1 /* 2 * refclock_nmea.c - clock driver for an NMEA GPS CLOCK 3 * Michael Petry Jun 20, 1994 4 * based on refclock_heathn.c 5 */ 6 #ifdef HAVE_CONFIG_H 7 #include <config.h> 8 #endif 9 10 #if defined(REFCLOCK) && defined(CLOCK_NMEA) 11 12 #include <stdio.h> 13 #include <ctype.h> 14 15 #include "ntpd.h" 16 #include "ntp_io.h" 17 #include "ntp_unixtime.h" 18 #include "ntp_refclock.h" 19 #include "ntp_stdlib.h" 20 21 #ifdef HAVE_PPSAPI 22 # include "ppsapi_timepps.h" 23 #endif /* HAVE_PPSAPI */ 24 25 #ifdef SYS_WINNT 26 extern int async_write(int, const void *, unsigned int); 27 #undef write 28 #define write(fd, data, octets) async_write(fd, data, octets) 29 #endif 30 31 /* 32 * This driver supports the NMEA GPS Receiver with 33 * 34 * Protype was refclock_trak.c, Thanks a lot. 35 * 36 * The receiver used spits out the NMEA sentences for boat navigation. 37 * And you thought it was an information superhighway. Try a raging river 38 * filled with rapids and whirlpools that rip away your data and warp time. 39 * 40 * If HAVE_PPSAPI is defined code to use the PPSAPI will be compiled in. 41 * On startup if initialization of the PPSAPI fails, it will fall back 42 * to the "normal" timestamps. 43 * 44 * The PPSAPI part of the driver understands fudge flag2 and flag3. If 45 * flag2 is set, it will use the clear edge of the pulse. If flag3 is 46 * set, kernel hardpps is enabled. 47 * 48 * GPS sentences other than RMC (the default) may be enabled by setting 49 * the relevent bits of 'mode' in the server configuration line 50 * server 127.127.20.x mode X 51 * 52 * bit 0 - enables RMC (1) 53 * bit 1 - enables GGA (2) 54 * bit 2 - enables GLL (4) 55 * multiple sentences may be selected 56 */ 57 58 /* 59 * Definitions 60 */ 61 #ifdef SYS_WINNT 62 # define DEVICE "COM%d:" /* COM 1 - 3 supported */ 63 #else 64 # define DEVICE "/dev/gps%d" /* name of radio device */ 65 #endif 66 #define SPEED232 B4800 /* uart speed (4800 bps) */ 67 #define PRECISION (-9) /* precision assumed (about 2 ms) */ 68 #define PPS_PRECISION (-20) /* precision assumed (about 1 us) */ 69 #define REFID "GPS\0" /* reference id */ 70 #define DESCRIPTION "NMEA GPS Clock" /* who we are */ 71 #define NANOSECOND 1000000000 /* one second (ns) */ 72 #define RANGEGATE 500000 /* range gate (ns) */ 73 74 #define LENNMEA 75 /* min timecode length */ 75 76 /* 77 * Tables to compute the ddd of year form icky dd/mm timecode. Viva la 78 * leap. 79 */ 80 static int day1tab[] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}; 81 static int day2tab[] = {31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}; 82 83 /* 84 * Unit control structure 85 */ 86 struct nmeaunit { 87 int pollcnt; /* poll message counter */ 88 int polled; /* Hand in a sample? */ 89 l_fp tstamp; /* timestamp of last poll */ 90 #ifdef HAVE_PPSAPI 91 struct timespec ts; /* last timestamp */ 92 pps_params_t pps_params; /* pps parameters */ 93 pps_info_t pps_info; /* last pps data */ 94 pps_handle_t handle; /* pps handlebars */ 95 #endif /* HAVE_PPSAPI */ 96 }; 97 98 /* 99 * Function prototypes 100 */ 101 static int nmea_start P((int, struct peer *)); 102 static void nmea_shutdown P((int, struct peer *)); 103 #ifdef HAVE_PPSAPI 104 static void