/* * Asterisk -- An open source telephony toolkit. * * Copyright (C) 1999 - 2005, Digium, Inc. * * Mark Spencer * * Includes code and algorithms from the Zapata library. * * See http://www.asterisk.org for more information about * the Asterisk project. Please do not directly contact * any of the maintainers of this project for assistance; * the project provides a web site, mailing lists and IRC * channels for your use. * * This program is free software, distributed under the terms of * the GNU General Public License Version 2. See the LICENSE file * at the top of the source tree. */ /*! \file * * \brief FSK Modulator/Demodulator * * \author Mark Spencer * * \arg Includes code and algorithms from the Zapata library. * */ #include "asterisk.h" ASTERISK_FILE_VERSION(__FILE__, "$Revision$") #include "asterisk/fskmodem.h" #define NBW 2 #define BWLIST {75,800} #define NF 6 #define FLIST {1400,1800,1200,2200,1300,2100} #define STATE_SEARCH_STARTBIT 0 #define STATE_SEARCH_STARTBIT2 1 #define STATE_SEARCH_STARTBIT3 2 #define STATE_GET_BYTE 3 static inline int iget_sample(short **buffer, int *len) { int retval; retval = (int) **buffer; (*buffer)++; (*len)--; return retval; } #define IGET_SAMPLE iget_sample(&buffer, len) /*! \brief Coefficients for input filters * Coefficients table, generated by program "mkfilter" * mkfilter is part of the zapatatelephony.org distribution * Format: coef[IDX_FREC][IDX_BW][IDX_COEF] * IDX_COEF = 0 => 1/GAIN * IDX_COEF = 1-6 => Coefficientes y[n] */ static double coef_in[NF][NBW][8]={ { { 1.8229206611e-04,-7.8997325866e-01,2.2401819940e+00,-4.6751353581e+00,5.5080745712e+00,-5.0571565772e+00,2.6215820004e+00,0.0000000000e+00, }, { 9.8532175289e-02,-5.6297236492e-02,3.3146713415e-01,-9.2239200436e-01,1.4844365184e+00,-2.0183258642e+00,2.0074154497e+00,0.0000000000e+00, }, }, { { 1.8229206610e-04,-7.8997325866e-01,7.7191410839e-01,-2.8075643964e+00,1.6948618347e+00,-3.0367273700e+00,9.0333559408e-01,0.0000000000e+00, }, { 9.8531161839e-02,-5.6297236492e-02,1.1421579050e-01,-4.8122536483e-01,4.0121072432e-01,-7.4834487567e-01,6.9170822332e-01,0.0000000000e+00, }, }, { { 1.8229206611e-04,-7.8997325866e-01,2.9003821430e+00,-6.1082779024e+00,7.7169345751e+00,-6.6075999680e+00,3.3941838836e+00,0.0000000000e+00, }, { 9.8539686961e-02,-5.6297236492e-02,4.2915323820e-01,-1.2609358633e+00,2.2399213250e+00,-2.9928879142e+00,2.5990173742e+00,0.0000000000e+00, }, }, { { 1.8229206610e-04,-7.8997325866e-01,-7.7191410839e-01,-2.8075643964e+00,-1.6948618347e+00,-3.0367273700e+00,-9.0333559408e-01,0.0000000000e+00, }, { 9.8531161839e-02,-5.6297236492e-02,-1.1421579050e-01,-4.8122536483e-01,-4.0121072432e-01,-7.4834487567e-01,-6.9170822332e-01,0.0000000000e+00, }, }, { { 1.8229206611e-04,-7.8997325866e-01,2.5782298908e+00,-5.3629717478e+00,6.5890882172e+00,-5.8012914776e+00,3.0171839130e+00,0.0000000000e+00, }, { 9.8534230718e-02,-5.6297236492e-02,3.8148618075e-01,-1.0848760410e+00,1.8441165168e+00,-2.4860666655e+00,2.3103384142e+00,0.0000000000e+00, }, }, { { 1.8229206610e-04,-7.8997325866e-01,-3.8715051001e-01,-2.6192408538e+00,-8.3977994034e-01,-2.8329897913e+00,-4.5306444352e-01,0.0000000000e+00, }, { 