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/contrib/ntp/ntpd/refclock_chu.c

https://bitbucket.org/freebsd/freebsd-head/
C | 1687 lines | 1044 code | 124 blank | 519 comment | 187 complexity | 80c4a4fc3e837b9804bf43bab4d88afd MD5 | raw file
   1/*
   2 * refclock_chu - clock driver for Canadian CHU time/frequency station
   3 */
   4#ifdef HAVE_CONFIG_H
   5#include <config.h>
   6#endif
   7
   8#if defined(REFCLOCK) && defined(CLOCK_CHU)
   9
  10#include "ntpd.h"
  11#include "ntp_io.h"
  12#include "ntp_refclock.h"
  13#include "ntp_calendar.h"
  14#include "ntp_stdlib.h"
  15
  16#include <stdio.h>
  17#include <ctype.h>
  18#include <math.h>
  19
  20#ifdef HAVE_AUDIO
  21#include "audio.h"
  22#endif /* HAVE_AUDIO */
  23
  24#define ICOM 	1		/* undefine to suppress ICOM code */
  25
  26#ifdef ICOM
  27#include "icom.h"
  28#endif /* ICOM */
  29
  30/*
  31 * Audio CHU demodulator/decoder
  32 *
  33 * This driver synchronizes the computer time using data encoded in
  34 * radio transmissions from Canadian time/frequency station CHU in
  35 * Ottawa, Ontario. Transmissions are made continuously on 3330 kHz,
  36 * 7335 kHz and 14670 kHz in upper sideband, compatible AM mode. An
  37 * ordinary shortwave receiver can be tuned manually to one of these
  38 * frequencies or, in the case of ICOM receivers, the receiver can be
  39 * tuned automatically using this program as propagation conditions
  40 * change throughout the day and night.
  41 *
  42 * The driver receives, demodulates and decodes the radio signals when
  43 * connected to the audio codec of a suported workstation hardware and
  44 * operating system. These include Solaris, SunOS, FreeBSD, NetBSD and
  45 * Linux. In this implementation, only one audio driver and codec can be
  46 * supported on a single machine.
  47 *
  48 * The driver can be compiled to use a Bell 103 compatible modem or
  49 * modem chip to receive the radio signal and demodulate the data.
  50 * Alternatively, the driver can be compiled to use the audio codec of
  51 * the Sun workstation or another with compatible audio drivers. In the
  52 * latter case, the driver implements the modem using DSP routines, so
  53 * the radio can be connected directly to either the microphone on line
  54 * input port. In either case, the driver decodes the data using a
  55 * maximum likelihood technique which exploits the considerable degree
  56 * of redundancy available to maximize accuracy and minimize errors.
  57 *
  58 * The CHU time broadcast includes an audio signal compatible with the
  59 * Bell 103 modem standard (mark = 2225 Hz, space = 2025 Hz). It consist
  60 * of nine, ten-character bursts transmitted at 300 bps and beginning
  61 * each second from second 31 to second 39 of the minute. Each character
  62 * consists of eight data bits plus one start bit and two stop bits to
  63 * encode two hex digits. The burst data consist of five characters (ten
  64 * hex digits) followed by a repeat of these characters. In format A,
  65 * the characters are repeated in the same polarity; in format B, the
  66 * characters are repeated in the opposite polarity.
  67 *
  68 * Format A bursts are sent at seconds 32 through 39 of the minute in
  69 * hex digits
  70 *
  71 *	6dddhhmmss6dddhhmmss
  72 *
  73 * The first ten digits encode a frame marker (6) followed by the day
  74 * (ddd), hour (hh in UTC), minute (mm) and the second (ss). Since
  75 * format A bursts are sent during the third decade of seconds the tens
  76 * digit of ss is always 3. The driver uses this to determine correct
  77 * burst synchronization. These digits are then repeated with the same
  78 * polarity.
  79 *
  80 * Format B bursts are sent at second 31 of the minute in hex digits
  81 *
  82 *	xdyyyyttaaxdyyyyttaa
  83 *
  84 * The first ten digits encode a code (x described below) followed by
  85 * the DUT1 (d in deciseconds), Gregorian year (yyyy), difference TAI -
  86 * UTC (tt) and daylight time indicator (aa) peculiar to Canada. These
  87 * digits are then repeated with inverted polarity.
  88 *
  89 * The x is coded
  90 *
  91 * 1 Sign of DUT (0 = +)
  92 * 2 Leap second warning. One second will be added.
  93 * 4 Leap second warning. One second will be subtracted.
  94 * 8 Even parity bit for this nibble.
  95 *
  96 * By design, the last stop bit of the last character in the burst
  97 * coincides with 0.5 second. Since characters have 11 bits and are
  98 * transmitted at 300 bps, the last stop bit of the first character
  99 * coincides with 0.5 - 10 * 11/300 = 0.133 second. Depending on the
 100 * UART, character interrupts can vary somewhere between the beginning
 101 * of bit 9 and end of bit 11. These eccentricities can be corrected
 102 * along with the radio propagation delay using fudge time 1.
 103 *
 104 * Debugging aids
 105 *
 106 * The timecode format used for debugging and data recording includes
 107 * data helpful in diagnosing problems with the radio signal and serial
 108 * connections. With debugging enabled (-d on the ntpd command line),
 109 * the driver produces one line for each burst in two formats
 110 * corresponding to format A and B. Following is format A:
 111 *
 112 *	n b f s m code
 113 *
 114 * where n is the number of characters in the burst (0-11), b the burst
 115 * distance (0-40), f the field alignment (-1, 0, 1), s the
 116 * synchronization distance (0-16), m the burst number (2-9) and code
 117 * the burst characters as received. Note that the hex digits in each
 118 * character are reversed, so the burst
 119 *
 120 *	10 38 0 16 9 06851292930685129293
 121 *
 122 * is interpreted as containing 11 characters with burst distance 38,
 123 * field alignment 0, synchronization distance 16 and burst number 9.
 124 * The nibble-swapped timecode shows day 58, hour 21, minute 29 and
 125 * second 39.
 126 *
 127 * When the audio driver is compiled, format A is preceded by
 128 * the current gain (0-255) and relative signal level (0-9999). The
 129 * receiver folume control should be set so that the gain is somewhere
 130 * near the middle of the range 0-255, which results in a signal level
 131 * near 1000.
 132 *
 133 * Following is format B:
 134 * 
 135 *	n b s code
 136 *
 137 * where n is the number of characters in the burst (0-11), b the burst
 138 * distance (0-40), s the synchronization distance (0-40) and code the
 139 * burst characters as received. Note that the hex digits in each
 140 * character are reversed and the last ten digits inverted, so the burst
 141 *
 142 *	11 40 1091891300ef6e76ecff
 143 *
 144 * is interpreted as containing 11 characters with burst distance 40.
 145 * The nibble-swapped timecode shows DUT1 +0.1 second, year 1998 and TAI
 146 * - UTC 31 seconds.
 147 *
 148 * In addition to the above, the reference timecode is updated and
 149 * written to the clockstats file and debug score after the last burst
 150 * received in the minute. The format is
 151 *
 152 *	qq yyyy ddd hh:mm:ss nn dd tt
 153 *
 154 * where qq are the error flags, as described below, yyyy is the year,
 155 * ddd the day, hh:mm:ss the time of day, nn the number of format A
 156 * bursts received during the previous minute, dd the decoding distance
 157 * and tt the number of timestamps. The error flags are cleared after
 158 * every update.
 159 *
 160 * Fudge factors
 161 *
 162 * For accuracies better than the low millisceconds, fudge time1 can be
 163 * set to the radio propagation delay from CHU to the receiver. This can
 164 * be done conviently using the minimuf program.
 165 *
 166 * Fudge flag4 causes the dubugging output described above to be
 167 * recorded in the clockstats file. When the audio driver is compiled,
 168 * fudge flag2 selects the audio input port, where 0 is the mike port
 169 * (default) and 1 is the line-in port. It does not seem useful to
 170 * select the compact disc player port. Fudge flag3 enables audio
 171 * monitoring of the input signal. For this purpose, the monitor gain is
 172 * set to a default value.
 173 *
 174 * The audio codec code is normally compiled in the driver if the
 175 * architecture supports it (HAVE_AUDIO defined), but is used only if
 176 * the link /dev/chu_audio is defined and valid. The serial port code is
 177 * always compiled in the driver, but is used only if the autdio codec
 178 * is not available and the link /dev/chu%d is defined and valid.
