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    On 09/09/2014 08:17 PM, Jacob Gilbert wrote:
    <blockquote
cite="mid:CAC52AkAg3snLQvZK2pqBaj7YDXT7Dfka31cbYKsGXWPbB6q=0Q@mail.gmail.com"
      type="cite">
      <div dir="ltr">Thank you Marcus. I had erroneously assumed the tag
        was an indication that the samples following it were post-retune
        as opposed to it being more of an acknowledgement that the tune
        request had been performed by the driver. It makes sense though
        given how quick DSP tuning is.
        <div><br>
        </div>
        <div>If I were to move to timed commands to perform more
          deterministic retuning, do you know if a tag be generated at
          the time of retuning? And if so, would that have some level of
          assurance that subsequent data is corresponding to the newly
          tuned frequency?</div>
      </div>
    </blockquote>
    B2xx don't support timed commands anyway, as far as I know.<br>
    <br>
    What magnitude of latency are you observing, and at what sample
    rates?<br>
    <br>
    <br>
    <blockquote
cite="mid:CAC52AkAg3snLQvZK2pqBaj7YDXT7Dfka31cbYKsGXWPbB6q=0Q@mail.gmail.com"
      type="cite">
      <div dir="ltr">
        <div><br>
        </div>
        <div>Thanks,</div>
        <div>Jacob</div>
      </div>
      <div class="gmail_extra"><br>
        <div class="gmail_quote">On Tue, Sep 9, 2014 at 8:05 PM, Marcus
          D. Leech via USRP-users <span dir="ltr"><<a
              moz-do-not-send="true"
              href="mailto:usrp-users@lists.ettus.com" target="_blank">usrp-users@lists.ettus.com</a>></span>
          wrote:<br>
          <blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt
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              <div>
                <div class="h5"> On 09/09/2014 08:01 PM, Jacob Gilbert
                  via USRP-users wrote: </div>
              </div>
              <blockquote type="cite">
                <div>
                  <div class="h5">
                    <div dir="ltr"><br>
                      Hello,
                      <div><br>
                      </div>
                      <div>I am having some trouble with a USRP B210 and
                        quickly retuning it for a wideband survey
                        application. I have an OOT GR block which
                        retunes (DSP only, since the LO retune takes
                        quite a while) the USRP via a call to the
                        usrp_source block's retune method, waits for the
                        stream tag, passes some data forward, then
                        repeats.</div>
                      <div><br>
                      </div>
                      <div>The issue I am currently having is on
                        occasion the stream tag indicating the retune
                        will arrive well before the data is actually
                        valid for the frequency the tag is indicating it
                        just tuned to. I had originally thought the uhd
                        source block would insert a stream tag when the
                        USRP indicated the retune had been completed,
                        however in looking into usrp_source_impl.cc:145,
                        it looks like the tag is appended (or indicated
                        it should be appended) immediately after the
                        tune call is made regardless of whether or not
                        the tune in the FPGA has actually completed.</div>
                      <div><br>
                      </div>
                      <div>Is this correct? And if so, is there a better
                        way to know when a DSP-only tune has completed
                        and the data stream is valid for the new
                        frequency?</div>
                      <div><br>
                      </div>
                      <div><br>
                      </div>
                      <div>Thanks,</div>
                      <div><br>
                        Jacob</div>
                    </div>
                  </div>
                </div>
                <pre><fieldset></fieldset>
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</pre>
              </blockquote>
              The FPGA-only tune happens so quickly that the way it is
              currently written is "correct", modulo latencies in Gnu
              Radios internal buffering mechanisms,<br>
                which are definitely outside the scope of what the
              hardware can control.<br>
              <br>
              There will be ambiguous data after a retune, since you
              don't really know how many samples are "in flight" after
              doing that.<span class="HOEnZb"><font color="#888888"><br>
                  <br>
                  <br>
                  <br>
                  <pre cols="72">-- 
Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
<a moz-do-not-send="true" href="http://www.sbrac.org" target="_blank">http://www.sbrac.org</a>
</pre>
                </font></span></div>
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            <br>
          </blockquote>
        </div>
        <br>
      </div>
    </blockquote>
    <br>
    <br>
    <pre class="moz-signature" cols="72">-- 
Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
<a class="moz-txt-link-freetext" href="http://www.sbrac.org">http://www.sbrac.org</a>
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