2 * refclock_wwv - clock driver for NIST WWV/H time/frequency station
8 #if defined(REFCLOCK) && defined(CLOCK_WWV)
12 #include "ntp_refclock.h"
13 #include "ntp_calendar.h"
14 #include "ntp_stdlib.h"
20 #ifdef HAVE_SYS_IOCTL_H
21 # include <sys/ioctl.h>
22 #endif /* HAVE_SYS_IOCTL_H */
31 * Audio WWV/H demodulator/decoder
33 * This driver synchronizes the computer time using data encoded in
34 * radio transmissions from NIST time/frequency stations WWV in Boulder,
35 * CO, and WWVH in Kauai, HI. Transmissions are made continuously on
36 * 2.5, 5, 10 and 15 MHz from WWV and WWVH, and 20 MHz from WWV. An
37 * ordinary AM 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 weasons, both day and night.
42 * The driver requires an audio codec or sound card with sampling rate 8
43 * kHz and mu-law companding. This is the same standard as used by the
44 * telephone industry and is supported by most hardware and operating
45 * systems, including Solaris, SunOS, FreeBSD, NetBSD and Linux. In this
46 * implementation, only one audio driver and codec can be supported on a
49 * The demodulation and decoding algorithms used in this driver are
50 * based on those developed for the TAPR DSP93 development board and the
51 * TI 320C25 digital signal processor described in: Mills, D.L. A
52 * precision radio clock for WWV transmissions. Electrical Engineering
53 * Report 97-8-1, University of Delaware, August 1997, 25 pp., available
54 * from www.eecis.udel.edu/~mills/reports.html. The algorithms described
55 * in this report have been modified somewhat to improve performance
56 * under weak signal conditions and to provide an automatic station
57 * identification feature.
59 * The ICOM code is normally compiled in the driver. It isn't used,
60 * unless the mode keyword on the server configuration command specifies
61 * a nonzero ICOM ID select code. The C-IV trace is turned on if the
62 * debug level is greater than one.
66 * Fudge flag4 causes the debugging output described above to be
67 * recorded in the clockstats file. Fudge flag2 selects the audio input
68 * port, where 0 is the mike port (default) and 1 is the line-in port.
69 * It does not seem useful to select the compact disc player port. Fudge
70 * flag3 enables audio monitoring of the input signal. For this purpose,
71 * the monitor gain is set to a default value.
73 * CEVNT_BADTIME invalid date or time
74 * CEVNT_PROP propagation failure - no stations heard
75 * CEVNT_TIMEOUT timeout (see newgame() below)
78 * General definitions. These ordinarily do not need to be changed.
80 #define DEVICE_AUDIO "/dev/audio" /* audio device name */
81 #define AUDIO_BUFSIZ 320 /* audio buffer size (50 ms) */
82 #define PRECISION (-10) /* precision assumed (about 1 ms) */
83 #define DESCRIPTION "WWV/H Audio Demodulator/Decoder" /* WRU */
84 #define WWV_SEC 8000 /* second epoch (sample rate) (Hz) */
85 #define WWV_MIN (WWV_SEC * 60) /* minute epoch */
86 #define OFFSET 128 /* companded sample offset */
87 #define SIZE 256 /* decompanding table size */
88 #define MAXAMP 6000. /* max signal level reference */
89 #define MAXCLP 100 /* max clips above reference per s */
90 #define MAXSNR 40. /* max SNR reference */
91 #define MAXFREQ 1.5 /* max frequency tolerance (187 PPM) */
92 #define DATCYC 170 /* data filter cycles */
93 #define DATSIZ (DATCYC * MS) /* data filter size */
94 #define SYNCYC 800 /* minute filter cycles */
95 #define SYNSIZ (SYNCYC * MS) /* minute filter size */
96 #define TCKCYC 5 /* tick filter cycles */
97 #define TCKSIZ (TCKCYC * MS) /* tick filter size */
98 #define NCHAN 5 /* number of radio channels */
99 #define AUDIO_PHI 5e-6 /* dispersion growth factor */
100 #define TBUF 128 /* max monitor line length */
103 * Tunable parameters. The DGAIN parameter can be changed to fit the
104 * audio response of the radio at 100 Hz. The WWV/WWVH data subcarrier
105 * is transmitted at about 20 percent percent modulation; the matched
106 * filter boosts it by a factor of 17 and the receiver response does
107 * what it does. The compromise value works for ICOM radios. If the
108 * radio is not tunable, the DCHAN parameter can be changed to fit the
109 * expected best propagation frequency: higher if further from the
110 * transmitter, lower if nearer. The compromise value works for the US
113 #define DCHAN 3 /* default radio channel (15 Mhz) */
114 #define DGAIN 5. /* subcarrier gain */
117 * General purpose status bits (status)
119 * SELV and/or SELH are set when WWV or WWVH have been heard and cleared
120 * on signal loss. SSYNC is set when the second sync pulse has been
121 * acquired and cleared by signal loss. MSYNC is set when the minute
122 * sync pulse has been acquired. DSYNC is set when the units digit has
123 * has reached the threshold and INSYNC is set when all nine digits have
124 * reached the threshold. The MSYNC, DSYNC and INSYNC bits are cleared
125 * only by timeout, upon which the driver starts over from scratch.
127 * DGATE is lit if the data bit amplitude or SNR is below thresholds and
128 * BGATE is lit if the pulse width amplitude or SNR is below thresolds.
129 * LEPSEC is set during the last minute of the leap day. At the end of
130 * this minute the driver inserts second 60 in the seconds state machine
131 * and the minute sync slips a second.
133 #define MSYNC 0x0001 /* minute epoch sync */
134 #define SSYNC 0x0002 /* second epoch sync */
135 #define DSYNC 0x0004 /* minute units sync */
136 #define INSYNC 0x0008 /* clock synchronized */
137 #define FGATE 0x0010 /* frequency gate */
138 #define DGATE 0x0020 /* data pulse amplitude error */
139 #define BGATE 0x0040 /* data pulse width error */
140 #define METRIC 0x0080 /* one or more stations heard */
141 #define LEPSEC 0x1000 /* leap minute */
144 * Station scoreboard bits
146 * These are used to establish the signal quality for each of the five
147 * frequencies and two stations.
149 #define SELV 0x0100 /* WWV station select */
150 #define SELH 0x0200 /* WWVH station select */
153 * Alarm status bits (alarm)
155 * These bits indicate various alarm conditions, which are decoded to
156 * form the quality character included in the timecode.
158 #define CMPERR 0x1 /* digit or misc bit compare error */
159 #define LOWERR 0x2 /* low bit or digit amplitude or SNR */
160 #define NINERR 0x4 /* less than nine digits in minute */
161 #define SYNERR 0x8 /* not tracking second sync */
164 * Watchcat timeouts (watch)
166 * If these timeouts expire, the status bits are mashed to zero and the
167 * driver starts from scratch. Suitably more refined procedures may be
168 * developed in future. All these are in minutes.
170 #define ACQSN 6 /* station acquisition timeout */
171 #define DATA 15 /* unit minutes timeout */
172 #define SYNCH 40 /* station sync timeout */
173 #define PANIC (2 * 1440) /* panic timeout */
176 * Thresholds. These establish the minimum signal level, minimum SNR and
177 * maximum jitter thresholds which establish the error and false alarm
178 * rates of the driver. The values defined here may be on the
179 * adventurous side in the interest of the highest sensitivity.
181 #define MTHR 13. /* minute sync gate (percent) */
182 #define TTHR 50. /* minute sync threshold (percent) */
183 #define AWND 20 /* minute sync jitter threshold (ms) */
184 #define ATHR 2500. /* QRZ minute sync threshold */
185 #define ASNR 20. /* QRZ minute sync SNR threshold (dB) */
186 #define QTHR 2500. /* QSY minute sync threshold */
187 #define QSNR 20. /* QSY minute sync SNR threshold (dB) */
188 #define STHR 2500. /* second sync threshold */
189 #define SSNR 15. /* second sync SNR threshold (dB) */
190 #define SCMP 10 /* second sync compare threshold */
191 #define DTHR 1000. /* bit threshold */
192 #define DSNR 10. /* bit SNR threshold (dB) */
193 #define AMIN 3 /* min bit count */
194 #define AMAX 6 /* max bit count */
195 #define BTHR 1000. /* digit threshold */
196 #define BSNR 3. /* digit likelihood threshold (dB) */
197 #define BCMP 3 /* digit compare threshold */
198 #define MAXERR 40 /* maximum error alarm */
201 * Tone frequency definitions. The increments are for 4.5-deg sine
204 #define MS (WWV_SEC / 1000) /* samples per millisecond */
205 #define IN100 ((100 * 80) / WWV_SEC) /* 100 Hz increment */
206 #define IN1000 ((1000 * 80) / WWV_SEC) /* 1000 Hz increment */
207 #define IN1200 ((1200 * 80) / WWV_SEC) /* 1200 Hz increment */
210 * Acquisition and tracking time constants
212 #define MINAVG 8 /* min averaging time */
213 #define MAXAVG 1024 /* max averaging time */
214 #define FCONST 3 /* frequency time constant */
215 #define TCONST 16 /* data bit/digit time constant */
218 * Miscellaneous status bits (misc)
220 * These bits correspond to designated bits in the WWV/H timecode. The
221 * bit probabilities are exponentially averaged over several minutes and
222 * processed by a integrator and threshold.
224 #define DUT1 0x01 /* 56 DUT .1 */
225 #define DUT2 0x02 /* 57 DUT .2 */
226 #define DUT4 0x04 /* 58 DUT .4 */
227 #define DUTS 0x08 /* 50 DUT sign */
228 #define DST1 0x10 /* 55 DST1 leap warning */
229 #define DST2 0x20 /* 2 DST2 DST1 delayed one day */
230 #define SECWAR 0x40 /* 3 leap second warning */
233 * The on-time synchronization point is the positive-going zero crossing
234 * of the first cycle of the 5-ms second pulse. The IIR baseband filter
235 * phase delay is 0.91 ms, while the receiver delay is approximately 4.7
236 * ms at 1000 Hz. The fudge value -0.45 ms due to the codec and other
237 * causes was determined by calibrating to a PPS signal from a GPS
238 * receiver. The additional propagation delay specific to each receiver
239 * location can be programmed in the fudge time1 and time2 values for
240 * WWV and WWVH, respectively.
242 * The resulting offsets with a 2.4-GHz P4 running FreeBSD 6.1 are
243 * generally within .02 ms short-term with .02 ms jitter. The long-term
244 * offsets vary up to 0.3 ms due to ionosperhic layer height variations.
245 * The processor load due to the driver is 5.8 percent.
247 #define PDELAY ((.91 + 4.7 - 0.45) / 1000) /* system delay (s) */
250 * Table of sine values at 4.5-degree increments. This is used by the
251 * synchronous matched filter demodulators.
