refclock_wwv.c

网络时间协议NTP 源码 版本v4.2.0b 该源码用于linux平台下

 * DST decode (DST2 DST1) for prettyprint
 */
char dstcod[] = {
	'S',			/* 00 standard time */
	'I',			/* 01 set clock ahead at 0200 local */
	'O',			/* 10 set clock back at 0200 local */
	'D'			/* 11 daylight time */
};

/*
 * The decoding matrix consists of nine row vectors, one for each digit
 * of the timecode. The digits are stored from least to most significant
 * order. The maximum likelihood timecode is formed from the digits
 * corresponding to the maximum likelihood values reading in the
 * opposite order: yy ddd hh:mm.
 */
struct decvec {
	int radix;		/* radix (3, 4, 6, 10) */
	int digit;		/* current clock digit */
	int mldigit;		/* maximum likelihood digit */
	int count;		/* match count */
	double digprb;		/* max digit probability */
	double digsnr;		/* likelihood function (dB) */
	double like[10];	/* likelihood integrator 0-9 */
};

/*
 * The station structure (sp) is used to acquire the minute pulse from
 * WWV and/or WWVH. These stations are distinguished by the frequency
 * used for the second and minute sync pulses, 1000 Hz for WWV and 1200
 * Hz for WWVH. Other than frequency, the format is the same.
 */
struct sync {
	double	epoch;		/* accumulated epoch differences */
	double	maxeng;		/* sync max energy */
	double	noieng;		/* sync noise energy */
	long	pos;		/* max amplitude position */
	long	lastpos;	/* last max position */
	long	mepoch;		/* minute synch epoch */

	double	amp;		/* sync signal */
	double	syneng;		/* sync signal max 800 ms */
	double	synmax;		/* sync signal max 0 s */
	double	synsnr;		/* sync signal SNR */
	double	metric;		/* signal quality metric */
	int	reach;		/* reachability register */
	int	count;		/* bit counter */
	int	select;		/* select bits */
	char	refid[5];	/* reference identifier */
};

/*
 * The channel structure (cp) is used to mitigate between channels.
 */
struct chan {
	int	gain;		/* audio gain */
	struct sync wwv;	/* wwv station */
	struct sync wwvh;	/* wwvh station */
};

/*
 * WWV unit control structure (up)
 */
struct wwvunit {
	l_fp	timestamp;	/* audio sample timestamp */
	l_fp	tick;		/* audio sample increment */
	double	phase, freq;	/* logical clock phase and frequency */
	double	monitor;	/* audio monitor point */
#ifdef ICOM
	int	fd_icom;	/* ICOM file descriptor */
#endif /* ICOM */
	int	errflg;		/* error flags */
	int	watch;		/* watchcat */

	/*
	 * Audio codec variables
	 */
	double	comp[SIZE];	/* decompanding table */
	int	port;		/* codec port */
	int	gain;		/* codec gain */
	int	mongain;	/* codec monitor gain */
	int	clipcnt;	/* sample clipped count */

	/*
	 * Variables used to establish basic system timing
	 */
	int	avgint;		/* master time constant */
	int	tepoch;		/* sync epoch median */
	int	yepoch;		/* sync epoch */
	int	repoch;		/* buffered sync epoch */
	double	epomax;		/* second sync amplitude */
	double	eposnr;		/* second sync SNR */
	double	irig;		/* data I channel amplitude */
	double	qrig;		/* data Q channel amplitude */
	int	datapt;		/* 100 Hz ramp */
	double	datpha;		/* 100 Hz VFO control */
	int	rphase;		/* second sample counter */
	long	mphase;		/* minute sample counter */

	/*
	 * Variables used to mitigate which channel to use
	 */
	struct chan mitig[NCHAN]; /* channel data */
	struct sync *sptr;	/* station pointer */
	int	dchan;		/* data channel */
	int	schan;		/* probe channel */
	int	achan;		/* active channel */

	/*
	 * Variables used by the clock state machine
	 */
	struct decvec decvec[9]; /* decoding matrix */
	int	rsec;		/* seconds counter */
	int	digcnt;		/* count of digits synchronized */

	/*
	 * Variables used to estimate signal levels and bit/digit
	 * probabilities
	 */
	double	datsig;		/* data signal max */
	double	datsnr;		/* data signal SNR (dB) */

	/*
	 * Variables used to establish status and alarm conditions
	 */
	int	status;		/* status bits */
	int	alarm;		/* alarm flashers */
	int	misc;		/* miscellaneous timecode bits */
	int	errcnt;		/* data bit error counter */
};

