refclock_nmea.c

网络时间协议NTP 源码 版本v4.2.0b 该源码用于linux平台下

		if (pps_info.clear_sequence ==
		    up->pps_info.clear_sequence)
			return (0);
		ts = up->pps_info.clear_timestamp;
	} else {
		return (0);
	}
	if ((up->ts.tv_sec == ts.tv_sec) && (up->ts.tv_nsec == ts.tv_nsec))
		return (0);
	up->ts = ts;

	tstmp.l_ui = ts.tv_sec + JAN_1970;
	dtemp = ts.tv_nsec * FRAC / 1e9;
	tstmp.l_uf = (u_int32)dtemp;
	*tsptr = tstmp;
	return (1);
}
#endif /* HAVE_PPSAPI */

/*
 * 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;
	int month, day;
	int i;
	char *cp, *dp;
	int cmdtype;
	/* Use these variables to hold data until we decide its worth keeping */
	char	rd_lastcode[BMAX];
	l_fp	rd_tmp;
	u_short	rd_lencode;

	/*
	 * Initialize pointers and read the timecode and timestamp
	 */
	peer = (struct peer *)rbufp->recv_srcclock;
	pp = peer->procptr;
	up = (struct nmeaunit *)pp->unitptr;
	rd_lencode = (u_short)refclock_gtlin(rbufp, rd_lastcode, BMAX, &rd_tmp);

	/*
	 * There is a case that a <CR><LF> gives back a "blank" line
	 */
	if (rd_lencode == 0)
	    return;

#ifdef DEBUG
	if (debug)
	    printf("nmea: gpsread %d %s\n", rd_lencode,
		   rd_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
	 * For Magellan (ColorTrak) GLL probably datum (order of sentences)
	 * also mode (0,1,2,3) select sentence ANY/ALL, RMC, GGA, GLL
	 * $GPGLL,3513.8385,S,14900.7851,E,232420.594,A*21
  	 * $GPGGA,232420.59,3513.8385,S,14900.7851,E,1,05,3.4,00519,M,,,,*3F
	 * $GPRMB,...
	 * $GPRMC,232418.19,A,3513.8386,S,14900.7853,E,00.0,000.0,121199,12.,E*77
	 * $GPAPB,...
	 * $GPGSA,...
	 * $GPGSV,...
	 * $GPGSV,...
	 */
#define GPXXX	0
#define GPRMC	1
#define GPGGA	2
#define GPGLL	4
	cp = rd_lastcode;
	cmdtype=0;
	if(strncmp(cp,"$GPRMC",6)==0) {
		cmdtype=GPRMC;
	}
	else if(strncmp(cp,"$GPGGA",6)==0) {
		cmdtype=GPGGA;
	}
	else if(strncmp(cp,"$GPGLL",6)==0) {
		cmdtype=GPGLL;
	}
	else if(strncmp(cp,"$GPXXX",6)==0) {
		cmdtype=GPXXX;
	}
	else
	    return;


	/* See if I want to process this message type */
	if ( ((peer->ttl == 0) && (cmdtype != GPRMC))
           || ((peer->ttl != 0) && !(cmdtype & peer->ttl)) )
		return;

	pp->lencode = rd_lencode;
	strcpy(pp->a_lastcode,rd_lastcode);
	cp = pp->a_lastcode;

	pp->lastrec = up->tstamp = rd_tmp;
	up->pollcnt = 2;

#ifdef DEBUG
	if (debug)
	    printf("nmea: timecode %d %s\n", pp->lencode,
		   pp->a_lastcode);
#endif


	/* Grab field depending on clock string type */
	switch( cmdtype ) {
	    case GPRMC:
		/*
		 * Test for synchronization.  Check for quality byte.
		 */
		dp = field_parse(cp,2);
		if( dp[0] != 'A')
			pp->leap = LEAP_NOTINSYNC;
		else
			pp->leap = LEAP_NOWARNING;

		/* Now point at the time field */
		dp = field_parse(cp,1);
		break;


	    case GPGGA:
		/*
		 * Test for synchronization.  Check for quality byte.
		 */
		dp = field_parse(cp,6);
		if( dp[0] == '0')
			pp->leap = LEAP_NOTINSYNC;
		else
			pp->leap = LEAP_NOWARNING;

		/* Now point at the time field */
		dp = field_parse(cp,1);
		break;


	    case GPGLL:
		/*
		 * Test for synchronization.  Check for quality byte.
		 */
		dp = field_parse(cp,6);
		if( dp[0] != 'A')
			pp->leap = LEAP_NOTINSYNC;
		else
			pp->leap = LEAP_NOWARNING;

		/* Now point at the time field */
		dp = field_parse(cp,5);
		break;


	    case GPXXX:
		return;
	    default:
		return;

	}

		/*
		 *	Check time code format of NMEA
		 */

		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;
		}


	/*
	 * 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';
	/* Default to 0 milliseconds, if decimal convert milliseconds in
	   one, two or three digits
	*/
	pp->nsec = 0; 
	if (dp[6] == '.') {
		if (isdigit((int)dp[7])) {
			pp->nsec = (dp[7] - '0') * 100000000;
			if (isdigit((int)dp[8])) {
				pp->nsec += (dp[8] - '0') * 10000000;
				if (isdigit((int)dp[9])) {
					pp->nsec += (dp[9] - '0') * 1000000;
				}
			}
		}
	}

	if (pp->hour > 23 || pp->minute > 59 || pp->second > 59
	  || pp->nsec > 1000000000) {
		refclock_report(peer, CEVNT_BADTIME);
		return;
	}


	/*
	 * Convert date and check values.
	 */
	if (cmdtype==GPRMC) {
	    dp = field_parse(cp,9);
	    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';
	}
	else {
	/* 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;
	}

	if (month < 1 || month > 12 || day < 1) {
		refclock_report(peer, CEVNT_BADTIME);
		return;
	}

        /* Hmmmm this will be a nono for 2100,2200,2300 but I don't think I'll be here */
        /* good thing that 2000 is a leap year */
	/* pp->year will be 00-99 if read from GPS, 00->  (years since 1900) from tm_year */
	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;


#ifdef HAVE_PPSAPI
	/*
	 * If the PPSAPI is working, rather use its timestamps.
	 * assume that the PPS occurs on the second so blow any msec
	 */
	if (nmea_pps(up, &rd_tmp) == 1) {
		pp->lastrec = up->tstamp = rd_tmp;
		pp->nsec = 0;
	}
#endif /* HAVE_PPSAPI */

	/*
	 * 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;
	pp->lastref = pp->lastrec;
	refclock_receive(peer);

        /* If we get here - what we got from the clock is OK, so say so */
         refclock_report(peer, CEVNT_NOMINAL);

	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 */