254 0.000000e+00, 7.845910e-02, 1.564345e-01, 2.334454e-01, /* 0-3 */
255 3.090170e-01, 3.826834e-01, 4.539905e-01, 5.224986e-01, /* 4-7 */
256 5.877853e-01, 6.494480e-01, 7.071068e-01, 7.604060e-01, /* 8-11 */
257 8.090170e-01, 8.526402e-01, 8.910065e-01, 9.238795e-01, /* 12-15 */
258 9.510565e-01, 9.723699e-01, 9.876883e-01, 9.969173e-01, /* 16-19 */
259 1.000000e+00, 9.969173e-01, 9.876883e-01, 9.723699e-01, /* 20-23 */
260 9.510565e-01, 9.238795e-01, 8.910065e-01, 8.526402e-01, /* 24-27 */
261 8.090170e-01, 7.604060e-01, 7.071068e-01, 6.494480e-01, /* 28-31 */
262 5.877853e-01, 5.224986e-01, 4.539905e-01, 3.826834e-01, /* 32-35 */
263 3.090170e-01, 2.334454e-01, 1.564345e-01, 7.845910e-02, /* 36-39 */
264 -0.000000e+00, -7.845910e-02, -1.564345e-01, -2.334454e-01, /* 40-43 */
265 -3.090170e-01, -3.826834e-01, -4.539905e-01, -5.224986e-01, /* 44-47 */
266 -5.877853e-01, -6.494480e-01, -7.071068e-01, -7.604060e-01, /* 48-51 */
267 -8.090170e-01, -8.526402e-01, -8.910065e-01, -9.238795e-01, /* 52-55 */
268 -9.510565e-01, -9.723699e-01, -9.876883e-01, -9.969173e-01, /* 56-59 */
269 -1.000000e+00, -9.969173e-01, -9.876883e-01, -9.723699e-01, /* 60-63 */
270 -9.510565e-01, -9.238795e-01, -8.910065e-01, -8.526402e-01, /* 64-67 */
271 -8.090170e-01, -7.604060e-01, -7.071068e-01, -6.494480e-01, /* 68-71 */
272 -5.877853e-01, -5.224986e-01, -4.539905e-01, -3.826834e-01, /* 72-75 */
273 -3.090170e-01, -2.334454e-01, -1.564345e-01, -7.845910e-02, /* 76-79 */
274 0.000000e+00}; /* 80 */
277 * Decoder operations at the end of each second are driven by a state
278 * machine. The transition matrix consists of a dispatch table indexed
279 * by second number. Each entry in the table contains a case switch
280 * number and argument.
283 int sw; /* case switch number */
284 int arg; /* argument */
288 * Case switch numbers
290 #define IDLE 0 /* no operation */
291 #define COEF 1 /* BCD bit */
292 #define COEF1 2 /* BCD bit for minute unit */
293 #define COEF2 3 /* BCD bit not used */
294 #define DECIM9 4 /* BCD digit 0-9 */
295 #define DECIM6 5 /* BCD digit 0-6 */
296 #define DECIM3 6 /* BCD digit 0-3 */
297 #define DECIM2 7 /* BCD digit 0-2 */
298 #define MSCBIT 8 /* miscellaneous bit */
299 #define MSC20 9 /* miscellaneous bit */
300 #define MSC21 10 /* QSY probe channel */
301 #define MIN1 11 /* latch time */
302 #define MIN2 12 /* leap second */
303 #define SYNC2 13 /* latch minute sync pulse */
304 #define SYNC3 14 /* latch data pulse */
307 * Offsets in decoding matrix
309 #define MN 0 /* minute digits (2) */
310 #define HR 2 /* hour digits (2) */
311 #define DA 4 /* day digits (3) */
312 #define YR 7 /* year digits (2) */
314 struct progx progx[] = {
315 {SYNC2, 0}, /* 0 latch minute sync pulse */
316 {SYNC3, 0}, /* 1 latch data pulse */
317 {MSCBIT, DST2}, /* 2 dst2 */
318 {MSCBIT, SECWAR}, /* 3 lw */
319 {COEF, 0}, /* 4 1 year units */
323 {DECIM9, YR}, /* 8 */
324 {IDLE, 0}, /* 9 p1 */
325 {COEF1, 0}, /* 10 1 minute units */
326 {COEF1, 1}, /* 11 2 */
327 {COEF1, 2}, /* 12 4 */
328 {COEF1, 3}, /* 13 8 */
329 {DECIM9, MN}, /* 14 */
330 {COEF, 0}, /* 15 10 minute tens */
331 {COEF, 1}, /* 16 20 */
332 {COEF, 2}, /* 17 40 */
333 {COEF2, 3}, /* 18 80 (not used) */
334 {DECIM6, MN + 1}, /* 19 p2 */
335 {COEF, 0}, /* 20 1 hour units */
336 {COEF, 1}, /* 21 2 */
337 {COEF, 2}, /* 22 4 */
338 {COEF, 3}, /* 23 8 */
339 {DECIM9, HR}, /* 24 */
340 {COEF, 0}, /* 25 10 hour tens */
341 {COEF, 1}, /* 26 20 */
342 {COEF2, 2}, /* 27 40 (not used) */
343 {COEF2, 3}, /* 28 80 (not used) */
344 {DECIM2, HR + 1}, /* 29 p3 */
345 {COEF, 0}, /* 30 1 day units */
346 {COEF, 1}, /* 31 2 */
347 {COEF, 2}, /* 32 4 */
348 {COEF, 3}, /* 33 8 */
349 {DECIM9, DA}, /* 34 */
350 {COEF, 0}, /* 35 10 day tens */
351 {COEF, 1}, /* 36 20 */
352 {COEF, 2}, /* 37 40 */
353 {COEF, 3}, /* 38 80 */
354 {DECIM9, DA + 1}, /* 39 p4 */
355 {COEF, 0}, /* 40 100 day hundreds */
356 {COEF, 1}, /* 41 200 */
357 {COEF2, 2}, /* 42 400 (not used) */
358 {COEF2, 3}, /* 43 800 (not used) */
359 {DECIM3, DA + 2}, /* 44 */
364 {IDLE, 0}, /* 49 p5 */
365 {MSCBIT, DUTS}, /* 50 dut+- */
366 {COEF, 0}, /* 51 10 year tens */
367 {COEF, 1}, /* 52 20 */
368 {COEF, 2}, /* 53 40 */
369 {COEF, 3}, /* 54 80 */
370 {MSC20, DST1}, /* 55 dst1 */
371 {MSCBIT, DUT1}, /* 56 0.1 dut */
372 {MSCBIT, DUT2}, /* 57 0.2 */
373 {MSC21, DUT4}, /* 58 0.4 QSY probe channel */
374 {MIN1, 0}, /* 59 p6 latch time */
375 {MIN2, 0} /* 60 leap second */
379 * BCD coefficients for maximum-likelihood digit decode
381 #define P15 1. /* max positive number */
382 #define N15 -1. /* max negative number */
387 #define P9 (P15 / 4) /* mark (+1) */
388 #define N9 (N15 / 4) /* space (-1) */
391 {N9, N9, N9, N9}, /* 0 */
392 {P9, N9, N9, N9}, /* 1 */
393 {N9, P9, N9, N9}, /* 2 */
394 {P9, P9, N9, N9}, /* 3 */
395 {N9, N9, P9, N9}, /* 4 */
396 {P9, N9, P9, N9}, /* 5 */
397 {N9, P9, P9, N9}, /* 6 */
398 {P9, P9, P9, N9}, /* 7 */
399 {N9, N9, N9, P9}, /* 8 */
400 {P9, N9, N9, P9}, /* 9 */
401 {0, 0, 0, 0} /* backstop */
405 * Digits 0-6 (minute tens)
407 #define P6 (P15 / 3) /* mark (+1) */
408 #define N6 (N15 / 3) /* space (-1) */
411 {N6, N6, N6, 0}, /* 0 */
412 {P6, N6, N6, 0}, /* 1 */
413 {N6, P6, N6, 0}, /* 2 */
414 {P6, P6, N6, 0}, /* 3 */
415 {N6, N6, P6, 0}, /* 4 */
416 {P6, N6, P6, 0}, /* 5 */
417 {N6, P6, P6, 0}, /* 6 */
418 {0, 0, 0, 0} /* backstop */
422 * Digits 0-3 (day hundreds)
424 #define P3 (P15 / 2) /* mark (+1) */
425 #define N3 (N15 / 2) /* space (-1) */
428 {N3, N3, 0, 0}, /* 0 */
429 {P3, N3, 0, 0}, /* 1 */
430 {N3, P3, 0, 0}, /* 2 */
431 {P3, P3, 0, 0}, /* 3 */
432 {0, 0, 0, 0} /* backstop */
436 * Digits 0-2 (hour tens)
438 #define P2 (P15 / 2) /* mark (+1) */
439 #define N2 (N15 / 2) /* space (-1) */
442 {N2, N2, 0, 0}, /* 0 */
443 {P2, N2, 0, 0}, /* 1 */
444 {N2, P2, 0, 0}, /* 2 */
445 {0, 0, 0, 0} /* backstop */
449 * DST decode (DST2 DST1) for prettyprint
452 'S', /* 00 standard time */
453 'I', /* 01 set clock ahead at 0200 local */
454 'O', /* 10 set clock back at 0200 local */
455 'D' /* 11 daylight time */
459 * The decoding matrix consists of nine row vectors, one for each digit
460 * of the timecode. The digits are stored from least to most significant
461 * order. The maximum-likelihood timecode is formed from the digits
462 * corresponding to the maximum-likelihood values reading in the
463 * opposite order: yy ddd hh:mm.
466 int radix; /* radix (3, 4, 6, 10) */
467 int digit; /* current clock digit */
468 int count; /* match count */
469 double digprb; /* max digit probability */
470 double digsnr; /* likelihood function (dB) */
471 double like[10]; /* likelihood integrator 0-9 */
475 * The station structure (sp) is used to acquire the minute pulse from
476 * WWV and/or WWVH. These stations are distinguished by the frequency
477 * used for the second and minute sync pulses, 1000 Hz for WWV and 1200
478 * Hz for WWVH. Other than frequency, the format is the same.
481 double epoch; /* accumulated epoch differences */
482 double maxeng; /* sync max energy */
483 double noieng; /* sync noise energy */
484 long pos; /* max amplitude position */
485 long lastpos; /* last max position */
486 long mepoch; /* minute synch epoch */
488 double amp; /* sync signal */
489 double syneng; /* sync signal max */
490 double synmax; /* sync signal max latched at 0 s */
491 double synsnr; /* sync signal SNR */
492 double metric; /* signal quality metric */
493 int reach; /* reachability register */
494 int count; /* bit counter */
495 int select; /* select bits */
496 char refid[5]; /* reference identifier */
500 * The channel structure (cp) is used to mitigate between channels.
