/* $NetBSD: refclock_nmea.c,v 1.1.1.1 2000/03/29 12:38:53 simonb Exp $ */ /* * refclock_nmea.c - clock driver for an NMEA GPS CLOCK * Michael Petry Jun 20, 1994 * based on refclock_heathn.c */ #ifdef HAVE_CONFIG_H #include #endif #if defined(REFCLOCK) && defined(CLOCK_NMEA) #include #include #include #include #include "ntpd.h" #include "ntp_io.h" #include "ntp_refclock.h" #include "ntp_stdlib.h" /* * This driver supports the NMEA GPS Receiver with * * Protype was refclock_trak.c, Thanks a lot. * * The receiver used spits out the NMEA sentences for boat navigation. * And you thought it was an information superhighway. Try a raging river * filled with rapids and whirlpools that rip away your data and warp time. */ /* * Definitions */ #ifdef SYS_WINNT # define DEVICE "COM%d:" /* COM 1 - 3 supported */ #else # define DEVICE "/dev/gps%d" /* name of radio device */ #endif #define SPEED232 B4800 /* uart speed (4800 bps) */ #define PRECISION (-9) /* precision assumed (about 2 ms) */ #define DCD_PRECISION (-20) /* precision assumed (about 1 us) */ #define REFID "GPS\0" /* reference id */ #define DESCRIPTION "NMEA GPS Clock" /* who we are */ #define LENNMEA 75 /* min timecode length */ /* * Tables to compute the ddd of year form icky dd/mm timecode. Viva la * leap. */ static int day1tab[] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}; static int day2tab[] = {31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}; /* * Unit control structure */ struct nmeaunit { int pollcnt; /* poll message counter */ int polled; /* Hand in a sample? */ l_fp tstamp; /* timestamp of last poll */ }; /* * Function prototypes */ static int nmea_start P((int, struct peer *)); static void nmea_shutdown P((int, struct peer *)); static void nmea_receive P((struct recvbuf *)); static void nmea_poll P((int, struct peer *)); static void gps_send P((int, const char *, struct peer *)); static char *field_parse P((char *, int)); /* * Transfer vector */ struct refclock refclock_nmea = { nmea_start, /* start up driver */ nmea_shutdown, /* shut down driver */ nmea_poll, /* transmit poll message */ noentry, /* handle control */ noentry, /* initialize driver */ noentry, /* buginfo */ NOFLAGS /* not used */ }; /* * nmea_start - open the GPS devices and initialize data for processing */ static int nmea_start( int unit, struct peer *peer ) { register struct nmeaunit *up; struct refclockproc *pp; int fd; char device[20]; /* * Open serial port. Use CLK line discipline, if available. */ (void)sprintf(device, DEVICE, unit); if (!(fd = refclock_open(device, SPEED232, LDISC_CLK))) return (0); /* * Allocate and initialize unit structure */ if (!(up = (struct nmeaunit *) emalloc(sizeof(struct nmeaunit)))) { (void) close(fd); return (0); } memset((char *)up, 0, sizeof(struct nmeaunit)); pp = peer->procptr; pp->io.clock_recv = nmea_receive; pp->io.srcclock = (caddr_t)peer; pp->io.datalen = 0; pp->io.fd = fd; if (!io_addclock(&pp->io)) { (void) close(fd); free(up); return (0); } pp->unitptr = (caddr_t)up; /* * Initialize miscellaneous variables */ peer->precision = DCD_PRECISION; pp->clockdesc = DESCRIPTION; memcpy((char *)&pp->refid, REFID, 4); up->pollcnt = 2; gps_send(pp->io.fd,"$PMOTG,RMC,0000*1D\r\n", peer); return (1); } /* * nmea_shutdown - shut down a GPS clock */ static void nmea_shutdown( int unit, struct peer *peer ) { register struct nmeaunit *up; struct refclockproc *pp; pp = peer->procptr; up = (struct nmeaunit *)pp->unitptr; io_closeclock(&pp->io); free(up); } /* * nmea_receive - receive data from the serial interface */ static void nmea_receive( struct recvbuf *rbufp ) { register struct nmeaunit *up; struct refclockproc *pp; struct peer *peer; l_fp trtmp; int month, day; int i; char *cp, *dp; int cmdtype; /* * Initialize pointers and read the timecode and timestamp */ peer = (struct peer *)rbufp->recv_srcclock; pp = peer->procptr; up = (struct nmeaunit *)pp->unitptr; pp->lencode = refclock_gtlin(rbufp, pp->a_lastcode, BMAX, &trtmp); /* * There is a case that a gives back a "blank" line */ if (pp->lencode == 0) return; /* * We get a buffer and timestamp for each . */ pp->lastrec = up->tstamp = trtmp; up->pollcnt = 2; #ifdef DEBUG if (debug) printf("nmea: timecode %d %s\n", pp->lencode, pp->a_lastcode); #endif /* * We check the timecode format and decode its contents. The * we only