/*
 * refclock_wwv - clock driver for NIST WWV/H time/frequency station
 */
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#if defined(REFCLOCK) && defined(CLOCK_WWV)

#include "ntpd.h"
#include "ntp_io.h"
#include "ntp_refclock.h"
#include "ntp_calendar.h"
#include "ntp_stdlib.h"
#include "audio.h"

#include <stdio.h>
#include <ctype.h>
#include <math.h>
#ifdef HAVE_SYS_IOCTL_H
# include <sys/ioctl.h>
#endif /* HAVE_SYS_IOCTL_H */

#define ICOM 1

#ifdef ICOM
#include "icom.h"
#endif /* ICOM */

/*
 * Audio WWV/H demodulator/decoder
 *
 * This driver synchronizes the computer time using data encoded in
 * radio transmissions from NIST time/frequency stations WWV in Boulder,
 * CO, and WWVH in Kauai, HI. Transmissions are made continuously on
 * 2.5, 5, 10 and 15 MHz from WWV and WWVH, and 20 MHz from WWV. An
 * ordinary AM shortwave receiver can be tuned manually to one of these
 * frequencies or, in the case of ICOM receivers, the receiver can be
 * tuned automatically using this program as propagation conditions
 * change throughout the weasons, both day and night.
 *
 * The driver receives, demodulates and decodes the radio signals when
 * connected to the audio codec of a workstation running Solaris, SunOS
 * FreeBSD or Linux, and with a little help, other workstations with
 * similar codecs or sound cards. In this implementation, only one audio
 * driver and codec can be supported on a single machine.
 *
 * The demodulation and decoding algorithms used in this driver are
 * based on those developed for the TAPR DSP93 development board and the
 * TI 320C25 digital signal processor described in: Mills, D.L. A
 * precision radio clock for WWV transmissions. Electrical Engineering
 * Report 97-8-1, University of Delaware, August 1997, 25 pp., available
 * from www.eecis.udel.edu/~mills/reports.html. The algorithms described
 * in this report have been modified somewhat to improve performance
 * under weak signal conditions and to provide an automatic station
 * identification feature.
 *
 * The ICOM code is normally compiled in the driver. It isn't used,
 * unless the mode keyword on the server configuration command specifies
 * a nonzero ICOM ID select code. The C-IV trace is turned on if the
 * debug level is greater than one.
 *
 * Fudge factors
 *
 * Fudge flag4 causes the dubugging output described above to be
 * recorded in the clockstats file. Fudge flag2 selects the audio input
 * port, where 0 is the mike port (default) and 1 is the line-in port.
 * It does not seem useful to select the compact disc player port. Fudge
 * flag3 enables audio monitoring of the input signal. For this purpose,
 * the monitor gain is set to a default value.
 */
/*
 * General definitions. These ordinarily do not need to be changed.
 */
#define	DEVICE_AUDIO	"/dev/audio" /* audio device name */
#define	AUDIO_BUFSIZ	320	/* audio buffer size (50 ms) */
#define	PRECISION	(-10)	/* precision assumed (about 1 ms) */
#define	DESCRIPTION	"WWV/H Audio Demodulator/Decoder" /* WRU */
#define SECOND		8000	/* second epoch (sample rate) (Hz) */
#define MINUTE		(SECOND * 60) /* minute epoch */
#define OFFSET		128	/* companded sample offset */
#define SIZE		256	/* decompanding table size */
#define	MAXAMP		6000.	/* max signal level reference */
#define	MAXCLP		100	/* max clips above reference per s */
#define MAXSNR		40.	/* max SNR reference */
#define MAXFREQ		1.5	/* max frequency tolerance (187 PPM) */
#define DATCYC		170	/* data filter cycles */
#define DATSIZ		(DATCYC * MS) /* data filter size */
#define SYNCYC		800	/* minute filter cycles */
#define SYNSIZ		(SYNCYC * MS) /* minute filter size */
#define TCKCYC		5	/* tick filter cycles */
#define TCKSIZ		(TCKCYC * MS) /* tick filter size */
#define NCHAN		5	/* number of radio channels */
#define	AUDIO_PHI	5e-6	/* dispersion growth factor */

/*
 * Tunable parameters. The DGAIN parameter can be changed to fit the
 * audio response of the radio at 100 Hz. The WWV/WWVH data subcarrier
 * is transmitted at about 20 percent percent modulation; the matched
 * filter boosts it by a factor of 17 and the receiver response does
 * what it does. The compromise value works for ICOM radios. If the
 * radio is not tunable, the DCHAN parameter can be changed to fit the
 * expected best propagation frequency: higher if further from the
 * transmitter, lower if nearer. The compromise value works for the US
 * right coast. The FREQ_OFFSET parameter can be used as a frequency
 * vernier to correct codec requency if greater than MAXFREQ.
 */
#define DCHAN		3	/* default radio channel (15 Mhz) */
#define DGAIN		5.	/* subcarrier gain */
#define	FREQ_OFFSET	0.	/* codec frequency correction (PPM) */

/*
 * General purpose status bits (status)
 *
 * SELV and/or SELH are set when WWV or WWVH have been heard and cleared
 * on signal loss. SSYNC is set when the second sync pulse has been
 * acquired and cleared by signal loss. MSYNC is set when the minute
 * sync pulse has been acquired. DSYNC is set when the units digit has
 * has reached the threshold and INSYNC is set when all nine digits have
 * reached the threshold. The MSYNC, DSYNC and INSYNC bits are cleared
 * only by timeout, upon which the driver starts over from scratch.
 *
 * DGATE is lit if the data bit amplitude or SNR is below thresholds and
 * BGATE is lit if the pulse width amplitude or SNR is below thresolds.
 * LEPSEC is set during the last minute of the leap day. At the end of
 * this minute the driver inserts second 60 in the seconds state machine
 * and the minute sync slips a second.
 */
#define MSYNC		0x0001	/* minute epoch sync */
#define SSYNC		0x0002	/* second epoch sync */
#define DSYNC		0x0004	/* minute units sync */
#define INSYNC		0x0008	/* clock synchronized */
#define FGATE		0x0010	/* frequency gate */
#define DGATE		0x0020	/* data pulse amplitude error */
#define BGATE		0x0040	/* data pulse width error */
#define LEPSEC		0x1000	/* leap minute */