503 int gain; /* audio gain */
504 struct sync wwv; /* wwv station */
505 struct sync wwvh; /* wwvh station */
509 * WWV unit control structure (up)
512 l_fp timestamp; /* audio sample timestamp */
513 l_fp tick; /* audio sample increment */
514 double phase, freq; /* logical clock phase and frequency */
515 double monitor; /* audio monitor point */
516 double pdelay; /* propagation delay (s) */
518 int fd_icom; /* ICOM file descriptor */
520 int errflg; /* error flags */
521 int watch; /* watchcat */
524 * Audio codec variables
526 double comp[SIZE]; /* decompanding table */
527 int port; /* codec port */
528 int gain; /* codec gain */
529 int mongain; /* codec monitor gain */
530 int clipcnt; /* sample clipped count */
533 * Variables used to establish basic system timing
535 int avgint; /* master time constant */
536 int yepoch; /* sync epoch */
537 int repoch; /* buffered sync epoch */
538 double epomax; /* second sync amplitude */
539 double eposnr; /* second sync SNR */
540 double irig; /* data I channel amplitude */
541 double qrig; /* data Q channel amplitude */
542 int datapt; /* 100 Hz ramp */
543 double datpha; /* 100 Hz VFO control */
544 int rphase; /* second sample counter */
545 long mphase; /* minute sample counter */
548 * Variables used to mitigate which channel to use
550 struct chan mitig[NCHAN]; /* channel data */
551 struct sync *sptr; /* station pointer */
552 int dchan; /* data channel */
553 int schan; /* probe channel */
554 int achan; /* active channel */
557 * Variables used by the clock state machine
559 struct decvec decvec[9]; /* decoding matrix */
560 int rsec; /* seconds counter */
561 int digcnt; /* count of digits synchronized */
564 * Variables used to estimate signal levels and bit/digit
567 double datsig; /* data signal max */
568 double datsnr; /* data signal SNR (dB) */
571 * Variables used to establish status and alarm conditions
573 int status; /* status bits */
574 int alarm; /* alarm flashers */
575 int misc; /* miscellaneous timecode bits */
576 int errcnt; /* data bit error counter */
580 * Function prototypes
582 static int wwv_start (int, struct peer *);
583 static void wwv_shutdown (int, struct peer *);
584 static void wwv_receive (struct recvbuf *);
585 static void wwv_poll (int, struct peer *);
588 * More function prototypes
590 static void wwv_epoch (struct peer *);
591 static void wwv_rf (struct peer *, double);
592 static void wwv_endpoc (struct peer *, int);
593 static void wwv_rsec (struct peer *, double);
594 static void wwv_qrz (struct peer *, struct sync *, int);
595 static void wwv_corr4 (struct peer *, struct decvec *,
596 double [], double [][4]);
597 static void wwv_gain (struct peer *);
598 static void wwv_tsec (struct peer *);
599 static int timecode (struct wwvunit *, char *, size_t);
600 static double wwv_snr (double, double);
601 static int carry (struct decvec *);
602 static int wwv_newchan (struct peer *);
603 static void wwv_newgame (struct peer *);
604 static double wwv_metric (struct sync *);
605 static void wwv_clock (struct peer *);
607 static int wwv_qsy (struct peer *, int);
610 static double qsy[NCHAN] = {2.5, 5, 10, 15, 20}; /* frequencies (MHz) */
615 struct refclock refclock_wwv = {
616 wwv_start, /* start up driver */
617 wwv_shutdown, /* shut down driver */
618 wwv_poll, /* transmit poll message */
619 noentry, /* not used (old wwv_control) */
620 noentry, /* initialize driver (not used) */
621 noentry, /* not used (old wwv_buginfo) */
622 NOFLAGS /* not used */
627 * wwv_start - open the devices and initialize data for processing
631 int unit, /* instance number (used by PCM) */
632 struct peer *peer /* peer structure pointer */
635 struct refclockproc *pp;
644 int fd; /* file descriptor */
646 double step; /* codec adjustment */
651 fd = audio_init(DEVICE_AUDIO, AUDIO_BUFSIZ, unit);
660 * Allocate and initialize unit structure
662 up = emalloc_zero(sizeof(*up));
664 pp->io.clock_recv = wwv_receive;
665 pp->io.srcclock = peer;
668 if (!io_addclock(&pp->io)) {
676 * Initialize miscellaneous variables
678 peer->precision = PRECISION;
679 pp->clockdesc = DESCRIPTION;
682 * The companded samples are encoded sign-magnitude. The table
683 * contains all the 256 values in the interest of speed.
685 up->comp[0] = up->comp[OFFSET] = 0.;
686 up->comp[1] = 1.; up->comp[OFFSET + 1] = -1.;
687 up->comp[2] = 3.; up->comp[OFFSET + 2] = -3.;
689 for (i = 3; i < OFFSET; i++) {
690 up->comp[i] = up->comp[i - 1] + step;
691 up->comp[OFFSET + i] = -up->comp[i];
695 DTOLFP(1. / WWV_SEC, &up->tick);
698 * Initialize the decoding matrix with the radix for each digit
701 up->decvec[MN].radix = 10; /* minutes */
702 up->decvec[MN + 1].radix = 6;
703 up->decvec[HR].radix = 10; /* hours */
704 up->decvec[HR + 1].radix = 3;
705 up->decvec[DA].radix = 10; /* days */
706 up->decvec[DA + 1].radix = 10;
707 up->decvec[DA + 2].radix = 4;
708 up->decvec[YR].radix = 10; /* years */
709 up->decvec[YR + 1].radix = 10;
713 * Initialize autotune if available. Note that the ICOM select
714 * code must be less than 128, so the high order bit can be used
715 * to select the line speed 0 (9600 bps) or 1 (1200 bps). Note
716 * we don't complain if the ICOM device is not there; but, if it
717 * is, the radio better be working.
724 if (peer->ttl != 0) {
725 if (peer->ttl & 0x80)
726 up->fd_icom = icom_init("/dev/icom", B1200,
729 up->fd_icom = icom_init("/dev/icom", B9600,
732 if (up->fd_icom > 0) {
733 if (wwv_qsy(peer, DCHAN) != 0) {
734 msyslog(LOG_NOTICE, "icom: radio not found");
738 msyslog(LOG_NOTICE, "icom: autotune enabled");
744 * Let the games begin.
752 * wwv_shutdown - shut down the clock
756 int unit, /* instance number (not used) */
757 struct peer *peer /* peer structure pointer */
760 struct refclockproc *pp;
768 io_closeclock(&pp->io);
778 * wwv_receive - receive data from the audio device
780 * This routine reads input samples and adjusts the logical clock to
781 * track the A/D sample clock by dropping or duplicating codec samples.
782 * It also controls the A/D signal level with an AGC loop to mimimize
783 * quantization noise and avoid overload.
787 struct recvbuf *rbufp /* receive buffer structure pointer */
791 struct refclockproc *pp;
797 double sample; /* codec sample */
798 u_char *dpt; /* buffer pointer */
799 int bufcnt; /* buffer counter */
802 peer = rbufp->recv_peer;
807 * Main loop - read until there ain't no more. Note codec
808 * samples are bit-inverted.
810 DTOLFP((double)rbufp->recv_length / WWV_SEC, <emp);
811 L_SUB(&rbufp->recv_time, <emp);
812 up->timestamp = rbufp->recv_time;
813 dpt = rbufp->recv_buffer;
814 for (bufcnt = 0; bufcnt < rbufp->recv_length; bufcnt++) {
815 sample = up->comp[~*dpt++ & 0xff];
818 * Clip noise spikes greater than MAXAMP (6000) and
819 * record the number of clips to be used later by the
822 if (sample > MAXAMP) {
825 } else if (sample < -MAXAMP) {
831 * Variable frequency oscillator. The codec oscillator
832 * runs at the nominal rate of 8000 samples per second,
833 * or 125 us per sample. A frequency change of one unit
834 * results in either duplicating or deleting one sample
835 * per second, which results in a frequency change of
838 up->phase += (up->freq + clock_codec) / WWV_SEC;
839 if (up->phase >= .5) {
841 } else if (up->phase < -.5) {
843 wwv_rf(peer, sample);
844 wwv_rf(peer, sample);
846 wwv_rf(peer, sample);
848 L_ADD(&up->timestamp, &up->tick);
852 * Set the input port and monitor gain for the next buffer.
854 if (pp->sloppyclockflag & CLK_FLAG2)
858 if (pp->sloppyclockflag & CLK_FLAG3)
859 up->mongain = MONGAIN;
866 * wwv_poll - called by the transmit procedure
868 * This routine keeps track of status. If no offset samples have been
869 * processed during a poll interval, a timeout event is declared. If
870 * errors have have occurred during the interval, they are reported as
875 int unit, /* instance number (not used) */
876 struct peer *peer /* peer structure pointer */
879 struct refclockproc *pp;
885 refclock_report(peer, up->errflg);
892 * wwv_rf - process signals and demodulate to baseband
894 * This routine grooms and filters decompanded raw audio samples. The
895 * output signal is the 100-Hz filtered baseband data signal in
896 * quadrature phase. The routine also determines the minute synch epoch,
897 * as well as certain signal maxima, minima and related values.
899 * There are two 1-s ramps used by this program. Both count the 8000
900 * logical clock samples spanning exactly one second. The epoch ramp
901 * counts the samples starting at an arbitrary time. The rphase ramp
902 * counts the samples starting at the 5-ms second sync pulse found
903 * during the epoch ramp.
905 * There are two 1-m ramps used by this program. The mphase ramp counts
906 * the 480,000 logical clock samples spanning exactly one minute and
907 * starting at an arbitrary time. The rsec ramp counts the 60 seconds of
908 * the minute starting at the 800-ms minute sync pulse found during the
909 * mphase ramp. The rsec ramp drives the seconds state machine to
910 * determine the bits and digits of the timecode.
912 * Demodulation operations are based on three synthesized quadrature
913 * sinusoids: 100 Hz for the data signal, 1000 Hz for the WWV sync
914 * signal and 1200 Hz for the WWVH sync signal. These drive synchronous
915 * matched filters for the data signal (170 ms at 100 Hz), WWV minute
916 * sync signal (800 ms at 1000 Hz) and WWVH minute sync signal (800 ms
917 * at 1200 Hz). Two additional matched filters are switched in
918 * as required for the WWV second sync signal (5 cycles at 1000 Hz) and
919 * WWVH second sync signal (6 cycles at 1200 Hz).
