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Re: Communication using Packets

From: Evgeny Hahamovich
Subject: Re: Communication using Packets
Date: Sun, 7 Nov 2021 11:05:38 +0200

Thanks for your help Paul.
I tried to apply your fix, but didn't understand where to do it. If I open the python code of the Tx, but I don't see anywhere any append or the array usage you mentioned :(

On Sat, Nov 6, 2021 at 9:43 AM Paul Atreides <maud.dib1984@gmail.com> wrote:
I was able to get around the swig errors in the embedded block, but still need to do more testing to see if the modulated data is exactly what it should be. It looks correct so far. 
I replaced append with numpy.append and also used “import array” to copy the final char_list to a byte array
new_array=array.array(“B”, char_list) 
That seemed to be what got around the swig issue as it was complaining about the second argument.
“return _pmt_swig.init_u8vector(k, data)”
“argument 2 of type 'std::vector< uint8_t,std::allocator< uint8_t > > const &'“

 <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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