fsk: multibit decoder
This commit is contained in:
Kamal Mostafa
parent
c790603bf6
commit
80c8a62073
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@ -3,7 +3,7 @@ AM_CFLAGS = -Wall -Werror
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INCLUDES = $(DEPS_CFLAGS)
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bin_PROGRAMS = minimodem tscope
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bin_PROGRAMS = minimodem tscope fsk
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SIMPLEAUDIO_SRC=\
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simpleaudio.c \
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@ -13,6 +13,8 @@ SIMPLEAUDIO_SRC=\
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minimodem_LDADD = $(DEPS_LIBS)
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minimodem_SOURCES = minimodem.c tscope_print.c $(SIMPLEAUDIO_SRC)
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fsk_LDADD = $(DEPS_LIBS)
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fsk_SOURCES = fsk.c tscope_print.c $(SIMPLEAUDIO_SRC)
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tscope_LDADD = $(DEPS_LIBS)
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tscope_SOURCES = tscope.c tscope_print.c
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@ -32,7 +32,7 @@ POST_INSTALL = :
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NORMAL_UNINSTALL = :
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PRE_UNINSTALL = :
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POST_UNINSTALL = :
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bin_PROGRAMS = minimodem$(EXEEXT) tscope$(EXEEXT)
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bin_PROGRAMS = minimodem$(EXEEXT) tscope$(EXEEXT) fsk$(EXEEXT)
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subdir = src
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DIST_COMMON = $(srcdir)/Makefile.am $(srcdir)/Makefile.in
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ACLOCAL_M4 = $(top_srcdir)/aclocal.m4
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@ -47,10 +47,13 @@ am__installdirs = "$(DESTDIR)$(bindir)"
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PROGRAMS = $(bin_PROGRAMS)
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am__objects_1 = simpleaudio.$(OBJEXT) simpleaudio-pulse.$(OBJEXT) \
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simpleaudio-sndfile.$(OBJEXT)
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am_fsk_OBJECTS = fsk.$(OBJEXT) tscope_print.$(OBJEXT) $(am__objects_1)
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fsk_OBJECTS = $(am_fsk_OBJECTS)
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am__DEPENDENCIES_1 =
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fsk_DEPENDENCIES = $(am__DEPENDENCIES_1)
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am_minimodem_OBJECTS = minimodem.$(OBJEXT) tscope_print.$(OBJEXT) \
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$(am__objects_1)
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minimodem_OBJECTS = $(am_minimodem_OBJECTS)
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am__DEPENDENCIES_1 =
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minimodem_DEPENDENCIES = $(am__DEPENDENCIES_1)
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am_tscope_OBJECTS = tscope.$(OBJEXT) tscope_print.$(OBJEXT)
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tscope_OBJECTS = $(am_tscope_OBJECTS)
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@ -63,8 +66,8 @@ COMPILE = $(CC) $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) $(AM_CPPFLAGS) \
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$(CPPFLAGS) $(AM_CFLAGS) $(CFLAGS)
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CCLD = $(CC)
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LINK = $(CCLD) $(AM_CFLAGS) $(CFLAGS) $(AM_LDFLAGS) $(LDFLAGS) -o $@
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SOURCES = $(minimodem_SOURCES) $(tscope_SOURCES)
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DIST_SOURCES = $(minimodem_SOURCES) $(tscope_SOURCES)
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SOURCES = $(fsk_SOURCES) $(minimodem_SOURCES) $(tscope_SOURCES)
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DIST_SOURCES = $(fsk_SOURCES) $(minimodem_SOURCES) $(tscope_SOURCES)
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ETAGS = etags
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CTAGS = ctags
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DISTFILES = $(DIST_COMMON) $(DIST_SOURCES) $(TEXINFOS) $(EXTRA_DIST)
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@ -165,6 +168,8 @@ SIMPLEAUDIO_SRC = \
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minimodem_LDADD = $(DEPS_LIBS)
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minimodem_SOURCES = minimodem.c tscope_print.c $(SIMPLEAUDIO_SRC)
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fsk_LDADD = $(DEPS_LIBS)
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fsk_SOURCES = fsk.c tscope_print.c $(SIMPLEAUDIO_SRC)
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tscope_LDADD = $(DEPS_LIBS)
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tscope_SOURCES = tscope.c tscope_print.c
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all: all-am
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@ -238,6 +243,9 @@ uninstall-binPROGRAMS:
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clean-binPROGRAMS:
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-test -z "$(bin_PROGRAMS)" || rm -f $(bin_PROGRAMS)
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fsk$(EXEEXT): $(fsk_OBJECTS) $(fsk_DEPENDENCIES)
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@rm -f fsk$(EXEEXT)
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$(LINK) $(fsk_OBJECTS) $(fsk_LDADD) $(LIBS)
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minimodem$(EXEEXT): $(minimodem_OBJECTS) $(minimodem_DEPENDENCIES)
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@rm -f minimodem$(EXEEXT)
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$(LINK) $(minimodem_OBJECTS) $(minimodem_LDADD) $(LIBS)
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@ -251,6 +259,7 @@ mostlyclean-compile:
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distclean-compile:
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-rm -f *.tab.c