 179 *
 180 * The ICOM code is normally compiled in the driver if selected (ICOM
 181 * defined), but is used only if the link /dev/icom%d is defined and
 182 * valid and the mode keyword on the server configuration command
 183 * specifies a nonzero mode (ICOM ID select code). The C-IV speed is
 184 * 9600 bps if the high order 0x80 bit of the mode is zero and 1200 bps
 185 * if one. The C-IV trace is turned on if the debug level is greater
 186 * than one.
 187 */
 188/*
 189 * Interface definitions
 190 */
 191#define	SPEED232	B300	/* uart speed (300 baud) */
 192#define	PRECISION	(-10)	/* precision assumed (about 1 ms) */
 193#define	REFID		"CHU"	/* reference ID */
 194#define	DEVICE		"/dev/chu%d" /* device name and unit */
 195#define	SPEED232	B300	/* UART speed (300 baud) */
 196#ifdef ICOM
 197#define TUNE		.001	/* offset for narrow filter (kHz) */
 198#define DWELL		5	/* minutes in a probe cycle */
 199#define NCHAN		3	/* number of channels */
 200#define ISTAGE		3	/* number of integrator stages */
 201#endif /* ICOM */
 202
 203#ifdef HAVE_AUDIO
 204/*
 205 * Audio demodulator definitions
 206 */
 207#define SECOND		8000	/* nominal sample rate (Hz) */
 208#define BAUD		300	/* modulation rate (bps) */
 209#define OFFSET		128	/* companded sample offset */
 210#define SIZE		256	/* decompanding table size */
 211#define	MAXAMP		6000.	/* maximum signal level */
 212#define	MAXCLP		100	/* max clips above reference per s */
 213#define LIMIT		1000.	/* soft limiter threshold */
 214#define AGAIN		6.	/* baseband gain */
 215#define LAG		10	/* discriminator lag */
 216#define	DEVICE_AUDIO	"/dev/audio" /* device name */
 217#define	DESCRIPTION	"CHU Audio/Modem Receiver" /* WRU */
 218#define	AUDIO_BUFSIZ	240	/* audio buffer size (30 ms) */
 219#else
 220#define	DESCRIPTION	"CHU Modem Receiver" /* WRU */
 221#endif /* HAVE_AUDIO */
 222
 223/*
 224 * Decoder definitions
 225 */
 226#define CHAR		(11. / 300.) /* character time (s) */
 227#define	FUDGE		.185	/* offset to first stop bit (s) */
 228#define BURST		11	/* max characters per burst */
 229#define MINCHAR		9	/* min characters per burst */
 230#define MINDIST		28	/* min burst distance (of 40)  */
 231#define MINBURST	4	/* min bursts in minute */
 232#define MINSYNC		8	/* min sync distance (of 16) */
 233#define MINSTAMP	20	/* min timestamps (of 60) */
 234#define METRIC		50.	/* min channel metric */
 235#define PANIC		1440	/* panic timeout (m) */
 236#define HOLD		30	/* reach hold (m) */
 237
 238/*
 239 * Hex extension codes (>= 16)
 240 */
 241#define HEX_MISS	16	/* miss _ */
 242#define HEX_SOFT	17	/* soft error * */
 243#define HEX_HARD	18	/* hard error = */
 244
 245/*
 246 * Status bits (status)
 247 */
 248#define RUNT		0x0001	/* runt burst */
 249#define NOISE		0x0002	/* noise burst */
 250#define BFRAME		0x0004	/* invalid format B frame sync */
 251#define BFORMAT		0x0008	/* invalid format B data */
 252#define AFRAME		0x0010	/* invalid format A frame sync */
 253#define AFORMAT		0x0020	/* invalid format A data */
 254#define DECODE		0x0040	/* invalid data decode */
 255#define STAMP		0x0080	/* too few timestamps */
 256#define AVALID		0x0100	/* valid A frame */
 257#define BVALID		0x0200	/* valid B frame */
 258#define INSYNC		0x0400	/* clock synchronized */
 259
 260/*
 261 * Alarm status bits (alarm)
 262 *
 263 * These alarms are set at the end of a minute in which at least one
 264 * burst was received. SYNERR is raised if the AFRAME or BFRAME status
 265 * bits are set during the minute, FMTERR is raised if the AFORMAT or
 266 * BFORMAT status bits are set, DECERR is raised if the DECODE status
 267 * bit is set and TSPERR is raised if the STAMP status bit is set.
 268 */
 269#define SYNERR		0x01	/* frame sync error */
 270#define FMTERR		0x02	/* data format error */
 271#define DECERR		0x04	/* data decoding error */
 272#define TSPERR		0x08	/* insufficient data */
 273
 274#ifdef HAVE_AUDIO
 275/*
 276 * Maximum likelihood UART structure. There are eight of these
 277 * corresponding to the number of phases.
 278 */ 
 279struct surv {
 280	double	shift[12];	/* mark register */
 281	double	es_max, es_min;	/* max/min envelope signals */
 282	double	dist;		/* sample distance */
 283	int	uart;		/* decoded character */
 284};
 285#endif /* HAVE_AUDIO */
 286
 287#ifdef ICOM
 288/*
 289 * CHU station structure. There are three of these corresponding to the
 290 * three frequencies.
 291 */
 292struct xmtr {
 293	double	integ[ISTAGE];	/* circular integrator */
 294	double	metric;		/* integrator sum */
 295	int	iptr;		/* integrator pointer */
 296	int	probe;		/* dwells since last probe */
 297};
 298#endif /* ICOM */
 299
 300/*
 301 * CHU unit control structure
 302 */
 303struct chuunit {
 304	u_char	decode[20][16];	/* maximum likelihood decoding matrix */
 305	l_fp	cstamp[BURST];	/* character timestamps */
 306	l_fp	tstamp[MAXSTAGE]; /* timestamp samples */
 307	l_fp	timestamp;	/* current buffer timestamp */
 308	l_fp	laststamp;	/* last buffer timestamp */
 309	l_fp	charstamp;	/* character time as a l_fp */
 310	int	errflg;		/* error flags */
 311	int	status;		/* status bits */
 312	char	ident[5];	/* station ID and channel */
 313#ifdef ICOM
 314	int	fd_icom;	/* ICOM file descriptor */
 315	int	chan;		/* data channel */
 316	int	achan;		/* active channel */
 317	int	dwell;		/* dwell cycle */
 318	struct xmtr xmtr[NCHAN]; /* station metric */
 319#endif /* ICOM */
 320
 321	/*
 322	 * Character burst variables
 323	 */
 324	int	cbuf[BURST];	/* character buffer */
 325	int	ntstamp;	/* number of timestamp samples */
 326	int	ndx;		/* buffer start index */
 327	int	prevsec;	/* previous burst second */
 328	int	burdist;	/* burst distance */
 329	int	syndist;	/* sync distance */
 330	int	burstcnt;	/* format A bursts this minute */
 331
 332	/*
 333	 * Format particulars
 334	 */
 335	int	leap;		/* leap/dut code */
 336	int	dut;		/* UTC1 correction */
 337	int	tai;		/* TAI - UTC correction */
 338	int	dst;		/* Canadian DST code */
 339
 340#ifdef HAVE_AUDIO
 341	/*
 342	 * Audio codec variables
 343	 */
 344	int	fd_audio;	/* audio port file descriptor */
 345	double	comp[SIZE];	/* decompanding table */
 346	int	port;		/* codec port */
 347	int	gain;		/* codec gain */
 348	int	mongain;	/* codec monitor gain */
 349	int	clipcnt;	/* sample clip count */
 350	int	seccnt;		/* second interval counter */
 351
 352	/*
 353	 * Modem variables
 354	 */
 355	l_fp	tick;		/* audio sample increment */
 356	double	bpf[9];		/* IIR bandpass filter */
 357	double	disc[LAG];	/* discriminator shift register */
 358	double	lpf[27];	/* FIR lowpass filter */
 359	double	monitor;	/* audio monitor */
 360	double	maxsignal;	/* signal level */
 361	int	discptr;	/* discriminator pointer */
 362
 363	/*
 364	 * Maximum likelihood UART variables
 365	 */
 366	double	baud;		/* baud interval */
 367	struct surv surv[8];	/* UART survivor structures */
 368	int	decptr;		/* decode pointer */
 369	int	dbrk;		/* holdoff counter */
 370#endif /* HAVE_AUDIO */
 371};
 372
 373/*
 374 * Function prototypes
 375 */
 376static	int	chu_start	P((int, struct peer *));
 377static	void	chu_shutdown	P((int, struct peer *));
 378static	void	chu_receive	P((struct recvbuf *));
 379static	void	chu_poll	P((int, struct peer *));
 380
 381/*
 382 * More function prototypes
 383 */
 384static	void	chu_decode	P((struct peer *, int));
 385static	void	chu_burst	P((struct peer *));
 386static	void	chu_clear	P((struct peer *));
 387static	void	chu_a		P((struct peer *, int));
 388static	void	chu_b		P((struct peer *, int));
 389static	int	chu_dist	P((int, int));
 390static	double	chu_major	P((struct peer *));
 391#ifdef HAVE_AUDIO
 392static	void	chu_uart	P((struct surv *, double));
 393static	void	chu_rf		P((struct peer *, double));
 394static	void	chu_gain	P((struct peer *));
 395static	void	chu_audio_receive P((struct recvbuf *rbufp));
 396#endif /* HAVE_AUDIO */
 397#ifdef ICOM
 398static	int	chu_newchan	P((struct peer *, double));
 399#endif /* ICOM */
 400static	void	chu_serial_receive P((struct recvbuf *rbufp));
 401
 402/*
 403 * Global variables
 404 */
 405static char hexchar[] = "0123456789abcdef_*=";
 406
 407#ifdef ICOM
 408/*
 409 * Note the tuned frequencies are 1 kHz higher than the carrier. CHU
 410 * transmits on USB with carrier so we can use AM and the narrow SSB
 411 * filter.
