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minimodem: handle arbitrary --startbits N 

minimodem --startbits N works for rx and tx, where (0 <= N <= 20).

Thanks Martyn (kronalias), for reporting.
This commit is contained in:
Kamal Mostafa 2013-03-20 11:31:44 -07:00
parent b76b5a3fa3
commit d774ad74dd
1 changed files with 17 additions and 6 deletions
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23
src/minimodem.c
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@ -344,7 +344,7 @@ main( int argc, char*argv[] )
unsigned int bfsk_mark_f = 0;
unsigned int bfsk_space_f = 0;
unsigned int bfsk_inverted_freqs = 0;
int bfsk_nstartbits = -1; // actually only supports 0 or 1 startbit
int bfsk_nstartbits = -1;
float bfsk_nstopbits = -1;
unsigned int bfsk_sync_on_data = 0;
unsigned int bfsk_sync_byte = -1;
@ -509,7 +509,9 @@ main( int argc, char*argv[] )
break;
case MINIMODEM_OPT_STARTBITS:
bfsk_nstartbits = atoi(optarg);
assert( bfsk_nstartbits == 0 || bfsk_nstartbits == 1 );
// Note: bfsk_nstartbits is limited by arrays
// expect_bits_string[32] and fsk.c:bit_something[32]
assert( bfsk_nstartbits >= 0 && bfsk_nstartbits <= 20 );
break;
case MINIMODEM_OPT_STOPBITS:
bfsk_nstopbits = atof(optarg);
@ -790,8 +792,14 @@ main( int argc, char*argv[] )
* we need 11 data-bits worth of samples, and we will scan through one bits
* worth at a time, hence we need a minimum total input buffer size of 12
* data-bits. */
unsigned int nbits = 0;
nbits += 1; // prev stop bit (last whole stop bit)
nbits += bfsk_nstartbits; // start bits
nbits += 8; // (n_data_bits)
nbits += 1; // stop bit (first whole stop bit)
// FIXME EXPLAIN +1 goes with extra bit when scanning
size_t samplebuf_size = ceilf(nsamples_per_bit) * (12+1);
size_t samplebuf_size = ceilf(nsamples_per_bit) * (nbits+1);
samplebuf_size *= 2; // account for the half-buf filling method
#define SAMPLE_BUF_DIVISOR 12
#ifdef SAMPLE_BUF_DIVISOR
@ -957,13 +965,14 @@ main( int argc, char*argv[] )
// start--v v--stop
// char *expect_bits_string = "10dddddddd1";
//
char expect_bits_string[33];
char expect_bits_string[32];
int j = 0;
if ( bfsk_nstopbits != 0.0 )
expect_bits_string[j++] = '1';
if ( bfsk_nstartbits != 0 ) // FIXME -- sets only one start bit
expect_bits_string[j++] = '0';
int i;
// Nb. only integer number of start bits works (for rx)
for ( i=0; i<bfsk_nstartbits; i++ )
expect_bits_string[j++] = '0';
for ( i=0; i<bfsk_n_data_bits; i++,j++ ) {
if ( ! carrier && bfsk_sync_on_data )
expect_bits_string[j] = ( (bfsk_sync_byte>>i)&1 ) + '0';
@ -978,6 +987,8 @@ main( int argc, char*argv[] )
unsigned int expect_n_bits = strlen(expect_bits_string);
unsigned int expect_nsamples = nsamples_per_bit * expect_n_bits;
// fprintf(stderr, "ebs = '%s' (%lu) ; expect_nsamples=%u samples_nvalid=%lu\n", expect_bits_string, strlen(expect_bits_string), expect_nsamples, samples_nvalid);
if ( samples_nvalid < expect_nsamples )
break;