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@AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/fsk.Po@am__quote@
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@AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/minimodem.Po@am__quote@
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@AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/simpleaudio-pulse.Po@am__quote@
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@AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/simpleaudio-sndfile.Po@am__quote@
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@ -0,0 +1,437 @@
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#define USE_FFT
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#include <malloc.h>
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#include <string.h>
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#include <math.h> // fabs, hypotf
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#ifdef USE_FFT
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#include <fftw3.h>
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#endif
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#include <errno.h>
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#include <stdio.h>
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#include <ctype.h>
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//#define FSK_DEBUG
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#ifdef FSK_DEBUG
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# define debug_log(format, args...) fprintf(stderr, format, ## args)
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#else
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# define debug_log(format, args...)
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#endif
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typedef struct fsk_plan fsk_plan;
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struct fsk_plan {
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float sample_rate;
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float f_mark;
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float f_space;
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float filter_bw;
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unsigned int n_data_bits;
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#ifdef USE_FFT
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int fftsize; // fftw wants this to be signed. why?
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unsigned int b_mark;
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unsigned int b_space;
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fftwf_plan fftplan;
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float *fftin;
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fftwf_complex *fftout;
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#endif
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};
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fsk_plan *
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fsk_plan_new(
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float sample_rate,
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float f_mark,
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float f_space,
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float filter_bw,
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unsigned int n_data_bits
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)
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{
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fsk_plan *fskp = malloc(sizeof(fsk_plan));
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if ( !fskp )
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return NULL;
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fskp->sample_rate = sample_rate;
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fskp->f_mark = f_mark;
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fskp->f_space = f_space;
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fskp->filter_bw = filter_bw;
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fskp->n_data_bits = n_data_bits;
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#ifdef USE_FFT
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unsigned int fft_bw = filter_bw;
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float fft_half_bw = (float)fft_bw / 2.0;
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fskp->fftsize = (sample_rate + fft_half_bw) / fft_bw;
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unsigned int nbands = fskp->fftsize / 2 + 1;
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fskp->b_mark = (f_mark + fft_half_bw) / fft_bw;
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fskp->b_space = (f_space + fft_half_bw) / fft_bw;
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if ( fskp->b_mark >= nbands || fskp->b_space >= nbands ) {
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fprintf(stderr, "b_mark=%u or b_space=%u is invalid (nbands=%u)\n",
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fskp->b_mark, fskp->b_space, nbands);
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free(fskp);
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errno = EINVAL;
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return NULL;
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}
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debug_log("### b_mark=%u b_space=%u fftsize=%u\n",
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fskp->b_mark, fskp->b_space, fskp->fftsize);
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// FIXME:
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unsigned int pa_nchannels = 1;
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// FIXME check these:
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fskp->fftin = fftwf_malloc(fskp->fftsize * sizeof(float) * pa_nchannels);
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fskp->fftout = fftwf_malloc(nbands * sizeof(fftwf_complex) * pa_nchannels);
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/* complex fftw plan, works for N channels: */
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fskp->fftplan = fftwf_plan_many_dft_r2c(