/*
 * Function prototypes
 */
static	int	wwv_start	P((int, struct peer *));
static	void	wwv_shutdown	P((int, struct peer *));
static	void	wwv_receive	P((struct recvbuf *));
static	void	wwv_poll	P((int, struct peer *));

/*
 * More function prototypes
 */
static	void	wwv_epoch	P((struct peer *));
static	void	wwv_rf		P((struct peer *, double));
static	void	wwv_endpoc	P((struct peer *, int));
static	void	wwv_rsec	P((struct peer *, double));
static	void	wwv_qrz		P((struct peer *, struct sync *, int));
static	void	wwv_corr4	P((struct peer *, struct decvec *,
				    double [], double [][4]));
static	void	wwv_gain	P((struct peer *));
static	void	wwv_tsec	P((struct peer *));
static	int	timecode	P((struct wwvunit *, char *));
static	double	wwv_snr		P((double, double));
static	int	carry		P((struct decvec *));
static	int	wwv_newchan	P((struct peer *));
static	void	wwv_newgame	P((struct peer *, int));
static	double	wwv_metric	P((struct sync *));
static	void	wwv_clock	P((struct peer *));
#ifdef ICOM
static	int	wwv_qsy		P((struct peer *, int));
#endif /* ICOM */

static double qsy[NCHAN] = {2.5, 5, 10, 15, 20}; /* frequencies (MHz) */

/*
 * Transfer vector
 */
struct	refclock refclock_wwv = {
	wwv_start,		/* start up driver */
	wwv_shutdown,		/* shut down driver */
	wwv_poll,		/* transmit poll message */
	noentry,		/* not used (old wwv_control) */
	noentry,		/* initialize driver (not used) */
	noentry,		/* not used (old wwv_buginfo) */
	NOFLAGS			/* not used */
};


/*
 * wwv_start - open the devices and initialize data for processing
 */
static int
wwv_start(
	int	unit,		/* instance number (used by PCM) */
	struct peer *peer	/* peer structure pointer */
	)
{
	struct refclockproc *pp;
	struct wwvunit *up;
#ifdef ICOM
	int	temp;
#endif /* ICOM */

	/*
	 * Local variables
	 */
	int	fd;		/* file descriptor */
	int	i;		/* index */
	double	step;		/* codec adjustment */

	/*
	 * Open audio device
	 */
	fd = audio_init(DEVICE_AUDIO, AUDIO_BUFSIZ, unit);
	if (fd < 0)
		return (0);
#ifdef DEBUG
	if (debug)
		audio_show();
#endif

	/*
	 * Allocate and initialize unit structure
	 */
	if (!(up = (struct wwvunit *)emalloc(sizeof(struct wwvunit)))) {
		close(fd);
		return (0);
	}
	memset(up, 0, sizeof(struct wwvunit));
	pp = peer->procptr;
	pp->unitptr = (caddr_t)up;
	pp->io.clock_recv = wwv_receive;
	pp->io.srcclock = (caddr_t)peer;
	pp->io.datalen = 0;
	pp->io.fd = fd;
	if (!io_addclock(&pp->io)) {
		close(fd);
		free(up);
		return (0);
	}

	/*
	 * Initialize miscellaneous variables
	 */
	peer->precision = PRECISION;
	pp->clockdesc = DESCRIPTION;

	/*
	 * The companded samples are encoded sign-magnitude. The table
	 * contains all the 256 values in the interest of speed.
	 */
	up->comp[0] = up->comp[OFFSET] = 0.;
	up->comp[1] = 1.; up->comp[OFFSET + 1] = -1.;
	up->comp[2] = 3.; up->comp[OFFSET + 2] = -3.;
	step = 2.;
	for (i = 3; i < OFFSET; i++) {
		up->comp[i] = up->comp[i - 1] + step;
		up->comp[OFFSET + i] = -up->comp[i];
                if (i % 16 == 0)
		    step *= 2.;
	}
	DTOLFP(1. / SECOND, &up->tick);

	/*
	 * Initialize the decoding matrix with the radix for each digit
	 * position.
	 */
	up->decvec[MN].radix = 10;	/* minutes */
	up->decvec[MN + 1].radix = 6;
	up->decvec[HR].radix = 10;	/* hours */
	up->decvec[HR + 1].radix = 3;
	up->decvec[DA].radix = 10;	/* days */
	up->decvec[DA + 1].radix = 10;
	up->decvec[DA + 2].radix = 4;
	up->decvec[YR].radix = 10;	/* years */
	up->decvec[YR + 1].radix = 10;

