Sat Aug 6 00:39:32 2011

Asterisk developer's documentation


tdd.c

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00001 /*
00002  * Asterisk -- An open source telephony toolkit.
00003  *
00004  * Copyright (C) 1999 - 2005, Digium, Inc.
00005  *
00006  * Mark Spencer <markster@digium.com>
00007  *
00008  * Includes code and algorithms from the Zapata library.
00009  *
00010  * See http://www.asterisk.org for more information about
00011  * the Asterisk project. Please do not directly contact
00012  * any of the maintainers of this project for assistance;
00013  * the project provides a web site, mailing lists and IRC
00014  * channels for your use.
00015  *
00016  * This program is free software, distributed under the terms of
00017  * the GNU General Public License Version 2. See the LICENSE file
00018  * at the top of the source tree.
00019  */
00020 
00021 /*! \file
00022  *
00023  * \brief TTY/TDD Generation support 
00024  *
00025  * \author Mark Spencer <markster@digium.com>
00026  *
00027  * \note Includes code and algorithms from the Zapata library.
00028  */
00029 
00030 #include "asterisk.h"
00031 
00032 ASTERISK_FILE_VERSION(__FILE__, "$Revision: 89042 $")
00033 
00034 #include <time.h>
00035 #include <string.h>
00036 #include <stdio.h>
00037 #include <stdlib.h>
00038 #include <unistd.h>
00039 #include <math.h>
00040 #include <ctype.h>
00041 
00042 #include "asterisk/ulaw.h"
00043 #include "asterisk/tdd.h"
00044 #include "asterisk/logger.h"
00045 #include "asterisk/fskmodem.h"
00046 #include "ecdisa.h"
00047 
00048 struct tdd_state {
00049    fsk_data fskd;
00050    char rawdata[256];
00051    short oldstuff[4096];
00052    int oldlen;
00053    int pos;
00054    int modo;
00055    int mode;
00056    int charnum;
00057 };
00058 
00059 static float dr[4], di[4];
00060 static float tddsb = 176.0;  /* 45.5 baud */
00061 
00062 #define TDD_SPACE 1800.0      /* 1800 hz for "0" */
00063 #define TDD_MARK  1400.0      /* 1400 hz for "1" */
00064 
00065 static int tdd_decode_baudot(struct tdd_state *tdd,unsigned char data)  /* covert baudot into ASCII */
00066 {
00067    static char ltrs[32] = { '<','E','\n','A',' ','S','I','U',
00068                             '\n','D','R','J','N','F','C','K',
00069                             'T','Z','L','W','H','Y','P','Q',
00070                             'O','B','G','^','M','X','V','^' };
00071    static char figs[32] = { '<','3','\n','-',' ','\'','8','7',
00072                             '\n','$','4','\'',',','!',':','(',
00073                             '5','\"',')','2','=','6','0','1',
00074                             '9','?','+','^','.','/',';','^' };
00075    int d = 0;  /* return 0 if not decodeable */
00076    switch (data) {
00077    case 0x1f:
00078       tdd->modo = 0;
00079       break;
00080    case 0x1b:
00081       tdd->modo = 1;
00082       break;
00083    default:
00084       if (tdd->modo == 0)
00085          d = ltrs[data];
00086       else
00087          d = figs[data];
00088       break;
00089    }
00090    return d;
00091 }
00092 
00093 void tdd_init(void)
00094 {
00095    /* Initialize stuff for inverse FFT */
00096    dr[0] = cos(TDD_SPACE * 2.0 * M_PI / 8000.0);
00097    di[0] = sin(TDD_SPACE * 2.0 * M_PI / 8000.0);
00098    dr[1] = cos(TDD_MARK * 2.0 * M_PI / 8000.0);
00099    di[1] = sin(TDD_MARK * 2.0 * M_PI / 8000.0);
00100 }
00101 
00102 struct tdd_state *tdd_new(void)
00103 {
00104    struct tdd_state *tdd;
00105    tdd = calloc(1, sizeof(*tdd));