9.8531160936e-02,-5.6297236492e-02,-5.7284484199e-02,-4.3673866734e-01,-1.9564766257e-01,-6.2028156584e-01,-3.4692356122e-01,0.0000000000e+00, }, }, }; /*! \brief Coefficients for output filter * Coefficients table, generated by program "mkfilter" * Format: coef[IDX_BW][IDX_COEF] * IDX_COEF = 0 => 1/GAIN * IDX_COEF = 1-6 => Coefficientes y[n] */ static double coef_out[NBW][8]={ { 1.3868644653e-08,-6.3283665042e-01,4.0895057217e+00,-1.1020074592e+01,1.5850766191e+01,-1.2835109292e+01,5.5477477340e+00,0.0000000000e+00, }, { 3.1262119724e-03,-7.8390522307e-03,8.5209627801e-02,-4.0804129163e-01,1.1157139955e+00,-1.8767603680e+00,1.8916395224e+00,0.0000000000e+00 }, }; /*! Integer Pass Band demodulator filter */ static inline int ibpdfilter(struct filter_struct * fs, int in) { int i,j; int s; int64_t s_interim; /* integer filter */ s = in * fs->icoefs[0]; fs->ixv[(fs->ip + 6) & 7] = s; s = (fs->ixv[fs->ip] + fs->ixv[(fs->ip + 6) & 7]) + 6 * (fs->ixv[(fs->ip + 1) & 7] + fs->ixv[(fs->ip + 5) & 7]) + 15 * (fs->ixv[(fs->ip + 2) & 7] + fs->ixv[(fs->ip + 4) & 7]) + 20 * fs->ixv[(fs->ip + 3) & 7]; for (i = 1, j = fs->ip; i < 7; i++, j++) { /* Promote operation to 64 bit to prevent overflow that occurred in 32 bit) */ s_interim = (int64_t)(fs->iyv[j & 7]) * (int64_t)(fs->icoefs[i]) / (int64_t)(1024); s += (int) s_interim; } fs->iyv[j & 7] = s; fs->ip++; fs->ip &= 7; return s; } /*! Integer Band Pass filter */ static inline int ibpfilter(struct filter_struct * fs, int in) { int i, j; int s; int64_t s_interim; /* integer filter */ s = in * fs->icoefs[0] / 256; fs->ixv[(fs->ip + 6) & 7] = s; s = (fs->ixv[(fs->ip + 6) & 7] - fs->ixv[fs->ip]) + 3 * (fs->ixv[(fs->ip + 2) & 7] - fs->ixv[(fs->ip + 4) & 7]); for (i = 1, j = fs->ip; i < 7; i++, j++) { s_interim = (int64_t)(fs->iyv[j & 7]) * (int64_t)(fs->icoefs[i]) / (int64_t)(256); s += (int) s_interim; } fs->iyv[j & 7] = s; fs->ip++; fs->ip &= 7; return s; } static inline int idemodulator(fsk_data *fskd, int *retval, int x) { int is, im, id; int ilin2; is = ibpfilter(&fskd->space_filter, x); im = ibpfilter(&fskd->mark_filter, x); ilin2 = ((im * im) - (is * is)) / (256 * 256); id = ibpdfilter(&fskd->demod_filter, ilin2); *retval = id; return 0; } static int get_bit_raw(fsk_data *fskd, short *buffer, int *len) { /* This function implements a DPLL to synchronize with the bits */ int f; int ix; /* PLL coeffs are set up in callerid_new */ for (f = 0;;) { if (idemodulator(fskd, &ix, IGET_SAMPLE)) return(-1); if ((ix * fskd->xi0) < 0) { /* Transicion */ if (!f) { if (fskd->icont < (fskd->pllispb2)) { fskd->icont += fskd->pllids; } else { fskd->icont -= fskd->pllids; } f = 1; } } fskd->xi0 = ix; fskd->icont += 32; if (fskd->icont > fskd->pllispb) { fskd->icont -= fskd->pllispb; break; } } f = (ix > 0) ? 