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1 /*
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2 * SpanDSP - a series of DSP components for telephony
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3 *
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4 * v22bis.h - ITU V.22bis modem receive part
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5 *
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6 * Written by Steve Underwood <steveu@coppice.org>
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7 *
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8 * Copyright (C) 2004 Steve Underwood
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9 *
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10 * All rights reserved.
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11 *
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12 * This program is free software; you can redistribute it and/or modify
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13 * it under the terms of the GNU General Public License version 2, as
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14 * published by the Free Software Foundation.
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15 *
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16 * This program is distributed in the hope that it will be useful,
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17 * but WITHOUT ANY WARRANTY; without even the implied warranty of
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18 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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19 * GNU General Public License for more details.
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20 *
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21 * You should have received a copy of the GNU General Public License
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22 * along with this program; if not, write to the Free Software
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23 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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24 *
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25 * $Id: v22bis.h,v 1.19 2006/10/24 13:45:28 steveu Exp $
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26 */
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27
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28 /*! \file */
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29
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30 /*! \page v22bis_page The V.22bis modem
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31 \section v22bis_page_sec_1 What does it do?
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32 The V.22bis modem is a duplex modem for general data use on the PSTN, at rates
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33 of 1200 and 2400 bits/second. It is a compatible extension of the V.22 modem,
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34 which is a 1200 bits/second only design. It is a band-split design, using carriers
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35 of 1200Hz and 2400Hz. It is the fastest PSTN modem in general use which does not
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36 use echo-cancellation.
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37
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38 \section v22bis__page_sec_2 How does it work?
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39 V.22bis uses 4PSK modulation at 1200 bits/second or 16QAM modulation at 2400
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40 bits/second. At 1200bps the symbols are so long that a fixed compromise equaliser
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41 is sufficient to recover the 4PSK signal reliably. At 2400bps an adaptive
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42 equaliser is necessary.
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43
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44 The V.22bis training sequence includes sections which allow the modems to determine
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45 if the far modem can support (or is willing to support) 2400bps operation. The
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46 modems will automatically use 2400bps if both ends are willing to use that speed,
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47 or 1200bps if one or both ends to not acknowledge that 2400bps is OK.
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48 */
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49
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50 #if !defined(_V22BIS_H_)
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51 #define _V22BIS_H_
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52
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53 #define V22BIS_EQUALIZER_LEN 7 /* this much to the left and this much to the right */
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54 #define V22BIS_EQUALIZER_MASK 15 /* one less than a power of 2 >= (2*V22BIS_EQUALIZER_LEN + 1) */
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55
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56 #define V22BIS_TX_FILTER_STEPS 9
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57
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58 #define V22BIS_RX_FILTER_STEPS 37
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59
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60 /*!
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61 V.22bis modem receive side descriptor. This defines the working state for a
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62 single instance of a V.22bis modem receiver.
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63 */
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64 typedef struct
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65 {
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66 /*! \brief The bit rate of the modem. Valid values are 1200 and 2400. */
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67 int bit_rate;
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68 /*! \brief TRUE is this is the calling side modem. */
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69 int caller;
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70 /*! \brief The callback function used to put each bit received. */
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71 put_bit_func_t put_bit;
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72 /*! \brief The callback function used to get the next bit to be transmitted. */
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73 get_bit_func_t get_bit;
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74 /*! \brief A user specified opaque pointer passed to the callback routines. */
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75 void *user_data;
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76
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77 /* RECEIVE SECTION */
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78
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79 /*! \brief A callback function which may be enabled to report every symbol's
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80 constellation position. */
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81 qam_report_handler_t *qam_report;
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82 /*! \brief A user specified opaque pointer passed to the qam_report callback
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83 routine. */
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84 void *qam_user_data;
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85
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86 /*! \brief The route raised cosine (RRC) pulse shaping filter buffer. */
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87 float rx_rrc_filter[2*V22BIS_RX_FILTER_STEPS];
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88 /*! \brief Current offset into the RRC pulse shaping filter buffer. */
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89 int rx_rrc_filter_step;
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90
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91 /*! \brief The register for the data scrambler. */
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92 unsigned int rx_scramble_reg;
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93 /*! \brief A counter for the number of consecutive bits of repeating pattern through
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94 the scrambler. */
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95 int rx_scrambler_pattern_count;
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96 /*! \brief 0 if receiving user data. A training stage value during training */
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97 int rx_training;
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98 int rx_training_count;
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99 float training_error;
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100 int carrier_present;
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101
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102 /*! \brief The current phase of the carrier (i.e. the DDS parameter). */
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103 uint32_t rx_carrier_phase;
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104 /*! \brief The update rate for the phase of the carrier (i.e. the DDS increment). */
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105 int32_t rx_carrier_phase_rate;
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106 float carrier_track_p;
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107 float carrier_track_i;
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108
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109 power_meter_t rx_power;
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110 int32_t carrier_on_power;
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111 int32_t carrier_off_power;
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112 float agc_scaling;
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113
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114 int rx_constellation_state;
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115
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116 float eq_delta;
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117 /*! \brief The adaptive equalizer coefficients */
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118 complexf_t eq_coeff[2*V22BIS_EQUALIZER_LEN + 1];
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119 complexf_t eq_buf[V22BIS_EQUALIZER_MASK + 1];
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120 /*! \brief Current offset into equalizer buffer. */
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121 int eq_step;
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122 int eq_put_step;
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123
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124 /*! \brief Integration variable for damping the Gardner algorithm tests. */
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125 int gardner_integrate;
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126 /*! \brief Current step size of Gardner algorithm integration. */
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127 int gardner_step;
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128 /*! \brief The total symbol timing correction since the carrier came up.
