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Re: Communication using Packets

From: Paul Atreides
Subject: Re: Communication using Packets
Date: Thu, 4 Nov 2021 23:23:18 -0400

Good news. I just tested both of the examples on GNURadio and the issue described here does not occur.
I'll test again on 3.8 and see if I can reproduce the issue.

On Thu, Nov 4, 2021 at 6:24 PM Paul Atreides <maud.dib1984@gmail.com> wrote:
Im also having the same error in this stage of the tutorial, running GNURadio 3.8.(3?)

Playing around with the embedded block and I also re-typed most of the lines. there were some white spaces I thought might be problematic, but I don’t think they were. 

Wondering if it’s because the message_pub is trying to send a list inside a pmt which I think PMT’s are by nature immutable. is there a python_to_pmt(char_list) needed here? I’m gonna try it on 3.9 a little later see if I still have the error. I’ll report back. 

<end transmission>

On Nov 4, 2021, at 11:34, Evgeny Hahamovich <evgymail@gmail.com> wrote:

Thank you Barry. Trying to follow your example. Here are 2 issues I encountered, will be glad if you can have a look:

In the Tx, the flow seems to be running, but I don't see any signal, and also I get the following error message:

handler caught exception: in method 'init_u8vector', argument 2 of type 'std::vector< uint8_t,std::allocator< uint8_t > > const &'
Traceback (most recent call last):
  File "/usr/local/lib/python3/dist-packages/gnuradio/gr/gateway.py", line 78, in eval
    try: self._callback(arg)
  File "/home/.../epy_block_0.py", line 37, in handle_msg
    self.message_port_pub(pmt.intern('PDU_out'), pmt.cons(pmt.PMT_NIL,pmt.init_u8vector(out_len,(char_list))))
  File "/usr/local/lib/python3/dist-packages/pmt/pmt_swig.py", line 2775, in init_u8vector
    return _pmt_swig.init_u8vector(k, data)
TypeError: in method 'init_u8vector', argument 2 of type 'std::vector< uint8_t,std::allocator< uint8_t > > const &'
thread[thread-per-block[11]: <block Packet Format(3)>]: SWIG director method error. Error detected when calling 'feval_p.eval'

do you know what could it mean?

In the Rx, since I'm using GNURadio 3.8, I replaced the Adaptive Algorithm block with the CMA Equalizer block, and I'm wondering, should I also add a Polyphase clock sync block before it?

Thank you,

On Thu, Nov 4, 2021 at 2:09 AM Barry Duggan <barry@dcsmail.net> wrote:
Hi Evgeny,

Recently I wrote a tutorial on https://wiki.gnuradio.org/index.php/Packet_Communications which should give you a basic understanding. Be sure to study the Prerequisites first! I did find that the examples did not work "out of the box".

Good luck.
Barry Duggan KV4FV

On Tue, 2 Nov 2021 18:12:10 +0200, Evgeny Hahamovich wrote:

Hi all,

I am interested to learn how to use the Packet Communications concept, and
hope to get your advice. I am trying to start with some QPSK or something
similar, based on the packet_tx & packet_rx examples, but getting lost
along the way...

Can you maybe guide me to something basic I can use to start? Getting
totally lost with this :(
Especially with all the header parameters I should set up...

Thank you,

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