nmea_control P((int, struct refclockstat *, struct 105 refclockstat *, struct peer *)); 106 static int nmea_ppsapi P((struct peer *, int, int)); 107 static int nmea_pps P((struct nmeaunit *, l_fp *)); 108 #endif /* HAVE_PPSAPI */ 109 static void nmea_receive P((struct recvbuf *)); 110 static void nmea_poll P((int, struct peer *)); 111 static void gps_send P((int, const char *, struct peer *)); 112 static char *field_parse P((char *, int)); 113 114 /* 115 * Transfer vector 116 */ 117 struct refclock refclock_nmea = { 118 nmea_start, /* start up driver */ 119 nmea_shutdown, /* shut down driver */ 120 nmea_poll, /* transmit poll message */ 121 #ifdef HAVE_PPSAPI 122 nmea_control, /* fudge control */ 123 #else 124 noentry, /* fudge control */ 125 #endif /* HAVE_PPSAPI */ 126 noentry, /* initialize driver */ 127 noentry, /* buginfo */ 128 NOFLAGS /* not used */ 129 }; 130 131 /* 132 * nmea_start - open the GPS devices and initialize data for processing 133 */ 134 static int 135 nmea_start( 136 int unit, 137 struct peer *peer 138 ) 139 { 140 register struct nmeaunit *up; 141 struct refclockproc *pp; 142 int fd; 143 char device[20]; 144 145 /* 146 * Open serial port. Use CLK line discipline, if available. 147 */ 148 (void)sprintf(device, DEVICE, unit); 149 150 fd = refclock_open(device, SPEED232, LDISC_CLK); 151 if (fd <= 0) { 152 #ifdef HAVE_READLINK 153 /* nmead support added by Jon Miner (cp_n18@yahoo.com) 154 * 155 * See http://home.hiwaay.net/~taylorc/gps/nmea-server/ 156 * for information about nmead 157 * 158 * To use this, you need to create a link from /dev/gpsX to 159 * the server:port where nmead is running. Something like this: 160 * 161 * ln -s server:port /dev/gps1 162 */ 163 char buffer[80]; 164 char *nmea_host; 165 int nmea_port; 166 int len; 167 struct hostent *he; 168 struct protoent *p; 169 struct sockaddr_in so_addr; 170 171 if ((len = readlink(device,buffer,sizeof(buffer))) == -1) 172 return(0); 173 buffer[len] = 0; 174 175 if ((nmea_host = strtok(buffer,":")) == NULL) 176 return(0); 177 178 nmea_port = atoi(strtok(NULL,":")); 179 180 if ((he = gethostbyname(nmea_host)) == NULL) 181 return(0); 182 if ((p = getprotobyname("ip")) == NULL) 183 return(0); 184 so_addr.sin_family = AF_INET; 185 so_addr.sin_port = htons(nmea_port); 186 so_addr.sin_addr = *((struct in_addr *) he->h_addr); 187 188 if ((fd = socket(PF_INET,SOCK_STREAM,p->p_proto)) == -1) 189 return(0); 190 if (connect(fd,(struct sockaddr *)&so_addr,SOCKLEN(&so_addr)) == -1) { 191 close(fd); 192 return (0); 193 } 194 #else 195 return (0); 196 #endif 197 } 198 199 /* 200 * Allocate and initialize unit structure 201 */ 202 up = (struct nmeaunit *)emalloc(sizeof(struct nmeaunit)); 203 if (up == NULL) { 204 (void) close(fd); 205 return (0); 206 } 207 memset((char *)up, 0, sizeof(struct nmeaunit)); 208 pp = peer->procptr; 209 pp->io.clock_recv = nmea_receive; 210 pp->io.srcclock = (caddr_t)peer; 211 pp->io.datalen = 0; 212 pp->io.fd = fd; 213 if (!io_addclock(&pp->io)) { 214 (void) close(fd); 215 free(up); 216 return (0); 217 } 218 pp->unitptr = (caddr_t)up; 219 220 /* 221 * Initialize miscellaneous variables 222 */ 223 peer->precision = PRECISION; 224 pp->clockdesc = DESCRIPTION; 225 memcpy((char *)&pp->refid, REFID, 4); 226 up->pollcnt = 2; 227 gps_send(pp->io.fd,"$PMOTG,RMC,0000*1D\r\n", peer); 228 229 #ifdef HAVE_PPSAPI 230 /* 231 * Start the PPSAPI interface if it is there. Default to use 232 * the assert edge and do not enable the kernel hardpps. 