FSK Modem Support. More...
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Data Structures | |
struct | fsk_data |
Defines | |
#define | NCOLA 0x4000 |
#define | PARITY_EVEN 1 |
#define | PARITY_NONE 0 |
#define | PARITY_ODD 2 |
Functions | |
int | fsk_serial (fsk_data *fskd, short *buffer, int *len, int *outbyte) |
FSK Modem Support.
Definition in file fskmodem_float.h.
#define NCOLA 0x4000 |
Definition at line 32 of file fskmodem_float.h.
Referenced by demodulator().
#define PARITY_EVEN 1 |
Definition at line 28 of file fskmodem_float.h.
#define PARITY_NONE 0 |
Definition at line 27 of file fskmodem_float.h.
#define PARITY_ODD 2 |
Definition at line 29 of file fskmodem_float.h.
int fsk_serial | ( | fsk_data * | fskd, |
short * | buffer, | ||
int * | len, | ||
int * | outbyte | ||
) |
Definition at line 222 of file fskmodem_float.c.
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 */ /* 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 (demodulator(fskd, &fskd->x1, GET_SAMPLE)) return -1; samples++; for (;;) { search_startbit2: if (*len <= 0) { fskd->state = STATE_SEARCH_STARTBIT2; return 0; } samples++; if (demodulator(fskd, &fskd->x2, GET_SAMPLE)) return(-1); #if 0 printf("x2 = %5.5f ", fskd->x2); #endif if (fskd->x2 < -0.5) break; } search_startbit3: /* We await for 0.5 bits before using DPLL */ i = fskd->spb/2; if (*len < i) { fskd->state = STATE_SEARCH_STARTBIT3; return 0; } for (; i>0; i--) { if (demodulator(fskd, &fskd->x1, GET_SAMPLE)) return(-1); #if 0 printf("x1 = %5.5f ", fskd->x1); #endif samples++; } /* x1 must be negative (start bit confirmation) */ } while (fskd->x1 > 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->nstop;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; }