127 lines
3.1 KiB
C++
Executable File
127 lines
3.1 KiB
C++
Executable File
/*
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* High Speed modem to transfer data in a 2,7kHz SSB channel
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* =========================================================
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* Author: DJ0ABR
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*
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* (c) DJ0ABR
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* www.dj0abr.de
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*
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*/
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#include "hsmodem.h"
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#ifdef _WIN32_
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#include "fftw_lib/fftw3.h"
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#endif
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#ifdef _LINUX_
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#include <fftw3.h>
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#endif
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#define FFT_AUDIOSAMPLERATE 8000
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double *din = NULL; // input data for fft
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fftw_complex *cpout = NULL; // ouput data from fft
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fftw_plan plan = NULL;
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#define fft_rate (FFT_AUDIOSAMPLERATE / 10) // resolution: 10 Hz
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int fftidx = 0;
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int fftcnt = fft_rate/2+1; // number of output values
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uint16_t fftout[FFT_AUDIOSAMPLERATE / 10/2+1];
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int downsamp = 0;
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int downphase = 0;
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uint16_t *make_waterfall(float fre, int *retlen)
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{
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// Downsampling:
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// needed 8000 bit/s
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// caprate 48k: downsample by 6
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// caprate 44,1k: downsample by 5,5
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if (caprate == 48000)
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{
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if (++downsamp < 6) return NULL;
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}
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if (caprate == 44100)
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{
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if (downphase <= 1100)
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{
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if (++downsamp < 5) return NULL;
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}
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else
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{
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if (++downsamp < 6) return NULL;
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}
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if(++downphase >= 2000) downphase = 0;
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}
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downsamp = 0;
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int fftrdy = 0;
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// fre are the float samples
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// fill into the fft input buffer
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din[fftidx++] = fre;
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if(fftidx == fft_rate)
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{
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fftidx = 0;
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// the fft buffer is full, execute the FFT
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fftw_execute(plan);
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for (int j = 0; j < fftcnt; j++)
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{
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// calculate absolute value (magnitute without phase)
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float fre = (float)cpout[j][0];
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float fim = (float)cpout[j][1];
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float mag = sqrt((fre * fre) + (fim * fim));
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fftout[j] = (uint16_t)mag;
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fftrdy = 1;
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}
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}
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if(fftrdy == 1)
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{
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*retlen = fftcnt;
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return fftout;
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}
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return NULL;
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}
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void init_fft()
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{
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char fn[300];
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sprintf(fn, "capture_fft_%d", fft_rate); // wisdom file for each capture rate
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fftw_import_wisdom_from_filename(fn);
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din = (double *)fftw_malloc(sizeof(double) * fft_rate);
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cpout = (fftw_complex *)fftw_malloc(sizeof(fftw_complex) * fft_rate);
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plan = fftw_plan_dft_r2c_1d(fft_rate, din, cpout, FFTW_MEASURE);
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fftw_export_wisdom_to_filename(fn);
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}
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void exit_fft()
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{
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if(plan) fftw_destroy_plan(plan);
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if(din) fftw_free(din);
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if(cpout) fftw_free(cpout);
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}
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