/*
 * Station scoreboard bits
 *
 * These are used to establish the signal quality for each of the five
 * frequencies and two stations.
 */
#define SELV		0x0100	/* WWV station select */
#define SELH		0x0200	/* WWVH station select */

/*
 * Alarm status bits (alarm)
 *
 * These bits indicate various alarm conditions, which are decoded to
 * form the quality character included in the timecode.
 */
#define CMPERR		1	/* digit or misc bit compare error */
#define LOWERR		2	/* low bit or digit amplitude or SNR */
#define NINERR		4	/* less than nine digits in minute */
#define SYNERR		8	/* not tracking second sync */

/*
 * Watchcat timeouts (watch)
 *
 * If these timeouts expire, the status bits are mashed to zero and the
 * driver starts from scratch. Suitably more refined procedures may be
 * developed in future. All these are in minutes.
 */
#define ACQSN		6	/* station acquisition timeout */
#define DATA		15	/* unit minutes timeout */
#define SYNCH		40	/* station sync timeout */
#define PANIC		(2 * 1440) /* panic timeout */

/*
 * Thresholds. These establish the minimum signal level, minimum SNR and
 * maximum jitter thresholds which establish the error and false alarm
 * rates of the driver. The values defined here may be on the
 * adventurous side in the interest of the highest sensitivity.
 */
#define MTHR		13.	/* minute sync gate (percent) */
#define TTHR		50.	/* minute sync threshold (percent) */
#define AWND		20	/* minute sync jitter threshold (ms) */
#define ATHR		2500.	/* QRZ minute sync threshold */
#define ASNR		20.	/* QRZ minute sync SNR threshold (dB) */
#define QTHR		2500.	/* QSY minute sync threshold */
#define QSNR		20.	/* QSY minute sync SNR threshold (dB) */
#define STHR		2500.	/* second sync threshold */
#define	SSNR		15.	/* second sync SNR threshold (dB) */
#define SCMP		10 	/* second sync compare threshold */
#define DTHR		1000.	/* bit threshold */
#define DSNR		10.	/* bit SNR threshold (dB) */
#define AMIN		3	/* min bit count */
#define AMAX		6	/* max bit count */
#define BTHR		1000.	/* digit threshold */
#define BSNR		3.	/* digit likelihood threshold (dB) */
#define BCMP		3	/* digit compare threshold */
#define	MAXERR		40	/* maximum error alarm */

/*
 * Tone frequency definitions. The increments are for 4.5-deg sine
 * table.
 */
#define MS		(SECOND / 1000) /* samples per millisecond */
#define IN100		((100 * 80) / SECOND) /* 100 Hz increment */
#define IN1000		((1000 * 80) / SECOND) /* 1000 Hz increment */
#define IN1200		((1200 * 80) / SECOND) /* 1200 Hz increment */

/*
 * Acquisition and tracking time constants
 */
#define MINAVG		8	/* min averaging time */
#define MAXAVG		1024	/* max averaging time */
#define FCONST		3	/* frequency time constant */
#define TCONST		16	/* data bit/digit time constant */

/*
 * Miscellaneous status bits (misc)
 *
 * These bits correspond to designated bits in the WWV/H timecode. The
 * bit probabilities are exponentially averaged over several minutes and
 * processed by a integrator and threshold.
 */
#define DUT1		0x01	/* 56 DUT .1 */
#define DUT2		0x02	/* 57 DUT .2 */
#define DUT4		0x04	/* 58 DUT .4 */
#define DUTS		0x08	/* 50 DUT sign */
#define DST1		0x10	/* 55 DST1 leap warning */
#define DST2		0x20	/* 2 DST2 DST1 delayed one day */
#define SECWAR		0x40	/* 3 leap second warning */

/*
 * The on-time synchronization point for the driver is the second epoch
 * sync pulse produced by the FIR matched filters. As the 5-ms delay of
 * these filters is compensated, the program delay is 1.1 ms due to the
 * 600-Hz IIR bandpass filter. The measured receiver delay is 4.7 ms and
 * the codec delay less than 0.2 ms. The additional propagation delay
 * specific to each receiver location can be programmed in the fudge
 * time1 and time2 values for WWV and WWVH, respectively.
 */
#define PDELAY	(.0011 + .0047 + .0002)	/* net system delay (s) */

/*
 * Table of sine values at 4.5-degree increments. This is used by the
 * synchronous matched filter demodulators.
 */
double sintab[] = {
 0.000000e+00,  7.845910e-02,  1.564345e-01,  2.334454e-01, /* 0-3 */
 3.090170e-01,  3.826834e-01,  4.539905e-01,  5.224986e-01, /* 4-7 */
 5.877853e-01,  6.494480e-01,  7.071068e-01,  7.604060e-01, /* 8-11 */
 8.090170e-01,  8.526402e-01,  8.910065e-01,  9.238795e-01, /* 12-15 */
 9.510565e-01,  9.723699e-01,  9.876883e-01,  9.969173e-01, /* 16-19 */
 1.000000e+00,  9.969173e-01,  9.876883e-01,  9.723699e-01, /* 20-23 */
 9.510565e-01,  9.238795e-01,  8.910065e-01,  8.526402e-01, /* 24-27 */
 8.090170e-01,  7.604060e-01,  7.071068e-01,  6.494480e-01, /* 28-31 */
 5.877853e-01,  5.224986e-01,  4.539905e-01,  3.826834e-01, /* 32-35 */
 3.090170e-01,  2.334454e-01,  1.564345e-01,  7.845910e-02, /* 36-39 */
-0.000000e+00, -7.845910e-02, -1.564345e-01, -2.334454e-01, /* 40-43 */
-3.090170e-01, -3.826834e-01, -4.539905e-01, -5.224986e-01, /* 44-47 */
-5.877853e-01, -6.494480e-01, -7.071068e-01, -7.604060e-01, /* 48-51 */
-8.090170e-01, -8.526402e-01, -8.910065e-01, -9.238795e-01, /* 52-55 */
-9.510565e-01, -9.723699e-01, -9.876883e-01, -9.969173e-01, /* 56-59 */
-1.000000e+00, -9.969173e-01, -9.876883e-01, -9.723699e-01, /* 60-63 */
-9.510565e-01, -9.238795e-01, -8.910065e-01, -8.526402e-01, /* 64-67 */
-8.090170e-01, -7.604060e-01, -7.071068e-01, -6.494480e-01, /* 68-71 */
-5.877853e-01, -5.224986e-01, -4.539905e-01, -3.826834e-01, /* 72-75 */
-3.090170e-01, -2.334454e-01, -1.564345e-01, -7.845910e-02, /* 76-79 */
 0.000000e+00};						    /* 80 */

