int fsk_serial(fsk_data *fskd, short *buffer, int *len, int *outbyte) { 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 fsk_serie(fsk_data *fskd, short *buffer, int *len, int *outbyte) { int a; int i,j,n1,r; int samples=0; int olen; 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; } /* Esperamos bit de start */ 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 (demodulador(zap,&x1)) return(-1); for(;;) { if (demodulador(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! */ if (demodulador(fskd,&fskd->x1,GET_SAMPLE)) return(-1); samples++; for(;;) { search_startbit2: if (!*len) { fskd->state = STATE_SEARCH_STARTBIT2; return 0; } samples++; if (demodulador(fskd,&fskd->x2,GET_SAMPLE)) return(-1); #if 0 printf("x2 = %5.5f ", fskd->x2); #endif if (fskd->x2 < -0.5) break; } search_startbit3: /* Esperamos 0.5 bits antes de usar DPLL */ i=fskd->spb/2; if (*len < i) { fskd->state = STATE_SEARCH_STARTBIT3; return 0; } for(;i;i--) { if (demodulador(fskd,&fskd->x1,GET_SAMPLE)) return(-1); #if 0 printf("x1 = %5.5f ", fskd->x1); #endif samples++; } /* x1 debe ser negativo (confirmación del bit de start) */ } 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; } /* Leemos ahora los bits de datos */ 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; /* Leemos bit de paridad (si existe) y la comprobamos */ if (fskd->paridad) { olen = *len; i=get_bit_raw(fskd, buffer, len); buffer += (olen - *len); if (i == -1) return(-1); if (i) n1++; if (fskd->paridad==1) { /* paridad=1 (par) */ if (n1&1) a|=0x100; /* error */ } else { /* paridad=2 (impar) */ if (!(n1&1)) a|=0x100; /* error */ } } /* Leemos bits de STOP. Todos deben ser 1 */ for (j=fskd->nstop;j;j--) { r = get_bit_raw(fskd, buffer, len); if (r == -1) return(-1); if (!r) a|=0x200; } /* Por fin retornamos */ /* Bit 8 : Error de paridad */ /* Bit 9 : Error de Framming */ *outbyte = a; fskd->state = STATE_SEARCH_STARTBIT; return 1; }