/* * refclock_wwv - clock driver for NIST WWV/H time/frequency station */ #ifdef HAVE_CONFIG_H #include <config.h> #endif #if defined(REFCLOCK) && defined(CLOCK_WWV) #include "ntpd.h" #include "ntp_io.h" #include "ntp_refclock.h" #include "ntp_calendar.h" #include "ntp_stdlib.h" #include "audio.h" #include <stdio.h> #include <ctype.h> #include <math.h> #ifdef HAVE_SYS_IOCTL_H # include <sys/ioctl.h> #endif /* HAVE_SYS_IOCTL_H */ #define ICOM 1 #ifdef ICOM #include "icom.h" #endif /* ICOM */ /* * Audio WWV/H demodulator/decoder * * This driver synchronizes the computer time using data encoded in * radio transmissions from NIST time/frequency stations WWV in Boulder, * CO, and WWVH in Kauai, HI. Transmissions are made continuously on * 2.5, 5, 10 and 15 MHz from WWV and WWVH, and 20 MHz from WWV. An * ordinary AM shortwave receiver can be tuned manually to one of these * frequencies or, in the case of ICOM receivers, the receiver can be * tuned automatically using this program as propagation conditions * change throughout the weasons, both day and night. * * The driver requires an audio codec or sound card with sampling rate 8 * kHz and mu-law companding. This is the same standard as used by the * telephone industry and is supported by most hardware and operating * systems, including Solaris, SunOS, FreeBSD, NetBSD and Linux. In this * implementation, only one audio driver and codec can be supported on a * single machine. * * The demodulation and decoding algorithms used in this driver are * based on those developed for the TAPR DSP93 development board and the * TI 320C25 digital signal processor described in: Mills, D.L. A * precision radio clock for WWV transmissions. Electrical Engineering * Report 97-8-1, University of Delaware, August 1997, 25 pp., available * from www.eecis.udel.edu/~mills/reports.html. The algorithms described * in this report have been modified somewhat to improve performance * under weak signal conditions and to provide an automatic station * identification feature. * * The ICOM code is normally compiled in the driver. It isn't used, * unless the mode keyword on the server configuration command specifies * a nonzero ICOM ID select code. The C-IV trace is turned on if the * debug level is greater than one. * * Fudge factors * * Fudge flag4 causes the dubugging output described above to be * recorded in the clockstats file. Fudge flag2 selects the audio input * port, where 0 is the mike port (default) and 1 is the line-in port. * It does not seem useful to select the compact disc player port. Fudge * flag3 enables audio monitoring of the input signal. For this purpose, * the monitor gain is set to a default value. * * CEVNT_BADTIME invalid date or time * CEVNT_PROP propagation failure - no stations heard * CEVNT_TIMEOUT timeout (see newgame() below) */ /* * General definitions. These ordinarily do not need to be changed. */ #define DEVICE_AUDIO "/dev/audio" /* audio device name */ #define AUDIO_BUFSIZ 320 /* audio buffer size (50 ms) */ #define PRECISION (-10) /* precision assumed (about 1 ms) */ #define DESCRIPTION "WWV/H Audio Demodulator/Decoder" /* WRU */ #define SECOND 8000 /* second epoch (sample rate) (Hz) */ #define MINUTE (SECOND * 60) /* minute epoch */ #define OFFSET 128 /* companded sample offset */ #define SIZE 256 /* decompanding table size */ #define MAXAMP 6000. /* max signal level reference */ #define MAXCLP 100 /* max clips above reference per s */ #define MAXSNR 40. /* max SNR reference */ #define MAXFREQ 1.5 /* max frequency tolerance (187 PPM) */ #define DATCYC 170 /* data filter cycles */ #define DATSIZ (DATCYC * MS) /* data filter size */ #define SYNCYC 800 /* minute filter cycles */ #define SYNSIZ (SYNCYC * MS) /* minute filter size */ #define TCKCYC 5 /* tick filter cycles */ #define TCKSIZ (TCKCYC * MS) /* tick filter size */ #define NCHAN 5 /* number of radio channels */ #define AUDIO_PHI 5e-6 /* dispersion growth factor */ #define TBUF 128 /* max monitor line length */ /* * Tunable parameters. The DGAIN parameter can be changed to fit the * audio response of the radio at 100 Hz. The WWV/WWVH data subcarrier * is transmitted at about 20 percent percent modulation; the matched * filter boosts it by a factor of 17 and the receiver response does * what it does. The compromise