care about a few of them. The most important being * the $GPRMC format * $GPRMC,hhmmss,a,fddmm.xx,n,dddmmm.xx,w,zz.z,yyy.,ddmmyy,dd,v*CC * $GPGGA,162617.0,4548.339,N,00837.719,E,1,07,0.97,00262,M,048,M,,*5D */ #define GPRMC 0 #define GPXXX 1 #define GPGGA 2 cp = pp->a_lastcode; cmdtype=0; if(strncmp(cp,"$GPRMC",6)==0) { cmdtype=GPRMC; } else if(strncmp(cp,"$GPGGA",6)==0) { cmdtype=GPGGA; } else if(strncmp(cp,"$GPXXX",6)==0) { cmdtype=GPXXX; } else return; switch( cmdtype ) { case GPRMC: case GPGGA: /* * Check time code format of NMEA */ dp = field_parse(cp,1); if( !isdigit((int)dp[0]) || !isdigit((int)dp[1]) || !isdigit((int)dp[2]) || !isdigit((int)dp[3]) || !isdigit((int)dp[4]) || !isdigit((int)dp[5]) ) { refclock_report(peer, CEVNT_BADREPLY); return; } /* * Test for synchronization. Check for quality byte. */ switch( cmdtype ) { case GPRMC: dp = field_parse(cp,2); if( dp[0] != 'A') { refclock_report(peer, CEVNT_BADREPLY); return; } break; case GPGGA: dp = field_parse(cp,6); if( dp[0] == '0') { refclock_report(peer, CEVNT_BADREPLY); return; } break; } break; case GPXXX: return; default: return; } if (cmdtype ==GPGGA) { /* only time */ time_t tt = time(NULL); struct tm * t = gmtime(&tt); day = t->tm_mday; month = t->tm_mon + 1; pp->year= t->tm_year; } else { dp = field_parse(cp,9); /* * Convert date and check values. */ day = dp[0] - '0'; day = (day * 10) + dp[1] - '0'; month = dp[2] - '0'; month = (month * 10) + dp[3] - '0'; pp->year = dp[4] - '0'; pp->year = (pp->year * 10) + dp[5] - '0'; } if (month < 1 || month > 12 || day < 1) { refclock_report(peer, CEVNT_BADTIME); return; } if (pp->year % 4) { if (day > day1tab[month - 1]) { refclock_report(peer, CEVNT_BADTIME); return; } for (i = 0; i < month - 1; i++) day += day1tab[i]; } else { if (day > day2tab[month - 1]) { refclock_report(peer, CEVNT_BADTIME); return; } for (i = 0; i < month - 1; i++) day += day2tab[i]; } pp->day = day; dp = field_parse(cp,1); /* * Convert time and check values. */ pp->hour = ((dp[0] - '0') * 10) + dp[1] - '0'; pp->minute = ((dp[2] - '0') * 10) + dp[3] - '0'; pp->second = ((dp[4] - '0') * 10) + dp[5] - '0'; pp->msec = 0; if (dp[6] == '.') { if (isdigit((int)dp[7])) { pp->msec += (dp[7] - '0') * 100; if (isdigit((int)dp[8])) { pp->msec += (dp[8] - '0') * 10; if (isdigit((int)dp[9])) { pp->msec += (dp[9] - '0'); } } } } if (pp->hour > 23 || pp->minute > 59 || pp->second > 59 || pp->msec > 1000) { refclock_report(peer, CEVNT_BADTIME); return; } /* * Process the new sample in the median filter and determine the * reference clock offset and dispersion. We use lastrec as both * the reference time and receive time, in order to avoid being * cute, like setting the reference time later than the receive * time, which may cause a paranoid protocol module to chuck out * the data. */ if (!refclock_process(pp)) { refclock_report(peer, CEVNT_BADTIME); return; } /* * Only go on if we had been polled. */ if (!up->polled) return; up->polled = 0; refclock_receive(peer); record_clock_stats(&peer->srcadr, pp->a_lastcode); } /* * nmea_poll - called by the transmit procedure * * We go to great pains to avoid changing state here, since there may be * more than one eavesdropper receiving the same timecode. */ static void nmea_poll( int unit, struct peer *peer ) { register struct nmeaunit *up; struct refclockproc *pp; pp = peer->procptr; up = (struct nmeaunit *)pp->unitptr; if (up->pollcnt == 0) refclock_report(peer, CEVNT_TIMEOUT); else up->pollcnt--; pp->polls++; up->polled = 1; /* * usually nmea_receive can get a timestamp every second */ gps_send(pp->io.fd,"$PMOTG,RMC,0000*1D\r\n", peer); } /* * * gps_send(fd,cmd, peer) Sends a command to the GPS receiver. * as gps_send(fd,"rqts,u\r", peer); * * We don't currently send any data, but would like to send * RTCM SC104 messages for differential positioning. It should * also give us better time. Without a PPS output, we're * Just fooling ourselves because of the serial code paths * */ static void gps_send( int fd, const char *cmd, struct peer *peer ) { if (write(fd, cmd, strlen(cmd)) == -1) { refclock_report(peer, CEVNT_FAULT); } } static char * field_parse( char *cp, int fn ) { char *tp; int i = fn; for (tp = cp; *tp != '\0'; tp++) { if (*tp == ',') i--; if (i == 0) break; } return (++tp); } #else int refclock_nmea_bs; #endif /* REFCLOCK */