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Re: [Discuss-gnuradio] Fwd: Newbie: usage of PDU to Tagged Stream block


From: Dave NotTelling
Subject: Re: [Discuss-gnuradio] Fwd: Newbie: usage of PDU to Tagged Stream block
Date: Sun, 5 Mar 2017 12:26:47 -0500

Here is your graph with a slight modification of your graph to show what happens if you have the CAR populated.



On Sun, Mar 5, 2017 at 12:20 PM, Dave NotTelling <address@hidden> wrote:
You don't see any output from the Tag Debug block because it only shows the tags, not the data.  You actually don't have any tags in your data.  You just have a PMT object with a NIL CAR and a populated CDR.  Since there are no elements in the CAR, you get no tags.  I personally got confused because I thought that if I passed in a valid CAR/CDR combo to the pmt generator then it would just overwrite the CDR portion.  Not so, it actually ignores whatever data comes in.  Check out http://gnuradio.org/doc/doxygen/page_pmt.html for more info about PMT objects.

On Sun, Mar 5, 2017 at 8:33 AM, Jorge Carpio <address@hidden> wrote:
Hi all,

I'm pretty new to GNU Radio, I followed the tutorials and made some simple flowgraphs to use with an USRP. Recently took a look at the gr-digital packet communication examples.

I'm having trouble figuring out the right way to use the PDU to Tagged Stream block. I connected a Random PDU Generator to the input of the block, expecting a tagged stream to be produced at the output. But I must have misunderstood something, because there is no way I can see the samples being produced in the tagged stream of bytes. I can only see the length tags in the output stream, but no trace of the PDU data. Not even when I try to write the stream to a file or to stdout.


Attached is the flowgraph I'm using.

Cheers,
Jorge

 


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