Re: [Discuss-gnuradio] Appending SYNC block to data

Wed, 29 Jun 2016 00:34:12 -0700 

Here's an example block that's very similar to what you want to do.

https://github.com/gnuradio/gnuradio/blob/master/gr-dtv/lib/catv/catv_frame_sync_enc_bb_impl.cc

Note the use of set_output_multiple() and the forecast function.

Ron

On 06/28/2016 10:48 AM, Olivier Goyette wrote:

I did a simple test :

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <gnuradio/io_signature.h>
#include <stdio.h>
#include "ADD_SYNC_impl.h"

#define TAB_SIZE 420

namespace gr {
  namespace UAT {

    ADD_SYNC::sptr
    ADD_SYNC::make()
    {
      return gnuradio::get_initial_sptr
        (new ADD_SYNC_impl());
    }

    /*
     * The private constructor
     */
    ADD_SYNC_impl::ADD_SYNC_impl()
      : gr::block("ADD_SYNC",
              gr::io_signature::make(1, 1, sizeof(unsigned char)),
              gr::io_signature::make(1, 1, sizeof(unsigned char)))
    {}

    /*
     * Our virtual destructor.
     */
    ADD_SYNC_impl::~ADD_SYNC_impl()
    {
    }

    void
ADD_SYNC_impl::forecast (int noutput_items, gr_vector_int &ninput_items_required) 
    {
      /* <+forecast+> e.g. ninput_items_required[0] = noutput_items */
    }

    int
    ADD_SYNC_impl::general_work (int noutput_items,
                       gr_vector_int &ninput_items,
                       gr_vector_const_void_star &input_items,
                       gr_vector_void_star &output_items)
    {
      const unsigned char *in = (const unsigned char *) input_items[0];
      char *out = (char *) output_items[0];
      //unsigned long preamble = 0b111010101100110111011010010011100010;
//unsigned char tab[TAB_SIZE] = {1,1,1,0,1,0,1,0,1,1,0,0,1,1,0,1,1,1,0,1,1,0,1,0,0,1,0,0,1,1,1,0,0,0,1,0}; 

      for(int i = 0; i < noutput_items; i++)
      {
          out[i] = in[i];
      }

      for(int x = 0; x < TAB_SIZE; x++)
      {
          printf("%u", out[x]);
          printf(" ");
      }
      printf("\n\n");


      consume_each (noutput_items);

      // Tell runtime system how many output items we produced.
      return noutput_items;
    }

  } /* namespace UAT */
} /* namespace gr */

I'm printing the input to the output directly and here is the results :

Generating: '/home/lassena/Documents/top_block.py'

Generating: '/home/lassena/Documents/top_block.py'

Executing: /usr/bin/python2 -u /home/lassena/Documents/top_block.py
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I got long chains of '0' and sometimes something comes out but it doesn't make any sense since I'm supposed to be printing only '1' and '0'...There is something i'm missing somewhere.
2016-06-28 13:10 GMT-04:00 Johannes Demel <de...@ant.uni-bremen.de <mailto:de...@ant.uni-bremen.de>>: 

    Hi Olivier,

    is there a reason, besides you print the values afterwards, that
    you copy your input data to your tab array?

    Write a test which puts in your frame and checks if the output is
    prepended by your sync word. [syncword, payload].
    Just write your preamble to the output buffer and then continue
    with the input.

    Besides, I'd recommend using constants instead of a define for
    TAB_SIZE.

    Cheers
    Johannes


    On 28.06.2016 18:27, Olivier Goyette wrote:

        Hi everyone,

        I'm actually coding a SYNC block for my application. I need to
        append a
        36 bits sync word to some data coming from a Reed Solomon
        encoder. What
        I did is to initialize an array with my 36 bits sequence and then,
        plugging the data in the rest of the array. The total length
        of my SYNC
        + PAYLOAD + FEC PARITY is 420. So with basic calculation, 420
        - 36 =
        384, is the length that is left to fill the array. Actually, I
        can't get
        the data I'm sending into the array. I'm a bit newbie with
        programming
        GNU radio blocks so I'd like some help to understand. I'm
        giving my code
        for you to see :

        #ifdef HAVE_CONFIG_H
        #include "config.h"
        #endif

        #include <gnuradio/io_signature.h>
        #include <stdio.h>
        #include "ADD_SYNC_impl.h"

        #define TAB_SIZE 420

        namespace gr {
           namespace UAT {

             ADD_SYNC::sptr
             ADD_SYNC::make()
             {
               return gnuradio::get_initial_sptr
                 (new ADD_SYNC_impl());
             }

             /*
              * The private constructor
              */
             ADD_SYNC_impl::ADD_SYNC_impl()
               : gr::block("ADD_SYNC",
                       gr::io_signature::make(1, 1, sizeof(unsigned
        char)),
                       gr::io_signature::make(1, 1, sizeof(unsigned
        char)))
             {}

             /*
              * Our virtual destructor.
              */
             ADD_SYNC_impl::~ADD_SYNC_impl()
             {
             }

             void
             ADD_SYNC_impl::forecast (int noutput_items, gr_vector_int
        &ninput_items_required)
             {
               /* <+forecast+> e.g. ninput_items_required[0] =
        noutput_items */
             }

             int
             ADD_SYNC_impl::general_work (int noutput_items,
                                gr_vector_int &ninput_items,
                                gr_vector_const_void_star &input_items,
                                gr_vector_void_star &output_items)
             {
               const unsigned char *in = (const unsigned char *)
        input_items[0];
               char *out = (char *) output_items[0];
               //unsigned long preamble =
        0b111010101100110111011010010011100010;
               unsigned char tab[TAB_SIZE] =
        
{1,1,1,0,1,0,1,0,1,1,0,0,1,1,0,1,1,1,0,1,1,0,1,0,0,1,0,0,1,1,1,0,0,0,1,0};

               for(int i = 36; i < TAB_SIZE; i++)
               {
                   tab[i] = in[i];// Data should be inserted here???
               }

               for(int x = 0; x < TAB_SIZE; x++)
               {
                   printf("%u", tab[x]);// Printing what's in the tab
                   printf(" ");
               }
               printf("\n\n");


               consume_each (noutput_items);

               // Tell runtime system how many output items we produced.
               return noutput_items;
             }

           } /* namespace UAT */
        } /* namespace gr */




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