358 lines
9.5 KiB
C
358 lines
9.5 KiB
C
/*
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* Asterisk -- An open source telephony toolkit.
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*
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* Copyright (C) 1999 - 2005, Digium, Inc.
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*
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* Mark Spencer <markster@digium.com>
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*
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* Includes code and algorithms from the Zapata library.
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*
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* See http://www.asterisk.org for more information about
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* the Asterisk project. Please do not directly contact
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* any of the maintainers of this project for assistance;
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* the project provides a web site, mailing lists and IRC
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* channels for your use.
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*
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* This program is free software, distributed under the terms of
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* the GNU General Public License Version 2. See the LICENSE file
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* at the top of the source tree.
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*/
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/*! \file
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*
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* \brief FSK Modulator/Demodulator
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*
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* \author Mark Spencer <markster@digium.com>
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*
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* \arg Includes code and algorithms from the Zapata library.
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*
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*/
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#include "asterisk.h"
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ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
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#include <stdio.h>
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#include "asterisk/fskmodem.h"
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#define NBW 2
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#define BWLIST {75,800}
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#define NF 6
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#define FLIST {1400,1800,1200,2200,1300,2100}
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#define STATE_SEARCH_STARTBIT 0
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#define STATE_SEARCH_STARTBIT2 1
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#define STATE_SEARCH_STARTBIT3 2
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#define STATE_GET_BYTE 3
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static inline float get_sample(short **buffer, int *len)
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{
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float retval;
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retval = (float) **buffer / 256;
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(*buffer)++;
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(*len)--;
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return retval;
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};
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#define GET_SAMPLE get_sample(&buffer, len)
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/*! \brief Coefficients for input filters
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* Coefficients table, generated by program "mkfilter"
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* mkfilter is part of the zapatatelephony.org distribution
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* Format: coef[IDX_FREC][IDX_BW][IDX_COEF]
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* IDX_COEF = 0 => 1/GAIN
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* IDX_COEF = 1-6 => Coefficientes y[n]
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*/
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static double coef_in[NF][NBW][8] = {
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{
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{ 1.8229206611e-04,-7.8997325866e-01,2.2401819940e+00,-4.6751353581e+00,5.5080745712e+00,-5.0571565772e+00,2.6215820004e+00,0.0000000000e+00, },
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{ 9.8532175289e-02,-5.6297236492e-02,3.3146713415e-01,-9.2239200436e-01,1.4844365184e+00,-2.0183258642e+00,2.0074154497e+00,0.0000000000e+00, },
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},
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{
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{ 1.8229206610e-04,-7.8997325866e-01,7.7191410839e-01,-2.8075643964e+00,1.6948618347e+00,-3.0367273700e+00,9.0333559408e-01,0.0000000000e+00, } ,
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{ 9.8531161839e-02,-5.6297236492e-02,1.1421579050e-01,-4.8122536483e-01,4.0121072432e-01,-7.4834487567e-01,6.9170822332e-01,0.0000000000e+00, },
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},
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{
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{ 1.8229206611e-04,-7.8997325866e-01,2.9003821430e+00,-6.1082779024e+00,7.7169345751e+00,-6.6075999680e+00,3.3941838836e+00,0.0000000000e+00, },
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{ 9.8539686961e-02,-5.6297236492e-02,4.2915323820e-01,-1.2609358633e+00,2.2399213250e+00,-2.9928879142e+00,2.5990173742e+00,0.0000000000e+00, },
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},
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{
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{ 1.8229206610e-04,-7.8997325866e-01,-7.7191410839e-01,-2.8075643964e+00,-1.6948618347e+00,-3.0367273700e+00,-9.0333559408e-01,0.0000000000e+00, },
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{ 9.8531161839e-02,-5.6297236492e-02,-1.1421579050e-01,-4.8122536483e-01,-4.0121072432e-01,-7.4834487567e-01,-6.9170822332e-01,0.0000000000e+00, },
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},
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{
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{ 1.8229206611e-04,-7.8997325866e-01,2.5782298908e+00,-5.3629717478e+00,6.5890882172e+00,-5.8012914776e+00,3.0171839130e+00,0.0000000000e+00, },
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{ 9.8534230718e-02,-5.6297236492e-02,3.8148618075e-01,-1.0848760410e+00,1.8441165168e+00,-2.4860666655e+00,2.3103384142e+00,0.0000000000e+00, },
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},
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{
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{ 1.8229206610e-04,-7.8997325866e-01,-3.8715051001e-01,-2.6192408538e+00,-8.3977994034e-01,-2.8329897913e+00,-4.5306444352e-01,0.0000000000e+00, },
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{ 9.8531160936e-02,-5.6297236492e-02,-5.7284484199e-02,-4.3673866734e-01,-1.9564766257e-01,-6.2028156584e-01,-3.4692356122e-01,0.0000000000e+00, },
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},
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};
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/*! \brief Coefficients for output filter
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* Coefficients table, generated by program "mkfilter"
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* Format: coef[IDX_BW][IDX_COEF]
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* IDX_COEF = 0 => 1/GAIN
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* IDX_COEF = 1-6 => Coefficientes y[n]
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*/
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static double coef_out[NBW][8] = {
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{ 1.3868644653e-08,-6.3283665042e-01,4.0895057217e+00,-1.1020074592e+01,1.5850766191e+01,-1.2835109292e+01,5.5477477340e+00,0.0000000000e+00, },