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129 This is only for performance analysis purposes. */
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130 int total_baud_timing_correction;
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131 /*! \brief The current fractional phase of the baud timing. */
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132 int rx_baud_phase;
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133
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134 int sixteen_way_decisions;
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135
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136 /* TRANSMIT SECTION */
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137
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138 /*! \brief The gain factor needed to achieve the specified output power. */
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139 float tx_gain;
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140
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141 /*! \brief The route raised cosine (RRC) pulse shaping filter buffer. */
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142 complexf_t tx_rrc_filter[2*V22BIS_TX_FILTER_STEPS];
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143 /*! \brief Current offset into the RRC pulse shaping filter buffer. */
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144 int tx_rrc_filter_step;
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145
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146 /*! \brief The register for the data scrambler. */
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147 unsigned int tx_scramble_reg;
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148 /*! \brief A counter for the number of consecutive bits of repeating pattern through
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149 the scrambler. */
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150 int tx_scrambler_pattern_count;
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151 /*! \brief 0 if transmitting user data. A training stage value during training */
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152 int tx_training;
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153 /*! \brief A counter used to track progress through sending the training sequence. */
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154 int tx_training_count;
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155
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156 /*! \brief The current phase of the carrier (i.e. the DDS parameter). */
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157 uint32_t tx_carrier_phase;
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158 /*! \brief The update rate for the phase of the carrier (i.e. the DDS increment). */
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159 int32_t tx_carrier_phase_rate;
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160 /*! \brief The current phase of the guard tone (i.e. the DDS parameter). */
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161 uint32_t guard_phase;
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162 /*! \brief The update rate for the phase of the guard tone (i.e. the DDS increment). */
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163 int32_t guard_phase_rate;
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164 float guard_level;
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165 /*! \brief The current fractional phase of the baud timing. */
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166 int tx_baud_phase;
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167 /*! \brief The code number for the current position in the constellation. */
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168 int tx_constellation_state;
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169 /*! \brief An indicator to mark that we are tidying up to stop transmission. */
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170 int shutdown;
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171 /*! \brief The get_bit function in use at any instant. */
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172 get_bit_func_t current_get_bit;
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173
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174 int detected_unscrambled_ones;
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175 int detected_unscrambled_zeros;
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176
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177 int detected_unscrambled_ones_or_zeros;
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178 int detected_unscrambled_0011_ending;
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179 int detected_scrambled_ones_or_zeros_at_1200bps;
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180 int detected_scrambled_ones_at_2400bps;
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181
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182 /*! \brief Error and flow logging control */
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183 logging_state_t logging;
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184 } v22bis_state_t;
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185
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186 extern const complexf_t v22bis_constellation[16];
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187
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188 #ifdef __cplusplus
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189 extern "C" {
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190 #endif
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191
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192 /*! Reinitialise an existing V.22bis modem receive context.
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193 \brief Reinitialise an existing V.22bis modem receive context.
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194 \param s The modem context.
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195 \param rate The bit rate of the modem. Valid values are 1200 and 2400.
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196 \return 0 for OK, -1 for bad parameter */
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197 int v22bis_rx_restart(v22bis_state_t *s, int bit_rate);
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198
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199 /*! Process a block of received V.22bis modem audio samples.
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200 \brief Process a block of received V.22bis modem audio samples.
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201 \param s The modem context.