923 struct peer *peer, /* peerstructure pointer */
924 double isig /* input signal */
927 struct refclockproc *pp;
929 struct sync *sp, *rp;
931 static double lpf[5]; /* 150-Hz lpf delay line */
932 double data; /* lpf output */
933 static double bpf[9]; /* 1000/1200-Hz bpf delay line */
934 double syncx; /* bpf output */
935 static double mf[41]; /* 1000/1200-Hz mf delay line */
936 double mfsync; /* mf output */
938 static int iptr; /* data channel pointer */
939 static double ibuf[DATSIZ]; /* data I channel delay line */
940 static double qbuf[DATSIZ]; /* data Q channel delay line */
942 static int jptr; /* sync channel pointer */
943 static int kptr; /* tick channel pointer */
945 static int csinptr; /* wwv channel phase */
946 static double cibuf[SYNSIZ]; /* wwv I channel delay line */
947 static double cqbuf[SYNSIZ]; /* wwv Q channel delay line */
948 static double ciamp; /* wwv I channel amplitude */
949 static double cqamp; /* wwv Q channel amplitude */
951 static double csibuf[TCKSIZ]; /* wwv I tick delay line */
952 static double csqbuf[TCKSIZ]; /* wwv Q tick delay line */
953 static double csiamp; /* wwv I tick amplitude */
954 static double csqamp; /* wwv Q tick amplitude */
956 static int hsinptr; /* wwvh channel phase */
957 static double hibuf[SYNSIZ]; /* wwvh I channel delay line */
958 static double hqbuf[SYNSIZ]; /* wwvh Q channel delay line */
959 static double hiamp; /* wwvh I channel amplitude */
960 static double hqamp; /* wwvh Q channel amplitude */
962 static double hsibuf[TCKSIZ]; /* wwvh I tick delay line */
963 static double hsqbuf[TCKSIZ]; /* wwvh Q tick delay line */
964 static double hsiamp; /* wwvh I tick amplitude */
965 static double hsqamp; /* wwvh Q tick amplitude */
967 static double epobuf[WWV_SEC]; /* second sync comb filter */
968 static double epomax, nxtmax; /* second sync amplitude buffer */
969 static int epopos; /* epoch second sync position buffer */
971 static int iniflg; /* initialization flag */
972 int epoch; /* comb filter index */
981 memset((char *)lpf, 0, sizeof(lpf));
982 memset((char *)bpf, 0, sizeof(bpf));
983 memset((char *)mf, 0, sizeof(mf));
984 memset((char *)ibuf, 0, sizeof(ibuf));
985 memset((char *)qbuf, 0, sizeof(qbuf));
986 memset((char *)cibuf, 0, sizeof(cibuf));
987 memset((char *)cqbuf, 0, sizeof(cqbuf));
988 memset((char *)csibuf, 0, sizeof(csibuf));
989 memset((char *)csqbuf, 0, sizeof(csqbuf));
990 memset((char *)hibuf, 0, sizeof(hibuf));
991 memset((char *)hqbuf, 0, sizeof(hqbuf));
992 memset((char *)hsibuf, 0, sizeof(hsibuf));
993 memset((char *)hsqbuf, 0, sizeof(hsqbuf));
994 memset((char *)epobuf, 0, sizeof(epobuf));
998 * Baseband data demodulation. The 100-Hz subcarrier is
999 * extracted using a 150-Hz IIR lowpass filter. This attenuates
1000 * the 1000/1200-Hz sync signals, as well as the 440-Hz and
1001 * 600-Hz tones and most of the noise and voice modulation
1004 * The subcarrier is transmitted 10 dB down from the carrier.
1005 * The DGAIN parameter can be adjusted for this and to
1006 * compensate for the radio audio response at 100 Hz.
1008 * Matlab IIR 4th-order IIR elliptic, 150 Hz lowpass, 0.2 dB
1009 * passband ripple, -50 dB stopband ripple, phase delay 0.97 ms.
1011 data = (lpf[4] = lpf[3]) * 8.360961e-01;
1012 data += (lpf[3] = lpf[2]) * -3.481740e+00;
1013 data += (lpf[2] = lpf[1]) * 5.452988e+00;
1014 data += (lpf[1] = lpf[0]) * -3.807229e+00;
1015 lpf[0] = isig * DGAIN - data;
1016 data = lpf[0] * 3.281435e-03
1017 + lpf[1] * -1.149947e-02
1018 + lpf[2] * 1.654858e-02
1019 + lpf[3] * -1.149947e-02
1020 + lpf[4] * 3.281435e-03;
1023 * The 100-Hz data signal is demodulated using a pair of
1024 * quadrature multipliers, matched filters and a phase lock
1025 * loop. The I and Q quadrature data signals are produced by
1026 * multiplying the filtered signal by 100-Hz sine and cosine
1027 * signals, respectively. The signals are processed by 170-ms
1028 * synchronous matched filters to produce the amplitude and
1029 * phase signals used by the demodulator. The signals are scaled
1030 * to produce unit energy at the maximum value.
1033 up->datapt = (up->datapt + IN100) % 80;
1034 dtemp = sintab[i] * data / (MS / 2. * DATCYC);
1035 up->irig -= ibuf[iptr];
1040 dtemp = sintab[i] * data / (MS / 2. * DATCYC);
1041 up->qrig -= qbuf[iptr];
1044 iptr = (iptr + 1) % DATSIZ;
1047 * Baseband sync demodulation. The 1000/1200 sync signals are
1048 * extracted using a 600-Hz IIR bandpass filter. This removes
1049 * the 100-Hz data subcarrier, as well as the 440-Hz and 600-Hz
1050 * tones and most of the noise and voice modulation components.
1052 * Matlab 4th-order IIR elliptic, 800-1400 Hz bandpass, 0.2 dB
1053 * passband ripple, -50 dB stopband ripple, phase delay 0.91 ms.
1055 syncx = (bpf[8] = bpf[7]) * 4.897278e-01;
1056 syncx += (bpf[7] = bpf[6]) * -2.765914e+00;
1057 syncx += (bpf[6] = bpf[5]) * 8.110921e+00;
1058 syncx += (bpf[5] = bpf[4]) * -1.517732e+01;
1059 syncx += (bpf[4] = bpf[3]) * 1.975197e+01;
1060 syncx += (bpf[3] = bpf[2]) * -1.814365e+01;
1061 syncx += (bpf[2] = bpf[1]) * 1.159783e+01;
1062 syncx += (bpf[1] = bpf[0]) * -4.735040e+00;
1063 bpf[0] = isig - syncx;
1064 syncx = bpf[0] * 8.203628e-03
1065 + bpf[1] * -2.375732e-02
1066 + bpf[2] * 3.353214e-02
1067 + bpf[3] * -4.080258e-02
1068 + bpf[4] * 4.605479e-02
1069 + bpf[5] * -4.080258e-02
1070 + bpf[6] * 3.353214e-02
1071 + bpf[7] * -2.375732e-02
1072 + bpf[8] * 8.203628e-03;
1075 * The 1000/1200 sync signals are demodulated using a pair of
1076 * quadrature multipliers and matched filters. However,
1077 * synchronous demodulation at these frequencies is impractical,
1078 * so only the signal amplitude is used. The I and Q quadrature
1079 * sync signals are produced by multiplying the filtered signal
1080 * by 1000-Hz (WWV) and 1200-Hz (WWVH) sine and cosine signals,
1081 * respectively. The WWV and WWVH signals are processed by 800-
1082 * ms synchronous matched filters and combined to produce the
1083 * minute sync signal and detect which one (or both) the WWV or
1084 * WWVH signal is present. The WWV and WWVH signals are also
1085 * processed by 5-ms synchronous matched filters and combined to
1086 * produce the second sync signal. The signals are scaled to
1087 * produce unit energy at the maximum value.
1089 * Note the master timing ramps, which run continuously. The
1090 * minute counter (mphase) counts the samples in the minute,
1091 * while the second counter (epoch) counts the samples in the
1094 up->mphase = (up->mphase + 1) % WWV_MIN;
1095 epoch = up->mphase % WWV_SEC;
1101 csinptr = (csinptr + IN1000) % 80;
1103 dtemp = sintab[i] * syncx / (MS / 2.);
1104 ciamp -= cibuf[jptr];
1105 cibuf[jptr] = dtemp;
1107 csiamp -= csibuf[kptr];
1108 csibuf[kptr] = dtemp;
1112 dtemp = sintab[i] * syncx / (MS / 2.);
1113 cqamp -= cqbuf[jptr];
1114 cqbuf[jptr] = dtemp;
1116 csqamp -= csqbuf[kptr];
1117 csqbuf[kptr] = dtemp;
1120 sp = &up->mitig[up->achan].wwv;
1121 sp->amp = sqrt(ciamp * ciamp + cqamp * cqamp) / SYNCYC;
1122 if (!(up->status & MSYNC))
1123 wwv_qrz(peer, sp, (int)(pp->fudgetime1 * WWV_SEC));
1129 hsinptr = (hsinptr + IN1200) % 80;
1131 dtemp = sintab[i] * syncx / (MS / 2.);
1132 hiamp -= hibuf[jptr];
1133 hibuf[jptr] = dtemp;
1135 hsiamp -= hsibuf[kptr];
1136 hsibuf[kptr] = dtemp;
1140 dtemp = sintab[i] * syncx / (MS / 2.);
1141 hqamp -= hqbuf[jptr];
1142 hqbuf[jptr] = dtemp;
1144 hsqamp -= hsqbuf[kptr];
1145 hsqbuf[kptr] = dtemp;
1148 rp = &up->mitig[up->achan].wwvh;
1149 rp->amp = sqrt(hiamp * hiamp + hqamp * hqamp) / SYNCYC;
1150 if (!(up->status & MSYNC))
1151 wwv_qrz(peer, rp, (int)(pp->fudgetime2 * WWV_SEC));
1152 jptr = (jptr + 1) % SYNSIZ;
1153 kptr = (kptr + 1) % TCKSIZ;
1156 * The following section is called once per minute. It does
1157 * housekeeping and timeout functions and empties the dustbins.
1159 if (up->mphase == 0) {
1161 if (!(up->status & MSYNC)) {
1164 * If minute sync has not been acquired before
1165 * ACQSN timeout (6 min), or if no signal is
1166 * heard, the program cycles to the next
1167 * frequency and tries again.
1169 if (!wwv_newchan(peer))
1174 * If the leap bit is set, set the minute epoch
1175 * back one second so the station processes
1176 * don't miss a beat.