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/*rank*/1, &fskp->fftsize, /*howmany*/pa_nchannels,
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fskp->fftin, NULL, /*istride*/pa_nchannels, /*idist*/1,
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fskp->fftout, NULL, /*ostride*/1, /*odist*/nbands,
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FFTW_ESTIMATE);
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if ( !fskp->fftplan ) {
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fprintf(stderr, "fftwf_plan_dft_r2c_1d() failed\n");
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fftwf_free(fskp->fftin);
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fftwf_free(fskp->fftout);
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free(fskp);
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errno = EINVAL;
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return NULL;
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}
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#endif
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return fskp;
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}
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void
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fsk_plan_destroy( fsk_plan *fskp )
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{
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fftwf_free(fskp->fftin);
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fftwf_free(fskp->fftout);
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fftwf_destroy_plan(fskp->fftplan);
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free(fskp);
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}
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static inline float
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band_mag( fftwf_complex * const cplx, unsigned int band, float scalar )
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{
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float re = cplx[band][0];
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float im = cplx[band][1];
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float mag = hypotf(re, im) * scalar;
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return mag;
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}
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static void
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fsk_bit_analyze( fsk_plan *fskp, float *samples, unsigned int bit_nsamples,
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float *mag_mark_outp, float *mag_space_outp)
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{
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unsigned int pa_nchannels = 1;
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bzero(fskp->fftin, (fskp->fftsize * sizeof(float) * pa_nchannels));
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memcpy(fskp->fftin, samples, bit_nsamples * sizeof(float));
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fftwf_execute(fskp->fftplan);
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float magscalar = 1.0 / ((float)bit_nsamples/2.0);
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*mag_mark_outp = band_mag(fskp->fftout, fskp->b_mark, magscalar);
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*mag_space_outp = band_mag(fskp->fftout, fskp->b_space, magscalar);
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debug_log( "\t%.2f %.2f %s sig=%.2f\n",
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*mag_mark_outp, *mag_space_outp,
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*mag_mark_outp > *mag_space_outp ? "mark " : " space",
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fabs(*mag_mark_outp - *mag_space_outp)
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);
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}
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static float
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fsk_frame_decode( fsk_plan *fskp, float *samples, unsigned int frame_nsamples,
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unsigned int *bits_outp )
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{
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float v = 0;
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/* 1 prev_stop + n_data_bits + 1 start + 1 stop == n_data_bits + 3 */
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float samples_per_bit = (float)frame_nsamples / (fskp->n_data_bits + 3);
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unsigned int bit_nsamples = (float)(samples_per_bit + 0.5);
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// 0123456789A
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// isddddddddp i == idle bit (a.k.a. previous stop bit)
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// s == start bit
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// d == data bits
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// p == stop bit
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// MSddddddddM <-- expected mark/space framing pattern
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unsigned int begin_i_idlebit = 0;
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unsigned int begin_s_startbit = (float)(samples_per_bit * 1 + 0.5);
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unsigned int begin_p_stopbit = (float)(samples_per_bit * 10 + 0.5);
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/*
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* To optimize performance for a streaming scenario, check start bit first,
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* then stop, then idle bits... we're "searching" for start, must validate
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* stop, and finally we want to to collect idle's v value. After all that
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* collect the n_data_bits
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*/
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float sM, sS, pM, pS, iM, iS;
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unsigned int bit;
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debug_log("\t\tstart ");
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fsk_bit_analyze(fskp, samples+begin_s_startbit, bit_nsamples, &sM, &sS);
