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

[Frederik Wing]

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.
I don't think it's because of an outdated version of UHD as the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.
> - 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:
>         ##################################################
>         # 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