 412 */
 413static double qsy[NCHAN] = {3.330, 7.335, 14.670}; /* freq (MHz) */
 414#endif /* ICOM */
 415
 416/*
 417 * Transfer vector
 418 */
 419struct	refclock refclock_chu = {
 420	chu_start,		/* start up driver */
 421	chu_shutdown,		/* shut down driver */
 422	chu_poll,		/* transmit poll message */
 423	noentry,		/* not used (old chu_control) */
 424	noentry,		/* initialize driver (not used) */
 425	noentry,		/* not used (old chu_buginfo) */
 426	NOFLAGS			/* not used */
 427};
 428
 429
 430/*
 431 * chu_start - open the devices and initialize data for processing
 432 */
 433static int
 434chu_start(
 435	int	unit,		/* instance number (not used) */
 436	struct peer *peer	/* peer structure pointer */
 437	)
 438{
 439	struct chuunit *up;
 440	struct refclockproc *pp;
 441	char device[20];	/* device name */
 442	int	fd;		/* file descriptor */
 443#ifdef ICOM
 444	int	temp;
 445#endif /* ICOM */
 446#ifdef HAVE_AUDIO
 447	int	fd_audio;	/* audio port file descriptor */
 448	int	i;		/* index */
 449	double	step;		/* codec adjustment */
 450
 451	/*
 452	 * Open audio device.
 453	 */
 454	fd_audio = audio_init(DEVICE_AUDIO, AUDIO_BUFSIZ, unit);
 455#ifdef DEBUG
 456	if (fd_audio > 0 && debug)
 457		audio_show();
 458#endif
 459
 460	/*
 461	 * Open serial port in raw mode.
 462	 */
 463	if (fd_audio > 0) {
 464		fd = fd_audio;
 465	} else {
 466		sprintf(device, DEVICE, unit);
 467		fd = refclock_open(device, SPEED232, LDISC_RAW);
 468	}
 469#else /* HAVE_AUDIO */
 470
 471	/*
 472	 * Open serial port in raw mode.
 473	 */
 474	sprintf(device, DEVICE, unit);
 475	fd = refclock_open(device, SPEED232, LDISC_RAW);
 476#endif /* HAVE_AUDIO */
 477	if (fd <= 0)
 478		return (0);
 479
 480	/*
 481	 * Allocate and initialize unit structure
 482	 */
 483	if (!(up = (struct chuunit *)
 484	      emalloc(sizeof(struct chuunit)))) {
 485		close(fd);
 486		return (0);
 487	}
 488	memset((char *)up, 0, sizeof(struct chuunit));
 489	pp = peer->procptr;
 490	pp->unitptr = (caddr_t)up;
 491	pp->io.clock_recv = chu_receive;
 492	pp->io.srcclock = (caddr_t)peer;
 493	pp->io.datalen = 0;
 494	pp->io.fd = fd;
 495	if (!io_addclock(&pp->io)) {
 496		close(fd);
 497		free(up);
 498		return (0);
 499	}
 500
 501	/*
 502	 * Initialize miscellaneous variables
 503	 */
 504	peer->precision = PRECISION;
 505	pp->clockdesc = DESCRIPTION;
 506	strcpy(up->ident, "CHU");
 507	memcpy(&peer->refid, up->ident, 4); 
 508	DTOLFP(CHAR, &up->charstamp);
 509#ifdef HAVE_AUDIO
 510
 511	/*
 512	 * The companded samples are encoded sign-magnitude. The table
 513	 * contains all the 256 values in the interest of speed. We do
 514	 * this even if the audio codec is not available. C'est la lazy.
 515	 */
 516	up->fd_audio = fd_audio;
 517	up->gain = 127;
 518	up->comp[0] = up->comp[OFFSET] = 0.;
 519	up->comp[1] = 1; up->comp[OFFSET + 1] = -1.;
 520	up->comp[2] = 3; up->comp[OFFSET + 2] = -3.;
 521	step = 2.;
 522	for (i = 3; i < OFFSET; i++) {
 523		up->comp[i] = up->comp[i - 1] + step;
 524		up->comp[OFFSET + i] = -up->comp[i];
 525                if (i % 16 == 0)
 526                	step *= 2.;
 527	}
 528	DTOLFP(1. / SECOND, &up->tick);
 529#endif /* HAVE_AUDIO */
 530#ifdef ICOM
 531	temp = 0;
 532#ifdef DEBUG
 533	if (debug > 1)
 534		temp = P_TRACE;
 535#endif
 536	if (peer->ttl > 0) {
 537		if (peer->ttl & 0x80)
 538			up->fd_icom = icom_init("/dev/icom", B1200,
 539			    temp);
 540		else
 541			up->fd_icom = icom_init("/dev/icom", B9600,
 542			    temp);
 543	}
 544	if (up->fd_icom > 0) {
 545		if (chu_newchan(peer, 0) != 0) {
 546			NLOG(NLOG_SYNCEVENT | NLOG_SYSEVENT)
 547			    msyslog(LOG_NOTICE,
 548			    "icom: radio not found");
 549			up->errflg = CEVNT_FAULT;
 550			close(up->fd_icom);
 551			up->fd_icom = 0;
 552		} else {
 553			NLOG(NLOG_SYNCEVENT | NLOG_SYSEVENT)
 554			    msyslog(LOG_NOTICE,
 555			    "icom: autotune enabled");
 556		}
 557	}
 558#endif /* ICOM */
 559	return (1);
 560}
 561
 562
 563/*
 564 * chu_shutdown - shut down the clock
 565 */
 566static void
 567chu_shutdown(
 568	int	unit,		/* instance number (not used) */
 569	struct peer *peer	/* peer structure pointer */
 570	)
 571{
 572	struct chuunit *up;
 573	struct refclockproc *pp;
 574
 575	pp = peer->procptr;
 576	up = (struct chuunit *)pp->unitptr;
 577	if (up == NULL)
 578		return;
 579
 580	io_closeclock(&pp->io);
 581#ifdef ICOM
 582	if (up->fd_icom > 0)
 583		close(up->fd_icom);
 584#endif /* ICOM */
 585	free(up);
 586}
 587
 588
 589/*
 590 * chu_receive - receive data from the audio or serial device
 591 */
 592static void
 593chu_receive(
 594	struct recvbuf *rbufp	/* receive buffer structure pointer */
 595	)
 596{
 597#ifdef HAVE_AUDIO
 598	struct chuunit *up;
 599	struct refclockproc *pp;
 600	struct peer *peer;
 601
 602	peer = (struct peer *)rbufp->recv_srcclock;
 603	pp = peer->procptr;
 604	up = (struct chuunit *)pp->unitptr;
 605
 606	/*
 607	 * If the audio codec is warmed up, the buffer contains codec
 608	 * samples which need to be demodulated and decoded into CHU
 609	 * characters using the software UART. Otherwise, the buffer
 610	 * contains CHU characters from the serial port, so the software
 611	 * UART is bypassed. In this case the CPU will probably run a
 612	 * few degrees cooler.