/*
 * Decoder operations at the end of each second are driven by a state
 * machine. The transition matrix consists of a dispatch table indexed
 * by second number. Each entry in the table contains a case switch
 * number and argument.
 */
struct progx {
	int sw;			/* case switch number */
	int arg;		/* argument */
};

/*
 * Case switch numbers
 */
#define IDLE		0	/* no operation */
#define COEF		1	/* BCD bit */
#define COEF1		2	/* BCD bit for minute unit */
#define COEF2		3	/* BCD bit not used */
#define DECIM9		4	/* BCD digit 0-9 */
#define DECIM6		5	/* BCD digit 0-6 */
#define DECIM3		6	/* BCD digit 0-3 */
#define DECIM2		7	/* BCD digit 0-2 */
#define MSCBIT		8	/* miscellaneous bit */
#define MSC20		9	/* miscellaneous bit */		
#define MSC21		10	/* QSY probe channel */		
#define MIN1		11	/* latch time */		
#define MIN2		12	/* leap second */
#define SYNC2		13	/* latch minute sync pulse */		
#define SYNC3		14	/* latch data pulse */		

/*
 * Offsets in decoding matrix
 */
#define MN		0	/* minute digits (2) */
#define HR		2	/* hour digits (2) */
#define DA		4	/* day digits (3) */
#define YR		7	/* year digits (2) */

struct progx progx[] = {
	{SYNC2,	0},		/* 0 latch minute sync pulse */
	{SYNC3,	0},		/* 1 latch data pulse */
	{MSCBIT, DST2},		/* 2 dst2 */
	{MSCBIT, SECWAR},	/* 3 lw */
	{COEF,	0},		/* 4 1 year units */
	{COEF,	1},		/* 5 2 */
	{COEF,	2},		/* 6 4 */
	{COEF,	3},		/* 7 8 */
	{DECIM9, YR},		/* 8 */
	{IDLE,	0},		/* 9 p1 */
	{COEF1,	0},		/* 10 1 minute units */
	{COEF1,	1},		/* 11 2 */
	{COEF1,	2},		/* 12 4 */
	{COEF1,	3},		/* 13 8 */
	{DECIM9, MN},		/* 14 */
	{COEF,	0},		/* 15 10 minute tens */
	{COEF,	1},		/* 16 20 */
	{COEF,	2},		/* 17 40 */
	{COEF2,	3},		/* 18 80 (not used) */
	{DECIM6, MN + 1},	/* 19 p2 */
	{COEF,	0},		/* 20 1 hour units */
	{COEF,	1},		/* 21 2 */
	{COEF,	2},		/* 22 4 */
	{COEF,	3},		/* 23 8 */
	{DECIM9, HR},		/* 24 */
	{COEF,	0},		/* 25 10 hour tens */
	{COEF,	1},		/* 26 20 */
	{COEF2,	2},		/* 27 40 (not used) */
	{COEF2,	3},		/* 28 80 (not used) */
	{DECIM2, HR + 1},	/* 29 p3 */
	{COEF,	0},		/* 30 1 day units */
	{COEF,	1},		/* 31 2 */
	{COEF,	2},		/* 32 4 */
	{COEF,	3},		/* 33 8 */
	{DECIM9, DA},		/* 34 */
	{COEF,	0},		/* 35 10 day tens */
	{COEF,	1},		/* 36 20 */
	{COEF,	2},		/* 37 40 */
	{COEF,	3},		/* 38 80 */
	{DECIM9, DA + 1},	/* 39 p4 */
	{COEF,	0},		/* 40 100 day hundreds */
	{COEF,	1},		/* 41 200 */
	{COEF2,	2},		/* 42 400 (not used) */
	{COEF2,	3},		/* 43 800 (not used) */
	{DECIM3, DA + 2},	/* 44 */
	{IDLE,	0},		/* 45 */
	{IDLE,	0},		/* 46 */
	{IDLE,	0},		/* 47 */
	{IDLE,	0},		/* 48 */
	{IDLE,	0},		/* 49 p5 */
	{MSCBIT, DUTS},		/* 50 dut+- */
	{COEF,	0},		/* 51 10 year tens */
	{COEF,	1},		/* 52 20 */
	{COEF,	2},		/* 53 40 */
	{COEF,	3},		/* 54 80 */
	{MSC20, DST1},		/* 55 dst1 */
	{MSCBIT, DUT1},		/* 56 0.1 dut */
	{MSCBIT, DUT2},		/* 57 0.2 */
	{MSC21, DUT4},		/* 58 0.4 QSY probe channel */
	{MIN1,	0},		/* 59 p6 latch time */
	{MIN2,	0}		/* 60 leap second */
};

/*
 * BCD coefficients for maximum likelihood digit decode
 */
#define P15	1.		/* max positive number */
#define N15	-1.		/* max negative number */

/*
 * Digits 0-9
 */
#define P9	(P15 / 4)	/* mark (+1) */
#define N9	(N15 / 4)	/* space (-1) */

double bcd9[][4] = {
	{N9, N9, N9, N9}, 	/* 0 */
	{P9, N9, N9, N9}, 	/* 1 */
	{N9, P9, N9, N9}, 	/* 2 */
	{P9, P9, N9, N9}, 	/* 3 */
	{N9, N9, P9, N9}, 	/* 4 */
	{P9, N9, P9, N9}, 	/* 5 */
	{N9, P9, P9, N9}, 	/* 6 */
	{P9, P9, P9, N9}, 	/* 7 */
	{N9, N9, N9, P9}, 	/* 8 */
	{P9, N9, N9, P9}, 	/* 9 */
	{0, 0, 0, 0}		/* backstop */
};

