GNU Radio 2.x: gr_simple_correlator.h Source File

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# gr_simple_correlator.h

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    00001 /* -*- c++ -*- */
    00002 /*
    00003  * Copyright 2004 Free Software Foundation, Inc.
    00004  *
    00005  * This file is part of GNU Radio
    00006  *
    00007  * GNU Radio is free software; you can redistribute it and/or modify
    00008  * it under the terms of the GNU General Public License as published by
    00009  * the Free Software Foundation; either version 2, or (at your option)
    00010  * any later version.
    00011  *
    00012  * GNU Radio is distributed in the hope that it will be useful,
    00013  * but WITHOUT ANY WARRANTY; without even the implied warranty of
    00014  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    00015  * GNU General Public License for more details.
    00016  *
    00017  * You should have received a copy of the GNU General Public License
    00018  * along with GNU Radio; see the file COPYING.  If not, write to
    00019  * the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
    00020  * Boston, MA 02111-1307, USA.
    00021  */
    00022
    00023 #ifndef INCLUDED_GR_SIMPLE_CORRELATOR_H
    00024 #define INCLUDED_GR_SIMPLE_CORRELATOR_H
    00025
    00026 #include <gr_block.h>
    00027 #include <assert.h>
    00028
    00029 //#define       DEBUG_SIMPLE_CORRELATOR
    00030
    00031 class gr_simple_correlator;
    00032 typedef boost::shared_ptr<gr_simple_correlator> gr_simple_correlator_sptr;
    00033
    00034 gr_simple_correlator_sptr gr_make_simple_correlator (int payload_bytesize);
    00035
    00040 class gr_simple_correlator : public gr_block
    00041 {
    00042   static const int OVERSAMPLE = 8;
    00043   enum state_t { ST_LOOKING, ST_UNDER_THRESHOLD, ST_LOCKED };
    00044
    00045   int            d_payload_bytesize;
    00046   state_t        d_state;
    00047   unsigned int   d_osi;                         // over sample index [0,OVERSAMPLE-1]
    00048   unsigned int   d_transition_osi;              // first index where Hamming dist < thresh
    00049   unsigned int   d_center_osi;                  // center of bit
    00050   unsigned long long int d_shift_reg[OVERSAMPLE];
    00051   int            d_bblen;                       // length of bitbuf
    00052   unsigned char *d_bitbuf;                      // demodulated bits
    00053   int            d_bbi;                         // bitbuf index
    00054
    00055   static const int AVG_PERIOD = 512;            // must be power of 2 (for freq offset correction)
    00056   int   d_avbi;
    00057   float d_avgbuf[AVG_PERIOD];
    00058   float d_avg;
    00059   float d_accum;
    00060
    00061 #ifdef DEBUG_SIMPLE_CORRELATOR
    00062   FILE          *d_debug_fp;                    // binary log file
    00063 #endif
    00064
    00065   friend gr_simple_correlator_sptr gr_make_simple_correlator (int payload_bytesize);
    00066   gr_simple_correlator (int payload_bytesize);
    00067
    00068
    00069   inline int slice (float x)
    00070   {
    00071     return x >= d_avg ? 1 : 0;
    00072   }
    00073
    00074   void update_avg(float x);
    00075
    00076   void enter_locked ();
    00077   void enter_under_threshold ();
    00078   void enter_looking ();
    00079
    00080   static int add_index (int a, int b)
    00081   {
    00082     int t = a + b;
    00083     if (t >= OVERSAMPLE)
    00084       t -= OVERSAMPLE;
    00085     assert (t >= 0 && t < OVERSAMPLE);
    00086     return t;
    00087   }
    00088
    00089   static int sub_index (int a, int b)
    00090   {
    00091     int t = a - b;
    00092     if (t < 0)
    00093       t += OVERSAMPLE;
    00094     assert (t >= 0 && t < OVERSAMPLE);
    00095     return t;
    00096   }
    00097
    00098
    00099  public:
    00100   ~gr_simple_correlator ();
    00101
    00102   int general_work (int noutput_items,
    00103                     gr_vector_int &ninput_items,
    00104                     gr_vector_const_void_star &input_items,
    00105                     gr_vector_void_star &output_items);
    00106 };
    00107
    00108
    00109 #endif /* INCLUDED_GR_SIMPLE_CORRELATOR_H */