fsk: multibit decoder

This commit is contained in:
Kamal Mostafa 2011-06-03 23:26:00 -07:00
parent c790603bf6
commit 80c8a62073
3 changed files with 454 additions and 6 deletions

View File

@ -3,7 +3,7 @@ AM_CFLAGS = -Wall -Werror
INCLUDES = $(DEPS_CFLAGS) INCLUDES = $(DEPS_CFLAGS)
bin_PROGRAMS = minimodem tscope bin_PROGRAMS = minimodem tscope fsk
SIMPLEAUDIO_SRC=\ SIMPLEAUDIO_SRC=\
simpleaudio.c \ simpleaudio.c \
@ -13,6 +13,8 @@ SIMPLEAUDIO_SRC=\
minimodem_LDADD = $(DEPS_LIBS) minimodem_LDADD = $(DEPS_LIBS)
minimodem_SOURCES = minimodem.c tscope_print.c $(SIMPLEAUDIO_SRC) minimodem_SOURCES = minimodem.c tscope_print.c $(SIMPLEAUDIO_SRC)
fsk_LDADD = $(DEPS_LIBS)
fsk_SOURCES = fsk.c tscope_print.c $(SIMPLEAUDIO_SRC)
tscope_LDADD = $(DEPS_LIBS) tscope_LDADD = $(DEPS_LIBS)
tscope_SOURCES = tscope.c tscope_print.c tscope_SOURCES = tscope.c tscope_print.c

View File

@ -32,7 +32,7 @@ POST_INSTALL = :
NORMAL_UNINSTALL = : NORMAL_UNINSTALL = :
PRE_UNINSTALL = : PRE_UNINSTALL = :
POST_UNINSTALL = : POST_UNINSTALL = :
bin_PROGRAMS = minimodem$(EXEEXT) tscope$(EXEEXT) bin_PROGRAMS = minimodem$(EXEEXT) tscope$(EXEEXT) fsk$(EXEEXT)
subdir = src subdir = src
DIST_COMMON = $(srcdir)/Makefile.am $(srcdir)/Makefile.in DIST_COMMON = $(srcdir)/Makefile.am $(srcdir)/Makefile.in
ACLOCAL_M4 = $(top_srcdir)/aclocal.m4 ACLOCAL_M4 = $(top_srcdir)/aclocal.m4
@ -47,10 +47,13 @@ am__installdirs = "$(DESTDIR)$(bindir)"
PROGRAMS = $(bin_PROGRAMS) PROGRAMS = $(bin_PROGRAMS)
am__objects_1 = simpleaudio.$(OBJEXT) simpleaudio-pulse.$(OBJEXT) \ am__objects_1 = simpleaudio.$(OBJEXT) simpleaudio-pulse.$(OBJEXT) \
simpleaudio-sndfile.$(OBJEXT) simpleaudio-sndfile.$(OBJEXT)
am_fsk_OBJECTS = fsk.$(OBJEXT) tscope_print.$(OBJEXT) $(am__objects_1)
fsk_OBJECTS = $(am_fsk_OBJECTS)
am__DEPENDENCIES_1 =
fsk_DEPENDENCIES = $(am__DEPENDENCIES_1)
am_minimodem_OBJECTS = minimodem.$(OBJEXT) tscope_print.$(OBJEXT) \ am_minimodem_OBJECTS = minimodem.$(OBJEXT) tscope_print.$(OBJEXT) \
$(am__objects_1) $(am__objects_1)
minimodem_OBJECTS = $(am_minimodem_OBJECTS) minimodem_OBJECTS = $(am_minimodem_OBJECTS)
am__DEPENDENCIES_1 =
minimodem_DEPENDENCIES = $(am__DEPENDENCIES_1) minimodem_DEPENDENCIES = $(am__DEPENDENCIES_1)
am_tscope_OBJECTS = tscope.$(OBJEXT) tscope_print.$(OBJEXT) am_tscope_OBJECTS = tscope.$(OBJEXT) tscope_print.$(OBJEXT)
tscope_OBJECTS = $(am_tscope_OBJECTS) tscope_OBJECTS = $(am_tscope_OBJECTS)
@ -63,8 +66,8 @@ COMPILE = $(CC) $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) $(AM_CPPFLAGS) \
$(CPPFLAGS) $(AM_CFLAGS) $(CFLAGS) $(CPPFLAGS) $(AM_CFLAGS) $(CFLAGS)
CCLD = $(CC) CCLD = $(CC)
LINK = $(CCLD) $(AM_CFLAGS) $(CFLAGS) $(AM_LDFLAGS) $(LDFLAGS) -o $@ LINK = $(CCLD) $(AM_CFLAGS) $(CFLAGS) $(AM_LDFLAGS) $(LDFLAGS) -o $@