 613	 */
 614	if (up->fd_audio > 0)
 615		chu_audio_receive(rbufp);
 616	else
 617		chu_serial_receive(rbufp);
 618#else
 619	chu_serial_receive(rbufp);
 620#endif /* HAVE_AUDIO */
 621}
 622
 623
 624#ifdef HAVE_AUDIO
 625/*
 626 * chu_audio_receive - receive data from the audio device
 627 */
 628static void
 629chu_audio_receive(
 630	struct recvbuf *rbufp	/* receive buffer structure pointer */
 631	)
 632{
 633	struct chuunit *up;
 634	struct refclockproc *pp;
 635	struct peer *peer;
 636
 637	double	sample;		/* codec sample */
 638	u_char	*dpt;		/* buffer pointer */
 639	int	bufcnt;		/* buffer counter */
 640	l_fp	ltemp;		/* l_fp temp */
 641
 642	peer = (struct peer *)rbufp->recv_srcclock;
 643	pp = peer->procptr;
 644	up = (struct chuunit *)pp->unitptr;
 645
 646	/*
 647	 * Main loop - read until there ain't no more. Note codec
 648	 * samples are bit-inverted.
 649	 */
 650	DTOLFP((double)rbufp->recv_length / SECOND, &ltemp);
 651	L_SUB(&rbufp->recv_time, &ltemp);
 652	up->timestamp = rbufp->recv_time;
 653	dpt = rbufp->recv_buffer;
 654	for (bufcnt = 0; bufcnt < rbufp->recv_length; bufcnt++) {
 655		sample = up->comp[~*dpt++ & 0xff];
 656
 657		/*
 658		 * Clip noise spikes greater than MAXAMP. If no clips,
 659		 * increase the gain a tad; if the clips are too high, 
 660		 * decrease a tad.
 661		 */
 662		if (sample > MAXAMP) {
 663			sample = MAXAMP;
 664			up->clipcnt++;
 665		} else if (sample < -MAXAMP) {
 666			sample = -MAXAMP;
 667			up->clipcnt++;
 668		}
 669		chu_rf(peer, sample);
 670		L_ADD(&up->timestamp, &up->tick);
 671
 672		/*
 673		 * Once each second ride gain.
 674		 */
 675		up->seccnt = (up->seccnt + 1) % SECOND;
 676		if (up->seccnt == 0) {
 677			pp->second = (pp->second + 1) % 60;
 678			chu_gain(peer);
 679		}
 680	}
 681
 682	/*
 683	 * Set the input port and monitor gain for the next buffer.
 684	 */
 685	if (pp->sloppyclockflag & CLK_FLAG2)
 686		up->port = 2;
 687	else
 688		up->port = 1;
 689	if (pp->sloppyclockflag & CLK_FLAG3)
 690		up->mongain = MONGAIN;
 691	else
 692		up->mongain = 0;
 693}
 694
 695
 696/*
 697 * chu_rf - filter and demodulate the FSK signal
 698 *
 699 * This routine implements a 300-baud Bell 103 modem with mark 2225 Hz
 700 * and space 2025 Hz. It uses a bandpass filter followed by a soft
 701 * limiter, FM discriminator and lowpass filter. A maximum likelihood
 702 * decoder samples the baseband signal at eight times the baud rate and
 703 * detects the start bit of each character.
 704 *
 705 * The filters are built for speed, which explains the rather clumsy
 706 * code. Hopefully, the compiler will efficiently implement the move-
 707 * and-muiltiply-and-add operations.
 708 */
 709static void
 710chu_rf(
 711	struct peer *peer,	/* peer structure pointer */
 712	double	sample		/* analog sample */
 713	)
 714{
 715	struct refclockproc *pp;
 716	struct chuunit *up;
 717	struct surv *sp;
 718
 719	/*
 720	 * Local variables
 721	 */
 722	double	signal;		/* bandpass signal */
 723	double	limit;		/* limiter signal */
 724	double	disc;		/* discriminator signal */
 725	double	lpf;		/* lowpass signal */
 726	double	span;		/* UART signal span */
 727	double	dist;		/* UART signal distance */
 728	int	i, j;
 729
 730	pp = peer->procptr;
 731	up = (struct chuunit *)pp->unitptr;
 732
 733	/*
 734	 * Bandpass filter. 4th-order elliptic, 500-Hz bandpass centered
 735	 * at 2125 Hz. Passband ripple 0.3 dB, stopband ripple 50 dB.
 736	 */
 737	signal = (up->bpf[8] = up->bpf[7]) * 5.844676e-01;
 738	signal += (up->bpf[7] = up->bpf[6]) * 4.884860e-01;
 739	signal += (up->bpf[6] = up->bpf[5]) * 2.704384e+00;
 740	signal += (up->bpf[5] = up->bpf[4]) * 1.645032e+00;
 741	signal += (up->bpf[4] = up->bpf[3]) * 4.644557e+00;
 742	signal += (up->bpf[3] = up->bpf[2]) * 1.879165e+00;
 743	signal += (up->bpf[2] = up->bpf[1]) * 3.522634e+00;
 744	signal += (up->bpf[1] = up->bpf[0]) * 7.315738e-01;
 745	up->bpf[0] = sample - signal;
 746	signal = up->bpf[0] * 6.176213e-03
 747	    + up->bpf[1] * 3.156599e-03
 748	    + up->bpf[2] * 7.567487e-03
 749	    + up->bpf[3] * 4.344580e-03
 750	    + up->bpf[4] * 1.190128e-02
 751	    + up->bpf[5] * 4.344580e-03
 752	    + up->bpf[6] * 7.567487e-03
 753	    + up->bpf[7] * 3.156599e-03
 754	    + up->bpf[8] * 6.176213e-03;
 755
 756	up->monitor = signal / 4.;	/* note monitor after filter */
 757
 758	/*
 759	 * Soft limiter/discriminator. The 11-sample discriminator lag
 760	 * interval corresponds to three cycles of 2125 Hz, which
 761	 * requires the sample frequency to be 2125 * 11 / 3 = 7791.7
 762	 * Hz. The discriminator output varies +-0.5 interval for input
 763	 * frequency 2025-2225 Hz. However, we don't get to sample at
 764	 * this frequency, so the discriminator output is biased. Life
 765	 * at 8000 Hz sucks.
 766	 */
 767	limit = signal;
 768	if (limit > LIMIT)
 769		limit = LIMIT;
 770	else if (limit < -LIMIT)
 771		limit = -LIMIT;
 772	disc = up->disc[up->discptr] * -limit;
 773	up->disc[up->discptr] = limit;
 774	up->discptr = (up->discptr + 1 ) % LAG;
 775	if (disc >= 0)
 776		disc = SQRT(disc);
 777	else
 778		disc = -SQRT(-disc);
 779
 780	/*
 781	 * Lowpass filter. Raised cosine, Ts = 1 / 300, beta = 0.1.