/*
 * Digits 0-6 (minute tens)
 */
#define P6	(P15 / 3)	/* mark (+1) */
#define N6	(N15 / 3)	/* space (-1) */

double bcd6[][4] = {
	{N6, N6, N6, 0}, 	/* 0 */
	{P6, N6, N6, 0}, 	/* 1 */
	{N6, P6, N6, 0}, 	/* 2 */
	{P6, P6, N6, 0}, 	/* 3 */
	{N6, N6, P6, 0}, 	/* 4 */
	{P6, N6, P6, 0}, 	/* 5 */
	{N6, P6, P6, 0}, 	/* 6 */
	{0, 0, 0, 0}		/* backstop */
};

/*
 * Digits 0-3 (day hundreds)
 */
#define P3	(P15 / 2)	/* mark (+1) */
#define N3	(N15 / 2)	/* space (-1) */

double bcd3[][4] = {
	{N3, N3, 0, 0}, 	/* 0 */
	{P3, N3, 0, 0}, 	/* 1 */
	{N3, P3, 0, 0}, 	/* 2 */
	{P3, P3, 0, 0}, 	/* 3 */
	{0, 0, 0, 0}		/* backstop */
};

/*
 * Digits 0-2 (hour tens)
 */
#define P2	(P15 / 2)	/* mark (+1) */
#define N2	(N15 / 2)	/* space (-1) */

double bcd2[][4] = {
	{N2, N2, 0, 0}, 	/* 0 */
	{P2, N2, 0, 0}, 	/* 1 */
	{N2, P2, 0, 0}, 	/* 2 */
	{0, 0, 0, 0}		/* backstop */
};

/*
 * 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 */
	double	synmax;		/* sync signal max latched at 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	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 *));
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 /* DEBUG */

	/*
	 * 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 /* DEBUG */
	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);
	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;
	if (up == NULL)
		return;

	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 MAXAMP (6000) and
		 * record the number of clips to be used later by the
		 * AGC.
		 */
		if (sample > MAXAMP) {
			sample = MAXAMP;
			up->clipcnt++;
		} else if (sample < -MAXAMP) {
			sample = -MAXAMP;
			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 += FREQ_OFFSET / 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;
}


/*
 * wwv_poll - called by the transmit procedure
 *
 * This routine keeps track of status. If no offset samples have been
 * processed during a poll interval, a timeout event is declared. If
 * errors have have occurred during the interval, they are reported as
 * well.
 */
static void
wwv_poll(
	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;
	if (pp->coderecv == pp->codeproc)
		up->errflg = CEVNT_TIMEOUT;
	if (up->errflg)
		refclock_report(peer, up->errflg);
	up->errflg = 0;
	pp->polls++;
}


/*
 * wwv_rf - process signals and demodulate to baseband
 *
 * This routine grooms and filters decompanded raw audio samples. The
 * output signal is the 100-Hz filtered baseband data signal in
 * quadrature phase. The routine also determines the minute synch epoch,
 * as well as certain signal maxima, minima and related values.
 *
 * There are two 1-s ramps used by this program. Both count the 8000
 * logical clock samples spanning exactly one second. The epoch ramp
 * counts the samples starting at an arbitrary time. The rphase ramp
 * counts the samples starting at the 5-ms second sync pulse found
 * during the epoch ramp.
 *
 * There are two 1-m ramps used by this program. The mphase ramp counts
 * the 480,000 logical clock samples spanning exactly one minute and
 * starting at an arbitrary time. The rsec ramp counts the 60 seconds of
 * the minute starting at the 800-ms minute sync pulse found during the
 * mphase ramp. The rsec ramp drives the seconds state machine to
 * determine the bits and digits of the timecode. 
 *
 * Demodulation operations are based on three synthesized quadrature
 * sinusoids: 100 Hz for the data signal, 1000 Hz for the WWV sync
 * signal and 1200 Hz for the WWVH sync signal. These drive synchronous
 * matched filters for the data signal (170 ms at 100 Hz), WWV minute
 * sync signal (800 ms at 1000 Hz) and WWVH minute sync signal (800 ms
 * at 1200 Hz). Two additional matched filters are switched in
 * as required for the WWV second sync signal (5 cycles at 1000 Hz) and
 * WWVH second sync signal (6 cycles at 1200 Hz).
 */
static void
wwv_rf(
	struct peer *peer,	/* peerstructure pointer */
	double isig		/* input signal */
	)
{
	struct refclockproc *pp;
	struct wwvunit *up;
	struct sync *sp, *rp;

	static double lpf[5];	/* 150-Hz lpf delay line */
	double data;		/* lpf output */
	static double bpf[9];	/* 1000/1200-Hz bpf delay line */
	double syncx;		/* bpf output */
	static double mf[41];	/* 1000/1200-Hz mf delay line */
	double mfsync;		/* mf output */

	static int iptr;	/* data channel pointer */
	static double ibuf[DATSIZ]; /* data I channel delay line */
	static double qbuf[DATSIZ]; /* data Q channel delay line */

	static int jptr;	/* sync channel pointer */
	static int kptr;	/* tick channel pointer */

	static int csinptr;	/* wwv channel phase */
	static double cibuf[SYNSIZ]; /* wwv I channel delay line */
	static double cqbuf[SYNSIZ]; /* wwv Q channel delay line */
	static double ciamp;	/* wwv I channel amplitude */
	static double cqamp;	/* wwv Q channel amplitude */

	static double csibuf[TCKSIZ]; /* wwv I tick delay line */
	static double csqbuf[TCKSIZ]; /* wwv Q tick delay line */
	static double csiamp;	/* wwv I tick amplitude */
	static double csqamp;	/* wwv Q tick amplitude */

	static int hsinptr;	/* wwvh channel phase */
	static double hibuf[SYNSIZ]; /* wwvh I channel delay line */
	static double hqbuf[SYNSIZ]; /* wwvh Q channel delay line */
	static double hiamp;	/* wwvh I channel amplitude */
	static double hqamp;	/* wwvh Q channel amplitude */

	static double hsibuf[TCKSIZ]; /* wwvh I tick delay line */
	static double hsqbuf[TCKSIZ]; /* wwvh Q tick delay line */
	static double hsiamp;	/* wwvh I tick amplitude */
	static double hsqamp;	/* wwvh Q tick amplitude */

	static double epobuf[SECOND]; /* second sync comb filter */
	static double epomax, nxtmax; /* second sync amplitude buffer */
	static int epopos;	/* epoch second sync position buffer */

	static int iniflg;	/* initialization flag */
	int	pdelay;		/* propagation delay (samples) */
	int	epoch;		/* comb filter index */
	double	dtemp;
	int	i;

