3 * Copyright 2007 Free Software Foundation, Inc.
5 * This file is part of GNU Radio
7 * GNU Radio is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License as published by
9 * the Free Software Foundation; either version 3, or (at your option)
12 * GNU Radio is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 * GNU General Public License for more details.
17 * You should have received a copy of the GNU General Public License
18 * along with GNU Radio; see the file COPYING. If not, write to
19 * the Free Software Foundation, Inc., 51 Franklin Street,
20 * Boston, MA 02110-1301, USA.
24 * config.h is generated by configure. It contains the results
25 * of probing for features, options etc. It should be the first
26 * file included in your .cc file.
32 #include <cvsd_decode_bs.h>
33 #include <gr_io_signature.h>
37 * Create a new instance of cvsd_decode_bs and return
38 * a boost shared_ptr. This is effectively the public constructor.
41 cvsd_make_decode_bs (short min_step, short max_step, double step_decay,
42 double accum_decay, int K, int J,
43 short pos_accum_max, short neg_accum_max)
45 return cvsd_decode_bs_sptr (new cvsd_decode_bs (min_step, max_step,
46 step_decay, accum_decay, K, J,
47 pos_accum_max, neg_accum_max));
50 cvsd_decode_bs::cvsd_decode_bs (short min_step, short max_step, double step_decay,
51 double accum_decay, int K, int J,
52 short pos_accum_max, short neg_accum_max)
53 : gr_sync_interpolator ("cvsd_decode_bs",
54 gr_make_io_signature (1, 1, sizeof (unsigned char)),
55 gr_make_io_signature (1, 1, sizeof (short)),
57 d_min_step (min_step), d_max_step(max_step), d_step_decay(step_decay),
58 d_accum_decay(accum_decay), d_K(K), d_J(J),
59 d_pos_accum_max(pos_accum_max), d_neg_accum_max(neg_accum_max),
67 assert(d_pos_accum_max <= SHRT_MAX);
68 assert(d_neg_accum_max >= -SHRT_MAX);
72 // nothing else required in this example
76 cvsd_decode_bs::~cvsd_decode_bs ()
78 // nothing else required in this example
81 unsigned char cvsd_decode_bs::cvsd_bitwise_sum (unsigned int input)
83 unsigned int temp=input;
93 int cvsd_decode_bs::cvsd_round (double input)
102 unsigned int cvsd_decode_bs::cvsd_pow (short radix, short power)
104 double d_radix = (double) radix;
105 int i_power = (int) power;
108 output=pow(d_radix,i_power);
109 return ( (unsigned int) cvsd_round(output));
114 cvsd_decode_bs::work (int noutput_items,
115 gr_vector_const_void_star &input_items,
116 gr_vector_void_star &output_items)
120 const unsigned char *in = (const unsigned char *) input_items[0];
121 short *out = (short *) output_items[0];
124 short output_short=0; // 2 bytes 0 .. 65,535
125 unsigned char bit_count=0; // 1 byte, 0 .. 255
126 unsigned int mask=0; // 4 bytes, 0 .. 4,294,967,295
127 unsigned char input_byte=0; // 1 bytes
128 unsigned char input_bit=0; // 1 byte, 0 .. 255
130 // Loop through each input data point
131 for(i = 0; i < noutput_items/8.0; i++) {
134 // Initiliaze bit counter
138 // Compute the Appropriate Mask
139 mask=cvsd_pow(2,7-bit_count);
141 // Pull off the corresponding bit
142 input_bit = input_byte & mask;
144 // Update the bit counter
147 // Update runner with the next input bit
148 // Runner is a shift-register; shift left, add on newest output bit
149 d_runner = (d_runner<<1) | ((unsigned int) input_bit);
151 // Run this only if you have >= J bits in your shift register
152 if (d_loop_counter>=d_J) {
154 d_runner_mask=(cvsd_pow(2,d_J)-1);
155 if ((cvsd_bitwise_sum(d_runner & d_runner_mask)>=d_J)||(cvsd_bitwise_sum((~d_runner) & d_runner_mask)>=d_J)) {
157 d_stepsize = std::min( (short) (d_stepsize + d_min_step), d_max_step);
160 // No runs of 1s and 0s
161 d_stepsize = std::max( (short) cvsd_round(d_stepsize*d_step_decay), d_min_step);
165 // Update Accum (i.e. the reference value)
167 d_accum=d_accum+d_stepsize;
170 d_accum=d_accum-d_stepsize;
173 // Multiply by Accum_Decay
174 d_accum=(cvsd_round(d_accum*d_accum_decay));
176 // Check for overflow
177 if (d_accum >=((int) d_pos_accum_max)) {
178 d_accum=(int)d_pos_accum_max;
180 else if (d_accum <=((int) d_neg_accum_max)) {
181 d_accum=(int)d_neg_accum_max;
184 // Find the output short to write to the file
185 output_short=((short) d_accum);
187 if (d_loop_counter <= d_K) {
191 *(out++) = output_short;
196 return noutput_items;