 782	 */
 783	lpf = (up->lpf[26] = up->lpf[25]) * 2.538771e-02;
 784	lpf += (up->lpf[25] = up->lpf[24]) * 1.084671e-01;
 785	lpf += (up->lpf[24] = up->lpf[23]) * 2.003159e-01;
 786	lpf += (up->lpf[23] = up->lpf[22]) * 2.985303e-01;
 787	lpf += (up->lpf[22] = up->lpf[21]) * 4.003697e-01;
 788	lpf += (up->lpf[21] = up->lpf[20]) * 5.028552e-01;
 789	lpf += (up->lpf[20] = up->lpf[19]) * 6.028795e-01;
 790	lpf += (up->lpf[19] = up->lpf[18]) * 6.973249e-01;
 791	lpf += (up->lpf[18] = up->lpf[17]) * 7.831828e-01;
 792	lpf += (up->lpf[17] = up->lpf[16]) * 8.576717e-01;
 793	lpf += (up->lpf[16] = up->lpf[15]) * 9.183463e-01;
 794	lpf += (up->lpf[15] = up->lpf[14]) * 9.631951e-01;
 795	lpf += (up->lpf[14] = up->lpf[13]) * 9.907208e-01;
 796	lpf += (up->lpf[13] = up->lpf[12]) * 1.000000e+00;
 797	lpf += (up->lpf[12] = up->lpf[11]) * 9.907208e-01;
 798	lpf += (up->lpf[11] = up->lpf[10]) * 9.631951e-01;
 799	lpf += (up->lpf[10] = up->lpf[9]) * 9.183463e-01;
 800	lpf += (up->lpf[9] = up->lpf[8]) * 8.576717e-01;
 801	lpf += (up->lpf[8] = up->lpf[7]) * 7.831828e-01;
 802	lpf += (up->lpf[7] = up->lpf[6]) * 6.973249e-01;
 803	lpf += (up->lpf[6] = up->lpf[5]) * 6.028795e-01;
 804	lpf += (up->lpf[5] = up->lpf[4]) * 5.028552e-01;
 805	lpf += (up->lpf[4] = up->lpf[3]) * 4.003697e-01;
 806	lpf += (up->lpf[3] = up->lpf[2]) * 2.985303e-01;
 807	lpf += (up->lpf[2] = up->lpf[1]) * 2.003159e-01;
 808	lpf += (up->lpf[1] = up->lpf[0]) * 1.084671e-01;
 809	lpf += up->lpf[0] = disc * 2.538771e-02;
 810
 811	/*
 812	 * Maximum likelihood decoder. The UART updates each of the
 813	 * eight survivors and determines the span, slice level and
 814	 * tentative decoded character. Valid 11-bit characters are
 815	 * framed so that bit 1 and bit 11 (stop bits) are mark and bit
 816	 * 2 (start bit) is space. When a valid character is found, the
 817	 * survivor with maximum distance determines the final decoded
 818	 * character.
 819	 */
 820	up->baud += 1. / SECOND;
 821	if (up->baud > 1. / (BAUD * 8.)) {
 822		up->baud -= 1. / (BAUD * 8.);
 823		sp = &up->surv[up->decptr];
 824		span = sp->es_max - sp->es_min;
 825		up->maxsignal += (span - up->maxsignal) / 80.;
 826		if (up->dbrk > 0) {
 827			up->dbrk--;
 828		} else if ((sp->uart & 0x403) == 0x401 && span > 1000.)
 829		    {
 830			dist = 0;
 831			j = 0;
 832			for (i = 0; i < 8; i++) {
 833				if (up->surv[i].dist > dist) {
 834					dist = up->surv[i].dist;
 835					j = i;
 836				}
 837			}
 838			chu_decode(peer, (up->surv[j].uart >> 2) &
 839			    0xff);
 840			up->dbrk = 80;
 841		}
 842		up->decptr = (up->decptr + 1) % 8;
 843		chu_uart(sp, -lpf * AGAIN);
 844	}
 845}
 846
 847
 848/*
 849 * chu_uart - maximum likelihood UART
 850 *
 851 * This routine updates a shift register holding the last 11 envelope
 852 * samples. It then computes the slice level and span over these samples
 853 * and determines the tentative data bits and distance. The calling
 854 * program selects over the last eight survivors the one with maximum
 855 * distance to determine the decoded character.
 856 */
 857static void
 858chu_uart(
 859	struct surv *sp,	/* survivor structure pointer */
 860	double	sample		/* baseband signal */
 861	)
 862{
 863	double	es_max, es_min;	/* max/min envelope */
 864	double	slice;		/* slice level */
 865	double	dist;		/* distance */
 866	double	dtemp;
 867	int	i;
 868
 869	/*
 870	 * Save the sample and shift right. At the same time, measure
 871	 * the maximum and minimum over all eleven samples.
 872	 */
 873	es_max = -1e6;
 874	es_min = 1e6;
 875	sp->shift[0] = sample;
 876	for (i = 11; i > 0; i--) {
 877		sp->shift[i] = sp->shift[i - 1];
 878		if (sp->shift[i] > es_max)
 879			es_max = sp->shift[i];
 880		if (sp->shift[i] < es_min)
 881			es_min = sp->shift[i];
 882	}
 883
 884	/*
 885	 * Determine the slice level midway beteen the maximum and
 886	 * minimum and the span as the maximum less the minimum. Compute
 887	 * the distance on the assumption the first and last bits must
 888	 * be mark, the second space and the rest either mark or space.
 889	 */ 
 890	slice = (es_max + es_min) / 2.;
 891	dist = 0;
 892	sp->uart = 0;
 893	for (i = 1; i < 12; i++) {
 894		sp->uart <<= 1;
 895		dtemp = sp->shift[i];
 896		if (dtemp > slice)
 897			sp->uart |= 0x1;
 898		if (i == 1 || i == 11) {
 899			dist += dtemp - es_min;
 900		} else if (i == 10) {
 901			dist += es_max - dtemp;
 902		} else {
 903			if (dtemp > slice)
 904				dist += dtemp - es_min;
 905			else
 906				dist += es_max - dtemp;
 907		}
 908	}
 909	sp->es_max = es_max;
 910	sp->es_min = es_min;
 911	sp->dist = dist / (11 * (es_max - es_min));
 912}
 913#endif /* HAVE_AUDIO */
 914
 915
 916/*
 917 * chu_serial_receive - receive data from the serial device
 918 */
 919static void
 920chu_serial_receive(
 921	struct recvbuf *rbufp	/* receive buffer structure pointer */
 922	)
 923{
 924	struct chuunit *up;
 925	struct refclockproc *pp;
 926	struct peer *peer;
 927
 928	u_char	*dpt;		/* receive buffer pointer */
 929
 930	peer = (struct peer *)rbufp->recv_srcclock;
 931	pp = peer->procptr;
 932	up = (struct chuunit *)pp->unitptr;
 933
 934	/*
 935	 * Initialize pointers and read the timecode and timestamp.
 936	 */
 937	up->timestamp = rbufp->recv_time;
 938	dpt = (u_char *)&rbufp->recv_space;
 939	chu_decode(peer, *dpt);
 940}
 941
 942
 943/*
 944 * chu_decode - decode the character data
 945 */
 946static void
 947chu_decode(
 948	struct peer *peer,	/* peer structure pointer */
 949	int	hexhex		/* data character */
 950	)
 951{
 952	struct refclockproc *pp;
 953	struct chuunit *up;
 954
 955	l_fp	tstmp;		/* timestamp temp */
 956	double	dtemp;
 957
 958	pp = peer->procptr;
 959	up = (struct chuunit *)pp->unitptr;
 960
 961	/*
 962	 * If the interval since the last character is greater than the
 963	 * longest burst, process the last burst and start a new one. If
 964	 * the interval is less than this but greater than two
 965	 * characters, consider this a noise burst and reject it.
 966	 */
 967	tstmp = up->timestamp;
 968	if (L_ISZERO(&up->laststamp))
 969		up->laststamp = up->timestamp;
 970	L_SUB(&tstmp, &up->laststamp);
 971	up->laststamp = up->timestamp;
 972	LFPTOD(&tstmp, dtemp);
 973	if (dtemp > BURST * CHAR) {
 974		chu_burst(peer);
 975		up->ndx = 0;
 976	} else if (dtemp > 2.5 * CHAR) {
 977		up->ndx = 0;
 978	}
 979
 980	/*
 981	 * Append the character to the current burst and append the
 982	 * timestamp to the timestamp list.
 983	 */
 984	if (up->ndx < BURST) {
 985		up->cbuf[up->ndx] = hexhex & 0xff;
 986		up->cstamp[up->ndx] = up->timestamp;
 987		up->ndx++;
 988
 989	}
 990}
 991
 992
 993/*
 994 * chu_burst - search for valid burst format
 995 */
 996static void
 997chu_burst(
 998	struct peer *peer
 999	)
1000{
1001	struct chuunit *up;
1002	struct refclockproc *pp;
1003
1004	int	i;
1005
1006	pp = peer->procptr;
1007	up = (struct chuunit *)pp->unitptr;
1008
1009	/*
1010	 * Correlate a block of five characters with the next block of
1011	 * five characters. The burst distance is defined as the number
1012	 * of bits that match in the two blocks for format A and that
1013	 * match the inverse for format B.
