano <
javier.serrano.pareja at gmail.com> wrote:

> On Fri, Mar 1, 2013 at 10:40 AM, Azelio Boriani
> <azelio.boriani at screen.it> wrote:
> > The metastability from the PPS latching the counter is indeed a problem:
> > rarely do I see out of range numbers and have to filter them out.
>
> You cannot filter them out. One time you will have bit 10 wrong and
> you will be able to detect that, but what if it's bit 3, or bit 2, or
> both? How can you know? What I proposed in a previous message solves
> your problem: get the PPSReference signal into the Clk10MHz domain
> before using it. This is the tried and proven way to deal with
> metastability. I can provide a code snippet later if needed.
>
> Cheers,
>
> Javier
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