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{ 3.1262119724e-03,-7.8390522307e-03,8.5209627801e-02,-4.0804129163e-01,1.1157139955e+00,-1.8767603680e+00,1.8916395224e+00,0.0000000000e+00, },
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};
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/*! Band-pass filter for MARK frequency */
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static inline float filterM(fsk_data *fskd,float in)
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{
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int i, j;
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double s;
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double *pc;
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pc = &coef_in[fskd->f_mark_idx][fskd->bw][0];
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fskd->fmxv[(fskd->fmp+6)&7] = in*(*pc++);
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s = (fskd->fmxv[(fskd->fmp + 6) & 7] - fskd->fmxv[fskd->fmp]) + 3 * (fskd->fmxv[(fskd->fmp + 2) & 7] - fskd->fmxv[(fskd->fmp + 4) & 7]);
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for (i = 0, j = fskd->fmp; i < 6; i++, j++)
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s += fskd->fmyv[j&7]*(*pc++);
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fskd->fmyv[j&7] = s;
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fskd->fmp++;
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fskd->fmp &= 7;
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return s;
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}
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/*! Band-pass filter for SPACE frequency */
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static inline float filterS(fsk_data *fskd,float in)
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{
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int i, j;
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double s;
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double *pc;
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pc = &coef_in[fskd->f_space_idx][fskd->bw][0];
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fskd->fsxv[(fskd->fsp+6)&7] = in*(*pc++);
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s = (fskd->fsxv[(fskd->fsp + 6) & 7] - fskd->fsxv[fskd->fsp]) + 3 * (fskd->fsxv[(fskd->fsp + 2) & 7] - fskd->fsxv[(fskd->fsp + 4) & 7]);
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for (i = 0, j = fskd->fsp; i < 6; i++, j++)
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s += fskd->fsyv[j&7]*(*pc++);
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fskd->fsyv[j&7] = s;
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fskd->fsp++;
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fskd->fsp &= 7;
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return s;
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}
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/*! Low-pass filter for demodulated data */
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static inline float filterL(fsk_data *fskd,float in)
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{
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int i, j;
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double s;
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double *pc;
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pc = &coef_out[fskd->bw][0];
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fskd->flxv[(fskd->flp + 6) & 7] = in * (*pc++);
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s = (fskd->flxv[fskd->flp] + fskd->flxv[(fskd->flp+6)&7]) +
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6 * (fskd->flxv[(fskd->flp+1)&7] + fskd->flxv[(fskd->flp+5)&7]) +
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15 * (fskd->flxv[(fskd->flp+2)&7] + fskd->flxv[(fskd->flp+4)&7]) +
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20 * fskd->flxv[(fskd->flp+3)&7];
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for (i = 0,j = fskd->flp;i<6;i++,j++)
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s += fskd->flyv[j&7]*(*pc++);
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fskd->flyv[j&7] = s;
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fskd->flp++;
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fskd->flp &= 7;
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return s;
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}
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static inline int demodulator(fsk_data *fskd, float *retval, float x)
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{
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float xS,xM;
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fskd->cola_in[fskd->pcola] = x;
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xS = filterS(fskd,x);
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xM = filterM(fskd,x);
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fskd->cola_filter[fskd->pcola] = xM-xS;
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x = filterL(fskd,xM*xM - xS*xS);
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fskd->cola_demod[fskd->pcola++] = x;
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fskd->pcola &= (NCOLA-1);
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*retval = x;
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return 0;
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}
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static int get_bit_raw(fsk_data *fskd, short *buffer, int *len)
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{
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/* This function implements a DPLL to synchronize with the bits */
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float x,spb,spb2,ds;
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int f;
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spb = fskd->spb;
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if (fskd->spb == 7)
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spb = 8000.0 / 1200.0;
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ds = spb/32.;
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spb2 = spb/2.;
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for (f = 0;;) {
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if (demodulator(fskd, &x, GET_SAMPLE))
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return -1;
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if ((x * fskd->x0) < 0) { /* Transition */
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if (!f) {
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if (fskd->cont<(spb2))
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fskd->cont += ds;
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else
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fskd->cont -= ds;
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f = 1;
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}
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}
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fskd->x0 = x;
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fskd->cont += 1.;
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if (fskd->cont > spb) {
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fskd->cont -= spb;
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break;
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}
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}
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f = (x > 0) ? 0x80 : 0;
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return f;
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}
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int fsk_serial(fsk_data *fskd, short *buffer, int *len, int *outbyte)
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{
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int a;
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int i,j,n1,r;
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int samples = 0;
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int olen;
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switch (fskd->state) {
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/* Pick up where we left off */
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case STATE_SEARCH_STARTBIT2:
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goto search_startbit2;
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case STATE_SEARCH_STARTBIT3:
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goto search_startbit3;
