[USRP-users] 10us+ sample delay between daughterboards

Marcus D. Leech patchvonbraun at gmail.com
Thu Jul 23 09:50:00 EDT 2020


On 07/23/2020 06:13 AM, Marcus Müller via USRP-users wrote:
> I also just realized that you can be reaaaally silly. If you have a
> transistor and two resistors to spare, use the GPIO front panel
> connector to generate a faux-PPS pulse, buffer it using the transistor,
> and feed it back to the backpanel PPS input... might save you the extra
> device, but of course the RPi solution is still elegant, as it allows
> for not-quite-but-at-least-close-ish NTP synchronicity.
>
> Cheers,
> Marcus
>
You don't need any external hardware at all.

B2xx, X3xx, N3xx all have a synthetic internal 1PPS if there is no other 
source.

The code generated by GRC for the "unknown PPS case" needs to be 
post-facto modified so that instead of setting a 0, it sets it to system
   time (or whatever you desire).  This is simple to do.  It really 
would be nice if gr-uhd had an option to do this instead of setting to 
0, but
   it doesn't.





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