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I'm taking the GNU Radio discussion list into CC: here, as we're
also kind of talking more about general GNU Radio usage; feel free
to follow up on either list (you'll need to sign up for
discuss-gnuradio, though, if you want to directly post there, see
So, stream tags, PDUs and bursty transmission are three different
* Think of stream tags really as annotations tagged to your sample
* Think of PDUs just as buffer full of data/samples with a simple
"that's how many samples there are" header. They usually are
transported as messages, not as streams.<br>
* Think of tagged streams as the combination of specially formed
stream tags with the ability of blocks to understand that what it
sees are packets of items, marked by a "begin/length" tag. That
constructs a "packetized" or "burst" transmission mechanism atop of
the "normal" stream processing. <br>
So, the UHD USRP sink are able to consume a stream of samples,
usually. That's the "normal" modus of operation. If you tell the
sink to look for a specific length tag, it will switch to a mode
where it will expect the stream to contain that tag, and send out
the the bursts defined by those tags, either at the point of
reaching the USRP sink, or at the point in time contained in another
tag, the "tx_time" tag.<br>
So two ressources to point you at<br>
<li>The official Guided Tutorials of the GNU Radio community.
These are sequential, so I strongly recommend starting at part 1
and finishing with part 6 or 7, if you haven't already. </li>
<li>The GNU Radio doxygen, which contains a description of the
USRP sink and what tags it takes  .<br>
 <a class="moz-txt-link-freetext" href="https://lists.gnu.org/mailman/listinfo/discuss-gnuradio">https://lists.gnu.org/mailman/listinfo/discuss-gnuradio</a><br>
<a class="moz-txt-link-freetext" href="https://gnuradio.org/redmine/projects/gnuradio/wiki/Guided_Tutorials">https://gnuradio.org/redmine/projects/gnuradio/wiki/Guided_Tutorials</a><br>
 <a class="moz-txt-link-freetext" href="http://gnuradio.org/doc/doxygen/page_uhd.html">http://gnuradio.org/doc/doxygen/page_uhd.html</a><br>
<a class="moz-txt-link-freetext" href="http://gnuradio.org/doc/doxygen/classgr_1_1uhd_1_1usrp__sink.html">http://gnuradio.org/doc/doxygen/classgr_1_1uhd_1_1usrp__sink.html</a><br>
<div class="moz-cite-prefix">On 10/30/2015 06:18 PM, Marius via
<pre wrap="">Hi Martin,
Yesterday I started reading about stream tag and I’m still trying to understand how it works. I definitely know that this is the right track for me,
but I could’t find any explained python examples that could be similar to my project.
I’m not looking to create PDUs, but to be able to transmit a signal from a file, for a predefined nr. of seconds and at certain periods in time.
Please, If you have the time to send some links that you consider it will help me, knowing what I want to achieve with my program.
I know this looks easy for you, but for a newcomer in GNU Radio, trust me, it looks quite difficult.
I’ll take it easily and probably will manage to understand it.
USRP-users mailing list
<a class="moz-txt-link-abbreviated" href="mailto:USRPfirstname.lastname@example.org">USRPemail@example.com</a>
<a class="moz-txt-link-freetext" href="http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com">http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com</a>