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case STATE_GET_BYTE:
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goto getbyte;
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}
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/* We await for start bit */
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do {
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/* this was jesus's nice, reasonable, working (at least with RTTY) code
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to look for the beginning of the start bit. Unfortunately, since TTY/TDD's
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just start sending a start bit with nothing preceding it at the beginning
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of a transmission (what a LOSING design), we cant do it this elegantly */
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/*
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if (demodulator(zap,&x1)) return(-1);
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for (;;) {
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if (demodulator(zap,&x2)) return(-1);
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if (x1>0 && x2<0) break;
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x1 = x2;
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}
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*/
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/* this is now the imprecise, losing, but functional code to detect the
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beginning of a start bit in the TDD sceanario. It just looks for sufficient
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level to maybe, perhaps, guess, maybe that its maybe the beginning of
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a start bit, perhaps. This whole thing stinks! */
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if (demodulator(fskd, &fskd->x1, GET_SAMPLE))
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return -1;
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samples++;
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for (;;) {
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search_startbit2:
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if (*len <= 0) {
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fskd->state = STATE_SEARCH_STARTBIT2;
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return 0;
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}
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samples++;
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if (demodulator(fskd, &fskd->x2, GET_SAMPLE))
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return(-1);
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#if 0
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printf("x2 = %5.5f ", fskd->x2);
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#endif
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if (fskd->x2 < -0.5)
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break;
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}
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search_startbit3:
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/* We await for 0.5 bits before using DPLL */
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i = fskd->spb/2;
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if (*len < i) {
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fskd->state = STATE_SEARCH_STARTBIT3;
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return 0;
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}
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for (; i>0; i--) {
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if (demodulator(fskd, &fskd->x1, GET_SAMPLE))
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return(-1);
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#if 0
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printf("x1 = %5.5f ", fskd->x1);
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#endif
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samples++;
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}
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/* x1 must be negative (start bit confirmation) */
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} while (fskd->x1 > 0);
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fskd->state = STATE_GET_BYTE;
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getbyte:
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/* Need at least 80 samples (for 1200) or
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1320 (for 45.5) to be sure we'll have a byte */
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if (fskd->nbit < 8) {
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if (*len < 1320)
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return 0;
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} else {
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if (*len < 80)
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return 0;
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}
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/* Now we read the data bits */
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j = fskd->nbit;
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for (a = n1 = 0; j; j--) {
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olen = *len;
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i = get_bit_raw(fskd, buffer, len);
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buffer += (olen - *len);
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if (i == -1)
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return(-1);
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if (i)
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n1++;
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a >>= 1;
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a |= i;
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}
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j = 8-fskd->nbit;
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a >>= j;
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/* We read parity bit (if exists) and check parity */
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if (fskd->parity) {
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olen = *len;
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i = get_bit_raw(fskd, buffer, len);
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buffer += (olen - *len);
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if (i == -1)
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return(-1);
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if (i)
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n1++;
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if (fskd->parity == 1) { /* parity=1 (even) */
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if (n1&1)
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a |= 0x100; /* error */
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} else { /* parity=2 (odd) */
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if (!(n1&1))
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a |= 0x100; /* error */
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}
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}
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/* We read STOP bits. All of them must be 1 */
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for (j = fskd->nstop;j;j--) {
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r = get_bit_raw(fskd, buffer, len);
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if (r == -1)
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return(-1);
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if (!r)
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a |= 0x200;
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}
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/* And finally we return */
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/* Bit 8 : Parity error */
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/* Bit 9 : Framming error*/
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*outbyte = a;
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fskd->state = STATE_SEARCH_STARTBIT;
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return 1;
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}
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