1014	 */
1015	if (up->ndx < MINCHAR) {
1016		up->status |= RUNT;
1017		return;
1018	}
1019	up->burdist = 0;
1020	for (i = 0; i < 5 && i < up->ndx - 5; i++)
1021		up->burdist += chu_dist(up->cbuf[i], up->cbuf[i + 5]);
1022
1023	/*
1024	 * If the burst distance is at least MINDIST, this must be a
1025	 * format A burst; if the value is not greater than -MINDIST, it
1026	 * must be a format B burst. If the B burst is perfect, we
1027	 * believe it; otherwise, it is a noise burst and of no use to
1028	 * anybody.
1029	 */
1030	if (up->burdist >= MINDIST) {
1031		chu_a(peer, up->ndx);
1032	} else if (up->burdist <= -MINDIST) {
1033		chu_b(peer, up->ndx);
1034	} else {
1035		up->status |= NOISE;
1036		return;
1037	}
1038
1039	/*
1040	 * If this is a valid burst, wait a guard time of ten seconds to
1041	 * allow for more bursts, then arm the poll update routine to
1042	 * process the minute. Don't do this if this is called from the
1043	 * timer interrupt routine.
1044	 */
1045	if (peer->outdate != current_time)
1046		peer->nextdate = current_time + 10;
1047}
1048
1049
1050/*
1051 * chu_b - decode format B burst
1052 */
1053static void
1054chu_b(
1055	struct peer *peer,
1056	int	nchar
1057	)
1058{
1059	struct	refclockproc *pp;
1060	struct	chuunit *up;
1061
1062	u_char	code[11];	/* decoded timecode */
1063	char	tbuf[80];	/* trace buffer */
1064	l_fp	offset;		/* timestamp offset */
1065	int	i;
1066
1067	pp = peer->procptr;
1068	up = (struct chuunit *)pp->unitptr;
1069
1070	/*
1071	 * In a format B burst, a character is considered valid only if
1072	 * the first occurrence matches the last occurrence. The burst
1073	 * is considered valid only if all characters are valid; that
1074	 * is, only if the distance is 40. Note that once a valid frame
1075	 * has been found errors are ignored.
1076	 */
1077	sprintf(tbuf, "chuB %04x %2d %2d ", up->status, nchar,
1078	    -up->burdist);
1079	for (i = 0; i < nchar; i++)
1080		sprintf(&tbuf[strlen(tbuf)], "%02x", up->cbuf[i]);
1081	if (pp->sloppyclockflag & CLK_FLAG4)
1082		record_clock_stats(&peer->srcadr, tbuf);
1083#ifdef DEBUG
1084	if (debug)
1085		printf("%s\n", tbuf);
1086#endif
1087	if (up->burdist > -40) {
1088		up->status |= BFRAME;
1089		return;
1090	}
1091	up->status |= BVALID;
1092
1093	/*
1094	 * Convert the burst data to internal format. If this succeeds,
1095	 * save the timestamps for later.
1096	 */
1097	for (i = 0; i < 5; i++) {
1098		code[2 * i] = hexchar[up->cbuf[i] & 0xf];
1099		code[2 * i + 1] = hexchar[(up->cbuf[i] >>
1100		    4) & 0xf];
1101	}
1102	if (sscanf((char *)code, "%1x%1d%4d%2d%2x", &up->leap, &up->dut,
1103	    &pp->year, &up->tai, &up->dst) != 5) {
1104		up->status |= BFORMAT;
1105		return;
1106	}
1107	if (up->leap & 0x8)
1108		up->dut = -up->dut;
1109	offset.l_ui = 31;
1110	offset.l_f = 0;
1111	for (i = 0; i < nchar && i < 10; i++) {
1112		up->tstamp[up->ntstamp] = up->cstamp[i];
1113		L_SUB(&up->tstamp[up->ntstamp], &offset);
1114		L_ADD(&offset, &up->charstamp);
1115		if (up->ntstamp < MAXSTAGE - 1) 
1116			up->ntstamp++;
1117	}
1118}
1119
1120
1121/*
1122 * chu_a - decode format A burst
1123 */
1124static void
1125chu_a(
1126	struct peer *peer,
1127	int nchar
1128	)
1129{
1130	struct refclockproc *pp;
1131	struct chuunit *up;
1132
1133	char	tbuf[80];	/* trace buffer */
1134	l_fp	offset;		/* timestamp offset */
1135	int	val;		/* distance */
1136	int	temp;
1137	int	i, j, k;
1138
1139	pp = peer->procptr;
1140	up = (struct chuunit *)pp->unitptr;
1141
1142	/*
1143	 * Determine correct burst phase. There are three cases
1144	 * corresponding to in-phase, one character early or one
1145	 * character late. These cases are distinguished by the position
1146	 * of the framing digits x6 at positions 0 and 5 and x3 at
1147	 * positions 4 and 9. The correct phase is when the distance
1148	 * relative to the framing digits is maximum. The burst is valid
1149	 * only if the maximum distance is at least MINSYNC.
1150	 */
1151	up->syndist = k = 0;
1152	val = -16;
1153	for (i = -1; i < 2; i++) {
1154		temp = up->cbuf[i + 4] & 0xf;
1155		if (i >= 0)
1156			temp |= (up->cbuf[i] & 0xf) << 4;
1157		val = chu_dist(temp, 0x63);
1158		temp = (up->cbuf[i + 5] & 0xf) << 4;
1159		if (i + 9 < nchar)
1160			temp |= up->cbuf[i + 9] & 0xf;
1161		val += chu_dist(temp, 0x63);
1162		if (val > up->syndist) {
1163			up->syndist = val;
1164			k = i;
1165		}
1166	}
1167	temp = (up->cbuf[k + 4] >> 4) & 0xf;
1168	if (temp > 9 || k + 9 >= nchar || temp != ((up->cbuf[k + 9] >>
1169	    4) & 0xf))
1170		temp = 0;
1171#ifdef HAVE_AUDIO
1172	if (up->fd_audio)
1173		sprintf(tbuf, "chuA %04x %4.0f %2d %2d %2d %2d %1d ",
1174		    up->status, up->maxsignal, nchar, up->burdist, k,
1175		    up->syndist, temp);
1176	else
1177		sprintf(tbuf, "chuA %04x %2d %2d %2d %2d %1d ",
1178		    up->status, nchar, up->burdist, k, up->syndist,
1179		    temp);
1180
1181#else
1182	sprintf(tbuf, "chuA %04x %2d %2d %2d %2d %1d ", up->status,
1183	    nchar, up->burdist, k, up->syndist, temp);
1184#endif /* HAVE_AUDIO */
1185	for (i = 0; i < nchar; i++)
1186		sprintf(&tbuf[strlen(tbuf)], "%02x",
1187		    up->cbuf[i]);
1188	if (pp->sloppyclockflag & CLK_FLAG4)
1189		record_clock_stats(&peer->srcadr, tbuf);
1190#ifdef DEBUG
1191	if (debug)
1192		printf("%s\n", tbuf);
1193#endif
1194	if (up->syndist < MINSYNC) {
1195		up->status |= AFRAME;
1196		return;
1197	}
1198
1199	/*
1200	 * A valid burst requires the first seconds number to match the
1201	 * last seconds number. If so, the burst timestamps are
1202	 * corrected to the current minute and saved for later
1203	 * processing. In addition, the seconds decode is advanced from
1204	 * the previous burst to the current one.