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bit = sM > sS;
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if ( bit != 0 )
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return 0.0;
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v += sS - sM;
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debug_log("\t\tstop ");
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fsk_bit_analyze(fskp, samples+begin_p_stopbit, bit_nsamples, &pM, &pS);
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bit = pM > pS;
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if ( bit != 1 )
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return 0.0;
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v += pM - pS;
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debug_log("\t\tidle ");
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fsk_bit_analyze(fskp, samples+begin_i_idlebit, bit_nsamples, &iM, &iS);
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bit = iM > iS;
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if ( bit != 1 )
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return 0.0;
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v += iM - iS;
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unsigned int bits_out = 0;
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int i;
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for ( i=0; i<fskp->n_data_bits; i++ ) {
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unsigned int begin = (float)(samples_per_bit * (i+2) + 0.5);
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float dM, dS;
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debug_log("\t\tdata ");
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fsk_bit_analyze(fskp, samples+begin, bit_nsamples, &dM, &dS);
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bit = dM > dS;
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v += fabs(dM - dS);
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bits_out |= bit << i;
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}
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*bits_outp = bits_out;
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debug_log( "v=%f\n", v );
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return v;
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}
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int
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fsk_find_frame( fsk_plan *fskp, float *samples, unsigned int frame_nsamples,
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unsigned int try_max_nsamples,
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unsigned int try_step_nsamples,
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unsigned int *bits_outp
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)
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{
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unsigned int t;
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unsigned int best_t = 0;
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float best_v = 0.0;
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unsigned int best_bits = 0;
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for ( t=0; t<try_max_nsamples; t+=try_step_nsamples )
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{
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float v;
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unsigned int bits_out = 0;
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debug_log("try fsk_frame_decode(skip=%+d)\n", t);
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v = fsk_frame_decode(fskp, samples+t, frame_nsamples, &bits_out);
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if ( best_v < v ) {
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best_t = t;
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best_v = v;
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best_bits = bits_out;
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}
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}
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#define FSK_MINV (11 * 0.2)
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if ( best_v <= FSK_MINV ) {
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debug_log( "no frame\n" );
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return -1;
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}
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debug_log("DATA '%c' @ v=%f t=%d\n",
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isprint(best_bits)||isspace(best_bits) ? best_bits : '.',
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best_v, best_t);
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*bits_outp = best_bits;
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return best_t;
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}
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/****************************************************************************/
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#include <assert.h>
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#include <stdlib.h>
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#include "simpleaudio.h"
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#include "tscope_print.h"
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int
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main( int argc, char*argv[] )
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{
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int ret = 1;
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if ( argc < 2 ) {
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fprintf(stderr, "usage: fsk [filename] baud_rate [ mark_hz space_hz ]\n");
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return 1;
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}
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unsigned char textscope = 0;
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int argi = 1;
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if ( argi < argc && strcmp(argv[argi],"-s") == 0 ) {
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textscope = 1;
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argi++;
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}
