3 * Copyright 2009 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.
27 #include <noaa_hrpt_sync_fb.h>
28 #include <gr_io_signature.h>
30 inline int signum(float f)
32 return f >= 0.0 ? 1 : -1;
35 noaa_hrpt_sync_fb_sptr
36 noaa_make_hrpt_sync_fb(float alpha, float beta, float sps, float max_offset)
38 return gnuradio::get_initial_sptr(new noaa_hrpt_sync_fb(alpha, beta, sps, max_offset));
41 noaa_hrpt_sync_fb::noaa_hrpt_sync_fb(float alpha, float beta, float sps, float max_offset)
42 : gr_block("noaa_hrpt_sync_fb",
43 gr_make_io_signature(1, 1, sizeof(float)),
44 gr_make_io_signature(1, 1, sizeof(char))),
45 d_alpha(alpha), d_beta(beta),
46 d_sps(sps), d_max_offset(max_offset),
47 d_phase(0.0), d_freq(1.0/sps),
53 noaa_hrpt_sync_fb::general_work(int noutput_items,
54 gr_vector_int &ninput_items,
55 gr_vector_const_void_star &input_items,
56 gr_vector_void_star &output_items)
58 int ninputs = ninput_items[0];
59 const float *in = (const float *)input_items[0];
60 char *out = (char *)output_items[0];
63 while (i < ninputs && j < noutput_items) {
64 float sample = in[i++];
65 int sign = signum(sample);
68 // Train on zero crossings in center region of symbol
69 if (sign != d_last_sign) {
70 float phase_err = 0.0;
71 if (d_phase > 0.25 && d_phase < 0.75)
72 phase_err = d_phase-0.5;
73 else if (d_phase >= 0.75)
74 phase_err = d_phase - 1.0;
78 d_phase -= phase_err*d_alpha; // 1st order phase adjustment
79 d_freq -= phase_err*d_beta; // 2nd order frequency adjustment