Re: Synchronization: PPS and Tx signal in a USRP N200

[Marcus D. Leech]

On 2021-12-10 17:25, isaac mario tupac davila wrote:

Hello everyone!

My name is Isaac. I have a curious situation here... I've generated a pulsed signal per second. I've saved one second period in a .h5 file, so that I'm sure I'm having a fixed signal per second, and then repeat it in my GRC flowgraph. .

To use this signal as Tx I'm trying to synchronize a USRP N200 and a trimble in GRC. After run my flowgraph, this is what I see:

The yellow signals are the PPS of my trimble and my purple signals are my tx signal per second. They are periodic in time but when you see it deeper, the difference between the timble PPS and my Tx signal is approx 97 ms. I think this difference should be close to cero, as my USRP and trimble are synchronized. ¿What is happening here? ¿Is this a normal behavior? I'm using unknown PPS to configure my UHD:USRP sink in GRC....

I'll appreciate any help to clarify this behavior

Regards

Isaac T.

    Your flow-graph made very little sense to me.  If you want to
    synchronize your TX, you have to take explicit measures to ASK the
    USRP to schedule your transmits at specific times.
      The 1PPS signal only synchronizes an internal time-stamp clock in
    the unit.  It has NO WAY of knowing what the *meaning* of your
    samples are, so it can't possibly
      synchronize some arbitrary event in your continuous sample stream
    to 1PPS without you explicitly asking for when your bursts need to
    be sent.
    
https://kb.ettus.com/Synchronizing_USRP_Events_Using_Timed_Commands_in_UHD