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simpleaudio *sa;
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char *p;
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for ( p=argv[argi]; *p; p++ )
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if ( !isdigit(*p) )
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break;
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if ( *p ) {
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sa = simpleaudio_open_source_sndfile(argv[argi]);
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argi++;
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} else {
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sa = simpleaudio_open_source_pulseaudio(argv[0], "bfsk demodulator");
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}
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if ( !sa )
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return 1;
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unsigned int sample_rate = simpleaudio_get_rate(sa);
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// unsigned int nchannels = simpleaudio_get_channels(sa);
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unsigned int decode_rate;
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decode_rate = atoi(argv[argi++]);
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unsigned int band_width;
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band_width = decode_rate;
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/*
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* Bell 103: baud=300 mark=1270 space=1070
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* ITU-T V.21: baud=300 mark=1280 space=1080
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*/
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unsigned int bfsk_mark_f = 1270;
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unsigned int bfsk_space_f = 1070;
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// band_width = 10;
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band_width = 100; /* close enough */
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/*
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* Bell 202: baud=1200 mark=1200 space=2200
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*/
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if ( decode_rate >= 400 ) {
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bfsk_mark_f = 1200;
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bfsk_space_f = 2200;
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band_width = 200;
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}
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if ( argi < argc ) {
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assert(argc-argi == 2);
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bfsk_mark_f = atoi(argv[argi++]);
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bfsk_space_f = atoi(argv[argi++]);
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}
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/*
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* Prepare the input sample chunk rate
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*/
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int nsamples_per_bit = sample_rate / decode_rate;
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/*
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* Run the main loop
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*/
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ret = 0;
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fsk_plan *fskp = fsk_plan_new(sample_rate,
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bfsk_mark_f, bfsk_space_f,
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band_width, 8);
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if ( !fskp ) {
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fprintf(stderr, "fsk_plan_new() failed\n");
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return 1;
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}
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size_t fill_nsamples = nsamples_per_bit * 12;
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size_t buf_nsamples = fill_nsamples;
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float *samples = malloc(buf_nsamples * sizeof(float));
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size_t read_nsamples = fill_nsamples;
|
||||
float *read_bufptr = samples;
|
||||
|
||||
int carrier = 0;
|
||||
|
||||
while ( 1 ) {
|
||||
|
||||
debug_log( "@read samples+%ld n=%lu\n",
|
||||
read_bufptr - samples, read_nsamples);
|
||||
|
||||
if ((ret=simpleaudio_read(sa, read_bufptr, read_nsamples)) <= 0)
|
||||
break;
|
||||
// carrier_nsamples += read_nsamples;
|
||||
|
||||
|
||||
unsigned int frame_nsamples = nsamples_per_bit * 11;
|
||||
|
||||
unsigned int bits = 0;
|
||||
|
||||
unsigned int try_step_nsamples = nsamples_per_bit / 4;
|
||||
if ( try_step_nsamples == 0 )
|
||||
try_step_nsamples = 1;
|
||||
|
||||
|
||||
debug_log( "--------------------------\n");
|
||||
int t =
|
||||
fsk_find_frame(fskp, samples, frame_nsamples,
|
||||
/*try_max_nsamples*/ nsamples_per_bit,
|
||||
try_step_nsamples,
|
||||
&bits
|
||||
);
|
||||
|
||||
if ( t <= 0 ) {
|
||||
if ( carrier )
|
||||
fprintf(stderr, "\n### NOCARRIER ###\n");
|
||||
carrier = 0;
|
||||
|
||||
t = nsamples_per_bit;
|
||||
|
||||
} else {
|
||||
if ( !carrier )
|
||||
fprintf(stderr, "\n### CARRIER ###\n");
|
||||
carrier = 1;
|
||||
|
||||
// t += nsamples_per_bit * 10;
|
||||
t += nsamples_per_bit * 9.5;
|
||||
debug_log( "@ t=%u\n", t);
|
||||
|
||||
char the_byte = isprint(bits)||isspace(bits) ? bits : '.';
|
||||
printf( "%c", the_byte );
|
||||
fflush(stdout);
|
||||
|
||||
}
|
||||
|
||||
memmove(samples, samples+t, (fill_nsamples-t)*sizeof(float));
|
||||
read_bufptr = samples + (fill_nsamples-t);
|
||||
read_nsamples = t;
|
||||
|
||||
assert ( read_nsamples <= buf_nsamples );
|
||||
assert ( read_nsamples > 0 );
|
||||
|
||||
}
|
||||
|
||||
if ( ret != 0 )
|
||||
fprintf(stderr, "simpleaudio_read: error\n");
|
||||
|
||||
simpleaudio_close(sa);
|
||||
|
||||
fsk_plan_destroy(fskp);
|
||||
|
||||
return ret;
|
||||
}
|
||||
Loading…
Reference in New Issue