SOURCES = $(minimodem_SOURCES) $(tscope_SOURCES) SOURCES = $(fsk_SOURCES) $(minimodem_SOURCES) $(tscope_SOURCES)
DIST_SOURCES = $(minimodem_SOURCES) $(tscope_SOURCES) DIST_SOURCES = $(fsk_SOURCES) $(minimodem_SOURCES) $(tscope_SOURCES)
ETAGS = etags ETAGS = etags
CTAGS = ctags CTAGS = ctags
DISTFILES = $(DIST_COMMON) $(DIST_SOURCES) $(TEXINFOS) $(EXTRA_DIST) DISTFILES = $(DIST_COMMON) $(DIST_SOURCES) $(TEXINFOS) $(EXTRA_DIST)
@ -165,6 +168,8 @@ SIMPLEAUDIO_SRC = \
minimodem_LDADD = $(DEPS_LIBS) minimodem_LDADD = $(DEPS_LIBS)
minimodem_SOURCES = minimodem.c tscope_print.c $(SIMPLEAUDIO_SRC) minimodem_SOURCES = minimodem.c tscope_print.c $(SIMPLEAUDIO_SRC)
fsk_LDADD = $(DEPS_LIBS)
fsk_SOURCES = fsk.c tscope_print.c $(SIMPLEAUDIO_SRC)
tscope_LDADD = $(DEPS_LIBS) tscope_LDADD = $(DEPS_LIBS)
tscope_SOURCES = tscope.c tscope_print.c tscope_SOURCES = tscope.c tscope_print.c
all: all-am all: all-am
@ -238,6 +243,9 @@ uninstall-binPROGRAMS:
clean-binPROGRAMS: clean-binPROGRAMS:
-test -z "$(bin_PROGRAMS)" || rm -f $(bin_PROGRAMS) -test -z "$(bin_PROGRAMS)" || rm -f $(bin_PROGRAMS)
fsk$(EXEEXT): $(fsk_OBJECTS) $(fsk_DEPENDENCIES)
@rm -f fsk$(EXEEXT)
$(LINK) $(fsk_OBJECTS) $(fsk_LDADD) $(LIBS)
minimodem$(EXEEXT): $(minimodem_OBJECTS) $(minimodem_DEPENDENCIES) minimodem$(EXEEXT): $(minimodem_OBJECTS) $(minimodem_DEPENDENCIES)
@rm -f minimodem$(EXEEXT) @rm -f minimodem$(EXEEXT)
$(LINK) $(minimodem_OBJECTS) $(minimodem_LDADD) $(LIBS) $(LINK) $(minimodem_OBJECTS) $(minimodem_LDADD) $(LIBS)
@ -251,6 +259,7 @@ mostlyclean-compile:
distclean-compile: distclean-compile:
-rm -f *.tab.c -rm -f *.tab.c
@AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/fsk.Po@am__quote@
@AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/minimodem.Po@am__quote@ @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/minimodem.Po@am__quote@
@AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/simpleaudio-pulse.Po@am__quote@ @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/simpleaudio-pulse.Po@am__quote@
@AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/simpleaudio-sndfile.Po@am__quote@ @AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/simpleaudio-sndfile.Po@am__quote@

437
src/fsk.c Normal file
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@ -0,0 +1,437 @@
#define USE_FFT
#include <malloc.h>
#include <string.h>
#include <math.h> // fabs, hypotf
#ifdef USE_FFT
#include <fftw3.h>
#endif
#include <errno.h>
#include <stdio.h>
#include <ctype.h>
//#define FSK_DEBUG
#ifdef FSK_DEBUG
# define debug_log(format, args...) fprintf(stderr, format, ## args)
#else
# define debug_log(format, args...)
#endif
typedef struct fsk_plan fsk_plan;
struct fsk_plan {
float sample_rate;
float f_mark;
float f_space;
float filter_bw;
unsigned int n_data_bits;
#ifdef USE_FFT
int fftsize; // fftw wants this to be signed. why?
