GNU Radio 3.6.4 C++ API
digital_correlate_access_code_bb.h
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1 /* -*- c++ -*- */
2 /*
3  * Copyright 2005,2006,2011 Free Software Foundation, Inc.
4  *
5  * This file is part of GNU Radio
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7  * GNU Radio is free software; you can redistribute it and/or modify
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15  * GNU General Public License for more details.
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22 
23 #ifndef INCLUDED_DIGITAL_CORRELATE_ACCESS_CODE_BB_H
24 #define INCLUDED_DIGITAL_CORRELATE_ACCESS_CODE_BB_H
25 
26 #include <digital_api.h>
27 #include <gr_sync_block.h>
28 #include <string>
29 
32 
33 /*!
34  * \param access_code is represented with 1 byte per bit, e.g., "010101010111000100"
35  * \param threshold maximum number of bits that may be wrong
36  */
38 digital_make_correlate_access_code_bb (const std::string &access_code, int threshold);
39 
40 /*!
41  * \brief Examine input for specified access code, one bit at a time.
42  * \ingroup sync_blk
43  * \ingroup digital
44  *
45  * input: stream of bits, 1 bit per input byte (data in LSB)
46  * output: stream of bits, 2 bits per output byte (data in LSB, flag in next higher bit)
47  *
48  * Each output byte contains two valid bits, the data bit, and the
49  * flag bit. The LSB (bit 0) is the data bit, and is the original
50  * input data, delayed 64 bits. Bit 1 is the
51  * flag bit and is 1 if the corresponding data bit is the first data
52  * bit following the access code. Otherwise the flag bit is 0.
53  */
55 {
57  digital_make_correlate_access_code_bb (const std::string &access_code, int threshold);
58  private:
59  unsigned long long d_access_code; // access code to locate start of packet
60  // access code is left justified in the word
61  unsigned long long d_data_reg; // used to look for access_code
62  unsigned long long d_flag_reg; // keep track of decisions
63  unsigned long long d_flag_bit; // mask containing 1 bit which is location of new flag
64  unsigned long long d_mask; // masks access_code bits (top N bits are set where
65  // N is the number of bits in the access code)
66  unsigned int d_threshold; // how many bits may be wrong in sync vector
67 
68  protected:
69  digital_correlate_access_code_bb(const std::string &access_code, int threshold);
70 
71  public:
73 
74  int work(int noutput_items,
75  gr_vector_const_void_star &input_items,
76  gr_vector_void_star &output_items);
77 
78 
79  /*!
80  * \param access_code is represented with 1 byte per bit, e.g., "010101010111000100"
81  */
82  bool set_access_code (const std::string &access_code);
83 };
84 
85 #endif /* INCLUDED_DIGITAL_CORRELATE_ACCESS_CODE_BB_H */