00106    if (tdd) {
00107       tdd->fskd.spb = 176;        /* 45.5 baud */
00108       tdd->fskd.hdlc = 0;         /* Async */
00109       tdd->fskd.nbit = 5;         /* 5 bits */
00110       tdd->fskd.nstop = 1.5;      /* 1.5 stop bits */
00111       tdd->fskd.paridad = 0;      /* No parity */
00112       tdd->fskd.bw=0;             /* Filter 75 Hz */
00113       tdd->fskd.f_mark_idx = 0;   /* 1400 Hz */
00114       tdd->fskd.f_space_idx = 1;  /* 1800 Hz */
00115       tdd->fskd.pcola = 0;        /* No clue */
00116       tdd->fskd.cont = 0;         /* Digital PLL reset */
00117       tdd->fskd.x0 = 0.0;
00118       tdd->fskd.state = 0;
00119       tdd->pos = 0;
00120       tdd->mode = 0;
00121       tdd->charnum = 0;
00122    } else
00123       ast_log(LOG_WARNING, "Out of memory\n");
00124    return tdd;
00125 }
00126 
00127 int ast_tdd_gen_ecdisa(unsigned char *outbuf, int len)
00128 {
00129    int pos = 0;
00130    int cnt;
00131    while (len) {
00132       cnt = len > sizeof(ecdisa) ? sizeof(ecdisa) : len;
00133       memcpy(outbuf + pos, ecdisa, cnt);
00134       pos += cnt;
00135       len -= cnt;
00136    }
00137    return 0;
00138 }
00139 
00140 int tdd_feed(struct tdd_state *tdd, unsigned char *ubuf, int len)
00141 {
00142    int mylen = len;
00143    int olen;
00144    int b = 'X';
00145    int res;
00146    int c,x;
00147    short *buf = calloc(1, 2 * len + tdd->oldlen);
00148    short *obuf = buf;
00149    if (!buf) {
00150       ast_log(LOG_WARNING, "Out of memory\n");
00151       return -1;
00152    }
00153    memcpy(buf, tdd->oldstuff, tdd->oldlen);
00154    mylen += tdd->oldlen/2;
00155    for (x = 0; x < len; x++) 
00156       buf[x + tdd->oldlen / 2] = AST_MULAW(ubuf[x]);
00157    c = res = 0;
00158    while (mylen >= 1320) { /* has to have enough to work on */
00159       olen = mylen;
00160       res = fsk_serie(&tdd->fskd, buf, &mylen, &b);
00161       if (mylen < 0) {
00162          ast_log(LOG_ERROR, "fsk_serial made mylen < 0 (%d) (olen was %d)\n", mylen, olen);
00163          free(obuf);
00164          return -1;
00165       }
00166       buf += (olen - mylen);
00167       if (res < 0) {
00168          ast_log(LOG_NOTICE, "fsk_serial failed\n");
00169          free(obuf);
00170          return -1;
00171       }
00172       if (res == 1) {
00173          /* Ignore invalid bytes */
00174          if (b > 0x7f)
00175             continue;
00176          c = tdd_decode_baudot(tdd,b);
00177          if ((c < 1) || (c > 126))
00178             continue; /* if not valid */
00179          break;
00180       }
00181    }
00182    if (mylen) {
00183       memcpy(tdd->oldstuff, buf, mylen * 2);
00184       tdd->oldlen = mylen * 2;
00185    } else
00186       tdd->oldlen = 0;
00187    free(obuf);
00188    if (res) {
00189       tdd->mode = 2; 
00190 /* put it in mode where it
00191          reliably puts teleprinter in correct shift mode */
00192       return(c);
00193    }
00194    return 0;
00195 }
00196 
00197 void tdd_free(struct tdd_state *tdd)
00198 {
00199    free(tdd);
00200 }
00201 
00202 static inline float tdd_getcarrier(float *cr, float *ci, int bit)
00203 {
00204    /* Move along.  There's nothing to see here... */
00205    float t;
00206    t = *cr * dr[bit] - *ci * di[bit];
00207    *ci = *cr * di[bit] + *ci * dr[bit];
00208    *cr = t;
00209    
00210    t = 2.0 - (*cr * *cr + *ci * *ci);
00211    *cr *= t;
00212    *ci *= t;
00213    return *cr;
00214 }  
00215 
