FSK Modulator/Demodulator. More...
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Defines | |
| #define | BWLIST {75,800} |
| #define | FLIST {1400,1800,1200,2200,1300,2100} |
| #define | IGET_SAMPLE iget_sample(&buffer, len) |
| #define | NBW 2 |
| #define | NF 6 |
| #define | STATE_GET_BYTE 3 |
| #define | STATE_SEARCH_STARTBIT 0 |
| #define | STATE_SEARCH_STARTBIT2 1 |
| #define | STATE_SEARCH_STARTBIT3 2 |
Functions | |
| int | fsk_serial (fsk_data *fskd, short *buffer, int *len, int *outbyte) |
| int | fskmodem_init (fsk_data *fskd) |
| static int | get_bit_raw (fsk_data *fskd, short *buffer, int *len) |
| static int | ibpdfilter (struct filter_struct *fs, int in) |
| static int | ibpfilter (struct filter_struct *fs, int in) |
| static int | idemodulator (fsk_data *fskd, int *retval, int x) |
| static int | iget_sample (short **buffer, int *len) |
Variables | |
| static double | coef_in [NF][NBW][8] |
| Coefficients for input filters Coefficients table, generated by program "mkfilter" mkfilter is part of the zapatatelephony.org distribution Format: coef[IDX_FREC][IDX_BW][IDX_COEF] IDX_COEF = 0 => 1/GAIN IDX_COEF = 1-6 => Coefficientes y[n]. | |
| static double | coef_out [NBW][8] |
| Coefficients for output filter Coefficients table, generated by program "mkfilter" Format: coef[IDX_BW][IDX_COEF] IDX_COEF = 0 => 1/GAIN IDX_COEF = 1-6 => Coefficientes y[n]. | |
Detailed Description
FSK Modulator/Demodulator.
- Includes code and algorithms from the Zapata library.
Definition in file fskmodem_int.c.
Define Documentation
| #define BWLIST {75,800} |
Definition at line 42 of file fskmodem_int.c.
| #define FLIST {1400,1800,1200,2200,1300,2100} |
Definition at line 44 of file fskmodem_int.c.
| #define IGET_SAMPLE iget_sample(&buffer, len) |
Definition at line 60 of file fskmodem_int.c.
Referenced by fsk_serial(), and get_bit_raw().
| #define NBW 2 |
Definition at line 41 of file fskmodem_int.c.
| #define NF 6 |
Definition at line 43 of file fskmodem_int.c.
| #define STATE_GET_BYTE 3 |
Definition at line 49 of file fskmodem_int.c.
Referenced by fsk_serial().
| #define STATE_SEARCH_STARTBIT 0 |
Definition at line 46 of file fskmodem_int.c.
Referenced by fsk_serial().
| #define STATE_SEARCH_STARTBIT2 1 |
Definition at line 47 of file fskmodem_int.c.
Referenced by fsk_serial().
| #define STATE_SEARCH_STARTBIT3 2 |
Definition at line 48 of file fskmodem_int.c.
Referenced by fsk_serial().
Function Documentation
| int fsk_serial | ( | fsk_data * | fskd, |
| short * | buffer, | ||
| int * | len, | ||
| int * | outbyte | ||
| ) |
Definition at line 224 of file fskmodem_int.c.
References get_bit_raw(), idemodulator(), IGET_SAMPLE, fsk_data::instop, fsk_data::ispb, len(), fsk_data::nbit, fsk_data::parity, fsk_data::state, STATE_GET_BYTE, STATE_SEARCH_STARTBIT, STATE_SEARCH_STARTBIT2, STATE_SEARCH_STARTBIT3, fsk_data::xi1, and fsk_data::xi2.
Referenced by callerid_feed(), callerid_feed_jp(), and tdd_feed().
