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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) |
Definition in file fskmodem_float.h.
#define NCOLA 0x4000 |
#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().
00223 { 00224 int a; 00225 int i,j,n1,r; 00226 int samples = 0; 00227 int olen; 00228 00229 switch (fskd->state) { 00230 /* Pick up where we left off */ 00231 case STATE_SEARCH_STARTBIT2: 00232 goto search_startbit2; 00233 case STATE_SEARCH_STARTBIT3: 00234 goto search_startbit3; 00235 case STATE_GET_BYTE: 00236 goto getbyte; 00237 } 00238 /* We await for start bit */ 00239 do { 00240 /* this was jesus's nice, reasonable, working (at least with RTTY) code 00241 to look for the beginning of the start bit. Unfortunately, since TTY/TDD's 00242 just start sending a start bit with nothing preceding it at the beginning 00243 of a transmission (what a LOSING design), we cant do it this elegantly */ 00244 /* 00245 if (demodulator(zap,&x1)) return(-1); 00246 for (;;) { 00247 if (demodulator(zap,&x2)) return(-1); 00248 if (x1>0 && x2<0) break; 00249 x1 = x2; 00250 } 00251 */ 00252 /* this is now the imprecise, losing, but functional code to detect the 00253 beginning of a start bit in the TDD sceanario. It just looks for sufficient 00254 level to maybe, perhaps, guess, maybe that its maybe the beginning of 00255 a start bit, perhaps. This whole thing stinks! */ 00256 if (demodulator(fskd, &fskd->x1, GET_SAMPLE)) 00257 return -1; 00258 samples++; 00259 for (;;) { 00260 search_startbit2: 00261 if (*len <= 0) { 00262 fskd->state = STATE_SEARCH_STARTBIT2; 00263 return 0; 00264 } 00265 samples++; 00266 if (demodulator(fskd, &fskd->x2, GET_SAMPLE)) 00267 return(-1); 00268 #if 0 00269 printf("x2 = %5.5f ", fskd->x2); 00270 #endif 00271 if (fskd->x2 < -0.5) 00272 break; 00273 } 00274 search_startbit3: 00275 /* We await for 0.5 bits before using DPLL */ 00276 i = fskd->spb/2; 00277 if (*len < i) { 00278 fskd->state = STATE_SEARCH_STARTBIT3; 00279 return 0; 00280 } 00281 for (; i>0; i--) { 00282 if (demodulator(fskd, &fskd->x1, GET_SAMPLE)) 00283 return(-1); 00284 #if 0 00285 printf("x1 = %5.5f ", fskd->x1); 00286 #endif 00287 samples++; 00288 } 00289 00290 /* x1 must be negative (start bit confirmation) */ 00291 00292 } while (fskd->x1 > 0); 00293 fskd->state = STATE_GET_BYTE; 00294 00295 getbyte: 00296 00297 /* Need at least 80 samples (for 1200) or 00298 1320 (for 45.5) to be sure we'll have a byte */ 00299 if (fskd->nbit < 8) { 00300 if (*len < 1320) 00301 return 0; 00302 } else { 00303 if (*len < 80) 00304 return 0; 00305 } 00306 /* Now we read the data bits */ 00307 j = fskd->nbit; 00308 for (a = n1 = 0; j; j--) { 00309 olen = *len; 00310 i = get_bit_raw(fskd, buffer, len); 00311 buffer += (olen - *len); 00312 if (i == -1) 00313 return(-1); 00314 if (i) 00315 n1++; 00316 a >>= 1; 00317 a |= i; 00318 } 00319 j = 8-fskd->nbit; 00320 a >>= j; 00321 00322 /* We read parity bit (if exists) and check parity */ 00323 if (fskd->parity) { 00324 olen = *len; 00325 i = get_bit_raw(fskd, buffer, len); 00326 buffer += (olen - *len); 00327 if (i == -1) 00328 return(-1); 00329 if (i) 00330 n1++; 00331 if (fskd->parity == 1) { /* parity=1 (even) */ 00332 if (n1&1) 00333 a |= 0x100; /* error */ 00334 } else { /* parity=2 (odd) */ 00335 if (!(n1&1)) 00336 a |= 0x100; /* error */ 00337 } 00338 } 00339 00340 /* We read STOP bits. All of them must be 1 */ 00341 00342 for (j = fskd->nstop;j;j--) { 00343 r = get_bit_raw(fskd, buffer, len); 00344 if (r == -1) 00345 return(-1); 00346 if (!r) 00347 a |= 0x200; 00348 } 00349 00350 /* And finally we return */ 00351 /* Bit 8 : Parity error */ 00352 /* Bit 9 : Framming error*/ 00353 00354 *outbyte = a; 00355 fskd->state = STATE_SEARCH_STARTBIT; 00356 return 1; 00357 }