1178 if (up->status & LEPSEC) {
1179 up->mphase -= WWV_SEC;
1181 up->mphase += WWV_MIN;
1187 * When the channel metric reaches threshold and the second
1188 * counter matches the minute epoch within the second, the
1189 * driver has synchronized to the station. The second number is
1190 * the remaining seconds until the next minute epoch, while the
1191 * sync epoch is zero. Watch out for the first second; if
1192 * already synchronized to the second, the buffered sync epoch
1195 * Note the guard interval is 200 ms; if for some reason the
1196 * clock drifts more than that, it might wind up in the wrong
1197 * second. If the maximum frequency error is not more than about
1198 * 1 PPM, the clock can go as much as two days while still in
1201 if (up->status & MSYNC) {
1203 } else if (up->sptr != NULL) {
1205 if (sp->metric >= TTHR && epoch == sp->mepoch % WWV_SEC)
1207 up->rsec = (60 - sp->mepoch / WWV_SEC) % 60;
1209 up->status |= MSYNC;
1211 if (!(up->status & SSYNC))
1212 up->repoch = up->yepoch = epoch;
1214 up->repoch = up->yepoch;
1220 * The second sync pulse is extracted using 5-ms (40 sample) FIR
1221 * matched filters at 1000 Hz for WWV or 1200 Hz for WWVH. This
1222 * pulse is used for the most precise synchronization, since if
1223 * provides a resolution of one sample (125 us). The filters run
1224 * only if the station has been reliably determined.
1226 if (up->status & SELV)
1227 mfsync = sqrt(csiamp * csiamp + csqamp * csqamp) /
1229 else if (up->status & SELH)
1230 mfsync = sqrt(hsiamp * hsiamp + hsqamp * hsqamp) /
1236 * Enhance the seconds sync pulse using a 1-s (8000-sample) comb
1237 * filter. Correct for the FIR matched filter delay, which is 5
1238 * ms for both the WWV and WWVH filters, and also for the
1239 * propagation delay. Once each second look for second sync. If
1240 * not in minute sync, fiddle the codec gain. Note the SNR is
1241 * computed from the maximum sample and the envelope of the
1242 * sample 6 ms before it, so if we slip more than a cycle the
1243 * SNR should plummet. The signal is scaled to produce unit
1244 * energy at the maximum value.
1246 dtemp = (epobuf[epoch] += (mfsync - epobuf[epoch]) /
1248 if (dtemp > epomax) {
1256 nxtmax = fabs(epobuf[j]);
1259 up->epomax = epomax;
1260 up->eposnr = wwv_snr(epomax, nxtmax);
1261 epopos -= TCKCYC * MS;
1264 wwv_endpoc(peer, epopos);
1265 if (!(up->status & SSYNC))
1266 up->alarm |= SYNERR;
1268 if (!(up->status & MSYNC))
1275 * wwv_qrz - identify and acquire WWV/WWVH minute sync pulse
1277 * This routine implements a virtual station process used to acquire
1278 * minute sync and to mitigate among the ten frequency and station
1279 * combinations. During minute sync acquisition the process probes each
1280 * frequency and station in turn for the minute pulse, which
1281 * involves searching through the entire 480,000-sample minute. The
1282 * process finds the maximum signal and RMS noise plus signal. Then, the
1283 * actual noise is determined by subtracting the energy of the matched
1286 * Students of radar receiver technology will discover this algorithm
1287 * amounts to a range-gate discriminator. A valid pulse must have peak
1288 * amplitude at least QTHR (2500) and SNR at least QSNR (20) dB and the
1289 * difference between the current and previous epoch must be less than
1290 * AWND (20 ms). Note that the discriminator peak occurs about 800 ms
1291 * into the second, so the timing is retarded to the previous second
1296 struct peer *peer, /* peer structure pointer */
1297 struct sync *sp, /* sync channel structure */
1298 int pdelay /* propagation delay (samples) */
1301 struct refclockproc *pp;
1303 char tbuf[TBUF]; /* monitor buffer */
1310 * Find the sample with peak amplitude, which defines the minute
1311 * epoch. Accumulate all samples to determine the total noise
1314 epoch = up->mphase - pdelay - SYNSIZ;
1317 if (sp->amp > sp->maxeng) {
1318 sp->maxeng = sp->amp;
1321 sp->noieng += sp->amp;
1324 * At the end of the minute, determine the epoch of the minute
1325 * sync pulse, as well as the difference between the current and
1326 * previous epoches due to the intrinsic frequency error plus
1327 * jitter. When calculating the SNR, subtract the pulse energy
1328 * from the total noise energy and then normalize.
1330 if (up->mphase == 0) {
1331 sp->synmax = sp->maxeng;
1332 sp->synsnr = wwv_snr(sp->synmax, (sp->noieng -
1333 sp->synmax) / WWV_MIN);
1335 sp->lastpos = sp->pos;
1336 epoch = (sp->pos - sp->lastpos) % WWV_MIN;
1338 if (sp->reach & (1 << AMAX))
1340 if (sp->synmax > ATHR && sp->synsnr > ASNR) {
1341 if (labs(epoch) < AWND * MS) {
1344 sp->mepoch = sp->lastpos = sp->pos;
1345 } else if (sp->count == 1) {
1346 sp->lastpos = sp->pos;
1349 if (up->watch > ACQSN)
1352 sp->metric = wwv_metric(sp);
1353 if (pp->sloppyclockflag & CLK_FLAG4) {
1354 snprintf(tbuf, sizeof(tbuf),
1355 "wwv8 %04x %3d %s %04x %.0f %.0f/%.1f %ld %ld",
1356 up->status, up->gain, sp->refid,
1357 sp->reach & 0xffff, sp->metric, sp->synmax,
1358 sp->synsnr, sp->pos % WWV_SEC, epoch);
1359 record_clock_stats(&peer->srcadr, tbuf);
1362 printf("%s\n", tbuf);
1365 sp->maxeng = sp->noieng = 0;
1371 * wwv_endpoc - identify and acquire second sync pulse
1373 * This routine is called at the end of the second sync interval. It
1374 * determines the second sync epoch position within the second and
1375 * disciplines the sample clock using a frequency-lock loop (FLL).
1377 * Second sync is determined in the RF input routine as the maximum
1378 * over all 8000 samples in the second comb filter. To assure accurate
1379 * and reliable time and frequency discipline, this routine performs a
1380 * great deal of heavy-handed heuristic data filtering and grooming.
1384 struct peer *peer, /* peer structure pointer */
1385 int epopos /* epoch max position */
1388 struct refclockproc *pp;
1390 static int epoch_mf[3]; /* epoch median filter */
1391 static int tepoch; /* current second epoch */
1392 static int xepoch; /* last second epoch */
1393 static int zepoch; /* last run epoch */
1394 static int zcount; /* last run end time */
1395 static int scount; /* seconds counter */
1396 static int syncnt; /* run length counter */
1397 static int maxrun; /* longest run length */
1398 static int mepoch; /* longest run end epoch */
1399 static int mcount; /* longest run end time */
1400 static int avgcnt; /* averaging interval counter */
1401 static int avginc; /* averaging ratchet */
1402 static int iniflg; /* initialization flag */
1403 char tbuf[TBUF]; /* monitor buffer */
1415 * If the signal amplitude or SNR fall below thresholds, dim the
1416 * second sync lamp and wait for hotter ions. If no stations are
1417 * heard, we are either in a probe cycle or the ions are really
1421 if (up->epomax < STHR || up->eposnr < SSNR) {
1422 up->status &= ~(SSYNC | FGATE);
1423 avgcnt = syncnt = maxrun = 0;
1426 if (!(up->status & (SELV | SELH)))
1430 * A three-stage median filter is used to help denoise the
1431 * second sync pulse. The median sample becomes the candidate
1434 epoch_mf[2] = epoch_mf[1];
1435 epoch_mf[1] = epoch_mf[0];
1436 epoch_mf[0] = epopos;
1437 if (epoch_mf[0] > epoch_mf[1]) {
1438 if (epoch_mf[1] > epoch_mf[2])
1439 tepoch = epoch_mf[1]; /* 0 1 2 */
1440 else if (epoch_mf[2] > epoch_mf[0])
1441 tepoch = epoch_mf[0]; /* 2 0 1 */
1443 tepoch = epoch_mf[2]; /* 0 2 1 */
1445 if (epoch_mf[1] < epoch_mf[2])
1446 tepoch = epoch_mf[1]; /* 2 1 0 */
1447 else if (epoch_mf[2] < epoch_mf[0])
1448 tepoch = epoch_mf[0]; /* 1 0 2 */
1450 tepoch = epoch_mf[2]; /* 1 2 0 */
1455 * If the epoch candidate is the same as the last one, increment
1456 * the run counter. If not, save the length, epoch and end
1457 * time of the current run for use later and reset the counter.
1458 * The epoch is considered valid if the run is at least SCMP
1459 * (10) s, the minute is synchronized and the interval since the
1460 * last epoch is not greater than the averaging interval. Thus,
1461 * after a long absence, the program will wait a full averaging
1462 * interval while the comb filter charges up and noise
1465 tmp2 = (tepoch - xepoch) % WWV_SEC;
1468 if (syncnt > SCMP && up->status & MSYNC && (up->status &
1469 FGATE || scount - zcount <= up->avgint)) {
1470 up->status |= SSYNC;
1471 up->yepoch = tepoch;
1473 } else if (syncnt >= maxrun) {
1479 if ((pp->sloppyclockflag & CLK_FLAG4) && !(up->status &
1481 snprintf(tbuf, sizeof(tbuf),
1482 "wwv1 %04x %3d %4d %5.0f %5.1f %5d %4d %4d %4d",
1483 up->status, up->gain, tepoch, up->epomax,
1484 up->eposnr, tmp2, avgcnt, syncnt,
1486 record_clock_stats(&peer->srcadr, tbuf);
1489 printf("%s\n", tbuf);
1493 if (avgcnt < up->avgint) {
1499 * The sample clock frequency is disciplined using a first-order
1500 * feedback loop with time constant consistent with the Allan
1501 * intercept of typical computer clocks. During each averaging
1502 * interval the candidate epoch at the end of the longest run is
1503 * determined. If the longest run is zero, all epoches in the
1504 * interval are different, so the candidate epoch is the current
1505 * epoch. The frequency update is computed from the candidate
1506 * epoch difference (125-us units) and time difference (seconds)
1509 if (syncnt >= maxrun) {
1521 * The master clock runs at the codec sample frequency of 8000
1522 * Hz, so the intrinsic time resolution is 125 us. The frequency
1523 * resolution ranges from 18 PPM at the minimum averaging
1524 * interval of 8 s to 0.12 PPM at the maximum interval of 1024
1525 * s. An offset update is determined at the end of the longest
1526 * run in each averaging interval. The frequency adjustment is
1527 * computed from the difference between offset updates and the
1528 * interval between them.
1530 * The maximum frequency adjustment ranges from 187 PPM at the
1531 * minimum interval to 1.5 PPM at the maximum. If the adjustment
1532 * exceeds the maximum, the update is discarded and the
1533 * hysteresis counter is decremented. Otherwise, the frequency
1534 * is incremented by the adjustment, but clamped to the maximum
1535 * 187.5 PPM. If the update is less than half the maximum, the
1536 * hysteresis counter is incremented. If the counter increments
1537 * to +3, the averaging interval is doubled and the counter set
1538 * to zero; if it decrements to -3, the interval is halved and
1539 * the counter set to zero.