#ifdef ICOM
	/*
	 * Initialize autotune if available. Note that the ICOM select
	 * code must be less than 128, so the high order bit can be used
	 * to select the line speed 0 (9600 bps) or 1 (1200 bps).
	 */
	temp = 0;
#ifdef DEBUG
	if (debug > 1)
		temp = P_TRACE;
#endif
	if (peer->ttl != 0) {
		if (peer->ttl & 0x80)
			up->fd_icom = icom_init("/dev/icom", B1200,
			    temp);
		else
			up->fd_icom = icom_init("/dev/icom", B9600,
			    temp);
		if (up->fd_icom < 0) {
			NLOG(NLOG_SYNCEVENT | NLOG_SYSEVENT)
			    msyslog(LOG_NOTICE,
			    "icom: %m");
			up->errflg = CEVNT_FAULT;
		}
	}
	if (up->fd_icom > 0) {
		if (wwv_qsy(peer, DCHAN) != 0) {
			NLOG(NLOG_SYNCEVENT | NLOG_SYSEVENT)
			    msyslog(LOG_NOTICE,
			    "icom: radio not found");
			up->errflg = CEVNT_FAULT;
			close(up->fd_icom);
			up->fd_icom = 0;
		} else {
			NLOG(NLOG_SYNCEVENT | NLOG_SYSEVENT)
			    msyslog(LOG_NOTICE,
			    "icom: autotune enabled");
		}
	}
#endif /* ICOM */

	/*
	 * Let the games begin.
	 */
	wwv_newgame(peer, DCHAN);
	return (1);
}


/*
 * wwv_shutdown - shut down the clock
 */
static void
wwv_shutdown(
	int	unit,		/* instance number (not used) */
	struct peer *peer	/* peer structure pointer */
	)
{
	struct refclockproc *pp;
	struct wwvunit *up;

	pp = peer->procptr;
	up = (struct wwvunit *)pp->unitptr;
	io_closeclock(&pp->io);
#ifdef ICOM
	if (up->fd_icom > 0)
		close(up->fd_icom);
#endif /* ICOM */
	free(up);
}


/*
 * wwv_receive - receive data from the audio device
 *
 * This routine reads input samples and adjusts the logical clock to
 * track the A/D sample clock by dropping or duplicating codec samples.
 * It also controls the A/D signal level with an AGC loop to mimimize
 * quantization noise and avoid overload.
 */
static void
wwv_receive(
	struct recvbuf *rbufp	/* receive buffer structure pointer */
	)
{
	struct peer *peer;
	struct refclockproc *pp;
	struct wwvunit *up;

	/*
	 * Local variables
	 */
	double	sample;		/* codec sample */
	u_char	*dpt;		/* buffer pointer */
	int	bufcnt;		/* buffer counter */
	l_fp	ltemp;

	peer = (struct peer *)rbufp->recv_srcclock;
	pp = peer->procptr;
	up = (struct wwvunit *)pp->unitptr;

	/*
	 * Main loop - read until there ain't no more. Note codec
	 * samples are bit-inverted.
	 */
	DTOLFP((double)rbufp->recv_length / SECOND, &ltemp);
	L_SUB(&rbufp->recv_time, &ltemp);
	up->timestamp = rbufp->recv_time;
	dpt = rbufp->recv_buffer;
	for (bufcnt = 0; bufcnt < rbufp->recv_length; bufcnt++) {
		sample = up->comp[~*dpt++ & 0xff];

		/*
		 * Clip noise spikes greater than MAXSIG. If no clips,
		 * increase the gain a tad; if the clips are too high, 
		 * decrease a tad.
		 */
		if (sample > MAXSIG) {
			sample = MAXSIG;
			up->clipcnt++;
		} else if (sample < -MAXSIG) {
			sample = -MAXSIG;
			up->clipcnt++;
		}

		/*
		 * Variable frequency oscillator. The codec oscillator
		 * runs at the nominal rate of 8000 samples per second,
		 * or 125 us per sample. A frequency change of one unit
		 * results in either duplicating or deleting one sample
		 * per second, which results in a frequency change of
		 * 125 PPM.
		 */
		up->phase += up->freq / SECOND;
		up->phase += pp->fudgetime2 / 1e6;
		if (up->phase >= .5) {
			up->phase -= 1.;
		} else if (up->phase < -.5) {
			up->phase += 1.;
			wwv_rf(peer, sample);
			wwv_rf(peer, sample);
		} else {
			wwv_rf(peer, sample);
		}
		L_ADD(&up->timestamp, &up->tick);
	}

	/*
	 * Set the input port and monitor gain for the next buffer.
	 */
	if (pp->sloppyclockflag & CLK_FLAG2)
		up->port = 2;
	else
		up->port = 1;
	if (pp->sloppyclockflag & CLK_FLAG3)
		up->mongain = MONGAIN;
	else
		up->mongain = 0;
}


/*