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minimodem: transmit interactive zero latency; fix leader/trailer

This commit is contained in:
Kamal Mostafa 2011-07-13 20:37:17 -07:00
parent 836475faa3
commit 7686acc38e
1 changed files with 56 additions and 7 deletions
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63
src/minimodem.c
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@ -27,6 +27,8 @@
#include <ctype.h>
#include <math.h>
#include <assert.h>
#include <signal.h>
#include <sys/time.h>
#ifdef HAVE_CONFIG_H
#include "config.h"
@ -86,6 +88,32 @@ framebits_decode_baudot( char *dataout_p, unsigned int dataout_size,
}
int tx_transmitting = 0;
int tx_leader_bits_len = 2;
int tx_trailer_bits_len = 2;
simpleaudio *tx_sa_out;
float tx_bfsk_mark_f;
unsigned int tx_bit_nsamples;
void
tx_stop_transmit_sighandler( int sig )
{
// fprintf(stderr, "alarm\n");
int j;
for ( j=0; j<tx_trailer_bits_len; j++ )
simpleaudio_tone(tx_sa_out, tx_bfsk_mark_f, tx_bit_nsamples);
// 0.5 sec of zero samples to flush - FIXME lame
size_t sample_rate = simpleaudio_get_rate(tx_sa_out);
simpleaudio_tone(tx_sa_out, 0, sample_rate/2);
tx_transmitting = 0;
}
/*
* rudimentary BFSK transmitter
*/
@ -103,15 +131,35 @@ static void fsk_transmit_stdin(
size_t bit_nsamples = sample_rate / data_rate + 0.5;
int c;
simpleaudio_tone(sa_out, bfsk_mark_f, bit_nsamples); // 2.0 bit leader
simpleaudio_tone(sa_out, bfsk_mark_f, bit_nsamples);
tx_sa_out = sa_out;
tx_bfsk_mark_f = bfsk_mark_f;
tx_bit_nsamples = bit_nsamples;
// one-shot
struct itimerval itv = {
{0, 0}, // it_interval
{0, 1000000/(data_rate+data_rate*0.03) } // it_value
};
signal(SIGALRM, tx_stop_transmit_sighandler);
tx_transmitting = 0;
while ( (c = getchar()) != EOF )
{
setitimer(ITIMER_REAL, NULL, NULL);
// fprintf(stderr, "<c=%d>", c);
unsigned int nwords;
unsigned int bits[2];
nwords = framebits_encoder(bits, c);
if ( !tx_transmitting )
{
tx_transmitting = 1;
int j;
for ( j=0; j<tx_leader_bits_len; j++ )
simpleaudio_tone(sa_out, bfsk_mark_f, bit_nsamples);
}
unsigned int j;
for ( j=0; j<nwords; j++ ) {
simpleaudio_tone(sa_out, bfsk_space_f, bit_nsamples); // start
@ -124,13 +172,14 @@ static void fsk_transmit_stdin(
simpleaudio_tone(sa_out, bfsk_mark_f,
bit_nsamples * bfsk_txstopbits); // stop
}
setitimer(ITIMER_REAL, &itv, NULL);
}
simpleaudio_tone(sa_out, bfsk_mark_f, bit_nsamples); // 2.0 bit tail
simpleaudio_tone(sa_out, bfsk_mark_f, bit_nsamples);
// 0.5 sec of zero samples to flush - FIXME lame
simpleaudio_tone(sa_out, 0, sample_rate/2);
setitimer(ITIMER_REAL, NULL, NULL);
if ( !tx_transmitting )
return;
tx_stop_transmit_sighandler(0);
}