1541 dtemp = (mepoch - zepoch) % WWV_SEC;
1542 if (up->status & FGATE) {
1543 if (fabs(dtemp) < MAXFREQ * MINAVG) {
1544 up->freq += (dtemp / 2.) / ((mcount - zcount) *
1546 if (up->freq > MAXFREQ)
1548 else if (up->freq < -MAXFREQ)
1549 up->freq = -MAXFREQ;
1550 if (fabs(dtemp) < MAXFREQ * MINAVG / 2.) {
1554 if (up->avgint < MAXAVG) {
1564 if (up->avgint > MINAVG) {
1571 if (pp->sloppyclockflag & CLK_FLAG4) {
1572 snprintf(tbuf, sizeof(tbuf),
1573 "wwv2 %04x %5.0f %5.1f %5d %4d %4d %4d %4.0f %7.2f",
1574 up->status, up->epomax, up->eposnr, mepoch,
1575 up->avgint, maxrun, mcount - zcount, dtemp,
1576 up->freq * 1e6 / WWV_SEC);
1577 record_clock_stats(&peer->srcadr, tbuf);
1580 printf("%s\n", tbuf);
1585 * This is a valid update; set up for the next interval.
1587 up->status |= FGATE;
1590 avgcnt = syncnt = maxrun = 0;
1595 * wwv_epoch - epoch scanner
1597 * This routine extracts data signals from the 100-Hz subcarrier. It
1598 * scans the receiver second epoch to determine the signal amplitudes
1599 * and pulse timings. Receiver synchronization is determined by the
1600 * minute sync pulse detected in the wwv_rf() routine and the second
1601 * sync pulse detected in the wwv_epoch() routine. The transmitted
1602 * signals are delayed by the propagation delay, receiver delay and
1603 * filter delay of this program. Delay corrections are introduced
1604 * separately for WWV and WWVH.
1606 * Most communications radios use a highpass filter in the audio stages,
1607 * which can do nasty things to the subcarrier phase relative to the
1608 * sync pulses. Therefore, the data subcarrier reference phase is
1609 * disciplined using the hardlimited quadrature-phase signal sampled at
1610 * the same time as the in-phase signal. The phase tracking loop uses
1611 * phase adjustments of plus-minus one sample (125 us).
1615 struct peer *peer /* peer structure pointer */
1618 struct refclockproc *pp;
1621 static double sigmin, sigzer, sigone, engmax, engmin;
1627 * Find the maximum minute sync pulse energy for both the
1628 * WWV and WWVH stations. This will be used later for channel
1629 * and station mitigation. Also set the seconds epoch at 800 ms
1630 * well before the end of the second to make sure we never set
1631 * the epoch backwards.
1633 cp = &up->mitig[up->achan];
1634 if (cp->wwv.amp > cp->wwv.syneng)
1635 cp->wwv.syneng = cp->wwv.amp;
1636 if (cp->wwvh.amp > cp->wwvh.syneng)
1637 cp->wwvh.syneng = cp->wwvh.amp;
1638 if (up->rphase == 800 * MS)
1639 up->repoch = up->yepoch;
1642 * Use the signal amplitude at epoch 15 ms as the noise floor.
1643 * This gives a guard time of +-15 ms from the beginning of the
1644 * second until the second pulse rises at 30 ms. There is a
1645 * compromise here; we want to delay the sample as long as
1646 * possible to give the radio time to change frequency and the
1647 * AGC to stabilize, but as early as possible if the second
1648 * epoch is not exact.
1650 if (up->rphase == 15 * MS)
1651 sigmin = sigzer = sigone = up->irig;
1654 * Latch the data signal at 200 ms. Keep this around until the
1655 * end of the second. Use the signal energy as the peak to
1656 * compute the SNR. Use the Q sample to adjust the 100-Hz
1657 * reference oscillator phase.
1659 if (up->rphase == 200 * MS) {
1661 engmax = sqrt(up->irig * up->irig + up->qrig *
1663 up->datpha = up->qrig / up->avgint;
1664 if (up->datpha >= 0) {
1666 if (up->datapt >= 80)
1677 * Latch the data signal at 500 ms. Keep this around until the
1678 * end of the second.
1680 else if (up->rphase == 500 * MS)
1684 * At the end of the second crank the clock state machine and
1685 * adjust the codec gain. Note the epoch is buffered from the
1686 * center of the second in order to avoid jitter while the
1687 * seconds synch is diddling the epoch. Then, determine the true
1688 * offset and update the median filter in the driver interface.
1690 * Use the energy at the end of the second as the noise to
1691 * compute the SNR for the data pulse. This gives a better
1692 * measurement than the beginning of the second, especially when
1693 * returning from the probe channel. This gives a guard time of
1694 * 30 ms from the decay of the longest pulse to the rise of the
1698 if (up->mphase % WWV_SEC == up->repoch) {
1699 up->status &= ~(DGATE | BGATE);
1700 engmin = sqrt(up->irig * up->irig + up->qrig *
1702 up->datsig = engmax;
1703 up->datsnr = wwv_snr(engmax, engmin);
1706 * If the amplitude or SNR is below threshold, average a
1707 * 0 in the the integrators; otherwise, average the
1708 * bipolar signal. This is done to avoid noise polution.
1710 if (engmax < DTHR || up->datsnr < DSNR) {
1711 up->status |= DGATE;
1716 wwv_rsec(peer, sigone - sigzer);
1718 if (up->status & (DGATE | BGATE))
1720 if (up->errcnt > MAXERR)
1721 up->alarm |= LOWERR;
1723 cp = &up->mitig[up->achan];
1725 cp->wwvh.syneng = 0;
1732 * wwv_rsec - process receiver second
1734 * This routine is called at the end of each receiver second to
1735 * implement the per-second state machine. The machine assembles BCD
1736 * digit bits, decodes miscellaneous bits and dances the leap seconds.
1738 * Normally, the minute has 60 seconds numbered 0-59. If the leap
1739 * warning bit is set, the last minute (1439) of 30 June (day 181 or 182
1740 * for leap years) or 31 December (day 365 or 366 for leap years) is
1741 * augmented by one second numbered 60. This is accomplished by
1742 * extending the minute interval by one second and teaching the state
1743 * machine to ignore it.
1747 struct peer *peer, /* peer structure pointer */
1751 static int iniflg; /* initialization flag */
1752 static double bcddld[4]; /* BCD data bits */
1753 static double bitvec[61]; /* bit integrator for misc bits */
1754 struct refclockproc *pp;
1757 struct sync *sp, *rp;
1758 char tbuf[TBUF]; /* monitor buffer */
1769 * The bit represents the probability of a hit on zero (negative
1770 * values), a hit on one (positive values) or a miss (zero
1771 * value). The likelihood vector is the exponential average of
1772 * these probabilities. Only the bits of this vector
1773 * corresponding to the miscellaneous bits of the timecode are
1774 * used, but it's easier to do them all. After that, crank the
1775 * seconds state machine.
1779 bitvec[nsec] += (bit - bitvec[nsec]) / TCONST;
1780 sw = progx[nsec].sw;
1781 arg = progx[nsec].arg;
1784 * The minute state machine. Fly off to a particular section as
1785 * directed by the transition matrix and second number.
1790 * Ignore this second.
1792 case IDLE: /* 9, 45-49 */
1796 * Probe channel stuff
1798 * The WWV/H format contains data pulses in second 59 (position
1799 * identifier) and second 1, but not in second 0. The minute
1800 * sync pulse is contained in second 0. At the end of second 58
1801 * QSY to the probe channel, which rotates in turn over all
1802 * WWV/H frequencies. At the end of second 0 measure the minute
1803 * sync pulse. At the end of second 1 measure the data pulse and
1804 * QSY back to the data channel. Note that the actions commented
1805 * here happen at the end of the second numbered as shown.
1807 * At the end of second 0 save the minute sync amplitude latched
1808 * at 800 ms as the signal later used to calculate the SNR.
1811 cp = &up->mitig[up->achan];
1812 cp->wwv.synmax = cp->wwv.syneng;
1813 cp->wwvh.synmax = cp->wwvh.syneng;
1817 * At the end of second 1 use the minute sync amplitude latched
1818 * at 800 ms as the noise to calculate the SNR. If the minute
1819 * sync pulse and SNR are above thresholds and the data pulse
1820 * amplitude and SNR are above thresolds, shift a 1 into the
1821 * station reachability register; otherwise, shift a 0. The
1822 * number of 1 bits in the last six intervals is a component of
1823 * the channel metric computed by the wwv_metric() routine.
1824 * Finally, QSY back to the data channel.
1827 cp = &up->mitig[up->achan];
1833 sp->synsnr = wwv_snr(sp->synmax, sp->amp);
1835 if (sp->reach & (1 << AMAX))
1837 if (sp->synmax >= QTHR && sp->synsnr >= QSNR &&
1838 !(up->status & (DGATE | BGATE))) {
1842 sp->metric = wwv_metric(sp);
1848 rp->synsnr = wwv_snr(rp->synmax, rp->amp);
1850 if (rp->reach & (1 << AMAX))
1852 if (rp->synmax >= QTHR && rp->synsnr >= QSNR &&
1853 !(up->status & (DGATE | BGATE))) {
1857 rp->metric = wwv_metric(rp);
1858 if (pp->sloppyclockflag & CLK_FLAG4) {
1859 snprintf(tbuf, sizeof(tbuf),
1860 "wwv5 %04x %3d %4d %.0f/%.1f %.0f/%.1f %s %04x %.0f %.0f/%.1f %s %04x %.0f %.0f/%.1f",
1861 up->status, up->gain, up->yepoch,
1862 up->epomax, up->eposnr, up->datsig,
1864 sp->refid, sp->reach & 0xffff,
1865 sp->metric, sp->synmax, sp->synsnr,
1866 rp->refid, rp->reach & 0xffff,
1867 rp->metric, rp->synmax, rp->synsnr);
1868 record_clock_stats(&peer->srcadr, tbuf);
1871 printf("%s\n", tbuf);
1874 up->errcnt = up->digcnt = up->alarm = 0;
1877 * If synchronized to a station, restart if no stations
1878 * have been heard within the PANIC timeout (2 days). If
1879 * not and the minute digit has been found, restart if
1880 * not synchronized withing the SYNCH timeout (40 m). If
1881 * not, restart if the unit digit has not been found
1882 * within the DATA timeout (15 m).
1884 if (up->status & INSYNC) {
1885 if (up->watch > PANIC) {
1889 } else if (up->status & DSYNC) {
1890 if (up->watch > SYNCH) {
1894 } else if (up->watch > DATA) {
1902 * Save the bit probability in the BCD data vector at the index
1903 * given by the argument. Bits not used in the digit are forced
1906 case COEF1: /* 4-7 */
1910 case COEF: /* 10-13, 15-17, 20-23, 25-26,
1911 30-33, 35-38, 40-41, 51-54 */
1912 if (up->status & DSYNC)
1918 case COEF2: /* 18, 27-28, 42-43 */
1923 * Correlate coefficient vector with each valid digit vector and
1924 * save in decoding matrix. We step through the decoding matrix
1925 * digits correlating each with the coefficients and saving the
1926 * greatest and the next lower for later SNR calculation.