0x80 : 0; return f; } int fskmodem_init(fsk_data *fskd) { int i; fskd->space_filter.ip = 0; fskd->mark_filter.ip = 0; fskd->demod_filter.ip = 0; for ( i = 0 ; i < 7 ; i++ ) { fskd->space_filter.icoefs[i] = coef_in[fskd->f_space_idx][fskd->bw][i] * 256; fskd->space_filter.ixv[i] = 0;; fskd->space_filter.iyv[i] = 0;; fskd->mark_filter.icoefs[i] = coef_in[fskd->f_mark_idx][fskd->bw][i] * 256; fskd->mark_filter.ixv[i] = 0;; fskd->mark_filter.iyv[i] = 0;; fskd->demod_filter.icoefs[i] = coef_out[fskd->bw][i] * 1024; fskd->demod_filter.ixv[i] = 0;; fskd->demod_filter.iyv[i] = 0;; } return 0; } int fsk_serial(fsk_data *fskd, short *buffer, int *len, int *outbyte) { int a; int i, j, n1, r; int samples = 0; int olen; int beginlen = *len; int beginlenx; switch (fskd->state) { /* Pick up where we left off */ case STATE_SEARCH_STARTBIT2: goto search_startbit2; case STATE_SEARCH_STARTBIT3: goto search_startbit3; case STATE_GET_BYTE: goto getbyte; } /* We await for start bit */ do { /* this was jesus's nice, reasonable, working (at least with RTTY) code to look for the beginning of the start bit. Unfortunately, since TTY/TDD's just start sending a start bit with nothing preceding it at the beginning of a transmission (what a LOSING design), we cant do it this elegantly */ /* NOT USED if (demodulator(zap,&x1)) return -1; for(;;) { if (demodulator(zap,&x2)) return -1; if (x1>0 && x2<0) break; x1=x2; } */ /* this is now the imprecise, losing, but functional code to detect the beginning of a start bit in the TDD sceanario. It just looks for sufficient level to maybe, perhaps, guess, maybe that its maybe the beginning of a start bit, perhaps. This whole thing stinks! */ beginlenx = beginlen; /* just to avoid unused war warnings */ if (idemodulator(fskd, &fskd->xi1, IGET_SAMPLE)) return -1; samples++; for(;;) { search_startbit2: if (*len <= 0) { fskd->state = STATE_SEARCH_STARTBIT2; return 0; } samples++; if (idemodulator(fskd, &fskd->xi2, IGET_SAMPLE)) return -1; #if 0 printf("xi2 = %d ", fskd->xi2); #endif if (fskd->xi2 < 512) { break; } } search_startbit3: /* We await for 0.5 bits before using DPLL */ i = fskd->ispb / 2; if (*len < i) { fskd->state = STATE_SEARCH_STARTBIT3; return 0; } for (; i > 0; i--) { if (idemodulator(fskd, &fskd->xi1, IGET_SAMPLE)) return(-1); #if 0 printf("xi1 = %d ", fskd->xi1); #endif samples++; } /* x1 must be negative (start bit confirmation) */ } while (fskd->xi1 > 0); fskd->state = STATE_GET_BYTE; getbyte: /* Need at least 80 samples (for 1200) or 1320 (for 45.5) to be sure we'll have a byte */ if (fskd->nbit < 8) { if (*len < 1320) return 0; } else { if (*len < 80) return 0; } /* Now we read the data bits */ j = fskd->nbit; for (a = n1 = 0; j; j--) { olen = *len; i = get_bit_raw(fskd, buffer, len); buffer += (olen - *len); if (i == -1) return -1; if (i) n1++; a >>= 1; a |= i; } j = 8 - fskd->nbit; a >>= j; /* We read parity bit (if exists) and check parity */ if (fskd->parity) { olen = *len; i = get_bit_raw(fskd, buffer, len); buffer += (olen - *len); if (i == -1) return -1; if (i) n1++; if (fskd->parity == 1) { /* parity=1 (even) */ if (n1 & 1) a |= 0x100; /* error */ } else { /* parity=2 (odd) */ if (!(n1 & 1)) a |= 0x100; /* error */ } } /* We read STOP bits. All of them must be 1 */ for (j = fskd->instop; j; j--) { r = get_bit_raw(fskd, buffer, len); if (r == -1) return -1; if (!r) a |= 0x200; } /* And finally we return * Bit 8 : Parity error * Bit 9 : Framming error */ *outbyte = a; fskd->state = STATE_SEARCH_STARTBIT; return 1; }