Re: [Discuss-gnuradio] Reconfiguring OFDM flow graph at run time gives "FATAL: Missing a required length tag on port 0 at item" error

[Kartik Patel]

Hi Damindra,

In the OFDM Transmitter block, check the parameter Length Tag Name. Value of that parameter should be same as Length Tag Key parameter in Stream to Tagged Stream block.

See gr-digital/examples/ofdm/tx_ofdm.grc for an example.

Regards,

Kartik Patel

On Sat, Dec 24, 2016 4:19 AM, Damindra Bandara address@hidden wrote:

Hi,

I am trying to dynamically reconfigure some parameters of a flow graph. My flow graph is as follows.

File source --> stream to tagged stream --> OFDM transmitter --> usrp sink

In the top_block I do the following.

tb.stop()

tb.wait()

<do the reconfiguration>

tb.start()

I have done parameter reconfiguration earlier(before introducing OFDM TX) and it worked fine. However now when I try to do the reconfiguration I get the following error.

FATAL: Missing a required length tag on port 0 at item #160
thread[thread-per-block[2]: <block crc32_bb (16)>]: Missing length tag.
FATAL: Missing a required length tag on port 0 at item #160
thread[thread-per-block[18]: <block crc32_bb (27)>]: Missing length tag.
SSFATAL: Missing a required length tag on port 0 at item #0
FATAL: Missing a required length tag on port 0 at item #0
thread[thread-per-block[86]: <block ofdm_frame_equalizer_vcvc (62)>]: Missing length tag.
thread[thread-per-block[53]: <block ofdm_frame_equalizer_vcvc (93)>]: Missing length tag.
LLLLLLLLUU

I appreciate if someone could help me to figure out what is causing this issue and  how to fix it.

Thank you,

Damindra

 

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Damindra Savithri Bandara,

Ph.D. in Information Technology (Candidate)
George Mason University,
Fairfax,
Virginia