1928 case DECIM2: /* 29 */
1929 wwv_corr4(peer, &up->decvec[arg], bcddld, bcd2);
1932 case DECIM3: /* 44 */
1933 wwv_corr4(peer, &up->decvec[arg], bcddld, bcd3);
1936 case DECIM6: /* 19 */
1937 wwv_corr4(peer, &up->decvec[arg], bcddld, bcd6);
1940 case DECIM9: /* 8, 14, 24, 34, 39 */
1941 wwv_corr4(peer, &up->decvec[arg], bcddld, bcd9);
1945 * Miscellaneous bits. If above the positive threshold, declare
1946 * 1; if below the negative threshold, declare 0; otherwise
1947 * raise the BGATE bit. The design is intended to avoid
1948 * integrating noise under low SNR conditions.
1950 case MSC20: /* 55 */
1951 wwv_corr4(peer, &up->decvec[YR + 1], bcddld, bcd9);
1954 case MSCBIT: /* 2-3, 50, 56-57 */
1955 if (bitvec[nsec] > BTHR) {
1956 if (!(up->misc & arg))
1957 up->alarm |= CMPERR;
1959 } else if (bitvec[nsec] < -BTHR) {
1961 up->alarm |= CMPERR;
1964 up->status |= BGATE;
1969 * Save the data channel gain, then QSY to the probe channel and
1970 * dim the seconds comb filters. The www_newchan() routine will
1971 * light them back up.
1973 case MSC21: /* 58 */
1974 if (bitvec[nsec] > BTHR) {
1975 if (!(up->misc & arg))
1976 up->alarm |= CMPERR;
1978 } else if (bitvec[nsec] < -BTHR) {
1980 up->alarm |= CMPERR;
1983 up->status |= BGATE;
1985 up->status &= ~(SELV | SELH);
1987 if (up->fd_icom > 0) {
1988 up->schan = (up->schan + 1) % NCHAN;
1989 wwv_qsy(peer, up->schan);
1991 up->mitig[up->achan].gain = up->gain;
1994 up->mitig[up->achan].gain = up->gain;
2001 * During second 59 the receiver and codec AGC are settling
2002 * down, so the data pulse is unusable as quality metric. If
2003 * LEPSEC is set on the last minute of 30 June or 31 December,
2004 * the transmitter and receiver insert an extra second (60) in
2005 * the timescale and the minute sync repeats the second. Once
2006 * leaps occurred at intervals of about 18 months, but the last
2007 * leap before the most recent leap in 1995 was in 1998.
2010 if (up->status & LEPSEC)
2016 up->status &= ~LEPSEC;
2022 if ((pp->sloppyclockflag & CLK_FLAG4) && !(up->status &
2024 snprintf(tbuf, sizeof(tbuf),
2025 "wwv3 %2d %04x %3d %4d %5.0f %5.1f %5.0f %5.1f %5.0f",
2026 nsec, up->status, up->gain, up->yepoch, up->epomax,
2027 up->eposnr, up->datsig, up->datsnr, bit);
2028 record_clock_stats(&peer->srcadr, tbuf);
2031 printf("%s\n", tbuf);
2034 pp->disp += AUDIO_PHI;
2038 * The radio clock is set if the alarm bits are all zero. After that,
2039 * the time is considered valid if the second sync bit is lit. It should
2040 * not be a surprise, especially if the radio is not tunable, that
2041 * sometimes no stations are above the noise and the integrators
2042 * discharge below the thresholds. We assume that, after a day of signal
2043 * loss, the minute sync epoch will be in the same second. This requires
2044 * the codec frequency be accurate within 6 PPM. Practical experience
2045 * shows the frequency typically within 0.1 PPM, so after a day of
2046 * signal loss, the time should be within 8.6 ms..
2050 struct peer *peer /* peer unit pointer */
2053 struct refclockproc *pp;
2055 l_fp offset; /* offset in NTP seconds */
2059 if (!(up->status & SSYNC))
2060 up->alarm |= SYNERR;
2062 up->alarm |= NINERR;
2064 up->status |= INSYNC;
2065 if (up->status & INSYNC && up->status & SSYNC) {
2066 if (up->misc & SECWAR)
2067 pp->leap = LEAP_ADDSECOND;
2069 pp->leap = LEAP_NOWARNING;
2070 pp->second = up->rsec;
2071 pp->minute = up->decvec[MN].digit + up->decvec[MN +
2073 pp->hour = up->decvec[HR].digit + up->decvec[HR +
2075 pp->day = up->decvec[DA].digit + up->decvec[DA +
2076 1].digit * 10 + up->decvec[DA + 2].digit * 100;
2077 pp->year = up->decvec[YR].digit + up->decvec[YR +
2081 if (!clocktime(pp->day, pp->hour, pp->minute,
2082 pp->second, GMT, up->timestamp.l_ui,
2083 &pp->yearstart, &offset.l_ui)) {
2084 up->errflg = CEVNT_BADTIME;
2088 pp->lastref = up->timestamp;
2089 refclock_process_offset(pp, offset,
2090 up->timestamp, PDELAY + up->pdelay);
2091 refclock_receive(peer);
2094 pp->lencode = timecode(up, pp->a_lastcode,
2095 sizeof(pp->a_lastcode));
2096 record_clock_stats(&peer->srcadr, pp->a_lastcode);
2099 printf("wwv: timecode %d %s\n", pp->lencode,
2106 * wwv_corr4 - determine maximum-likelihood digit
2108 * This routine correlates the received digit vector with the BCD
2109 * coefficient vectors corresponding to all valid digits at the given
2110 * position in the decoding matrix. The maximum value corresponds to the
2111 * maximum-likelihood digit, while the ratio of this value to the next
2112 * lower value determines the likelihood function. Note that, if the
2113 * digit is invalid, the likelihood vector is averaged toward a miss.
2117 struct peer *peer, /* peer unit pointer */
2118 struct decvec *vp, /* decoding table pointer */
2119 double data[], /* received data vector */
2120 double tab[][4] /* correlation vector array */
2123 struct refclockproc *pp;
2125 double topmax, nxtmax; /* metrics */
2126 double acc; /* accumulator */
2127 char tbuf[TBUF]; /* monitor buffer */
2128 int mldigit; /* max likelihood digit */
2135 * Correlate digit vector with each BCD coefficient vector. If
2136 * any BCD digit bit is bad, consider all bits a miss. Until the
2137 * minute units digit has been resolved, don't to anything else.
2138 * Note the SNR is calculated as the ratio of the largest
2139 * likelihood value to the next largest likelihood value.
2142 topmax = nxtmax = -MAXAMP;
2143 for (i = 0; tab[i][0] != 0; i++) {
2145 for (j = 0; j < 4; j++)
2146 acc += data[j] * tab[i][j];
2147 acc = (vp->like[i] += (acc - vp->like[i]) / TCONST);
2152 } else if (acc > nxtmax) {
2156 vp->digprb = topmax;
2157 vp->digsnr = wwv_snr(topmax, nxtmax);
2160 * The current maximum-likelihood digit is compared to the last
2161 * maximum-likelihood digit. If different, the compare counter
2162 * and maximum-likelihood digit are reset. When the compare
2163 * counter reaches the BCMP threshold (3), the digit is assumed
2164 * correct. When the compare counter of all nine digits have
2165 * reached threshold, the clock is assumed correct.
2167 * Note that the clock display digit is set before the compare
2168 * counter has reached threshold; however, the clock display is
2169 * not considered correct until all nine clock digits have
2170 * reached threshold. This is intended as eye candy, but avoids
2171 * mistakes when the signal is low and the SNR is very marginal.
2173 if (vp->digprb < BTHR || vp->digsnr < BSNR) {
2174 up->status |= BGATE;
2176 if (vp->digit != mldigit) {
2177 up->alarm |= CMPERR;
2181 vp->digit = mldigit;
2183 if (vp->count < BCMP)
2185 if (vp->count == BCMP) {
2186 up->status |= DSYNC;
2191 if ((pp->sloppyclockflag & CLK_FLAG4) && !(up->status &
2193 snprintf(tbuf, sizeof(tbuf),
2194 "wwv4 %2d %04x %3d %4d %5.0f %2d %d %d %d %5.0f %5.1f",
2195 up->rsec - 1, up->status, up->gain, up->yepoch,
2196 up->epomax, vp->radix, vp->digit, mldigit,
2197 vp->count, vp->digprb, vp->digsnr);
2198 record_clock_stats(&peer->srcadr, tbuf);
2201 printf("%s\n", tbuf);
2208 * wwv_tsec - transmitter minute processing
2210 * This routine is called at the end of the transmitter minute. It
2211 * implements a state machine that advances the logical clock subject to
2212 * the funny rules that govern the conventional clock and calendar.
2216 struct peer *peer /* driver structure pointer */
2219 struct refclockproc *pp;
2221 int minute, day, isleap;
2228 * Advance minute unit of the day. Don't propagate carries until
2229 * the unit minute digit has been found.
2231 temp = carry(&up->decvec[MN]); /* minute units */
2232 if (!(up->status & DSYNC))
2236 * Propagate carries through the day.
2238 if (temp == 0) /* carry minutes */
2239 temp = carry(&up->decvec[MN + 1]);
2240 if (temp == 0) /* carry hours */
2241 temp = carry(&up->decvec[HR]);
2243 temp = carry(&up->decvec[HR + 1]);
2246 * Decode the current minute and day. Set leap day if the
2247 * timecode leap bit is set on 30 June or 31 December. Set leap
2248 * minute if the last minute on leap day, but only if the clock
2249 * is syncrhronized. This code fails in 2400 AD.
2251 minute = up->decvec[MN].digit + up->decvec[MN + 1].digit *
2252 10 + up->decvec[HR].digit * 60 + up->decvec[HR +
2254 day = up->decvec[DA].digit + up->decvec[DA + 1].digit * 10 +
2255 up->decvec[DA + 2].digit * 100;
2258 * Set the leap bit on the last minute of the leap day.
2260 isleap = up->decvec[YR].digit & 0x3;
2261 if (up->misc & SECWAR && up->status & INSYNC) {
2262 if ((day == (isleap ? 182 : 183) || day == (isleap ?
2263 365 : 366)) && minute == 1439)
2264 up->status |= LEPSEC;
2268 * Roll the day if this the first minute and propagate carries
2275 while (carry(&up->decvec[HR]) != 0); /* advance to minute 0 */
2276 while (carry(&up->decvec[HR + 1]) != 0);
2278 temp = carry(&up->decvec[DA]); /* carry days */
2280 temp = carry(&up->decvec[DA + 1]);
2282 temp = carry(&up->decvec[DA + 2]);
2285 * Roll the year if this the first day and propagate carries
2286 * through the century.
