Wed Jan 8 2020 09:49:47

Asterisk developer's documentation


fskmodem_int.c
Go to the documentation of this file.
1 /*
2  * Asterisk -- An open source telephony toolkit.
3  *
4  * Copyright (C) 1999 - 2005, Digium, Inc.
5  *
6  * Mark Spencer <markster@digium.com>
7  *
8  * Includes code and algorithms from the Zapata library.
9  *
10  * See http://www.asterisk.org for more information about
11  * the Asterisk project. Please do not directly contact
12  * any of the maintainers of this project for assistance;
13  * the project provides a web site, mailing lists and IRC
14  * channels for your use.
15  *
16  * This program is free software, distributed under the terms of
17  * the GNU General Public License Version 2. See the LICENSE file
18  * at the top of the source tree.
19  */
20 
21 /*! \file
22  *
23  * \brief FSK Modulator/Demodulator
24  *
25  * \author Mark Spencer <markster@digium.com>
26  *
27  * \arg Includes code and algorithms from the Zapata library.
28  *
29  */
30 
31 /*** MODULEINFO
32  <support_level>core</support_level>
33  ***/
34 
35 #include "asterisk.h"
36 
37 ASTERISK_FILE_VERSION(__FILE__, "$Revision: 369001 $")
38 
39 #include "asterisk/fskmodem.h"
40 
41 #define NBW 2
42 #define BWLIST {75,800}
43 #define NF 6
44 #define FLIST {1400,1800,1200,2200,1300,2100}
45 
46 #define STATE_SEARCH_STARTBIT 0
47 #define STATE_SEARCH_STARTBIT2 1
48 #define STATE_SEARCH_STARTBIT3 2
49 #define STATE_GET_BYTE 3
50 
51 static inline int iget_sample(short **buffer, int *len)
52 {
53  int retval;
54  retval = (int) **buffer;
55  (*buffer)++;
56  (*len)--;
57  return retval;
58 }
59 
60 #define IGET_SAMPLE iget_sample(&buffer, len)
61 /*! \brief Coefficients for input filters
62  * Coefficients table, generated by program "mkfilter"
63  * mkfilter is part of the zapatatelephony.org distribution
64  * Format: coef[IDX_FREC][IDX_BW][IDX_COEF]
65  * IDX_COEF = 0 => 1/GAIN
66  * IDX_COEF = 1-6 => Coefficientes y[n]
67 */
68 static double coef_in[NF][NBW][8]={
69  { { 1.8229206611e-04,-7.8997325866e-01,2.2401819940e+00,-4.6751353581e+00,5.5080745712e+00,-5.0571565772e+00,2.6215820004e+00,0.0000000000e+00,
70  }, { 9.8532175289e-02,-5.6297236492e-02,3.3146713415e-01,-9.2239200436e-01,1.4844365184e+00,-2.0183258642e+00,2.0074154497e+00,0.0000000000e+00,
71  }, }, { { 1.8229206610e-04,-7.8997325866e-01,7.7191410839e-01,-2.8075643964e+00,1.6948618347e+00,-3.0367273700e+00,9.0333559408e-01,0.0000000000e+00,
72  }, { 9.8531161839e-02,-5.6297236492e-02,1.1421579050e-01,-4.8122536483e-01,4.0121072432e-01,-7.4834487567e-01,6.9170822332e-01,0.0000000000e+00,
73  }, }, { { 1.8229206611e-04,-7.8997325866e-01,2.9003821430e+00,-6.1082779024e+00,7.7169345751e+00,-6.6075999680e+00,3.3941838836e+00,0.0000000000e+00,
74  }, { 9.8539686961e-02,-5.6297236492e-02,4.2915323820e-01,-1.2609358633e+00,2.2399213250e+00,-2.9928879142e+00,2.5990173742e+00,0.0000000000e+00,
75  }, }, { { 1.8229206610e-04,-7.8997325866e-01,-7.7191410839e-01,-2.8075643964e+00,-1.6948618347e+00,-3.0367273700e+00,-9.0333559408e-01,0.0000000000e+00,
76  }, { 9.8531161839e-02,-5.6297236492e-02,-1.1421579050e-01,-4.8122536483e-01,-4.0121072432e-01,-7.4834487567e-01,-6.9170822332e-01,0.0000000000e+00,
77  }, }, { { 1.8229206611e-04,-7.8997325866e-01,2.5782298908e+00,-5.3629717478e+00,6.5890882172e+00,-5.8012914776e+00,3.0171839130e+00,0.0000000000e+00,
