1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
|
/* -*- c++ -*- */
/*
* Copyright 2005,2012 Free Software Foundation, Inc.
*
* This file is part of GNU Radio
*
* GNU Radio is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 3, or (at your option)
* any later version.
*
* GNU Radio is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with GNU Radio; see the file COPYING. If not, write to
* the Free Software Foundation, Inc., 51 Franklin Street,
* Boston, MA 02110-1301, USA.
*/
#ifndef INCLUDED_GR_PACKET_SINK_H
#define INCLUDED_GR_PACKET_SINK_H
#include <digital_api.h>
#include <gr_sync_block.h>
#include <gr_msg_queue.h>
class digital_packet_sink;
typedef boost::shared_ptr<digital_packet_sink> digital_packet_sink_sptr;
DIGITAL_API digital_packet_sink_sptr
digital_make_packet_sink(const std::vector<unsigned char>& sync_vector,
gr_msg_queue_sptr target_queue,
int threshold = -1); // -1 -> use default
/*!
* \brief process received bits looking for packet sync, header, and process bits into packet
* \ingroup sink_blk
*
* input: stream of symbols to be sliced.
*
* output: none. Pushes assembled packet into target queue
*
* The packet sink takes in a stream of binary symbols that are sliced
* around 0. The bits are then checked for the \p sync_vector to
* determine find and decode the packet. It then expects a fixed
* length header of 2 16-bit shorts containing the payload length,
* followed by the payload. If the 2 16-bit shorts are not identical,
* this packet is ignored. Better algs are welcome.
*
* This block is not very useful anymore as it only works with 2-level
* modulations such as BPSK or GMSK. The block can generally be
* replaced with a correlate access code and frame sink blocks.
*
* \param sync_vector The synchronization vector as a vector of 1's and 0's.
* \param target_queue The message queue that packets are sent to.
* \param threshold Number of bits that can be incorrect in the \p sync_vector.
*/
class DIGITAL_API digital_packet_sink : public gr_sync_block
{
friend DIGITAL_API digital_packet_sink_sptr
digital_make_packet_sink(const std::vector<unsigned char>& sync_vector,
gr_msg_queue_sptr target_queue,
int threshold);
private:
enum state_t {STATE_SYNC_SEARCH, STATE_HAVE_SYNC, STATE_HAVE_HEADER};
static const int MAX_PKT_LEN = 4096;
static const int HEADERBITLEN = 32;
gr_msg_queue_sptr d_target_queue; // where to send the packet when received
unsigned long long d_sync_vector; // access code to locate start of packet
unsigned int d_threshold; // how many bits may be wrong in sync vector
state_t d_state;
unsigned long long d_shift_reg; // used to look for sync_vector
unsigned int d_header; // header bits
int d_headerbitlen_cnt; // how many so far
unsigned char d_packet[MAX_PKT_LEN]; // assembled payload
unsigned char d_packet_byte; // byte being assembled
int d_packet_byte_index; // which bit of d_packet_byte we're working on
int d_packetlen; // length of packet
int d_packetlen_cnt; // how many so far
protected:
digital_packet_sink(const std::vector<unsigned char>& sync_vector,
gr_msg_queue_sptr target_queue,
int threshold);
void enter_search();
void enter_have_sync();
void enter_have_header(int payload_len);
int slice(float x) { return x > 0 ? 1 : 0; }
bool header_ok()
{
// confirm that two copies of header info are identical
return ((d_header >> 16) ^ (d_header & 0xffff)) == 0;
}
int header_payload_len()
{
// header consists of two 16-bit shorts in network byte order
int t = (d_header >> 16) & 0xffff;
return t;
}
public:
~digital_packet_sink();
int work(int noutput_items,
gr_vector_const_void_star &input_items,
gr_vector_void_star &output_items);
//! return true if we detect carrier
bool carrier_sensed() const
{
return d_state != STATE_SYNC_SEARCH;
}
};
#endif /* INCLUDED_GR_PACKET_SINK_H */
|
