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minimodem -T stdin transmitter

This commit is contained in:
Kamal Mostafa 2011-06-18 11:29:48 -07:00
parent b7338563a7
commit 952962dde3
1 changed files with 62 additions and 5 deletions
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67
src/minimodem.c
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@ -53,17 +53,61 @@ frame_process_baudot( char *dataout_p, unsigned int dataout_size,
}
/*
* rudimentary BFSK transmitter
*/
static void fsk_transmit_stdin(
simpleaudio *sa_out,
float data_rate,
float bfsk_mark_f,
float bfsk_space_f,
int n_data_bits
)
{
size_t sample_rate = simpleaudio_get_rate(sa_out);
size_t bit_nsamples = sample_rate / data_rate + 0.5;
int c;
simpleaudio_tone(sa_out, bfsk_mark_f, sample_rate/2); // 0.5 sec leader
while ( (c = getchar()) != EOF )
{
simpleaudio_tone(sa_out, bfsk_space_f, bit_nsamples); // start
int i;
for ( i=0; i<n_data_bits; i++ ) { // data
unsigned int bit = ( c >> i ) & 1;
float tone_freq = bit == 1 ? bfsk_mark_f : bfsk_space_f;
simpleaudio_tone(sa_out, tone_freq, bit_nsamples);
}
simpleaudio_tone(sa_out, bfsk_mark_f, bit_nsamples); // stop
}
simpleaudio_tone(sa_out, bfsk_mark_f, sample_rate/2); // 0.5 sec tail
// 0.5 sec of zero samples to flush - FIXME lame
simpleaudio_tone(sa_out, 0, sample_rate/2);
}
int
main( int argc, char*argv[] )
{
if ( argc < 2 ) {
int TX_mode = 0;
int argi = 1;
if ( argi < argc && strncmp(argv[argi],"-T",3)==0 ) {
TX_mode = 1;
argi++;
}
if ( argi >= argc ) {
fprintf(stderr, "usage: minimodem {baud|mode} [filename] "
"[ band_width ] "
"[ mark_hz space_hz ]\n");
"[ mark_hz space_hz ]\n"
" minimodem -T {baud}\n"
);
return 1;
}
int argi = 1;
float decode_rate;
int decode_n_data_bits;
@ -109,14 +153,27 @@ main( int argc, char*argv[] )
/*
* RTTY: baud=45.45 mark/space=variable shift=-170
*/
bfsk_mark_f = 0;
bfsk_space_f = 0;
bfsk_mark_f = 1500;
bfsk_space_f = 1500 - 170;
band_width = 10;
// band_width = 68; // FIXME FIXME FIXME -- causes assert crash
autodetect_shift = 170;
}
if ( TX_mode ) {
simpleaudio *sa_out = NULL;
sa_out = simpleaudio_open_stream_pulseaudio(SA_STREAM_PLAYBACK,
argv[0], "output audio");
assert( sa_out );
fsk_transmit_stdin(sa_out,
decode_rate,
bfsk_mark_f, bfsk_space_f,
decode_n_data_bits
);
return 0;
}
/*
* Open the input audio stream
*/