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

	if (!iniflg) {
		iniflg = 1;
		memset((char *)lpf, 0, sizeof(lpf));
		memset((char *)bpf, 0, sizeof(bpf));
		memset((char *)mf, 0, sizeof(mf));
		memset((char *)ibuf, 0, sizeof(ibuf));
		memset((char *)qbuf, 0, sizeof(qbuf));
		memset((char *)cibuf, 0, sizeof(cibuf));
		memset((char *)cqbuf, 0, sizeof(cqbuf));
		memset((char *)csibuf, 0, sizeof(csibuf));
		memset((char *)csqbuf, 0, sizeof(csqbuf));
		memset((char *)hibuf, 0, sizeof(hibuf));
		memset((char *)hqbuf, 0, sizeof(hqbuf));
		memset((char *)hsibuf, 0, sizeof(hsibuf));
		memset((char *)hsqbuf, 0, sizeof(hsqbuf));
		memset((char *)epobuf, 0, sizeof(epobuf));
	}

	/*
	 * Baseband data demodulation. The 100-Hz subcarrier is
	 * extracted using a 150-Hz IIR lowpass filter. This attenuates
	 * the 1000/1200-Hz sync signals, as well as the 440-Hz and
	 * 600-Hz tones and most of the noise and voice modulation
	 * components.
	 *
	 * The subcarrier is transmitted 10 dB down from the carrier.
	 * The DGAIN parameter can be adjusted for this and to
	 * compensate for the radio audio response at 100 Hz.
	 *
	 * Matlab IIR 4th-order IIR elliptic, 150 Hz lowpass, 0.2 dB
	 * passband ripple, -50 dB stopband ripple.
	 */
	data = (lpf[4] = lpf[3]) * 8.360961e-01;
	data += (lpf[3] = lpf[2]) * -3.481740e+00;
	data += (lpf[2] = lpf[1]) * 5.452988e+00;
	data += (lpf[1] = lpf[0]) * -3.807229e+00;
	lpf[0] = isig * DGAIN - data;
	data = lpf[0] * 3.281435e-03
	    + lpf[1] * -1.149947e-02
	    + lpf[2] * 1.654858e-02
	    + lpf[3] * -1.149947e-02
	    + lpf[4] * 3.281435e-03;

	/*
	 * The 100-Hz data signal is demodulated using a pair of
	 * quadrature multipliers, matched filters and a phase lock
	 * loop. The I and Q quadrature data signals are produced by
	 * multiplying the filtered signal by 100-Hz sine and cosine
	 * signals, respectively. The signals are processed by 170-ms
	 * synchronous matched filters to produce the amplitude and
	 * phase signals used by the demodulator. The signals are scaled
	 * to produce unit energy at the maximum value.
	 */
	i = up->datapt;
	up->datapt = (up->datapt + IN100) % 80;
	dtemp = sintab[i] * data / (MS / 2. * DATCYC);
	up->irig -= ibuf[iptr];
	ibuf[iptr] = dtemp;
	up->irig += dtemp;

	i = (i + 20) % 80;
	dtemp = sintab[i] * data / (MS / 2. * DATCYC);
	up->qrig -= qbuf[iptr];
	qbuf[iptr] = dtemp;
	up->qrig += dtemp;
	iptr = (iptr + 1) % DATSIZ;

	/*
	 * Baseband sync demodulation. The 1000/1200 sync signals are
	 * extracted using a 600-Hz IIR bandpass filter. This removes
	 * the 100-Hz data subcarrier, as well as the 440-Hz and 600-Hz
	 * tones and most of the noise and voice modulation components.
	 *
	 * Matlab 4th-order IIR elliptic, 800-1400 Hz bandpass, 0.2 dB
	 * passband ripple, -50 dB stopband ripple.
	 */
	syncx = (bpf[8] = bpf[7]) * 4.897278e-01;
	syncx += (bpf[7] = bpf[6]) * -2.765914e+00;
	syncx += (bpf[6] = bpf[5]) * 8.110921e+00;
	syncx += (bpf[5] = bpf[4]) * -1.517732e+01;
	syncx += (bpf[4] = bpf[3]) * 1.975197e+01;
	syncx += (bpf[3] = bpf[2]) * -1.814365e+01;
	syncx += (bpf[2] = bpf[1]) * 1.159783e+01;
	syncx += (bpf[1] = bpf[0]) * -4.735040e+00;
	bpf[0] = isig - syncx;
	syncx = bpf[0] * 8.203628e-03
	    + bpf[1] * -2.375732e-02
	    + bpf[2] * 3.353214e-02
	    + bpf[3] * -4.080258e-02
	    + bpf[4] * 4.605479e-02
	    + bpf[5] * -4.080258e-02
	    + bpf[6] * 3.353214e-02
	    + bpf[7] * -2.375732e-02
	    + bpf[8] * 8.203628e-03;