233 */ 234 if (time_pps_create(fd, &up->handle) < 0) { 235 up->handle = 0; 236 msyslog(LOG_ERR, 237 "refclock_nmea: time_pps_create failed: %m"); 238 return (1); 239 } 240 return(nmea_ppsapi(peer, 0, 0)); 241 #else 242 return (1); 243 #endif /* HAVE_PPSAPI */ 244 } 245 246 /* 247 * nmea_shutdown - shut down a GPS clock 248 */ 249 static void 250 nmea_shutdown( 251 int unit, 252 struct peer *peer 253 ) 254 { 255 register struct nmeaunit *up; 256 struct refclockproc *pp; 257 258 pp = peer->procptr; 259 up = (struct nmeaunit *)pp->unitptr; 260 #ifdef HAVE_PPSAPI 261 if (up->handle != 0) 262 time_pps_destroy(up->handle); 263 #endif /* HAVE_PPSAPI */ 264 io_closeclock(&pp->io); 265 free(up); 266 } 267 268 #ifdef HAVE_PPSAPI 269 /* 270 * nmea_control - fudge control 271 */ 272 static void 273 nmea_control( 274 int unit, /* unit (not used */ 275 struct refclockstat *in, /* input parameters (not uded) */ 276 struct refclockstat *out, /* output parameters (not used) */ 277 struct peer *peer /* peer structure pointer */ 278 ) 279 { 280 struct refclockproc *pp; 281 282 pp = peer->procptr; 283 nmea_ppsapi(peer, pp->sloppyclockflag & CLK_FLAG2, 284 pp->sloppyclockflag & CLK_FLAG3); 285 } 286 287 288 /* 289 * Initialize PPSAPI 290 */ 291 int 292 nmea_ppsapi( 293 struct peer *peer, /* peer structure pointer */ 294 int enb_clear, /* clear enable */ 295 int enb_hardpps /* hardpps enable */ 296 ) 297 { 298 struct refclockproc *pp; 299 struct nmeaunit *up; 300 int capability; 301 302 pp = peer->procptr; 303 up = (struct nmeaunit *)pp->unitptr; 304 if (time_pps_getcap(up->handle, &capability) < 0) { 305 msyslog(LOG_ERR, 306 "refclock_nmea: time_pps_getcap failed: %m"); 307 return (0); 308 } 309 memset(&up->pps_params, 0, sizeof(pps_params_t)); 310 if (enb_clear) 311 up->pps_params.mode = capability & PPS_CAPTURECLEAR; 312 else 313 up->pps_params.mode = capability & PPS_CAPTUREASSERT; 314 if (!up->pps_params.mode) { 315 msyslog(LOG_ERR, 316 "refclock_nmea: invalid capture edge %d", 317 !enb_clear); 318 return (0); 319 } 320 up->pps_params.mode |= PPS_TSFMT_TSPEC; 321 if (time_pps_setparams(up->handle, &up->pps_params) < 0) { 322 msyslog(LOG_ERR, 323 "refclock_nmea: time_pps_setparams failed: %m"); 324 return (0); 325 } 326 if (enb_hardpps) { 327 if (time_pps_kcbind(up->handle, PPS_KC_HARDPPS, 328 up->pps_params.mode & ~PPS_TSFMT_TSPEC, 329 PPS_TSFMT_TSPEC) < 0) { 330 msyslog(LOG_ERR, 331 "refclock_nmea: time_pps_kcbind failed: %m"); 332 return (0); 333 } 334 pps_enable = 1; 335 } 336 peer->precision = PPS_PRECISION; 337 338 #if DEBUG 339 if (debug) { 340 time_pps_getparams(up->handle, &up->pps_params); 341 printf( 342 "refclock_ppsapi: capability 0x%x version %d mode 0x%x kern %d\n", 343 capability, up->pps_params.api_version, 344 up->pps_params.mode, enb_hardpps); 345 } 346 #endif 347 348 return (1); 349 } 350 351 /* 352 * Get PPSAPI timestamps. 353 * 354 * Return 0 on failure and 1 on success. 