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/* -*- c++ -*- */
/*
* Copyright 2009 Free Software Foundation, Inc.
*
* This file is part of GNU Radio
*
* GNU Radio is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 3, or (at your option)
* any later version.
*
* GNU Radio is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with GNU Radio; see the file COPYING. If not, write to
* the Free Software Foundation, Inc., 51 Franklin Street,
* Boston, MA 02110-1301, USA.
*/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include <noaa_hrpt_sync_fb.h>
#include <gr_io_signature.h>
inline int signum(float f)
{
return f >= 0.0 ? 1 : -1;
}
noaa_hrpt_sync_fb_sptr
noaa_make_hrpt_sync_fb(float alpha, float beta, float sps, float max_offset)
{
return gnuradio::get_initial_sptr(new noaa_hrpt_sync_fb(alpha, beta, sps, max_offset));
}
noaa_hrpt_sync_fb::noaa_hrpt_sync_fb(float alpha, float beta, float sps, float max_offset)
: gr_block("noaa_hrpt_sync_fb",
gr_make_io_signature(1, 1, sizeof(float)),
gr_make_io_signature(1, 1, sizeof(char))),
d_alpha(alpha), d_beta(beta),
d_sps(sps), d_max_offset(max_offset),
d_phase(0.0), d_freq(1.0/sps),
d_last_sign(1)
{
}
int
noaa_hrpt_sync_fb::general_work(int noutput_items,
gr_vector_int &ninput_items,
gr_vector_const_void_star &input_items,
gr_vector_void_star &output_items)
{
int ninputs = ninput_items[0];
const float *in = (const float *)input_items[0];
char *out = (char *)output_items[0];
int i = 0, j = 0;
while (i < ninputs && j < noutput_items) {
float sample = in[i++];
int sign = signum(sample);
d_phase += d_freq;
// Train on zero crossings in center region of symbol
if (sign != d_last_sign) {
float phase_err = 0.0;
if (d_phase > 0.25 && d_phase < 0.75)
phase_err = d_phase-0.5;
else if (d_phase >= 0.75)
phase_err = d_phase - 1.0;
else
phase_err = d_phase;
d_phase -= phase_err*d_alpha; // 1st order phase adjustment
d_freq -= phase_err*d_beta; // 2nd order frequency adjustment
d_last_sign = sign;
}
if (d_phase > 1.0) {
if (sample < 0.0)
out[j++] = 1;
else
out[j++] = 0;
d_phase -= 1.0;
}
}
consume_each(i);
return j;
}
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