	/*
	 * The 1000/1200 sync signals are demodulated using a pair of
	 * quadrature multipliers and matched filters. However,
	 * synchronous demodulation at these frequencies is impractical,
	 * so only the signal amplitude is used. The I and Q quadrature
	 * sync signals are produced by multiplying the filtered signal
	 * by 1000-Hz (WWV) and 1200-Hz (WWVH) sine and cosine signals,
	 * respectively. The WWV and WWVH signals are processed by 800-
	 * ms synchronous matched filters and combined to produce the
	 * minute sync signal and detect which one (or both) the WWV or
	 * WWVH signal is present. The WWV and WWVH signals are also
	 * processed by 5-ms synchronous matched filters and combined to
	 * produce the second sync signal. The signals are scaled to
	 * produce unit energy at the maximum value.
	 *
	 * Note the master timing ramps, which run continuously. The
	 * minute counter (mphase) counts the samples in the minute,
	 * while the second counter (epoch) counts the samples in the
	 * second.
	 */
	up->mphase = (up->mphase + 1) % MINUTE;
	epoch = up->mphase % SECOND;

	/*
	 * WWV
	 */
	i = csinptr;
	csinptr = (csinptr + IN1000) % 80;

	dtemp = sintab[i] * syncx / (MS / 2.);
	ciamp -= cibuf[jptr];
	cibuf[jptr] = dtemp;
	ciamp += dtemp;
	csiamp -= csibuf[kptr];
	csibuf[kptr] = dtemp;
	csiamp += dtemp;

	i = (i + 20) % 80;
	dtemp = sintab[i] * syncx / (MS / 2.);
	cqamp -= cqbuf[jptr];
	cqbuf[jptr] = dtemp;
	cqamp += dtemp;
	csqamp -= csqbuf[kptr];
	csqbuf[kptr] = dtemp;
	csqamp += dtemp;

	sp = &up->mitig[up->achan].wwv;
	sp->amp = sqrt(ciamp * ciamp + cqamp * cqamp) / SYNCYC;
	if (!(up->status & MSYNC))
		wwv_qrz(peer, sp, (int)(pp->fudgetime1 * SECOND));

	/*
	 * WWVH
	 */
	i = hsinptr;
	hsinptr = (hsinptr + IN1200) % 80;

	dtemp = sintab[i] * syncx / (MS / 2.);
	hiamp -= hibuf[jptr];
	hibuf[jptr] = dtemp;
	hiamp += dtemp;
	hsiamp -= hsibuf[kptr];
	hsibuf[kptr] = dtemp;
	hsiamp += dtemp;

	i = (i + 20) % 80;
	dtemp = sintab[i] * syncx / (MS / 2.);
	hqamp -= hqbuf[jptr];
	hqbuf[jptr] = dtemp;
	hqamp += dtemp;
	hsqamp -= hsqbuf[kptr];
	hsqbuf[kptr] = dtemp;
	hsqamp += dtemp;

	rp = &up->mitig[up->achan].wwvh;
	rp->amp = sqrt(hiamp * hiamp + hqamp * hqamp) / SYNCYC;
	if (!(up->status & MSYNC))
		wwv_qrz(peer, rp, (int)(pp->fudgetime2 * SECOND));
	jptr = (jptr + 1) % SYNSIZ;
	kptr = (kptr + 1) % TCKSIZ;

	/*
	 * The following section is called once per minute. It does
	 * housekeeping and timeout functions and empties the dustbins.
	 */
	if (up->mphase == 0) {
		up->watch++;
		if (!(up->status & MSYNC)) {

			/*
			 * If minute sync has not been acquired before
			 * ACQSN timeout (6 min), or if no signal is
			 * heard, the program cycles to the next
			 * frequency and tries again.
			 */
			if (!wwv_newchan(peer))
				up->watch = 0;
#ifdef ICOM
			if (up->fd_icom > 0)
				wwv_qsy(peer, up->dchan);
#endif /* ICOM */
		} else {

			/*
			 * If the leap bit is set, set the minute epoch
			 * back one second so the station processes
			 * don't miss a beat.
			 */
			if (up->status & LEPSEC) {
				up->mphase -= SECOND;
				if (up->mphase < 0)
					up->mphase += MINUTE;
			}
		}
	}

	/*
	 * When the channel metric reaches threshold and the second
	 * counter matches the minute epoch within the second, the
	 * driver has synchronized to the station. The second number is
	 * the remaining seconds until the next minute epoch, while the
	 * sync epoch is zero. Watch out for the first second; if
	 * already synchronized to the second, the buffered sync epoch
	 * must be set.
	 *
	 * Note the guard interval is 200 ms; if for some reason the
	 * clock drifts more than that, it might wind up in the wrong
	 * second. If the maximum frequency error is not more than about
	 * 1 PPM, the clock can go as much as two days while still in
	 * the same second.
	 */
	if (up->status & MSYNC) {
		wwv_epoch(peer);
	} else if (up->sptr != NULL) {
		sp = up->sptr;
		if (sp->metric >= TTHR && epoch == sp->mepoch % SECOND) 		    {
			up->rsec = (60 - sp->mepoch / SECOND) % 60;
			up->rphase = 0;
			up->status |= MSYNC;
			up->watch = 0;
			if (!(up->status & SSYNC))
				up->repoch = up->yepoch = epoch;
			else
				up->repoch = up->yepoch;
			
		}
	}

	/*
	 * The second sync pulse is extracted using 5-ms (40 sample) FIR
	 * matched filters at 1000 Hz for WWV or 1200 Hz for WWVH. This
	 * pulse is used for the most precise synchronization, since if
	 * provides a resolution of one sample (125 us). The filters run
	 * only if the station has been reliably determined.
	 */
	if (up->status & SELV) {
		pdelay = (int)(pp->fudgetime1 * SECOND);
		mfsync = sqrt(csiamp * csiamp + csqamp * csqamp) /
		    TCKCYC;
	} else if (up->status & SELH) {
		pdelay = (int)(pp->fudgetime2 * SECOND);
		mfsync = sqrt(hsiamp * hsiamp + hsqamp * hsqamp) /
		    TCKCYC;
	} else {
		pdelay = 0;
		mfsync = 0;
	}