{
int a;
int i, j, n1, r;
int samples = 0;
int olen;
int beginlen = *len;
int beginlenx;
switch (fskd->state) {
/* Pick up where we left off */
case STATE_SEARCH_STARTBIT2:
goto search_startbit2;
case STATE_SEARCH_STARTBIT3:
goto search_startbit3;
case STATE_GET_BYTE:
goto getbyte;
}
/* We await for start bit */
do {
/* this was jesus's nice, reasonable, working (at least with RTTY) code
to look for the beginning of the start bit. Unfortunately, since TTY/TDD's
just start sending a start bit with nothing preceding it at the beginning
of a transmission (what a LOSING design), we cant do it this elegantly */
/* NOT USED
if (demodulator(zap,&x1))
return -1;
for(;;) {
if (demodulator(zap,&x2))
return -1;
if (x1>0 && x2<0) break;
x1=x2;
}
*/
/* this is now the imprecise, losing, but functional code to detect the
beginning of a start bit in the TDD sceanario. It just looks for sufficient
level to maybe, perhaps, guess, maybe that its maybe the beginning of
a start bit, perhaps. This whole thing stinks! */
beginlenx = beginlen; /* just to avoid unused war warnings */
if (idemodulator(fskd, &fskd->xi1, IGET_SAMPLE))
return -1;
samples++;
for(;;) {
search_startbit2:
if (*len <= 0) {
fskd->state = STATE_SEARCH_STARTBIT2;
return 0;
}
samples++;
if (idemodulator(fskd, &fskd->xi2, IGET_SAMPLE))
return -1;
#if 0
printf("xi2 = %d ", fskd->xi2);
#endif
if (fskd->xi2 < 512) {
break;
}
}
search_startbit3:
/* We await for 0.5 bits before using DPLL */
i = fskd->ispb / 2;
if (*len < i) {
fskd->state = STATE_SEARCH_STARTBIT3;
return 0;
}
for (; i > 0; i--) {
if (idemodulator(fskd, &fskd->xi1, IGET_SAMPLE))
return(-1);
#if 0
printf("xi1 = %d ", fskd->xi1);
#endif
samples++;
}
/* x1 must be negative (start bit confirmation) */
} while (fskd->xi1 > 0);
fskd->state = STATE_GET_BYTE;
getbyte:
/* Need at least 80 samples (for 1200) or
1320 (for 45.5) to be sure we'll have a byte */
if (fskd->nbit < 8) {
if (*len < 1320)
return 0;
} else {
if (*len < 80)
return 0;
}
/* Now we read the data bits */
j = fskd->nbit;
for (a = n1 = 0; j; j--) {
olen = *len;
i = get_bit_raw(fskd, buffer, len);
buffer += (olen - *len);
if (i == -1)
return -1;
if (i)
n1++;
a >>= 1;
a |= i;
}
j = 8 - fskd->nbit;
a >>= j;
/* We read parity bit (if exists) and check parity */
if (fskd->parity) {
olen = *len;
i = get_bit_raw(fskd, buffer, len);
buffer += (olen - *len);
if (i == -1)
return -1;
if (i)
n1++;
if (fskd->parity == 1) { /* parity=1 (even) */
if (n1 & 1)
a |= 0x100; /* error */
} else { /* parity=2 (odd) */
if (!(n1 & 1))
a |= 0x100; /* error */
}
}
/* We read STOP bits. All of them must be 1 */
for (j = fskd->instop; j; j--) {
r = get_bit_raw(fskd, buffer, len);
if (r == -1)
return -1;
if (!r)
a |= 0x200;
}
/* And finally we return
* Bit 8 : Parity error
* Bit 9 : Framming error
*/
*outbyte = a;
fskd->state = STATE_SEARCH_STARTBIT;
return 1;
}
| int fskmodem_init | ( | fsk_data * | fskd | ) |
Definition at line 197 of file fskmodem_int.c.
References fsk_data::bw, fsk_data::demod_filter, fsk_data::f_mark_idx, fsk_data::f_space_idx, filter_struct::icoefs, filter_struct::ip, filter_struct::ixv, filter_struct::iyv, fsk_data::mark_filter, and fsk_data::space_filter.
Referenced by callerid_new(), and tdd_new().
{
int i;
fskd->space_filter.ip = 0;
fskd->mark_filter.ip = 0;
fskd->demod_filter.ip = 0;
for ( i = 0 ; i < 7 ; i++ ) {
fskd->space_filter.icoefs[i] =
coef_in[fskd->f_space_idx][fskd->bw][i] * 256;
fskd->space_filter.ixv[i] = 0;;
fskd->space_filter.iyv[i] = 0;;
fskd->mark_filter.icoefs[i] =
coef_in[fskd->f_mark_idx][fskd->bw][i] * 256;
fskd->mark_filter.ixv[i] = 0;;
fskd->mark_filter.iyv[i] = 0;;
fskd->demod_filter.icoefs[i] =
coef_out[fskd->bw][i] * 1024;
fskd->demod_filter.ixv[i] = 0;;
fskd->demod_filter.iyv[i] = 0;;
}
return 0;
}
| static int get_bit_raw | ( | fsk_data * | fskd, |
| short * | buffer, | ||
| int * | len | ||
| ) | [static] |
Definition at line 167 of file fskmodem_int.c.
References f, fsk_data::icont, idemodulator(), IGET_SAMPLE, fsk_data::pllids, fsk_data::pllispb, fsk_data::pllispb2, and fsk_data::xi0.
Referenced by fsk_serial().
