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

[Johannes Demel]

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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