-
Notifications
You must be signed in to change notification settings - Fork 1
/
analyze_psk.c
132 lines (105 loc) · 2.93 KB
/
analyze_psk.c
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
132
#include <fcntl.h>
#include <stdio.h>
#include <getopt.h>
#include <stdlib.h>
#include <stdarg.h>
#include <memory.h>
#include <math.h>
#include <ctype.h>
#include "fourier.h"
int rate = 8000;
int bps = 10;
double threshold = 0.01;
double carrier = 8000.0;
FILE* infile = NULL;
FILE* outfile = NULL;
void usage(char* cmd) {
printf("Usage: %s [-r sample rate] [-b baud] [-c carrier] [-h] [-x] [ -o file ] [ file ]\n"
"\t -r : Set sample rate (default = 8000)\n"
"\t -o : Write data to file\n"
"\t -x : Generate XPM with frequency spectrum\n"
"\t -b : Set transferred bits per second\n"
"\t -c : Set carrier frequency\n"
"\t -h : Display this message\n\n", cmd);
}
int main(int argc, char* argv[]) {
infile = stdin;
outfile = stdout;
int i = 0;
for(;;) switch(getopt(argc, argv, "r:shb:o:c:")) {
case 'r':
rate = atoi(optarg);
break;
case 'b': bps = atoi(optarg);
break;
case 'c':
carrier = atof(optarg);
break;
case 'o':
outfile = fopen(optarg, "w+");
if(outfile == NULL) {
perror(optarg);
exit(EXIT_FAILURE);
}
break;
case 'h': usage(argv[0]);
return EXIT_SUCCESS;
break;
case -1: goto done;
default: exit(EXIT_FAILURE);
}
done:
if(optind < argc) {
infile = fopen(argv[optind], "r");
if(infile == NULL) {
perror(argv[optind]);
exit(EXIT_FAILURE);
}
}
/* Calculate file length */
int file_length = 0;
fseek(infile, 0, SEEK_END);
file_length = ftell(infile);
fseek(infile, 0, SEEK_SET);
/* The buffer length to use */
int length = rate / (4 * bps);
/* Raw data buffer */
char* buffer = malloc(length);
/* Massaged data buffer */
double* dbuffer = malloc(length);
unsigned char bit_data = 0;
double old_carrier_phase[2] = { 0.0, 0.0 };
while((fread(buffer, 1, length, infile))) {
/* Transform into a double in the range -1 ... 1 */
for (i = 0; i < length; i++) {
dbuffer[i] = buffer[i] / 128.0;
}
double carrier_phase[2];
double carrier_strength = fourier1p(dbuffer, (float) length * carrier / (float)rate, length, &carrier_phase[0], &carrier_phase[1]);
if(carrier_strength < threshold) continue;
/* -- this is pretty useful in debuging
printf("C: %f (%f %f)\n",
carrier_strength, carrier_phase[0], carrier_phase[1]);
*/
/* (A+Bi)*(C-Di) = A*C + B*D + i(-A*D + B*C) */
double delta_re = carrier_phase[0] * old_carrier_phase[0] + carrier_phase[1]*old_carrier_phase[1];
double delta_im = -carrier_phase[1]*old_carrier_phase[0] + carrier_phase[0] * old_carrier_phase[1];
if(delta_re * delta_re > delta_im * delta_im) { /* phase diff is a multiple of pi */
if(delta_re > 0); /* No change */
else {
bit_data = bit_data * 2;
}
} else {
if(delta_im > 0) {
bit_data = bit_data * 2 + 1;
} else {
if(isprint(bit_data)) printf("%c", bit_data);
else printf("<%.2x>", bit_data);
bit_data = 0;
}
}
old_carrier_phase[0] = carrier_phase[0];
old_carrier_phase[1] = carrier_phase[1];
}
return EXIT_SUCCESS;
}