78  }, { 9.8534230718e-02,-5.6297236492e-02,3.8148618075e-01,-1.0848760410e+00,1.8441165168e+00,-2.4860666655e+00,2.3103384142e+00,0.0000000000e+00,
79  }, }, { { 1.8229206610e-04,-7.8997325866e-01,-3.8715051001e-01,-2.6192408538e+00,-8.3977994034e-01,-2.8329897913e+00,-4.5306444352e-01,0.0000000000e+00,
80  }, { 9.8531160936e-02,-5.6297236492e-02,-5.7284484199e-02,-4.3673866734e-01,-1.9564766257e-01,-6.2028156584e-01,-3.4692356122e-01,0.0000000000e+00,
81  }, },
82 };
83 
84 /*! \brief Coefficients for output filter
85  * Coefficients table, generated by program "mkfilter"
86  * Format: coef[IDX_BW][IDX_COEF]
87  * IDX_COEF = 0 => 1/GAIN
88  * IDX_COEF = 1-6 => Coefficientes y[n]
89 */
90 static double coef_out[NBW][8]={
91  { 1.3868644653e-08,-6.3283665042e-01,4.0895057217e+00,-1.1020074592e+01,1.5850766191e+01,-1.2835109292e+01,5.5477477340e+00,0.0000000000e+00,
92  }, { 3.1262119724e-03,-7.8390522307e-03,8.5209627801e-02,-4.0804129163e-01,1.1157139955e+00,-1.8767603680e+00,1.8916395224e+00,0.0000000000e+00
93  },
94 };
95 
96 /*! Integer Pass Band demodulator filter */
97 static inline int ibpdfilter(struct filter_struct * fs, int in)
98 {
99  int i,j;
100  int s;
101  int64_t s_interim;
102 
103  /* integer filter */
104  s = in * fs->icoefs[0];
105  fs->ixv[(fs->ip + 6) & 7] = s;
106 
107  s = (fs->ixv[fs->ip] + fs->ixv[(fs->ip + 6) & 7]) +
108  6 * (fs->ixv[(fs->ip + 1) & 7] + fs->ixv[(fs->ip + 5) & 7]) +
109  15 * (fs->ixv[(fs->ip + 2) & 7] + fs->ixv[(fs->ip + 4) & 7]) +
110  20 * fs->ixv[(fs->ip + 3) & 7];
111 
112  for (i = 1, j = fs->ip; i < 7; i++, j++) {
113  /* Promote operation to 64 bit to prevent overflow that occurred in 32 bit) */
114  s_interim = (int64_t)(fs->iyv[j & 7]) *
115  (int64_t)(fs->icoefs[i]) /
116  (int64_t)(1024);
117  s += (int) s_interim;
118  }
119  fs->iyv[j & 7] = s;
120  fs->ip++;
121  fs->ip &= 7;
122  return s;
123 }
124 
125 /*! Integer Band Pass filter */
126 static inline int ibpfilter(struct filter_struct * fs, int in)
127 {
128  int i, j;
129  int s;
130  int64_t s_interim;
131 
132  /* integer filter */
133  s = in * fs->icoefs[0] / 256;
134  fs->ixv[(fs->ip + 6) & 7] = s;
135 
136  s = (fs->ixv[(fs->ip + 6) & 7] - fs->ixv[fs->ip])
137  + 3 * (fs->ixv[(fs->ip + 2) & 7] - fs->ixv[(fs->ip + 4) & 7]);
138 
139  for (i = 1, j = fs->ip; i < 7; i++, j++) {
140  s_interim = (int64_t)(fs->iyv[j & 7]) *
141  (int64_t)(fs->icoefs[i]) /
142  (int64_t)(256);
143  s += (int) s_interim;
144  }
145  fs->iyv[j & 7] = s;
146  fs->ip++;
147  fs->ip &= 7;
148  return s;
149 }
150 
151 static inline int idemodulator(fsk_data *fskd, int *retval, int x)
152 {
153  int is, im, id;
154  int ilin2;
155 
156  is = ibpfilter(&fskd->space_filter, x);
157  im = ibpfilter(&fskd->mark_filter, x);
158 
159  ilin2 = ((im * im) - (is * is)) / (256 * 256);
160 
161  id = ibpdfilter(&fskd->demod_filter, ilin2);
162 
163  *retval = id;
164  return 0;
165 }
166 
167 static int get_bit_raw(fsk_data *fskd, short *buffer, int *len)
168 {
169  /* This function implements a DPLL to synchronize with the bits */
170  int f;
171 
172  int ix;
173  /* PLL coeffs are set up in callerid_new */
174  for (f = 0;;) {
175  if (idemodulator(fskd, &ix, IGET_SAMPLE)) return(-1);
