minimodem: --tx SAME emits 16 sync-byte preamble

Emit a preamble of 16 (hardcoded) sync-bytes if --sync-byte is
specified with --tx mode.  This makes --tx SAME emit the required
preamble of 16 0xAB's automatically.  So --rx SAME now directly
decodes the output of --tx SAME without needing to manually inject
the preamble byte(s), simplifying the test case.

Thanks to Harold Giddings, for reporting the issue.

src/minimodem.c

@@ -107,6 +107,8 @@ static void fsk_transmit_stdin(
 	int n_data_bits,
 	float bfsk_nstartbits,
 	float bfsk_nstopbits,
+	unsigned int bfsk_do_tx_sync_bytes,
+	unsigned int bfsk_sync_byte,
 	databits_encoder encode
 	)
 {
@@ -141,16 +143,23 @@ static void fsk_transmit_stdin(
 	// fprintf(stderr, "<c=%d>", c);
 	unsigned int nwords;
 	unsigned int bits[2];
+	unsigned int j;
 	nwords = encode(bits, c);
 
 	if ( !tx_transmitting )
 	{
 	    tx_transmitting = 1;
-	    int j;
+	    /* emit leader tone (mark) */
 	    for ( j=0; j<tx_leader_bits_len; j++ )
 		simpleaudio_tone(sa_out, bfsk_mark_f, bit_nsamples);
+	    /* emit "preamble" of sync bytes */
+	    for ( j=0; j<bfsk_do_tx_sync_bytes; j++ )
+		fsk_transmit_frame(sa_out, bfsk_sync_byte, n_data_bits,
+			    bit_nsamples, bfsk_mark_f, bfsk_space_f,
+			    bfsk_nstartbits, bfsk_nstopbits);
 	}
-	unsigned int j;
+
+	/* emit data bits */
 	for ( j=0; j<nwords; j++ )
 	    fsk_transmit_frame(sa_out, bits[j], n_data_bits,
 			bit_nsamples, bfsk_mark_f, bfsk_space_f,
@@ -363,6 +372,7 @@ main( int argc, char*argv[] )
     int bfsk_nstartbits = -1;
     float bfsk_nstopbits = -1;
     unsigned int bfsk_do_rx_sync = 0;
+    unsigned int bfsk_do_tx_sync_bytes = 0;
     unsigned int bfsk_sync_byte = -1;
     unsigned int bfsk_n_data_bits = 0;
     int autodetect_shift;
@@ -535,6 +545,7 @@ main( int argc, char*argv[] )
 			break;
 	    case MINIMODEM_OPT_SYNC_BYTE:
 			bfsk_do_rx_sync = 1;
+			bfsk_do_tx_sync_bytes = 16;
 			bfsk_sync_byte = strtol(optarg, NULL, 0);
 			break;
 	    case 'q':
@@ -638,6 +649,7 @@ main( int argc, char*argv[] )
 	bfsk_nstartbits = 0;
 	bfsk_nstopbits = 0;
 	bfsk_do_rx_sync = 1;
+	bfsk_do_tx_sync_bytes = 16;
 	bfsk_sync_byte = 0xAB;
 	bfsk_mark_f = 2083.0 + 1/3.0;
 	bfsk_space_f = 1562.5;
@@ -757,6 +769,8 @@ main( int argc, char*argv[] )
 				bfsk_n_data_bits,
 				bfsk_nstartbits,
 				bfsk_nstopbits,
+				bfsk_do_tx_sync_bytes,
+				bfsk_sync_byte,
 				bfsk_databits_encode
 				);
 

tests/test-80-SAME

@@ -0,0 +1 @@
+exec ./self-test testdata-ascii.txt SAME

tests/test-80-SAME-datastream

@@ -1,55 +0,0 @@
-#!/bin/bash
-
-MINIMODEM="${MINIMODEM-./minimodem}"
-[ -f "$MINIMODEM" ] || {
-    MINIMODEM="../src/minimodem"
-    [ -f "$MINIMODEM" ] || {
-	echo "E: cannot find minimodem in ./ or ../src/" 1>&2
-	exit 1
-    }
-}
-
-
-teststring="Testing 0 1 2 3 4.  This is only a test.  Testing 5 6 7 8 9.  This is only a test."
-[ "$1" != "" ] && teststring="$1"
-
-
-TMPF="/tmp/minimodem-test-$$"
-trap "rm -f $TMPF.*" 0
-
-set -e
-
-minimodem_tx_args="SAME"
-minimodem_rx_args="SAME"
-
-
-# insert the 0xAB SAME sync byte to simulate the start of a SAME
-# protocol bytestream.
-printf "JUNK\\xAB${teststring}" \
-| $MINIMODEM --tx --file $TMPF.wav $minimodem_tx_args
-
-# cp $TMPF.wav /tmp/x.wav
-
-$MINIMODEM --rx --file $TMPF.wav $minimodem_rx_args \
-	> $TMPF.out 2> $TMPF.err || {
-    cat $TMPF.err
-    exit 1
-}
-
-# printf "$teststring" | cmp - $TMPF.out
-printf "$teststring" | diff - $TMPF.out
-
-{
-    read xlitcarrier
-    read xlitblankline
-    read xlithashes xlitnocarrier stats
-    stats="${stats% ###}"
-} < $TMPF.err
-
-
-result="OK     "
-exitcode=0
-
-echo -e "$result $stats"
-
-exit $exitcode