[Discuss-gnuradio] Help - Custom block generating data @ 1:5115 input to output ratio causes flowgraph to hang -- how to prevent this

[John Andrews]

Hi,
I am posting this question again with better explanation as I got no help yet.

I have a custom C++ block that I use in the modified dbpsk.py modulation scheme. This block basically spreads each input data bit by 1023.

The flowgraph connect looks like this
self.connect(self,self.bytes2chunks,self.symbol_mapper,self.diffenc,self.CUSTOM_BLOCK,self.chunks2symbols,self.rrc_filter,self)

The CUSTOM_BLOCK outputs 5115 bytes for every input byte read therefore, in the flowgraph the input rate at self.chunks2symbols is 5115 times to that of input at self.CUSTOM_BLOCK. This causes the flowgraph to slow down incredibly to such an extent that I have to force kill it. I am using benchmark_tx.py to pass data to the flowgraph. 

I implemented the custom block in 2 different ways once by inheriting gr_block and the other by using gr_sync_interpolator but the result is still the same. What should I do to make it work smoothly?

Thanks

P.S - The work function is shown below when using gr_sync_interpolator.

 dsss_sync_spread_b::work(int noutput_items,gr_vector_const_void_star &input_items,gr_vector_void_star &output_items)
{  
  const unsigned char *in = (const unsigned char *)input_items[0];
  unsigned char *out = (unsigned char *)output_items[0];
  int data_items=noutput_items/interpolation(); // interploation() returns (d_length_PN * d_n_pn which is equal to 1023 * 5)
  int nout=0;
  for(int i=0;i<data_items;i++){
      if(in[i]&0x01){
      for(int j=0;j<interpolation();j++){
          out[nout]=d_pn_array1[j%d_length_PN];   // the array d_pn_array1 has datatype 'char' and is of size 1023. d_length_PN = 1023 and is initialised in the constructor and is never changed
          nout++;
      }
      }
      else{
      for(int j=0;j<d_length_PN*d_n_pn;j++){
          out[nout]=d_pn_array0[j%d_length_PN];  // the array d_pn_array2 has datatype 'char' and is of size 1023. 
d_length_PN = 1023 and is initialised in the constructor and is never changed
          nout++;
      }
      }
  }
  return noutput_items;
}


The general_work function when using gr_block is shown below,

int
dsss_spreading_b::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];
  unsigned char *out = (unsigned char *)output_items[0];
  int data_items=noutput_items/(d_length_PN*d_n_pn); // d_length_PN = 1023, d_n_pn = 5
  int nout=0;
  for(int i=0;i<data_items;i++){
      if(in[i]&0x01){
      for(int j=0;j<d_length_PN*d_n_pn;j++){
          out[nout]=d_pn_array1[j%d_length_PN];
          nout++;
      }
      }
      else{
      for(int j=0;j<d_length_PN*d_n_pn;j++){
          out[nout]=d_pn_array0[j%d_length_PN];
          nout++;
      }
      }
  }
  
   consume(0,data_items);
   return noutput_items;
}