00216 #define PUT_BYTE(a) do { \
00217    *(buf++) = (a); \
00218    bytes++; \
00219 } while(0)
00220 
00221 #define PUT_AUDIO_SAMPLE(y) do { \
00222    int index = (short)(rint(8192.0 * (y))); \
00223    *(buf++) = AST_LIN2MU(index); \
00224    bytes++; \
00225 } while(0)
00226    
00227 #define PUT_TDD_MARKMS do { \
00228    int x; \
00229    for (x=0;x<8;x++) \
00230       PUT_AUDIO_SAMPLE(tdd_getcarrier(&cr, &ci, 1)); \
00231 } while(0)
00232 
00233 #define PUT_TDD_BAUD(bit) do { \
00234    while (scont < tddsb) { \
00235       PUT_AUDIO_SAMPLE(tdd_getcarrier(&cr, &ci, bit)); \
00236       scont += 1.0; \
00237    } \
00238    scont -= tddsb; \
00239 } while(0)
00240 
00241 #define PUT_TDD_STOP do { \
00242    while (scont < (tddsb * 1.5)) { \
00243       PUT_AUDIO_SAMPLE(tdd_getcarrier(&cr, &ci, 1)); \
00244       scont += 1.0; \
00245    } \
00246    scont -= (tddsb * 1.5); \
00247 } while(0)
00248 
00249 
00250 #define PUT_TDD(byte) do { \
00251    int z; \
00252    unsigned char b = (byte); \
00253    PUT_TDD_BAUD(0);  /* Start bit */ \
00254    for (z = 0; z < 5; z++) { \
00255       PUT_TDD_BAUD(b & 1); \
00256       b >>= 1; \
00257    } \
00258    PUT_TDD_STOP;  /* Stop bit */ \
00259 } while(0); 
00260 
00261 int tdd_generate(struct tdd_state *tdd, unsigned char *buf, const char *str)
00262 {
00263    int bytes=0;
00264    int i,x;
00265    char  c;
00266    /*! Baudot letters */
00267    static unsigned char lstr[31] = "\000E\nA SIU\rDRJNFCKTZLWHYPQOBG\000MXV";
00268    /*! Baudot figures */
00269    static unsigned char fstr[31] = "\0003\n- \00787\r$4',!:(5\")2\0006019?+\000./;";
00270    /* Initial carriers (real/imaginary) */
00271    float cr = 1.0;
00272    float ci = 0.0;
00273    float scont = 0.0;
00274 
00275    for(x = 0; str[x]; x++) {
00276       /* Do synch for each 72th character */
00277       if ( (tdd->charnum++) % 72 == 0) 
00278          PUT_TDD(tdd->mode ? 27 /* FIGS */ : 31 /* LTRS */);
00279 
00280       c = toupper(str[x]);
00281 #if   0
00282       printf("%c",c); fflush(stdout);
00283 #endif
00284       if (c == 0) { /* send null */
00285          PUT_TDD(0);
00286          continue;
00287       }
00288       if (c == '\r') { /* send c/r */
00289          PUT_TDD(8);
00290          continue;
00291       }
00292       if (c == '\n') { /* send c/r and l/f */
00293          PUT_TDD(8);
00294          PUT_TDD(2);
00295          continue;
00296       }
00297       if (c == ' ') { /* send space */
00298          PUT_TDD(4);
00299          continue;
00300       }
00301       for (i = 0; i < 31; i++) {
00302          if (lstr[i] == c)
00303             break;
00304       }
00305       if (i < 31) {        /* if we found it */
00306          if (tdd->mode) { /* if in figs mode, change it */
00307             PUT_TDD(31); /* Send LTRS */
00308             tdd->mode = 0;
00309          }
00310          PUT_TDD(i);
00311          continue;
00312       }
00313       for (i = 0; i < 31; i++) {
00314          if (fstr[i] == c)
00315             break;
00316       }
00317       if (i < 31) {             /* if we found it */
00318          if (tdd->mode != 1) { /* if in ltrs mode, change it */
00319             PUT_TDD(27);      /* send FIGS */
00320             tdd->mode = 1;
00321          }
00322          PUT_TDD(i);           /* send byte */
00323          continue;
00324       }
00325    }
00326    return bytes;
00327 }
00328 

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