GNU Radio v3.6.2-149-ga6d285d9 C++ API
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00001 /* -*- c++ -*- */ 00002 /* 00003 * Copyright 2005,2012 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_GR_PACKET_SINK_H 00024 #define INCLUDED_GR_PACKET_SINK_H 00025 00026 #include <digital_api.h> 00027 #include <gr_sync_block.h> 00028 #include <gr_msg_queue.h> 00029 00030 class digital_packet_sink; 00031 typedef boost::shared_ptr<digital_packet_sink> digital_packet_sink_sptr; 00032 00033 DIGITAL_API digital_packet_sink_sptr 00034 digital_make_packet_sink(const std::vector<unsigned char>& sync_vector, 00035 gr_msg_queue_sptr target_queue, 00036 int threshold = -1); // -1 -> use default 00037 00038 /*! 00039 * \brief process received bits looking for packet sync, header, and process bits into packet 00040 * \ingroup sink_blk 00041 * 00042 * input: stream of symbols to be sliced. 00043 * 00044 * output: none. Pushes assembled packet into target queue 00045 * 00046 * The packet sink takes in a stream of binary symbols that are sliced 00047 * around 0. The bits are then checked for the \p sync_vector to 00048 * determine find and decode the packet. It then expects a fixed 00049 * length header of 2 16-bit shorts containing the payload length, 00050 * followed by the payload. If the 2 16-bit shorts are not identical, 00051 * this packet is ignored. Better algs are welcome. 00052 * 00053 * This block is not very useful anymore as it only works with 2-level 00054 * modulations such as BPSK or GMSK. The block can generally be 00055 * replaced with a correlate access code and frame sink blocks. 00056 * 00057 * \param sync_vector The synchronization vector as a vector of 1's and 0's. 00058 * \param target_queue The message queue that packets are sent to. 00059 * \param threshold Number of bits that can be incorrect in the \p sync_vector. 00060 */ 00061 class DIGITAL_API digital_packet_sink : public gr_sync_block 00062 { 00063 friend DIGITAL_API digital_packet_sink_sptr 00064 digital_make_packet_sink(const std::vector<unsigned char>& sync_vector, 00065 gr_msg_queue_sptr target_queue, 00066 int threshold); 00067 00068 private: 00069 enum state_t {STATE_SYNC_SEARCH, STATE_HAVE_SYNC, STATE_HAVE_HEADER}; 00070 00071 static const int MAX_PKT_LEN = 4096; 00072 static const int HEADERBITLEN = 32; 00073 00074 gr_msg_queue_sptr d_target_queue; // where to send the packet when received 00075 unsigned long long d_sync_vector; // access code to locate start of packet 00076 unsigned int d_threshold; // how many bits may be wrong in sync vector 00077 00078 state_t d_state; 00079 00080 unsigned long long d_shift_reg; // used to look for sync_vector 00081 00082 unsigned int d_header; // header bits 00083 int d_headerbitlen_cnt; // how many so far 00084 00085 unsigned char d_packet[MAX_PKT_LEN]; // assembled payload 00086 unsigned char d_packet_byte; // byte being assembled 00087 int d_packet_byte_index; // which bit of d_packet_byte we're working on 00088 int d_packetlen; // length of packet 00089 int d_packetlen_cnt; // how many so far 00090 00091 protected: 00092 digital_packet_sink(const std::vector<unsigned char>& sync_vector, 00093 gr_msg_queue_sptr target_queue, 00094 int threshold); 00095 00096 void enter_search(); 00097 void enter_have_sync(); 00098 void enter_have_header(int payload_len); 00099 00100 int slice(float x) { return x > 0 ? 1 : 0; } 00101 00102 bool header_ok() 00103 { 00104 // confirm that two copies of header info are identical 00105 return ((d_header >> 16) ^ (d_header & 0xffff)) == 0; 00106 } 00107 00108 int header_payload_len() 00109 { 00110 // header consists of two 16-bit shorts in network byte order 00111 int t = (d_header >> 16) & 0xffff; 00112 return t; 00113 } 00114 00115 public: 00116 ~digital_packet_sink(); 00117 00118 int work(int noutput_items, 00119 gr_vector_const_void_star &input_items, 00120 gr_vector_void_star &output_items); 00121 00122 00123 //! return true if we detect carrier 00124 bool carrier_sensed() const 00125 { 00126 return d_state != STATE_SYNC_SEARCH; 00127 } 00128 00129 }; 00130 00131 #endif /* INCLUDED_GR_PACKET_SINK_H */