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202 \param amp The audio sample buffer.
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203 \param len The number of samples in the buffer.
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204 \return The number of samples unprocessed. */
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205 int v22bis_rx(v22bis_state_t *s, const int16_t amp[], int len);
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206
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207 /*! Get a snapshot of the current equalizer coefficients.
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208 \brief Get a snapshot of the current equalizer coefficients.
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209 \param coeffs The vector of complex coefficients.
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210 \return The number of coefficients in the vector. */
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211 int v22bis_rx_equalizer_state(v22bis_state_t *s, complexf_t **coeffs);
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212
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213 /*! Get the current received carrier frequency.
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214 \param s The modem context.
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215 \return The frequency, in Hertz. */
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216 float v22bis_rx_carrier_frequency(v22bis_state_t *s);
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217
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218 /*! Get the current symbol timing correction since startup.
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219 \param s The modem context.
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220 \return The correction. */
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221 float v22bis_rx_symbol_timing_correction(v22bis_state_t *s);
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222
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223 /*! Get a current received signal power.
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224 \param s The modem context.
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225 \return The signal power, in dBm0. */
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226 float v22bis_rx_signal_power(v22bis_state_t *s);
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227
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228 /*! Set a handler routine to process QAM status reports
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229 \param s The modem context.
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230 \param handler The handler routine.
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231 \param user_data An opaque pointer passed to the handler routine. */
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232 void v22bis_rx_set_qam_report_handler(v22bis_state_t *s, qam_report_handler_t *handler, void *user_data);
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233
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234 /*! Generate a block of V.22bis modem audio samples.
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235 \brief Generate a block of V.22bis modem audio samples.
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236 \param s The modem context.
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237 \param amp The audio sample buffer.
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238 \param len The number of samples to be generated.
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239 \return The number of samples actually generated. */
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240 int v22bis_tx(v22bis_state_t *s, int16_t amp[], int len);
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241
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242 /*! Adjust a V.22bis modem transmit context's power output.
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243 \brief Adjust a V.22bis modem transmit context's output power.
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244 \param s The modem context.
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245 \param power The power level, in dBm0 */
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246 void v22bis_tx_power(v22bis_state_t *s, float power);
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247
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248 /*! Reinitialise an existing V.22bis modem context, so it may be reused.
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249 \brief Reinitialise an existing V.22bis modem context.
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250 \param s The modem context.
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251 \param bit_rate The bit rate of the modem. Valid values are 1200 and 2400.
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252 \return 0 for OK, -1 for bad parameter. */
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253 int v22bis_restart(v22bis_state_t *s, int bit_rate);
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254
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255 /*! Initialise a V.22bis modem context. This must be called before the first
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256 use of the context, to initialise its contents.
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257 \brief Initialise a V.22bis modem context.
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258 \param s The modem context.
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259 \param bit_rate The bit rate of the modem. Valid values are 1200 and 2400.
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260 \param guard The guard tone option. 0 = none, 1 = 550Hz, 2 = 1800Hz.
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261 \param caller TRUE if this is the calling modem.
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262 \param get_bit The callback routine used to get the data to be transmitted.
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263 \param put_bit The callback routine used to get the data to be transmitted.
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264 \param user_data An opaque pointer, passed in calls to the get and put routines.
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265 \return A pointer to the modem context, or NULL if there was a problem. */
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266 v22bis_state_t *v22bis_init(v22bis_state_t *s,
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267 int bit_rate,
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268 int guard,
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269 int caller,
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270 get_bit_func_t get_bit,
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271 put_bit_func_t put_bit,
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272 void *user_data);
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273
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274 /*! Change the get_bit function associated with a V.2bis modem context.
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275 \brief Change the get_bit function associated with a V.22bis modem context.
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276 \param s The modem context.
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277 \param get_bit The callback routine used to get the data to be transmitted.
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278 \param user_data An opaque pointer. */
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279 void v22bis_set_get_bit(v22bis_state_t *s, get_bit_func_t get_bit, void *user_data);
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280
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281 /*! Change the get_bit function associated with a V.2bis modem context.
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282 \brief Change the put_bit function associated with a V.22bis modem context.
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283 \param s The modem context.
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284 \param put_bit The callback routine used to process the data received.
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285 \param user_data An opaque pointer. */
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286 void v22bis_set_put_bit(v22bis_state_t *s, put_bit_func_t put_bit, void *user_data);
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287
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288 #ifdef __cplusplus
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289 }
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290 #endif
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291
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292 #endif
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293 /*- End of file ------------------------------------------------------------*/
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