176  if ((ix * fskd->xi0) < 0) { /* Transicion */
177  if (!f) {
178  if (fskd->icont < (fskd->pllispb2)) {
179  fskd->icont += fskd->pllids;
180  } else {
181  fskd->icont -= fskd->pllids;
182  }
183  f = 1;
184  }
185  }
186  fskd->xi0 = ix;
187  fskd->icont += 32;
188  if (fskd->icont > fskd->pllispb) {
189  fskd->icont -= fskd->pllispb;
190  break;
191  }
192  }
193  f = (ix > 0) ? 0x80 : 0;
194  return f;
195 }
196 
198 {
199  int i;
200 
201  fskd->space_filter.ip = 0;
202  fskd->mark_filter.ip = 0;
203  fskd->demod_filter.ip = 0;
204 
205  for ( i = 0 ; i < 7 ; i++ ) {
206  fskd->space_filter.icoefs[i] =
207  coef_in[fskd->f_space_idx][fskd->bw][i] * 256;
208  fskd->space_filter.ixv[i] = 0;;
209  fskd->space_filter.iyv[i] = 0;;
210 
211  fskd->mark_filter.icoefs[i] =
212  coef_in[fskd->f_mark_idx][fskd->bw][i] * 256;
213  fskd->mark_filter.ixv[i] = 0;;
214  fskd->mark_filter.iyv[i] = 0;;
215 
216  fskd->demod_filter.icoefs[i] =
217  coef_out[fskd->bw][i] * 1024;
218  fskd->demod_filter.ixv[i] = 0;;
219  fskd->demod_filter.iyv[i] = 0;;
220  }
221  return 0;
222 }
223 
224 int fsk_serial(fsk_data *fskd, short *buffer, int *len, int *outbyte)
225 {
226  int a;
227  int i, j, n1, r;
228  int samples = 0;
229  int olen;
230  int beginlen = *len;
231  int beginlenx;
232 
233  switch (fskd->state) {
234  /* Pick up where we left off */
236  goto search_startbit2;
238  goto search_startbit3;
239  case STATE_GET_BYTE:
240  goto getbyte;
241  }
242  /* We await for start bit */
243  do {
244  /* this was jesus's nice, reasonable, working (at least with RTTY) code
245  to look for the beginning of the start bit. Unfortunately, since TTY/TDD's
246  just start sending a start bit with nothing preceding it at the beginning
247  of a transmission (what a LOSING design), we cant do it this elegantly */
248  /* NOT USED
249  if (demodulator(zap,&x1))
250  return -1;
251  for(;;) {
252  if (demodulator(zap,&x2))
253  return -1;
254  if (x1>0 && x2<0) break;
255  x1=x2;
256  }
257  */
258  /* this is now the imprecise, losing, but functional code to detect the
259  beginning of a start bit in the TDD sceanario. It just looks for sufficient
260  level to maybe, perhaps, guess, maybe that its maybe the beginning of
261  a start bit, perhaps. This whole thing stinks! */
262  beginlenx = beginlen; /* just to avoid unused war warnings */
263  if (idemodulator(fskd, &fskd->xi1, IGET_SAMPLE))
264  return -1;
265  samples++;
266  for(;;) {
267 search_startbit2:
268  if (*len <= 0) {
270  return 0;
271  }
272  samples++;
273  if (idemodulator(fskd, &fskd->xi2, IGET_SAMPLE))
274  return -1;
275 #if 0
276  printf("xi2 = %d ", fskd->xi2);
277 #endif
278  if (fskd->xi2 < 512) {
279  break;
280  }
281  }
282 search_startbit3:
283  /* We await for 0.5 bits before using DPLL */
284  i = fskd->ispb / 2;
285  if (*len < i) {
287  return 0;
288  }
289  for (; i > 0; i--) {
290  if (idemodulator(fskd, &fskd->xi1, IGET_SAMPLE))
291  return(-1);
292 #if 0
293  printf("xi1 = %d ", fskd->xi1);
294 #endif
295  samples++;
296  }
297 
298  /* x1 must be negative (start bit confirmation) */
299 
300  } while (fskd->xi1 > 0);
301  fskd->state = STATE_GET_BYTE;
302 
303 getbyte:
304 
305  /* Need at least 80 samples (for 1200) or
306  1320 (for 45.5) to be sure we'll have a byte */
