Re: [Discuss-gnuradio] Transmitting bursts with GRC by inserting SOB and EOB

[Marcus Müller]

Hello Frederik,

On 10/20/2014 05:53 PM, Frederik Wing wrote:
> Thank you Martin for your fast response!
> > - You're using an ancient UHD version. Is there a reason you can't use a
> > newer one?
> I am using Ubuntu 14.04 LTS and just pulled GNU Radio and UHD from the
> packet sources. There is no newer version available. And I don't like to
> compile myself unless it is absolutely necessary.
Consider it outdated. Ubuntu's packet sources are most of the time horribly out 
of pace compared to GNU Radio's development process.
For UHD it's the same. Note that Ettus ships its own Ubuntu packages for UHD 
*and* GNU Radio, so you can get a non-ancient version of both without even 
compiling it.
By the way: GNU Radio is a software radio developer's framework. You can do 
great things with it without touching a compiler, but at many points it becomes 
helpful when one can write his own C++ block, so you definitely need to lose 
your fear of compilers if you want to use GNU Radio to its fullest potential :)
> I don't think it's because of an outdated version of UHD as the
> "tags_demo" application is working perfectly with my current version.
... Well, my old tube radio also still works ;)

Martin went through some work improving the uhd blocks in GNU Radio recently. 
You'll greatly profit.

And: seriously, please use something recent. Using an old version makes it 
really hard to get qualified help!
Also, all the tutorials on gnuradio.org of course revolve around recent 
versions, so if you want to learn GNU Radio,
you should learn it with a modern base.
> > - In current GNU Radio, you can use 'length tags' to mark bursts, if
> > that's any help.
> I tried using length tags by inserting an "Stream to tagged Stream"
> block and adding the length_tag_name property to the USRP Sink. Here is
> my sample code, now with a burst of 5 samples:
The GNU Radio doxygen contains documentation for the current GNU Radio build, 
containing the newly available message passing functionality.
Maybe that's of interest to you!

Greetings,
Marcus
> >          ##################################################
> >          # Variables
> >          ##################################################
> >          self.tx_gain = tx_gain = 15
> >          self.samp_rate = samp_rate = 200000
> >          self.f_center = f_center = 1.47e9
> >          self.device = device = "type=usrp2"
> >
> >          ##################################################
> >          # Blocks
> >          ##################################################
> >          self.usrp_sink = uhd.usrp_sink(
> >                  device_addr=device,
> >                  stream_args=uhd.stream_args(
> >                          cpu_format="fc32",
> >                          length_tag_name="packet_len",
> >                          channels=range(1),
> >                  ),
> >          )
> >          self.usrp_sink.set_samp_rate(samp_rate)
> >          self.usrp_sink.set_center_freq(f_center, 0)
> >          self.usrp_sink.set_gain(tx_gain, 0)
> >          self.usrp_sink.set_antenna("TX/RX", 0)
> >          self.blocks_vector_source_x_0 = blocks.vector_source_c((1,)*5,
> > False, 1, [])
> >          self.blocks_stream_to_tagged_stream_0 =
> > blocks.stream_to_tagged_stream(gr.sizeof_gr_complex, 1, 5, "packet_len")
> >
> >          ##################################################
> >          # Connections
> >          ##################################################
> >          self.connect((self.blocks_vector_source_x_0, 0),
> > (self.blocks_stream_to_tagged_stream_0, 0))
> >          self.connect((self.blocks_stream_to_tagged_stream_0, 0),
> > (self.usrp_sink, 0))
> It's not working either... I can still observe the carrier at the receiver.
> > - You'll know if your USRP hasn't acknowledged tx_eob if you see 'U's
> > between bursts.
> I am getting exactly one "U". Both for the code in my previous post as
> well as for the above one. It really seems like the USRP is not
> recognizing the stream tags.
>
> Any further ideas? Can someone reproduce this behaviour?
>
> Frederik
>
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