355 */ 356 static int 357 nmea_pps( 358 struct nmeaunit *up, 359 l_fp *tsptr 360 ) 361 { 362 pps_info_t pps_info; 363 struct timespec timeout, ts; 364 double dtemp; 365 l_fp tstmp; 366 367 /* 368 * Convert the timespec nanoseconds field to ntp l_fp units. 369 */ 370 if (up->handle == 0) 371 return (0); 372 timeout.tv_sec = 0; 373 timeout.tv_nsec = 0; 374 memcpy(&pps_info, &up->pps_info, sizeof(pps_info_t)); 375 if (time_pps_fetch(up->handle, PPS_TSFMT_TSPEC, &up->pps_info, 376 &timeout) < 0) 377 return (0); 378 if (up->pps_params.mode & PPS_CAPTUREASSERT) { 379 if (pps_info.assert_sequence == 380 up->pps_info.assert_sequence) 381 return (0); 382 ts = up->pps_info.assert_timestamp; 383 } else if (up->pps_params.mode & PPS_CAPTURECLEAR) { 384 if (pps_info.clear_sequence == 385 up->pps_info.clear_sequence) 386 return (0); 387 ts = up->pps_info.clear_timestamp; 388 } else { 389 return (0); 390 } 391 if ((up->ts.tv_sec == ts.tv_sec) && (up->ts.tv_nsec == ts.tv_nsec)) 392 return (0); 393 up->ts = ts; 394 395 tstmp.l_ui = ts.tv_sec + JAN_1970; 396 dtemp = ts.tv_nsec * FRAC / 1e9; 397 tstmp.l_uf = (u_int32)dtemp; 398 *tsptr = tstmp; 399 return (1); 400 } 401 #endif /* HAVE_PPSAPI */ 402 403 /* 404 * nmea_receive - receive data from the serial interface 405 */ 406 static void 407 nmea_receive( 408 struct recvbuf *rbufp 409 ) 410 { 411 register struct nmeaunit *up; 412 struct refclockproc *pp; 413 struct peer *peer; 414 int month, day; 415 int i; 416 char *cp, *dp; 417 int cmdtype; 418 /* Use these variables to hold data until we decide its worth keeping */ 419 char rd_lastcode[BMAX]; 420 l_fp rd_tmp; 421 u_short rd_lencode; 422 423 /* 424 * Initialize pointers and read the timecode and timestamp 425 */ 426 peer = (struct peer *)rbufp->recv_srcclock; 427 pp = peer->procptr; 428 up = (struct nmeaunit *)pp->unitptr; 429 rd_lencode = (u_short)refclock_gtlin(rbufp, rd_lastcode, BMAX, &rd_tmp); 430 431 /* 432 * There is a case that a <CR><LF> gives back a "blank" line 433 */ 434 if (rd_lencode == 0) 435 return; 436 437 #ifdef DEBUG 438 if (debug) 439 printf("nmea: gpsread %d %s\n", rd_lencode, 440 rd_lastcode); 441 #endif 442 443 /* 444 * We check the timecode format and decode its contents. The 445 * we only care about a few of them. The most important being 446 * the $GPRMC format 447 * $GPRMC,hhmmss,a,fddmm.xx,n,dddmmm.xx,w,zz.z,yyy.,ddmmyy,dd,v*CC 448 * For Magellan (ColorTrak) GLL probably datum (order of sentences) 449 * also mode (0,1,2,3) select sentence ANY/ALL, RMC, GGA, GLL 450 * $GPGLL,3513.8385,S,14900.7851,E,232420.594,A*21 451 * $GPGGA,232420.59,3513.8385,S,14900.7851,E,1,05,3.4,00519,M,,,,*3F 452 * $GPRMB,... 453 * $GPRMC,232418.19,A,3513.8386,S,14900.7853,E,00.0,000.0,121199,12.,E*77 454 * $GPAPB,... 455 * $GPGSA,... 456 * $GPGSV,... 457 * $GPGSV,... 458 */ 459 #define GPXXX 0 460 #define GPRMC 1 461 #define GPGGA 2 462 #define GPGLL 4 463 cp = rd_lastcode; 464 cmdtype=0; 465 if(strncmp(cp,"$GPRMC",6)==0) { 466 cmdtype=GPRMC; 467 } 468 else if(strncmp(cp,"$GPGGA",6)==0) { 469 cmdtype=GPGGA; 470 } 471 else if(strncmp(cp,"$GPGLL",6)==0) { 472 cmdtype=GPGLL; 473 } 474 else if(strncmp(cp,"$GPXXX",6)==0) { 475 cmdtype=GPXXX; 476 } 477 else 478 return; 479 480 481 /* See if I want to process this message type */ 482 if ( ((peer->ttl == 0) && (cmdtype != GPRMC)) 483 || ((peer->ttl != 0) && !