307  if (fskd->nbit < 8) {
308  if (*len < 1320)
309  return 0;
310  } else {
311  if (*len < 80)
312  return 0;
313  }
314 
315  /* Now we read the data bits */
316  j = fskd->nbit;
317  for (a = n1 = 0; j; j--) {
318  olen = *len;
319  i = get_bit_raw(fskd, buffer, len);
320  buffer += (olen - *len);
321  if (i == -1)
322  return -1;
323  if (i)
324  n1++;
325  a >>= 1;
326  a |= i;
327  }
328  j = 8 - fskd->nbit;
329  a >>= j;
330 
331  /* We read parity bit (if exists) and check parity */
332  if (fskd->parity) {
333  olen = *len;
334  i = get_bit_raw(fskd, buffer, len);
335  buffer += (olen - *len);
336  if (i == -1)
337  return -1;
338  if (i)
339  n1++;
340  if (fskd->parity == 1) { /* parity=1 (even) */
341  if (n1 & 1)
342  a |= 0x100; /* error */
343  } else { /* parity=2 (odd) */
344  if (!(n1 & 1))
345  a |= 0x100; /* error */
346  }
347  }
348 
349  /* We read STOP bits. All of them must be 1 */
350 
351  for (j = fskd->instop; j; j--) {
352  r = get_bit_raw(fskd, buffer, len);
353  if (r == -1)
354  return -1;
355  if (!r)
356  a |= 0x200;
357  }
358 
359  /* And finally we return
360  * Bit 8 : Parity error
361  * Bit 9 : Framming error
362  */
363 
364  *outbyte = a;
366  return 1;
367 }
#define STATE_GET_BYTE
Definition: fskmodem_int.c:49
Asterisk main include file. File version handling, generic pbx functions.
static int ibpdfilter(struct filter_struct *fs, int in)
Definition: fskmodem_int.c:97
#define NBW
Definition: fskmodem_int.c:41
#define STATE_SEARCH_STARTBIT
Definition: fskmodem_int.c:46
int pllids
Definition: fskmodem_int.h:60
int fskmodem_init(fsk_data *fskd)
Definition: fskmodem_int.c:197
#define STATE_SEARCH_STARTBIT2
Definition: fskmodem_int.c:47
static int iget_sample(short **buffer, int *len)
Definition: fskmodem_int.c:51
static int ibpfilter(struct filter_struct *fs, int in)
Definition: fskmodem_int.c:126
static double coef_out[NBW][8]
Coefficients for output filter Coefficients table, generated by program &quot;mkfilter&quot; Format: coef[IDX_B...
Definition: fskmodem_int.c:90
int instop
Definition: fskmodem_int.h:46
struct filter_struct demod_filter
Definition: fskmodem_int.h:65
int pllispb
Definition: fskmodem_int.h:59
struct filter_struct space_filter
Definition: fskmodem_int.h:64
int pllispb2
Definition: fskmodem_int.h:61
#define NF
Definition: fskmodem_int.c:43
static int len(struct ast_channel *chan, const char *cmd, char *data, char *buf, size_t buflen)
#define IGET_SAMPLE
Definition: fskmodem_int.c:60
int f_space_idx
static double coef_in[NF][NBW][8]
Coefficients for input filters Coefficients table, generated by program &quot;mkfilter&quot; mkfilter is part o...
Definition: fskmodem_int.c:68
static struct ast_format f[]
Definition: format_g726.c:181
static int get_bit_raw(fsk_data *fskd, short *buffer, int *len)
Definition: fskmodem_int.c:167
int f_mark_idx
enum queue_result id
Definition: app_queue.c:1090
int fsk_serial(fsk_data *fskd, short *buffer, int *len, int *outbyte)
static int idemodulator(fsk_data *fskd, int *retval, int x)
Definition: fskmodem_int.c:151
#define STATE_SEARCH_STARTBIT3
Definition: fskmodem_int.c:48
struct filter_struct mark_filter
Definition: fskmodem_int.h:63
#define ASTERISK_FILE_VERSION(file, version)
Register/unregister a source code file with the core.
Definition: asterisk.h:180