unsigned int b_mark;
unsigned int b_space;
fftwf_plan fftplan;
float *fftin;
fftwf_complex *fftout;
#endif
};
fsk_plan *
fsk_plan_new(
float sample_rate,
float f_mark,
float f_space,
float filter_bw,
unsigned int n_data_bits
)
{
fsk_plan *fskp = malloc(sizeof(fsk_plan));
if ( !fskp )
return NULL;
fskp->sample_rate = sample_rate;
fskp->f_mark = f_mark;
fskp->f_space = f_space;
fskp->filter_bw = filter_bw;
fskp->n_data_bits = n_data_bits;
#ifdef USE_FFT
unsigned int fft_bw = filter_bw;
float fft_half_bw = (float)fft_bw / 2.0;
fskp->fftsize = (sample_rate + fft_half_bw) / fft_bw;
unsigned int nbands = fskp->fftsize / 2 + 1;
fskp->b_mark = (f_mark + fft_half_bw) / fft_bw;
fskp->b_space = (f_space + fft_half_bw) / fft_bw;
if ( fskp->b_mark >= nbands || fskp->b_space >= nbands ) {
fprintf(stderr, "b_mark=%u or b_space=%u is invalid (nbands=%u)\n",
fskp->b_mark, fskp->b_space, nbands);
free(fskp);
errno = EINVAL;
return NULL;
}
debug_log("### b_mark=%u b_space=%u fftsize=%u\n",
fskp->b_mark, fskp->b_space, fskp->fftsize);
// FIXME:
unsigned int pa_nchannels = 1;
// FIXME check these:
fskp->fftin = fftwf_malloc(fskp->fftsize * sizeof(float) * pa_nchannels);
fskp->fftout = fftwf_malloc(nbands * sizeof(fftwf_complex) * pa_nchannels);
/* complex fftw plan, works for N channels: */
fskp->fftplan = fftwf_plan_many_dft_r2c(
/*rank*/1, &fskp->fftsize, /*howmany*/pa_nchannels,
fskp->fftin, NULL, /*istride*/pa_nchannels, /*idist*/1,
fskp->fftout, NULL, /*ostride*/1, /*odist*/nbands,
FFTW_ESTIMATE);
if ( !fskp->fftplan ) {
fprintf(stderr, "fftwf_plan_dft_r2c_1d() failed\n");
fftwf_free(fskp->fftin);
fftwf_free(fskp->fftout);
free(fskp);
errno = EINVAL;
return NULL;
}
#endif
return fskp;
}
void
fsk_plan_destroy( fsk_plan *fskp )
{
fftwf_free(fskp->fftin);
fftwf_free(fskp->fftout);
fftwf_destroy_plan(fskp->fftplan);
free(fskp);
}
static inline float
band_mag( fftwf_complex * const cplx, unsigned int band, float scalar )
{
float re = cplx[band][0];
float im = cplx[band][1];
float mag = hypotf(re, im) * scalar;
return mag;
}
static void
fsk_bit_analyze( fsk_plan *fskp, float *samples, unsigned int bit_nsamples,
float *mag_mark_outp, float *mag_space_outp)
{
unsigned int pa_nchannels = 1;
bzero(fskp->fftin, (fskp->fftsize * sizeof(float) * pa_nchannels));
memcpy(fskp->fftin, samples, bit_nsamples * sizeof(float));
fftwf_execute(fskp->fftplan);
float magscalar = 1.0 / ((float)bit_nsamples/2.0);
*mag_mark_outp = band_mag(fskp->fftout, fskp->b_mark, magscalar);
*mag_space_outp = band_mag(fskp->fftout, fskp->b_space, magscalar);
debug_log( "\t%.2f %.2f %s sig=%.2f\n",
*mag_mark_outp, *mag_space_outp,
*mag_mark_outp > *mag_space_outp ? "mark " : " space",
fabs(*mag_mark_outp - *mag_space_outp)
);
}
static float
fsk_frame_decode( fsk_plan *fskp, float *samples, unsigned int frame_nsamples,
unsigned int *bits_outp )
{
float v = 0;
/* 1 prev_stop + n_data_bits + 1 start + 1 stop == n_data_bits + 3 */
float samples_per_bit = (float)frame_nsamples / (fskp->n_data_bits + 3);
unsigned int bit_nsamples = (float)(samples_per_bit + 0.5);
// 0123456789A
// isddddddddp i == idle bit (a.k.a. previous stop bit)
// s == start bit
// d == data bits
// p == stop bit
// MSddddddddM <-- expected mark/space framing pattern
unsigned int begin_i_idlebit = 0;
unsigned int begin_s_startbit = (float)(samples_per_bit * 1 + 0.5);
unsigned int begin_p_stopbit = (float)(samples_per_bit * 10 + 0.5);
/*
* To optimize performance for a streaming scenario, check start bit first,
* then stop, then idle bits... we're "searching" for start, must validate
