GNU Radio 3.5.1 C++ API
digital_correlate_access_code_bb.h
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00001 /* -*- c++ -*- */
00002 /*
00003  * Copyright 2005,2006,2011 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 3, 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., 51 Franklin Street,
00020  * Boston, MA 02110-1301, USA.
00021  */
00022 
00023 #ifndef INCLUDED_DIGITAL_CORRELATE_ACCESS_CODE_BB_H
00024 #define INCLUDED_DIGITAL_CORRELATE_ACCESS_CODE_BB_H
00025 
00026 #include <digital_api.h>
00027 #include <gr_sync_block.h>
00028 #include <string>
00029 
00030 class digital_correlate_access_code_bb;
00031 typedef boost::shared_ptr<digital_correlate_access_code_bb> digital_correlate_access_code_bb_sptr;
00032 
00033 /*!
00034  * \param access_code is represented with 1 byte per bit, e.g., "010101010111000100"
00035  * \param threshold maximum number of bits that may be wrong
00036  */
00037 DIGITAL_API digital_correlate_access_code_bb_sptr 
00038 digital_make_correlate_access_code_bb (const std::string &access_code, int threshold);
00039 
00040 /*!
00041  * \brief Examine input for specified access code, one bit at a time.
00042  * \ingroup sync_blk
00043  * \ingroup digital
00044  *
00045  * input:  stream of bits, 1 bit per input byte (data in LSB)
00046  * output: stream of bits, 2 bits per output byte (data in LSB, flag in next higher bit)
00047  *
00048  * Each output byte contains two valid bits, the data bit, and the
00049  * flag bit.  The LSB (bit 0) is the data bit, and is the original
00050  * input data, delayed 64 bits.  Bit 1 is the
00051  * flag bit and is 1 if the corresponding data bit is the first data
00052  * bit following the access code. Otherwise the flag bit is 0.
00053  */
00054 class DIGITAL_API digital_correlate_access_code_bb : public gr_sync_block
00055 {
00056   friend DIGITAL_API digital_correlate_access_code_bb_sptr 
00057   digital_make_correlate_access_code_bb (const std::string &access_code, int threshold);
00058  private:
00059   unsigned long long d_access_code;     // access code to locate start of packet
00060                                         //   access code is left justified in the word
00061   unsigned long long d_data_reg;        // used to look for access_code
00062   unsigned long long d_flag_reg;        // keep track of decisions
00063   unsigned long long d_flag_bit;        // mask containing 1 bit which is location of new flag
00064   unsigned long long d_mask;            // masks access_code bits (top N bits are set where
00065                                         //   N is the number of bits in the access code)
00066   unsigned int       d_threshold;       // how many bits may be wrong in sync vector
00067 
00068  protected:
00069   digital_correlate_access_code_bb(const std::string &access_code, int threshold);
00070 
00071  public:
00072   ~digital_correlate_access_code_bb();
00073 
00074   int work(int noutput_items,
00075            gr_vector_const_void_star &input_items,
00076            gr_vector_void_star &output_items);
00077 
00078   
00079   /*!
00080    * \param access_code is represented with 1 byte per bit, e.g., "010101010111000100"
00081    */
00082   bool set_access_code (const std::string &access_code);
00083 };
00084 
00085 #endif /* INCLUDED_DIGITAL_CORRELATE_ACCESS_CODE_BB_H */