2288 if (day != (isleap ? 365 : 366))
2292 while (carry(&up->decvec[DA]) != 1); /* advance to day 1 */
2293 while (carry(&up->decvec[DA + 1]) != 0);
2294 while (carry(&up->decvec[DA + 2]) != 0);
2295 temp = carry(&up->decvec[YR]); /* carry years */
2297 carry(&up->decvec[YR + 1]);
2302 * carry - process digit
2304 * This routine rotates a likelihood vector one position and increments
2305 * the clock digit modulo the radix. It returns the new clock digit or
2306 * zero if a carry occurred. Once synchronized, the clock digit will
2307 * match the maximum-likelihood digit corresponding to that position.
2311 struct decvec *dp /* decoding table pointer */
2318 if (dp->digit == dp->radix)
2320 temp = dp->like[dp->radix - 1];
2321 for (j = dp->radix - 1; j > 0; j--)
2322 dp->like[j] = dp->like[j - 1];
2329 * wwv_snr - compute SNR or likelihood function
2333 double signal, /* signal */
2334 double noise /* noise */
2340 * This is a little tricky. Due to the way things are measured,
2341 * either or both the signal or noise amplitude can be negative
2342 * or zero. The intent is that, if the signal is negative or
2343 * zero, the SNR must always be zero. This can happen with the
2344 * subcarrier SNR before the phase has been aligned. On the
2345 * other hand, in the likelihood function the "noise" is the
2346 * next maximum down from the peak and this could be negative.
2347 * However, in this case the SNR is truly stupendous, so we
2348 * simply cap at MAXSNR dB (40).
2352 } else if (noise <= 0) {
2355 rval = 20. * log10(signal / noise);
2364 * wwv_newchan - change to new data channel
2366 * The radio actually appears to have ten channels, one channel for each
2367 * of five frequencies and each of two stations (WWV and WWVH), although
2368 * if not tunable only the DCHAN channel appears live. While the radio
2369 * is tuned to the working data channel frequency and station for most
2370 * of the minute, during seconds 59, 0 and 1 the radio is tuned to a
2371 * probe frequency in order to search for minute sync pulse and data
2372 * subcarrier from other transmitters.
2374 * The search for WWV and WWVH operates simultaneously, with WWV minute
2375 * sync pulse at 1000 Hz and WWVH at 1200 Hz. The probe frequency
2376 * rotates each minute over 2.5, 5, 10, 15 and 20 MHz in order and yes,
2377 * we all know WWVH is dark on 20 MHz, but few remember when WWV was lit
2380 * This routine selects the best channel using a metric computed from
2381 * the reachability register and minute pulse amplitude. Normally, the
2382 * award goes to the the channel with the highest metric; but, in case
2383 * of ties, the award goes to the channel with the highest minute sync
2384 * pulse amplitude and then to the highest frequency.
2386 * The routine performs an important squelch function to keep dirty data
2387 * from polluting the integrators. In order to consider a station valid,
2388 * the metric must be at least MTHR (13); otherwise, the station select
2389 * bits are cleared so the second sync is disabled and the data bit
2390 * integrators averaged to a miss.
2394 struct peer *peer /* peer structure pointer */
2397 struct refclockproc *pp;
2399 struct sync *sp, *rp;
2407 * Search all five station pairs looking for the channel with
2413 for (i = 0; i < NCHAN; i++) {
2414 rp = &up->mitig[i].wwvh;
2416 if (dtemp >= rank) {
2421 rp = &up->mitig[i].wwv;
2423 if (dtemp >= rank) {
2431 * If the strongest signal is less than the MTHR threshold (13),
2432 * we are beneath the waves, so squelch the second sync and
2433 * advance to the next station. This makes sure all stations are
2434 * scanned when the ions grow dim. If the strongest signal is
2435 * greater than the threshold, tune to that frequency and
2438 up->status &= ~(SELV | SELH);
2440 up->dchan = (up->dchan + 1) % NCHAN;
2441 if (up->status & METRIC) {
2442 up->status &= ~METRIC;
2443 refclock_report(peer, CEVNT_PROP);
2449 memcpy(&pp->refid, sp->refid, 4);
2450 peer->refid = pp->refid;
2451 up->status |= METRIC;
2452 if (sp->select & SELV) {
2454 up->pdelay = pp->fudgetime1;
2455 } else if (sp->select & SELH) {
2457 up->pdelay = pp->fudgetime2;
2464 if (up->fd_icom > 0)
2465 wwv_qsy(peer, up->dchan);
2472 * wwv_newgame - reset and start over
2474 * There are three conditions resulting in a new game:
2476 * 1 After finding the minute pulse (MSYNC lit), going 15 minutes
2477 * (DATA) without finding the unit seconds digit.
2479 * 2 After finding good data (DSYNC lit), going more than 40 minutes
2480 * (SYNCH) without finding station sync (INSYNC lit).
2482 * 3 After finding station sync (INSYNC lit), going more than 2 days
2483 * (PANIC) without finding any station.
2487 struct peer *peer /* peer structure pointer */
2490 struct refclockproc *pp;
2499 * Initialize strategic values. Note we set the leap bits
2500 * NOTINSYNC and the refid "NONE".
2503 up->errflg = CEVNT_TIMEOUT;
2504 peer->leap = LEAP_NOTINSYNC;
2505 up->watch = up->status = up->alarm = 0;
2506 up->avgint = MINAVG;
2508 up->gain = MAXGAIN / 2;
2511 * Initialize the station processes for audio gain, select bit,
2512 * station/frequency identifier and reference identifier. Start
2513 * probing at the strongest channel or the default channel if
2516 memset(up->mitig, 0, sizeof(up->mitig));
2517 for (i = 0; i < NCHAN; i++) {
2519 cp->gain = up->gain;
2520 cp->wwv.select = SELV;
2521 snprintf(cp->wwv.refid, sizeof(cp->wwv.refid), "WV%.0f",
2523 cp->wwvh.select = SELH;
2524 snprintf(cp->wwvh.refid, sizeof(cp->wwvh.refid), "WH%.0f",
2527 up->dchan = (DCHAN + NCHAN - 1) % NCHAN;
2529 up->schan = up->dchan;
2533 * wwv_metric - compute station metric
2535 * The most significant bits represent the number of ones in the
2536 * station reachability register. The least significant bits represent
2537 * the minute sync pulse amplitude. The combined value is scaled 0-100.
2541 struct sync *sp /* station pointer */
2546 dtemp = sp->count * MAXAMP;
2547 if (sp->synmax < MAXAMP)
2548 dtemp += sp->synmax;
2550 dtemp += MAXAMP - 1;
2551 dtemp /= (AMAX + 1) * MAXAMP;
2552 return (dtemp * 100.);
2558 * wwv_qsy - Tune ICOM receiver
2560 * This routine saves the AGC for the current channel, switches to a new
2561 * channel and restores the AGC for that channel. If a tunable receiver
2562 * is not available, just fake it.
2566 struct peer *peer, /* peer structure pointer */
2567 int chan /* channel */
2571 struct refclockproc *pp;
2576 if (up->fd_icom > 0) {
2577 up->mitig[up->achan].gain = up->gain;
2578 rval = icom_freq(up->fd_icom, peer->ttl & 0x7f,
2581 up->gain = up->mitig[up->achan].gain;
2589 * timecode - assemble timecode string and length
2591 * Prettytime format - similar to Spectracom
2593 * sq yy ddd hh:mm:ss ld dut lset agc iden sig errs freq avgt
2595 * s sync indicator ('?' or ' ')
2596 * q error bits (hex 0-F)
2597 * yyyy year of century
2601 * ss second of minute)
2602 * l leap second warning (' ' or 'L')
2603 * d DST state ('S', 'D', 'I', or 'O')
2604 * dut DUT sign and magnitude (0.1 s)
2605 * lset minutes since last clock update
2606 * agc audio gain (0-255)
2607 * iden reference identifier (station and frequency)
2608 * sig signal quality (0-100)
2609 * errs bit errors in last minute
2610 * freq frequency offset (PPM)
2611 * avgt averaging time (s)
2615 struct wwvunit *up, /* driver structure pointer */
2616 char * tc, /* target string */
2617 size_t tcsiz /* target max chars */
2621 int year, day, hour, minute, second, dut;
2622 char synchar, leapchar, dst;
2627 * Common fixed-format fields
2629 synchar = (up->status & INSYNC) ? ' ' : '?';
2630 year = up->decvec[YR].digit + up->decvec[YR + 1].digit * 10 +
2632 day = up->decvec[DA].digit + up->decvec[DA + 1].digit * 10 +
2633 up->decvec[DA + 2].digit * 100;
2634 hour = up->decvec[HR].digit + up->decvec[HR + 1].digit * 10;
2635 minute = up->decvec[MN].digit + up->decvec[MN + 1].digit * 10;
2637 leapchar = (up->misc & SECWAR) ? 'L' : ' ';
2638 dst = dstcod[(up->misc >> 4) & 0x3];
2639 dut = up->misc & 0x7;
2640 if (!(up->misc & DUTS))
2642 snprintf(tc, tcsiz, "%c%1X", synchar, up->alarm);
2643 snprintf(cptr, sizeof(cptr),
2644 " %4d %03d %02d:%02d:%02d %c%c %+d",
2645 year, day, hour, minute, second, leapchar, dst, dut);
2646 strlcat(tc, cptr, tcsiz);
2649 * Specific variable-format fields
2652 snprintf(cptr, sizeof(cptr), " %d %d %s %.0f %d %.1f %d",
2653 up->watch, up->mitig[up->dchan].gain, sp->refid,
2654 sp->metric, up->errcnt, up->freq / WWV_SEC * 1e6,
2656 strlcat(tc, cptr, tcsiz);
2663 * wwv_gain - adjust codec gain
2665 * This routine is called at the end of each second. During the second
2666 * the number of signal clips above the MAXAMP threshold (6000). If
2667 * there are no clips, the gain is bumped up; if there are more than
2668 * MAXCLP clips (100), it is bumped down. The decoder is relatively
2669 * insensitive to amplitude, so this crudity works just peachy. The
2670 * routine also jiggles the input port and selectively mutes the
2675 struct peer *peer /* peer structure pointer */
2678 struct refclockproc *pp;
2685 * Apparently, the codec uses only the high order bits of the
2686 * gain control field. Thus, it may take awhile for changes to
2687 * wiggle the hardware bits.
2689 if (up->clipcnt == 0) {
2691 if (up->gain > MAXGAIN)
2693 } else if (up->clipcnt > MAXCLP) {
2698 audio_gain(up->gain, up->mongain, up->port);
2708 int refclock_wwv_bs;
2709 #endif /* REFCLOCK */