1205	 */
1206	if (temp != 0) {
1207		pp->second = 30 + temp;
1208		offset.l_ui = 30 + temp;
1209		offset.l_f = 0;
1210		i = 0;
1211		if (k < 0)
1212			offset = up->charstamp;
1213		else if (k > 0)
1214			i = 1;
1215		for (; i < nchar && i < k + 10; i++) {
1216			up->tstamp[up->ntstamp] = up->cstamp[i];
1217			L_SUB(&up->tstamp[up->ntstamp], &offset);
1218			L_ADD(&offset, &up->charstamp);
1219			if (up->ntstamp < MAXSTAGE - 1) 
1220				up->ntstamp++;
1221		}
1222		while (temp > up->prevsec) {
1223			for (j = 15; j > 0; j--) {
1224				up->decode[9][j] = up->decode[9][j - 1];
1225				up->decode[19][j] =
1226				    up->decode[19][j - 1];
1227			}
1228			up->decode[9][j] = up->decode[19][j] = 0;
1229			up->prevsec++;
1230		}
1231	}
1232	i = -(2 * k);
1233	for (j = 0; j < nchar; j++) {
1234		if (i < 0 || i > 18) {
1235			i += 2;
1236			continue;
1237		}
1238		up->decode[i][up->cbuf[j] & 0xf]++;
1239		i++;
1240		up->decode[i][(up->cbuf[j] >> 4) & 0xf]++;
1241		i++;
1242	}
1243	up->status |= AVALID;
1244	up->burstcnt++;
1245}
1246
1247
1248/*
1249 * chu_poll - called by the transmit procedure
1250 */
1251static void
1252chu_poll(
1253	int unit,
1254	struct peer *peer	/* peer structure pointer */
1255	)
1256{
1257	struct refclockproc *pp;
1258	struct chuunit *up;
1259	l_fp	offset;
1260	char	synchar, qual, leapchar;
1261	int	minset, i;
1262	double	dtemp;
1263
1264	pp = peer->procptr;
1265	up = (struct chuunit *)pp->unitptr;
1266	if (pp->coderecv == pp->codeproc)
1267		up->errflg = CEVNT_TIMEOUT;
1268	else
1269		pp->polls++;
1270
1271	/*
1272	 * If once in sync and the radio has not been heard for awhile
1273	 * (30 m), it is no longer reachable. If not heard in a long
1274	 * while (one day), turn out the lights and start from scratch.
1275	 */
1276	minset = ((current_time - peer->update) + 30) / 60;
1277	if (up->status & INSYNC) {
1278		if (minset > PANIC)
1279			up->status = 0;
1280		else if (minset <= HOLD)
1281			peer->reach |= 1;
1282	}
1283
1284	/*
1285	 * Process the last burst, if still in the burst buffer.
1286	 * Don't mess with anything if nothing has been heard. If the
1287	 * minute contains a valid A frame and valid B frame, assume
1288	 * synchronized; however, believe the time only if within metric
1289	 * threshold. Note the quality indicator is only for
1290	 * diagnostics; the data are used only if in sync and above
1291	 * metric threshold.
1292	 */
1293	chu_burst(peer);
1294	if (up->burstcnt == 0) {
1295#ifdef ICOM
1296		chu_newchan(peer, 0);
1297#endif /* ICOM */
1298		return;
1299	}
1300	dtemp = chu_major(peer);
1301	qual = 0;
1302	if (up->status & (BFRAME | AFRAME))
1303		qual |= SYNERR;
1304	if (up->status & (BFORMAT | AFORMAT))
1305		qual |= FMTERR;
1306	if (up->status & DECODE)
1307		qual |= DECERR;
1308	if (up->status & STAMP)
1309		qual |= TSPERR;
1310	if (up->status & AVALID && up->status & BVALID)
1311		up->status |= INSYNC;
1312	synchar = leapchar = ' ';
1313	if (!(up->status & INSYNC)) {
1314		pp->leap = LEAP_NOTINSYNC;
1315		synchar = '?';
1316	} else if (up->leap & 0x2) {
1317		pp->leap = LEAP_ADDSECOND;
1318		leapchar = 'L';
1319	} else if (up->leap & 0x4) {
1320		pp->leap = LEAP_DELSECOND;
1321		leapchar = 'l';
1322	} else {
1323		pp->leap = LEAP_NOWARNING;
1324	}
1325#ifdef HAVE_AUDIO
1326	if (up->fd_audio)
1327		sprintf(pp->a_lastcode,
1328		    "%c%1X %04d %3d %02d:%02d:%02d %c%x %+d %d %d %s %.0f %d",
1329		    synchar, qual, pp->year, pp->day, pp->hour,
1330		    pp->minute, pp->second, leapchar, up->dst, up->dut,
1331		    minset, up->gain, up->ident, dtemp, up->ntstamp);
1332	else
1333		sprintf(pp->a_lastcode,
1334		    "%c%1X %04d %3d %02d:%02d:%02d %c%x %+d %d %s %.0f %d",
1335		    synchar, qual, pp->year, pp->day, pp->hour,
1336		    pp->minute, pp->second, leapchar, up->dst, up->dut,
1337		    minset, up->ident, dtemp, up->ntstamp);
1338#else
1339	sprintf(pp->a_lastcode,
1340	    "%c%1X %04d %3d %02d:%02d:%02d %c%x %+d %d %s %.0f %d",
1341	    synchar, qual, pp->year, pp->day, pp->hour, pp->minute,
1342	    pp->second, leapchar, up->dst, up->dut, minset, up->ident,
1343	    dtemp, up->ntstamp);
1344#endif /* HAVE_AUDIO */
1345	pp->lencode = strlen(pp->a_lastcode);
1346
1347	/*
1348	 * If in sync and the signal metric is above threshold, the
1349	 * timecode is ipso fatso valid and can be selected to
1350	 * discipline the clock. Be sure not to leave stray timestamps
1351	 * around if signals are too weak or the clock time is invalid.
1352	 */
1353	if (up->status & INSYNC && dtemp > METRIC) {
1354		if (!clocktime(pp->day, pp->hour, pp->minute, 0, GMT,
1355		    up->tstamp[0].l_ui, &pp->yearstart, &offset.l_ui)) {
1356			up->errflg = CEVNT_BADTIME;
1357		} else {
1358			offset.l_uf = 0;
1359			for (i = 0; i < up->ntstamp; i++)
1360				refclock_process_offset(pp, offset,
1361				    up->tstamp[i], FUDGE +
1362				    pp->fudgetime1);
1363			pp->lastref = up->timestamp;
1364			refclock_receive(peer);
1365		}
1366		record_clock_stats(&peer->srcadr, pp->a_lastcode);
1367	} else if (pp->sloppyclockflag & CLK_FLAG4) {
1368		record_clock_stats(&peer->srcadr, pp->a_lastcode);
1369	}
1370#ifdef DEBUG
1371	if (debug)
1372		printf("chu: timecode %d %s\n", pp->lencode,
1373		    pp->a_lastcode);
1374#endif
1375#ifdef ICOM
1376	chu_newchan(peer, dtemp);
1377#endif /* ICOM */
1378	chu_clear(peer);
1379	if (up->errflg)
1380		refclock_report(peer, up->errflg);
1381	up->errflg = 0;
1382}
1383
1384
1385/*
1386 * chu_major - majority decoder
1387 */
1388static double
1389chu_major(
1390	struct peer *peer	/* peer structure pointer */
1391	)
1392{
1393	struct refclockproc *pp;
1394	struct chuunit *up;
1395
1396	u_char	code[11];	/* decoded timecode */
1397	int	mindist;	/* minimum distance */
1398	int	val1, val2;	/* maximum distance */
1399	int	synchar;	/* stray cat */
1400	int	temp;
1401	int	i, j, k;
1402
1403	pp = peer->procptr;
1404	up = (struct chuunit *)pp->unitptr;
1405
1406	/*
1407	 * Majority decoder. Each burst encodes two replications at each
1408	 * digit position in the timecode. Each row of the decoding
1409	 * matrix encodes the number of occurrences of each digit found
1410	 * at the corresponding position. The maximum over all
1411	 * occurrences at each position is the distance for this
1412	 * position and the corresponding digit is the maximum
1413	 * likelihood candidate. If the distance is zero, assume a miss
1414	 * '_'; if the distance is not more than half the total number
1415	 * of occurrences, assume a soft error '*'; if two different
1416	 * digits with the same distance are found, assume a hard error
1417	 * '='. These will later cause a format error when the timecode
1418	 * is interpreted. The decoding distance is defined as the
1419	 * minimum distance over the first nine digits. The tenth digit
1420	 * varies over the seconds, so we don't count it.
1421	 */
1422	mindist = 16;
1423	for (i = 0; i < 9; i++) {
1424		val1 = val2 = 0;
1425		k = 0;
1426		for (j = 0; j < 16; j++) {
1427			temp = up->decode[i][j] + up->decode[i + 10][j];
1428			if (temp > val1) {
1429				val2 = val1;
1430				val1 = temp;
1431				k = j;
1432			}
1433		}
1434		if (val1 == 0)
1435			code[i] = HEX_MISS;
1436		else if (val1 == val2)
1437			code[i] = HEX_HARD;
1438		else if (val1 <= up->burstcnt)
1439			code[i] = HEX_SOFT;
1440		else
1441			code[i] = k;
1442		if (val1 < mindist)
1443			mindist = val1;
1444		code[i] = hexchar[code[i]];
1445	}
1446	code[i] = 0;
1447
1448	/*
1449	 * A valid timecode requires a minimum distance at least half
1450	 * the total number of occurrences. A valid timecode also
1451	 * requires at least 20 valid timestamps.