(cmdtype & peer->ttl)) ) 484 return; 485 486 pp->lencode = rd_lencode; 487 strcpy(pp->a_lastcode,rd_lastcode); 488 cp = pp->a_lastcode; 489 490 pp->lastrec = up->tstamp = rd_tmp; 491 up->pollcnt = 2; 492 493 #ifdef DEBUG 494 if (debug) 495 printf("nmea: timecode %d %s\n", pp->lencode, 496 pp->a_lastcode); 497 #endif 498 499 500 /* Grab field depending on clock string type */ 501 switch( cmdtype ) { 502 case GPRMC: 503 /* 504 * Test for synchronization. Check for quality byte. 505 */ 506 dp = field_parse(cp,2); 507 if( dp[0] != 'A') 508 pp->leap = LEAP_NOTINSYNC; 509 else 510 pp->leap = LEAP_NOWARNING; 511 512 /* Now point at the time field */ 513 dp = field_parse(cp,1); 514 break; 515 516 517 case GPGGA: 518 /* 519 * Test for synchronization. Check for quality byte. 520 */ 521 dp = field_parse(cp,6); 522 if( dp[0] == '0') 523 pp->leap = LEAP_NOTINSYNC; 524 else 525 pp->leap = LEAP_NOWARNING; 526 527 /* Now point at the time field */ 528 dp = field_parse(cp,1); 529 break; 530 531 532 case GPGLL: 533 /* 534 * Test for synchronization. Check for quality byte. 535 */ 536 dp = field_parse(cp,6); 537 if( dp[0] != 'A') 538 pp->leap = LEAP_NOTINSYNC; 539 else 540 pp->leap = LEAP_NOWARNING; 541 542 /* Now point at the time field */ 543 dp = field_parse(cp,5); 544 break; 545 546 547 case GPXXX: 548 return; 549 default: 550 return; 551 552 } 553 554 /* 555 * Check time code format of NMEA 556 */ 557 558 if( !isdigit((int)dp[0]) || 559 !isdigit((int)dp[1]) || 560 !isdigit((int)dp[2]) || 561 !isdigit((int)dp[3]) || 562 !isdigit((int)dp[4]) || 563 !isdigit((int)dp[5]) 564 ) { 565 refclock_report(peer, CEVNT_BADREPLY); 566 return; 567 } 568 569 570 /* 571 * Convert time and check values. 572 */ 573 pp->hour = ((dp[0] - '0') * 10) + dp[1] - '0'; 574 pp->minute = ((dp[2] - '0') * 10) + dp[3] - '0'; 575 pp->second = ((dp[4] - '0') * 10) + dp[5] - '0'; 576 /* Default to 0 milliseconds, if decimal convert milliseconds in 577 one, two or three digits 578 */ 579 pp->nsec = 0; 580 if (dp[6] == '.') { 581 if (isdigit((int)dp[7])) { 582 pp->nsec = (dp[7] - '0') * 100000000; 583 if (isdigit((int)dp[8])) { 584 pp->nsec += (dp[8] - '0') * 10000000; 585 if (isdigit((int)dp[9])) { 586 pp->nsec += (dp[9] - '0') * 1000000; 587 } 588 } 589 } 590 } 591 592 if (pp->hour > 23 || pp->minute > 59 || pp->second > 59 593 || pp->nsec > 1000000000) { 594 refclock_report(peer, CEVNT_BADTIME); 595 return; 596 } 597 598 599 /* 600 * Convert date and check values. 601 */ 602 if (cmdtype==GPRMC) { 603 dp = field_parse(cp,9); 604 day = dp[0] - '0'; 605 day = (day * 10) + dp[1] - '0'; 606 month = dp[2] - '0'; 607 month = (month * 10) + dp[3] - '0'; 608 pp->year = dp[4] - '0'; 609 pp->year = (pp->year * 10) + dp[5] - '0'; 610 } 611 else { 612 /* only time */ 613 time_t tt = time(NULL); 614 struct tm * t = gmtime(&tt); 615 day = t->tm_mday; 616 month = t->tm_mon + 1; 617 pp->year= t->tm_year; 618 } 619 620 if (month < 1 || month > 12 || day < 1) { 621 refclock_report(peer, CEVNT_BADTIME); 622 return; 623 } 624 625 /* Hmmmm this will be a nono for 2100,2200,2300 but I don't think I'll be here */ 626 /* good