	/*
	 * Enhance the seconds sync pulse using a 1-s (8000-sample) comb
	 * filter. Correct for the FIR matched filter delay, which is 5
	 * ms for both the WWV and WWVH filters, and also for the
	 * propagation delay. Once each second look for second sync. If
	 * not in minute sync, fiddle the codec gain. Note the SNR is
	 * computed from the maximum sample and the envelope of the
	 * sample 6 ms before it, so if we slip more than a cycle the
	 * SNR should plummet. The signal is scaled to produce unit
	 * energy at the maximum value.
	 */
	dtemp = (epobuf[epoch] += (mfsync - epobuf[epoch]) /
	    up->avgint);
	if (dtemp > epomax) {
		int	j;

		epomax = dtemp;
		epopos = epoch;
		j = epoch - 6 * MS;
		if (j < 0)
			j += SECOND;
		nxtmax = fabs(epobuf[j]);
	}
	if (epoch == 0) {
		up->epomax = epomax;
		up->eposnr = wwv_snr(epomax, nxtmax);
		epopos -= pdelay + TCKCYC * MS;
		if (epopos < 0)
			epopos += SECOND;
		wwv_endpoc(peer, epopos);
		if (!(up->status & SSYNC))
			up->alarm |= SYNERR;
		epomax = 0;
		if (!(up->status & MSYNC))
			wwv_gain(peer);
	}
}


/*
 * wwv_qrz - identify and acquire WWV/WWVH minute sync pulse
 *
 * This routine implements a virtual station process used to acquire
 * minute sync and to mitigate among the ten frequency and station
 * combinations. During minute sync acquisition the process probes each
 * frequency and station in turn for the minute pulse, which
 * involves searching through the entire 480,000-sample minute. The
 * process finds the maximum signal and RMS noise plus signal. Then, the
 * actual noise is determined by subtracting the energy of the matched
 * filter.
 *
 * Students of radar receiver technology will discover this algorithm
 * amounts to a range-gate discriminator. A valid pulse must have peak
 * amplitude at least QTHR (2500) and SNR at least QSNR (20) dB and the
 * difference between the current and previous epoch must be less than
 * AWND (20 ms). Note that the discriminator peak occurs about 800 ms
 * into the second, so the timing is retarded to the previous second
 * epoch.
 */
static void
wwv_qrz(
	struct peer *peer,	/* peer structure pointer */
	struct sync *sp,	/* sync channel structure */
	int	pdelay		/* propagation delay (samples) */
	)
{
	struct refclockproc *pp;
	struct wwvunit *up;
	char	tbuf[80];	/* monitor buffer */
	long	epoch;

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

	/*
	 * Find the sample with peak amplitude, which defines the minute
	 * epoch. Accumulate all samples to determine the total noise
	 * energy.
	 */
	epoch = up->mphase - pdelay - SYNSIZ;
	if (epoch < 0)
		epoch += MINUTE;
	if (sp->amp > sp->maxeng) {
		sp->maxeng = sp->amp;
		sp->pos = epoch;
	}
	sp->noieng += sp->amp;

	/*
	 * At the end of the minute, determine the epoch of the minute
	 * sync pulse, as well as the difference between the current and
	 * previous epoches due to the intrinsic frequency error plus
	 * jitter. When calculating the SNR, subtract the pulse energy
	 * from the total noise energy and then normalize.
	 */
	if (up->mphase == 0) {
		sp->synmax = sp->maxeng;
		sp->synsnr = wwv_snr(sp->synmax, (sp->noieng -
		    sp->synmax) / MINUTE);
		if (sp->count == 0)
			sp->lastpos = sp->pos;
		epoch = (sp->pos - sp->lastpos) % MINUTE;
		sp->reach <<= 1;
		if (sp->reach & (1 << AMAX))
			sp->count--;
		if (sp->synmax > ATHR && sp->synsnr > ASNR) {
			if (abs(epoch) < AWND * MS) {
				sp->reach |= 1;
				sp->count++;
				sp->mepoch = sp->lastpos = sp->pos;
			} else if (sp->count == 1) {
				sp->lastpos = sp->pos;
			}
		}
		if (up->watch > ACQSN)
			sp->metric = 0;
		else
			sp->metric = wwv_metric(sp);
		if (pp->sloppyclockflag & CLK_FLAG4) {
			sprintf(tbuf,
			    "wwv8 %04x %3d %s %04x %.0f %.0f/%.1f %4ld %4ld",
			    up->status, up->gain, sp->refid,
			    sp->reach & 0xffff, sp->metric, sp->synmax,
			    sp->synsnr, sp->pos % SECOND, epoch);
			record_clock_stats(&peer->srcadr, tbuf);
#ifdef DEBUG
			if (debug)
				printf("%s\n", tbuf);
#endif /* DEBUG */
		}
		sp->maxeng = sp->noieng = 0;
	}
}


/*
 * wwv_endpoc - identify and acquire second sync pulse
 *
 * This routine is called at the end of the second sync interval. It
 * determines the second sync epoch position within the second and
 * disciplines the sample clock using a frequency-lock loop (FLL).
 *
 * Second sync is determined in the RF input routine as the maximum
 * over all 8000 samples in the second comb filter. To assure accurate
 * and reliable time and frequency discipline, this routine performs a
 * great deal of heavy-handed heuristic data filtering and grooming.
 */
static void
wwv_endpoc(
	struct peer *peer,	/* peer structure pointer */
	int epopos		/* epoch max position */
	)
{
	struct refclockproc *pp;
	struct wwvunit *up;
	static int epoch_mf[3]; /* epoch median filter */
	static int tepoch;	/* current second epoch */
 	static int xepoch;	/* last second epoch */
 	static int zepoch;	/* last run epoch */
	static int zcount;	/* last run end time */
	static int scount;	/* seconds counter */
	static int syncnt;	/* run length counter */
	static int maxrun;	/* longest run length */
	static int mepoch;	/* longest run end epoch */
	static int mcount;	/* longest run end time */
	static int avgcnt;	/* averaging interval counter */
	static int avginc;	/* averaging ratchet */
	static int iniflg;	/* initialization flag */
	char tbuf[80];		/* monitor buffer */
	double dtemp;
	int tmp2;

	pp = peer->procptr;
	up = (struct wwvunit *)pp->unitptr;
	if (!iniflg) {
		iniflg = 1;
		memset((char *)epoch_mf, 0, sizeof(epoch_mf));
	}