1452	 */
1453	if (up->burstcnt < MINBURST || mindist < up->burstcnt)
1454		up->status |= DECODE;
1455	if (up->ntstamp < MINSTAMP)
1456		up->status |= STAMP;
1457
1458	/*
1459	 * Compute the timecode timestamp from the days, hours and
1460	 * minutes of the timecode. Use clocktime() for the aggregate
1461	 * minutes and the minute offset computed from the burst
1462	 * seconds. Note that this code relies on the filesystem time
1463	 * for the years and does not use the years of the timecode.
1464	 */
1465	if (sscanf((char *)code, "%1x%3d%2d%2d", &synchar, &pp->day,
1466	    &pp->hour, &pp->minute) != 4) {
1467		up->status |= AFORMAT;
1468		return (0);
1469	}
1470	if (up->status & (DECODE | STAMP)) {
1471		up->errflg = CEVNT_BADREPLY;
1472		return (0);
1473	}
1474	return (mindist * 100. / (2. * up->burstcnt));
1475}
1476
1477
1478/*
1479 * chu_clear - clear decoding matrix
1480 */
1481static void
1482chu_clear(
1483	struct peer *peer	/* peer structure pointer */
1484	)
1485{
1486	struct refclockproc *pp;
1487	struct chuunit *up;
1488	int	i, j;
1489
1490	pp = peer->procptr;
1491	up = (struct chuunit *)pp->unitptr;
1492
1493	/*
1494	 * Clear stuff for the minute.
1495	 */
1496	up->ndx = up->prevsec = 0;
1497	up->burstcnt = up->ntstamp = 0;
1498	up->status &= INSYNC;
1499	for (i = 0; i < 20; i++) {
1500		for (j = 0; j < 16; j++)
1501			up->decode[i][j] = 0;
1502	}
1503}
1504
1505#ifdef ICOM
1506/*
1507 * chu_newchan - called once per minute to find the best channel;
1508 * returns zero on success, nonzero if ICOM error.
1509 */
1510static int
1511chu_newchan(
1512	struct peer *peer,
1513	double	met
1514	)
1515{
1516	struct chuunit *up;
1517	struct refclockproc *pp;
1518	struct xmtr *sp;
1519	char	tbuf[80];	/* trace buffer */
1520	int	rval;
1521	double	metric;
1522	int	i, j;
1523
1524	pp = peer->procptr;
1525	up = (struct chuunit *)pp->unitptr;
1526
1527	/*
1528	 * The radio can be tuned to three channels: 0 (3330 kHz), 1
1529	 * (7335 kHz) and 2 (14670 kHz). There are five one-minute
1530	 * dwells in each cycle. During the first dwell the radio is
1531	 * tuned to one of three probe channels; during the remaining
1532	 * four dwells the radio is tuned to the data channel. The probe
1533	 * channel is selects as the least recently used. At the end of
1534	 * each dwell the channel metrics are measured and the highest
1535	 * one is selected as the data channel. 
1536	 */
1537	if (up->fd_icom <= 0)
1538		return (0);
1539
1540	sp = &up->xmtr[up->achan];
1541	sp->metric -= sp->integ[sp->iptr];
1542	sp->integ[sp->iptr] = met;
1543	sp->metric += sp->integ[sp->iptr];
1544	sp->iptr = (sp->iptr + 1) % ISTAGE;
1545	metric = 0;
1546	j = 0;
1547	for (i = 0; i < NCHAN; i++) {
1548		up->xmtr[i].probe++;
1549		if (i == up->achan)
1550			up->xmtr[i].probe = 0;
1551		if (up->xmtr[i].metric < metric)
1552			continue;
1553		metric = up->xmtr[i].metric;
1554		j = i;
1555	}
1556	if (j != up->chan && metric > 0) {
1557		up->chan = j;
1558		sprintf(tbuf, "chu: QSY to %.3f MHz metric %.0f",
1559		    qsy[up->chan], metric);
1560		if (pp->sloppyclockflag & CLK_FLAG4)
1561			record_clock_stats(&peer->srcadr, tbuf);
1562#ifdef DEBUG
1563		if (debug)
1564			printf("%s\n", tbuf);
1565#endif
1566	}
1567
1568	/*
1569	 * Start the next dwell. We speed up the initial sync a little.
1570	 * If not in sync and no bursts were heard the previous dwell,
1571	 * restart the probe.
1572	 */
1573	rval = 0;
1574	if (up->burstcnt == 0 && !(up->status & INSYNC))
1575		up->dwell = 0;
1576#ifdef DEBUG
1577	if (debug)
1578		printf(
1579		    "chu: at %ld dwell %d achan %d metric %.0f chan %d\n",
1580		    current_time, up->dwell, up->achan, sp->metric,
1581		    up->chan);
1582#endif
1583	if (up->dwell == 0) {
1584		rval = 0;
1585		for (i = 0; i < NCHAN; i++) {
1586			if (up->xmtr[i].probe < rval)
1587				continue;
1588			rval = up->xmtr[i].probe;
1589			up->achan = i;
1590		}
1591		rval = icom_freq(up->fd_icom, peer->ttl & 0x7f,
1592		    qsy[up->achan] + TUNE);
1593#ifdef DEBUG
1594		if (debug)
1595			printf("chu: at %ld probe channel %d\n",
1596		    current_time, up->achan);
1597#endif
1598	} else {
1599		if (up->achan != up->chan) {
1600			rval = icom_freq(up->fd_icom, peer->ttl & 0x7f,
1601			    qsy[up->chan] + TUNE);
1602			up->achan = up->chan;
1603		}
1604	}
1605	sprintf(up->ident, "CHU%d", up->achan);
1606	memcpy(&peer->refid, up->ident, 4); 
1607	up->dwell = (up->dwell + 1) % DWELL;
1608	return (rval);
1609}
1610#endif /* ICOM */
1611
1612/*
1613 * chu_dist - determine the distance of two octet arguments
1614 */
1615static int
1616chu_dist(
1617	int	x,		/* an octet of bits */
1618	int	y		/* another octet of bits */
1619	)
1620{
1621	int	val;		/* bit count */ 
1622	int	temp;
1623	int	i;
1624
1625	/*
1626	 * The distance is determined as the weight of the exclusive OR
1627	 * of the two arguments. The weight is determined by the number
1628	 * of one bits in the result. Each one bit increases the weight,
1629	 * while each zero bit decreases it.
1630	 */
1631	temp = x ^ y;
1632	val = 0;
1633	for (i = 0; i < 8; i++) {
1634		if ((temp & 0x1) == 0)
1635			val++;
1636		else
1637			val--;
1638		temp >>= 1;
1639	}
1640	return (val);
1641}
1642
1643
1644#ifdef HAVE_AUDIO
1645/*
1646 * chu_gain - adjust codec gain
1647 *
1648 * This routine is called once each second. If the signal envelope
1649 * amplitude is too low, the codec gain is bumped up by four units; if
1650 * too high, it is bumped down. The decoder is relatively insensitive to
1651 * amplitude, so this crudity works just fine. The input port is set and
1652 * the error flag is cleared, mostly to be ornery.
1653 */
1654static void
1655chu_gain(
1656	struct peer *peer	/* peer structure pointer */
1657	)
1658{
1659	struct refclockproc *pp;
1660	struct chuunit *up;
1661
1662	pp = peer->procptr;
1663	up = (struct chuunit *)pp->unitptr;
1664
1665	/*
1666	 * Apparently, the codec uses only the high order bits of the
1667	 * gain control field. Thus, it may take awhile for changes to
1668	 * wiggle the hardware bits.
1669	 */
1670	if (up->clipcnt == 0) {
1671		up->gain += 4;
1672		if (up->gain > MAXGAIN)
1673			up->gain = MAXGAIN;
1674	} else if (up->clipcnt > MAXCLP) {
1675		up->gain -= 4;
1676		if (up->gain < 0)
1677			up->gain = 0;
1678	}
1679	audio_gain(up->gain, up->mongain, up->port);
1680	up->clipcnt = 0;
1681}
1682#endif /* HAVE_AUDIO */
1683
1684
1685#else
1686int refclock_chu_bs;
1687#endif /* REFCLOCK */