{
/* This function implements a DPLL to synchronize with the bits */
int f;
int ix;
/* PLL coeffs are set up in callerid_new */
for (f = 0;;) {
if (idemodulator(fskd, &ix, IGET_SAMPLE)) return(-1);
if ((ix * fskd->xi0) < 0) { /* Transicion */
if (!f) {
if (fskd->icont < (fskd->pllispb2)) {
fskd->icont += fskd->pllids;
} else {
fskd->icont -= fskd->pllids;
}
f = 1;
}
}
fskd->xi0 = ix;
fskd->icont += 32;
if (fskd->icont > fskd->pllispb) {
fskd->icont -= fskd->pllispb;
break;
}
}
f = (ix > 0) ? 0x80 : 0;
return f;
}
| static int ibpdfilter | ( | struct filter_struct * | fs, |
| int | in | ||
| ) | [inline, static] |
Integer Pass Band demodulator filter
Definition at line 97 of file fskmodem_int.c.
References filter_struct::icoefs, filter_struct::ip, filter_struct::ixv, and filter_struct::iyv.
Referenced by idemodulator().
{
int i,j;
int s;
int64_t s_interim;
/* integer filter */
s = in * fs->icoefs[0];
fs->ixv[(fs->ip + 6) & 7] = s;
s = (fs->ixv[fs->ip] + fs->ixv[(fs->ip + 6) & 7]) +
6 * (fs->ixv[(fs->ip + 1) & 7] + fs->ixv[(fs->ip + 5) & 7]) +
15 * (fs->ixv[(fs->ip + 2) & 7] + fs->ixv[(fs->ip + 4) & 7]) +
20 * fs->ixv[(fs->ip + 3) & 7];
for (i = 1, j = fs->ip; i < 7; i++, j++) {
/* Promote operation to 64 bit to prevent overflow that occurred in 32 bit) */
s_interim = (int64_t)(fs->iyv[j & 7]) *
(int64_t)(fs->icoefs[i]) /
(int64_t)(1024);
s += (int) s_interim;
}
fs->iyv[j & 7] = s;
fs->ip++;
fs->ip &= 7;
return s;
}
| static int ibpfilter | ( | struct filter_struct * | fs, |
| int | in | ||
| ) | [inline, static] |
Integer Band Pass filter
Definition at line 126 of file fskmodem_int.c.
References filter_struct::icoefs, filter_struct::ip, filter_struct::ixv, and filter_struct::iyv.
Referenced by idemodulator().
{
int i, j;
int s;
int64_t s_interim;
/* integer filter */
s = in * fs->icoefs[0] / 256;
fs->ixv[(fs->ip + 6) & 7] = s;
s = (fs->ixv[(fs->ip + 6) & 7] - fs->ixv[fs->ip])
+ 3 * (fs->ixv[(fs->ip + 2) & 7] - fs->ixv[(fs->ip + 4) & 7]);
for (i = 1, j = fs->ip; i < 7; i++, j++) {
s_interim = (int64_t)(fs->iyv[j & 7]) *
(int64_t)(fs->icoefs[i]) /
(int64_t)(256);
s += (int) s_interim;
}
fs->iyv[j & 7] = s;
fs->ip++;
fs->ip &= 7;
return s;
}
| static int idemodulator | ( | fsk_data * | fskd, |
| int * | retval, | ||
| int | x | ||
| ) | [inline, static] |
Definition at line 151 of file fskmodem_int.c.
References fsk_data::demod_filter, ibpdfilter(), ibpfilter(), id, fsk_data::mark_filter, and fsk_data::space_filter.
Referenced by fsk_serial(), and get_bit_raw().
{
int is, im, id;
int ilin2;
is = ibpfilter(&fskd->space_filter, x);
im = ibpfilter(&fskd->mark_filter, x);
ilin2 = ((im * im) - (is * is)) / (256 * 256);
id = ibpdfilter(&fskd->demod_filter, ilin2);
*retval = id;
return 0;
}
| static int iget_sample | ( | short ** | buffer, |
| int * | len | ||
| ) | [inline, static] |
Definition at line 51 of file fskmodem_int.c.
{
int retval;
retval = (int) **buffer;
(*buffer)++;
(*len)--;
return retval;
}
Variable Documentation
Coefficients for input filters Coefficients table, generated by program "mkfilter" mkfilter is part of the zapatatelephony.org distribution Format: coef[IDX_FREC][IDX_BW][IDX_COEF] IDX_COEF = 0 => 1/GAIN IDX_COEF = 1-6 => Coefficientes y[n].
Definition at line 68 of file fskmodem_int.c.
{
{ 1.3868644653e-08,-6.3283665042e-01,4.0895057217e+00,-1.1020074592e+01,1.5850766191e+01,-1.2835109292e+01,5.5477477340e+00,0.0000000000e+00,
}, { 3.1262119724e-03,-7.8390522307e-03,8.5209627801e-02,-4.0804129163e-01,1.1157139955e+00,-1.8767603680e+00,1.8916395224e+00,0.0000000000e+00
},
}
Coefficients for output filter Coefficients table, generated by program "mkfilter" Format: coef[IDX_BW][IDX_COEF] IDX_COEF = 0 => 1/GAIN IDX_COEF = 1-6 => Coefficientes y[n].
Definition at line 90 of file fskmodem_int.c.