	/*
	 * If the signal amplitude or SNR fall below thresholds, dim the
	 * second sync lamp and wait for hotter ions. If no stations are
	 * heard, we are either in a probe cycle or the ions are really
	 * cold. 
	 */
	scount++;
	if (up->epomax < STHR || up->eposnr < SSNR) {
		up->status &= ~(SSYNC | FGATE);
		avgcnt = syncnt = maxrun = 0;
		return;
	}
	if (!(up->status & (SELV | SELH)))
		return;

	/*
	 * A three-stage median filter is used to help denoise the
	 * second sync pulse. The median sample becomes the candidate
	 * epoch.
	 */
	epoch_mf[2] = epoch_mf[1];
	epoch_mf[1] = epoch_mf[0];
	epoch_mf[0] = epopos;
	if (epoch_mf[0] > epoch_mf[1]) {
		if (epoch_mf[1] > epoch_mf[2])
			tepoch = epoch_mf[1];	/* 0 1 2 */
		else if (epoch_mf[2] > epoch_mf[0])
			tepoch = epoch_mf[0];	/* 2 0 1 */
		else
			tepoch = epoch_mf[2];	/* 0 2 1 */
	} else {
		if (epoch_mf[1] < epoch_mf[2])
			tepoch = epoch_mf[1];	/* 2 1 0 */
		else if (epoch_mf[2] < epoch_mf[0])
			tepoch = epoch_mf[0];	/* 1 0 2 */
		else
			tepoch = epoch_mf[2];	/* 1 2 0 */
	}


	/*
	 * If the epoch candidate is the same as the last one, increment
	 * the run counter. If not, save the length, epoch and end
	 * time of the current run for use later and reset the counter.
	 * The epoch is considered valid if the run is at least SCMP
	 * (10) s, the minute is synchronized and the interval since the
	 * last epoch  is not greater than the averaging interval. Thus,
	 * after a long absence, the program will wait a full averaging
	 * interval while the comb filter charges up and noise
	 * dissapates..
	 */
	tmp2 = (tepoch - xepoch) % SECOND;
	if (tmp2 == 0) {
		syncnt++;
		if (syncnt > SCMP && up->status & MSYNC && (up->status &
		    FGATE || scount - zcount <= up->avgint)) {
			up->status |= SSYNC;
			up->yepoch = tepoch;
		}
	} else if (syncnt >= maxrun) {
		maxrun = syncnt;
		mcount = scount;
		mepoch = xepoch;
		syncnt = 0;
	}
	if ((pp->sloppyclockflag & CLK_FLAG4) && !(up->status & MSYNC))
	    {
		sprintf(tbuf,
		    "wwv1 %04x %3d %4d %5.0f %5.1f %5d %4d %4d %4d",
		    up->status, up->gain, tepoch, up->epomax,
		    up->eposnr, tmp2, avgcnt, syncnt,
		    maxrun);
		record_clock_stats(&peer->srcadr, tbuf);
#ifdef DEBUG
		if (debug)
			printf("%s\n", tbuf);
#endif /* DEBUG */
	}
	avgcnt++;
	if (avgcnt < up->avgint) {
		xepoch = tepoch;
		return;
	}

	/*
	 * The sample clock frequency is disciplined using a first-order
	 * feedback loop with time constant consistent with the Allan
	 * intercept of typical computer clocks. During each averaging
	 * interval the candidate epoch at the end of the longest run is
	 * determined. If the longest run is zero, all epoches in the
	 * interval are different, so the candidate epoch is the current
	 * epoch. The frequency update is computed from the candidate
	 * epoch difference (125-us units) and time difference (seconds)
	 * between updates.
	 */
	if (syncnt >= maxrun) {
		maxrun = syncnt;
		mcount = scount;
		mepoch = xepoch;
	}
	xepoch = tepoch;
	if (maxrun == 0) {
		mepoch = tepoch;
		mcount = scount;
	}

	/*
	 * The master clock runs at the codec sample frequency of 8000
	 * Hz, so the intrinsic time resolution is 125 us. The frequency
	 * resolution ranges from 18 PPM at the minimum averaging
	 * interval of 8 s to 0.12 PPM at the maximum interval of 1024
	 * s. An offset update is determined at the end of the longest
	 * run in each averaging interval. The frequency adjustment is
	 * computed from the difference between offset updates and the
	 * interval between them.
	 *
	 * The maximum frequency adjustment ranges from 187 PPM at the
	 * minimum interval to 1.5 PPM at the maximum. If the adjustment
	 * exceeds the maximum, the update is discarded and the
	 * hysteresis counter is decremented. Otherwise, the frequency
	 * is incremented by the adjustment, but clamped to the maximum
	 * 187.5 PPM. If the update is less than half the maximum, the
	 * hysteresis counter is incremented. If the counter increments
	 * to +3, the averaging interval is doubled and the counter set
	 * to zero; if it decrements to -3, the interval is halved and
	 * the counter set to zero.
	 */
	dtemp = (mepoch - zepoch) % SECOND;
	if (up->status & FGATE) {
		if (abs(dtemp) < MAXFREQ * MINAVG) {
			up->freq += (dtemp / 2.) / ((mcount - zcount) *
			    FCONST);
			if (up->freq > MAXFREQ)
				up->freq = MAXFREQ;
			else if (up->freq < -MAXFREQ)
				up->freq = -MAXFREQ;
			if (abs(dtemp) < MAXFREQ * MINAVG / 2.) {
				if (avginc < 3) {
					avginc++;
				} else {
					if (up->avgint < MAXAVG) {
						up->avgint <<= 1;
						avginc = 0;
					}
				}
			}
		} else {
			if (avginc > -3) {
				avginc--;
			} else {
				if (up->avgint > MINAVG) {
					up->avgint >>= 1;
					avginc = 0;
				}
			}
		}
	}
	if (pp->sloppyclockflag & CLK_FLAG4) {
		sprintf(tbuf,
		    "wwv2 %04x %5.0f %5.1f %5d %4d %4d %4d %4.0f %7.2f",
		    up->status, up->epomax, up->eposnr, mepoch,
		    up->avgint, maxrun, mcount - zcount, dtemp,
		    up->freq * 1e6 / SECOND);
		r…