* stop, and finally we want to to collect idle's v value. After all that
* collect the n_data_bits
*/
float sM, sS, pM, pS, iM, iS;
unsigned int bit;
debug_log("\t\tstart ");
fsk_bit_analyze(fskp, samples+begin_s_startbit, bit_nsamples, &sM, &sS);
bit = sM > sS;
if ( bit != 0 )
return 0.0;
v += sS - sM;
debug_log("\t\tstop ");
fsk_bit_analyze(fskp, samples+begin_p_stopbit, bit_nsamples, &pM, &pS);
bit = pM > pS;
if ( bit != 1 )
return 0.0;
v += pM - pS;
debug_log("\t\tidle ");
fsk_bit_analyze(fskp, samples+begin_i_idlebit, bit_nsamples, &iM, &iS);
bit = iM > iS;
if ( bit != 1 )
return 0.0;
v += iM - iS;
unsigned int bits_out = 0;
int i;
for ( i=0; i<fskp->n_data_bits; i++ ) {
unsigned int begin = (float)(samples_per_bit * (i+2) + 0.5);
float dM, dS;
debug_log("\t\tdata ");
fsk_bit_analyze(fskp, samples+begin, bit_nsamples, &dM, &dS);
bit = dM > dS;
v += fabs(dM - dS);
bits_out |= bit << i;
}
*bits_outp = bits_out;
debug_log( "v=%f\n", v );
return v;
}
int
fsk_find_frame( fsk_plan *fskp, float *samples, unsigned int frame_nsamples,
unsigned int try_max_nsamples,
unsigned int try_step_nsamples,
unsigned int *bits_outp
)
{
unsigned int t;
unsigned int best_t = 0;
float best_v = 0.0;
unsigned int best_bits = 0;
for ( t=0; t<try_max_nsamples; t+=try_step_nsamples )
{
float v;
unsigned int bits_out = 0;
debug_log("try fsk_frame_decode(skip=%+d)\n", t);
v = fsk_frame_decode(fskp, samples+t, frame_nsamples, &bits_out);
if ( best_v < v ) {
best_t = t;
best_v = v;
best_bits = bits_out;
}
}
#define FSK_MINV (11 * 0.2)
if ( best_v <= FSK_MINV ) {
debug_log( "no frame\n" );
return -1;
}
debug_log("DATA '%c' @ v=%f t=%d\n",
isprint(best_bits)||isspace(best_bits) ? best_bits : '.',
best_v, best_t);
*bits_outp = best_bits;
return best_t;
}
/****************************************************************************/
#include <assert.h>
#include <stdlib.h>
#include "simpleaudio.h"
#include "tscope_print.h"
int
main( int argc, char*argv[] )
{
int ret = 1;
if ( argc < 2 ) {
fprintf(stderr, "usage: fsk [filename] baud_rate [ mark_hz space_hz ]\n");
return 1;
}
unsigned char textscope = 0;
int argi = 1;
if ( argi < argc && strcmp(argv[argi],"-s") == 0 ) {
textscope = 1;
argi++;
}
simpleaudio *sa;
char *p;
for ( p=argv[argi]; *p; p++ )
if ( !isdigit(*p) )
break;
if ( *p ) {
sa = simpleaudio_open_source_sndfile(argv[argi]);
argi++;
} else {
sa = simpleaudio_open_source_pulseaudio(argv[0], "bfsk demodulator");
}
if ( !sa )
return 1;
unsigned int sample_rate = simpleaudio_get_rate(sa);
// unsigned int nchannels = simpleaudio_get_channels(sa);
unsigned int decode_rate;
decode_rate = atoi(argv[argi++]);
unsigned int band_width;
band_width = decode_rate;
/*
* Bell 103: baud=300 mark=1270 space=1070
* ITU-T V.21: baud=300 mark=1280 space=1080
*/
unsigned int bfsk_mark_f = 1270;
unsigned int bfsk_space_f = 1070;
// band_width = 10;
band_width = 100; /* close enough */
/*
* Bell 202: baud=1200 mark=1200 space=2200
*/
if ( decode_rate >= 400 ) {
bfsk_mark_f = 1200;
bfsk_space_f = 2200;
band_width = 200;
}
if ( argi < argc ) {
assert(argc-argi == 2);
bfsk_mark_f = atoi(argv[argi++]);
bfsk_space_f = atoi(argv[argi++]);
}
/*
* Prepare the input sample chunk rate
*/
int nsamples_per_bit = sample_rate / decode_rate;
/*
* Run the main loop
*/
ret = 0;
fsk_plan *fskp = fsk_plan_new(sample_rate,
bfsk_mark_f, bfsk_space_f,
band_width, 8);
if ( !fskp ) {
fprintf(stderr, "fsk_plan_new() failed\n");
return 1;
}
size_t fill_nsamples = nsamples_per_bit * 12;
size_t buf_nsamples = fill_nsamples;
float *samples = malloc(buf_nsamples * sizeof(float));
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;
}