thing that 2000 is a leap year */ 627 /* pp->year will be 00-99 if read from GPS, 00-> (years since 1900) from tm_year */ 628 if (pp->year % 4) { 629 if (day > day1tab[month - 1]) { 630 refclock_report(peer, CEVNT_BADTIME); 631 return; 632 } 633 for (i = 0; i < month - 1; i++) 634 day += day1tab[i]; 635 } else { 636 if (day > day2tab[month - 1]) { 637 refclock_report(peer, CEVNT_BADTIME); 638 return; 639 } 640 for (i = 0; i < month - 1; i++) 641 day += day2tab[i]; 642 } 643 pp->day = day; 644 645 646 #ifdef HAVE_PPSAPI 647 /* 648 * If the PPSAPI is working, rather use its timestamps. 649 * assume that the PPS occurs on the second so blow any msec 650 */ 651 if (nmea_pps(up, &rd_tmp) == 1) { 652 pp->lastrec = up->tstamp = rd_tmp; 653 pp->nsec = 0; 654 } 655 #endif /* HAVE_PPSAPI */ 656 657 /* 658 * Process the new sample in the median filter and determine the 659 * reference clock offset and dispersion. We use lastrec as both 660 * the reference time and receive time, in order to avoid being 661 * cute, like setting the reference time later than the receive 662 * time, which may cause a paranoid protocol module to chuck out 663 * the data. 664 */ 665 666 if (!refclock_process(pp)) { 667 refclock_report(peer, CEVNT_BADTIME); 668 return; 669 } 670 671 672 673 /* 674 * Only go on if we had been polled. 675 */ 676 if (!up->polled) 677 return; 678 up->polled = 0; 679 pp->lastref = pp->lastrec; 680 refclock_receive(peer); 681 682 /* If we get here - what we got from the clock is OK, so say so */ 683 refclock_report(peer, CEVNT_NOMINAL); 684 685 record_clock_stats(&peer->srcadr, pp->a_lastcode); 686 687 } 688 689 /* 690 * nmea_poll - called by the transmit procedure 691 * 692 * We go to great pains to avoid changing state here, since there may be 693 * more than one eavesdropper receiving the same timecode. 694 */ 695 static void 696 nmea_poll( 697 int unit, 698 struct peer *peer 699 ) 700 { 701 register struct nmeaunit *up; 702 struct refclockproc *pp; 703 704 pp = peer->procptr; 705 up = (struct nmeaunit *)pp->unitptr; 706 if (up->pollcnt == 0) 707 refclock_report(peer, CEVNT_TIMEOUT); 708 else 709 up->pollcnt--; 710 pp->polls++; 711 up->polled = 1; 712 713 /* 714 * usually nmea_receive can get a timestamp every second 715 */ 716 717 gps_send(pp->io.fd,"$PMOTG,RMC,0000*1D\r\n", peer); 718 } 719 720 /* 721 * 722 * gps_send(fd,cmd, peer) Sends a command to the GPS receiver. 723 * as gps_send(fd,"rqts,u\r", peer); 724 * 725 * We don't currently send any data, but would like to send 726 * RTCM SC104 messages for differential positioning. It should 727 * also give us better time. Without a PPS output, we're 728 * Just fooling ourselves because of the serial code paths 729 * 730 */ 731 static void 732 gps_send( 733 int fd, 734 const char *cmd, 735 struct peer *peer 736 ) 737 { 738 739 if (write(fd, cmd, strlen(cmd)) == -1) { 740 refclock_report(peer, CEVNT_FAULT); 741 } 742 } 743 744 static char * 745 field_parse( 746 char *cp, 747 int fn 748 ) 749 { 750 char *tp; 751 int i = fn; 752 753 for (tp = cp; *tp != '\0'; tp++) { 754 if (*tp == ',') 755 i--; 756 if (i == 0) 757 break; 758 } 759 return (++tp); 760 } 761 #else 762 int refclock_nmea_bs; 763 #endif /* REFCLOCK */ 764