value works for ICOM radios. If the * radio is not tunable, the DCHAN parameter can be changed to fit the * expected best propagation frequency: higher if further from the * transmitter, lower if nearer. The compromise value works for the US * right coast. */ #define DCHAN 3 /* default radio channel (15 Mhz) */ #define DGAIN 5. /* subcarrier gain */ /* * General purpose status bits (status) * * SELV and/or SELH are set when WWV or WWVH have been heard and cleared * on signal loss. SSYNC is set when the second sync pulse has been * acquired and cleared by signal loss. MSYNC is set when the minute * sync pulse has been acquired. DSYNC is set when the units digit has * has reached the threshold and INSYNC is set when all nine digits have * reached the threshold. The MSYNC, DSYNC and INSYNC bits are cleared * only by timeout, upon which the driver starts over from scratch. * * DGATE is lit if the data bit amplitude or SNR is below thresholds and * BGATE is lit if the pulse width amplitude or SNR is below thresolds. * LEPSEC is set during the last minute of the leap day. At the end of * this minute the driver inserts second 60 in the seconds state machine * and the minute sync slips a second. */ #define MSYNC 0x0001 /* minute epoch sync */ #define SSYNC 0x0002 /* second epoch sync */ #define DSYNC 0x0004 /* minute units sync */ #define INSYNC 0x0008 /* clock synchronized */ #define FGATE 0x0010 /* frequency gate */ #define DGATE 0x0020 /* data pulse amplitude error */ #define BGATE 0x0040 /* data pulse width error */ #define METRIC 0x0080 /* one or more stations heard */ #define LEPSEC 0x1000 /* leap minute */ /* * Station scoreboard bits * * These are used to establish the signal quality for each of the five * frequencies and two stations. */ #define SELV 0x0100 /* WWV station select */ #define SELH 0x0200 /* WWVH station select */ /* * Alarm status bits (alarm) * * These bits indicate various alarm conditions, which are decoded to * form the quality character included in the timecode. */ #define CMPERR 0x1 /* digit or misc bit compare error */ #define LOWERR 0x2 /* low bit or digit amplitude or SNR */ #define NINERR 0x4 /* less than nine digits in minute */ #define SYNERR 0x8 /* not tracking second sync */ /* * Watchcat timeouts (watch) * * If these timeouts expire, the status bits are mashed to zero and the * driver starts from scratch. Suitably more refined procedures may be * developed in future. All these are in minutes. */ #define ACQSN 6 /* station acquisition timeout */ #define DATA 15 /* unit minutes timeout */ #define SYNCH 40 /* station sync timeout */ #define PANIC (2 * 1440) /* panic timeout */ /* * Thresholds. These establish the minimum signal level, minimum SNR and * maximum jitter thresholds which establish the error and false alarm * rates of the driver. The values defined here may be on the * adventurous side in the interest of the highest sensitivity. */ #define MTHR 13. /* minute sync gate (percent) */ #define TTHR 50. /* minute sync threshold (percent) */ #define AWND 20 /* minute sync jitter threshold (ms) */ #define ATHR 2500. /* QRZ minute sync threshold */ #define ASNR 20. /* QRZ minute sync SNR threshold (dB) */ #define QTHR 2500. /* QSY minute sync threshold */ #define QSNR 20. /* QSY minute sync SNR threshold (dB) */ #define STHR 2500. /* second sync threshold */ #define SSNR 15. /* second sync SNR threshold (dB) */ #define SCMP 10 /* second sync compare threshold */ #define DTHR 1000. /* bit threshold */ #define DSNR 10. /* bit SNR threshold (dB) */ #define AMIN 3 /* min bit count */ #define AMAX 6 /* max bit count */ #define BTHR 1000. /* digit threshold */ #define BSNR 3. /* digit likelihood threshold (dB) */ #define BCMP 3 /* digit compare threshold */ #define MAXERR 40 /* maximum error alarm */ /* * Tone frequency definitions. The increments are for 4.5-deg sine * table. */ #define MS (SECOND / 1000) /* samples per millisecond */ #define IN100 ((100 * 80) / SECOND) /* 100 Hz increment */ #define IN1000 ((1000 * 80) / SECOND) /* 1000 Hz increment */ #define IN1200 ((1200 * 80) / SECOND) /* 1200 Hz increment */ /* * Acquisition and tracking time constants */ #define MINAVG 8 /* min averaging time */ #define MAXAVG 1024 /* max averaging time */ #define FCONST 3 /* frequency time constant */ #define TCONST 16 /* data bit/digit time constant */ /* * Miscellaneous status bits (misc) * * These bits correspond to designated bits in the WWV/H timecode. The * bit probabilities are exponentially averaged over several minutes and * processed by a integrator and threshold. */ #define DUT1 0x01 /* 56 DUT .1 */ #define DUT2 0x02 /* 57 DUT .2 */ #define DUT4 0x04 /* 58 DUT .4 */ #define DUTS 0x08 /* 50 DUT sign */ #define DST1 0x10 /* 55 DST1 leap warning */ #define DST2 0x20 /* 2 DST2 DST1 delayed one day */ #define SECWAR 0x40 /* 3 leap second warning */ /* * The on-time synchronization point is the positive-going zero crossing * of the first cycle of the 5-ms second pulse. The IIR baseband filter * phase delay is 0.91 ms, while the receiver delay is approximately 4.7 * ms at 1000 Hz. The fudge value -0.45 ms due to the codec and other * causes was determined by calibrating to a PPS signal from a GPS * receiver. The additional propagation delay specific to each receiver * location can be programmed in the fudge time1 and time2 values for * WWV and WWVH, respectively. * * The resulting offsets with a 2.4-GHz P4 running FreeBSD 6.1 are * generally within .02 ms short-term with .02 ms jitter. The long-term * offsets vary up to 0.3 ms due to ionosperhic layer height variations. * The processor load due to the driver is 5.8 percent. */ #define PDELAY ((.91 + 4.7 - 0.45) / 1000) /* system delay (s) */ /* * Table of sine values at 4.5-degree increments. This is used by the * synchronous matched filter demodulators. */ double sintab[] = { 0.000000e+00, 7.845910e-02, 1.564345e-01, 2.334454e-01, /* 0-3 */ 3.090170e-01, 3.826834e-01, 4.539905e-01, 5.224986e-01, /* 4-7 */ 5.877853e-01, 6.494480e-01, 7.071068e-01, 7.604060e-01, /* 8-11 */ 8.090170e-01, 8.526402e-01, 8.910065e-01, 9.238795e-01, /* 12-15 */ 9.510565e-01, 9.723699e-01, 9.876883e-01, 9.969173e-01, /* 16-19 */ 1.000000e+00, 9.969173e-01, 9.876883e-01, 9.723699e-01, /* 20-23 */ 9.510565e-01, 9.238795e-01, 8.910065e-01, 8.526402e-01, /* 24-27 */ 8.090170e-01, 7.604060e-01, 7.071068e-01, 6.494480e-01, /* 28-31 */ 5.877853e-01, 5.224986e-01, 4.539905e-01, 3.826834e-01, /* 32-35 */ 3.090170e-01, 2.334454e-01, 1.564345e-01, 7.845910e-02, /* 36-39 */ -0.000000e+00, -7.845910e-02, -1.564345e-01, -2.334454e-01, /* 40-43 */ -3.090170e-01, -3.826834e-01, -4.539905e-01, -5.224986e-01, /* 44-47 */ -5.877853e-01, -6.494480e-01, -7.071068e-01, -7.604060e-01, /* 48-51 */ -8.090170e-01, -8.526402e-01, -8.910065e-01, -9.238795e-01, /* 52-55 */ -9.510565e-01, -9.723699e-01, -9.876883e-01, -9.969173e-01, /* 56-59 */ -1.000000e+00, -9.969173e-01, -9.876883e-01, -9.723699e-01, /* 60-63 */ -9.510565e-01, -9.238795e-01, -8.910065e-01, -8.526402e-01, /* 64-67 */ -8.090170e-01, -7.604060e-01, -7.071068e-01, -6.494480e-01, /* 68-71 */ -5.877853e-01, -5.224986e-01, -4.539905e-01, -3.826834e-01, /* 72-75 */ -3.090170e-01, -2.334454e-01, -1.564345e-01, -7.845910e-02, /* 76-79 */ 0.000000e+00}; /* 80 */ /* * Decoder operations at the end of each second are driven by a state * machine. The transition matrix consists of a dispatch table indexed * by second number. Each entry in the table contains a case switch * number and argument. */ struct progx { int sw; /* case switch number */ int arg; /* argument */ }; /* * Case switch numbers */ #define IDLE 0 /* no operation */ #define COEF 1 /* BCD bit */ #define COEF1 2 /* BCD bit for minute unit */ #define COEF2 3 /* BCD bit not used */ #define DECIM9 4 /* BCD digit 0-9 */ #define DECIM6 5 /* BCD digit 0-6 */ #define DECIM3 6 /* BCD digit 0-3 */ #define DECIM2 7 /* BCD digit 0-2 */ #define MSCBIT 8 /* miscellaneous bit */ #define MSC20 9 /* miscellaneous bit */ #define MSC21 10 /* QSY probe channel */ #define MIN1 11 /* latch time */ #define MIN2 12 /* leap second */ #define SYNC2 13 /* latch minute sync pulse */ #define SYNC3 14 /* latch data pulse */ /* * Offsets in decoding matrix */ #define MN 0 /* minute digits (2) */ #define HR 2 /* hour digits (2) */ #define DA 4 /* day digits (3) */ #define YR 7 /* year digits (2) */ struct progx progx[] = { {SYNC2, 0}, /* 0 latch minute sync pulse */ {SYNC3, 0}, /* 1 latch data pulse */ {MSCBIT, DST2}, /* 2 dst2 */ {MSCBIT, SECWAR}, /* 3 lw */ {COEF, 0}, /* 4 1 year units */ {COEF, 1}, /* 5 2 */ {COEF, 2}, /* 6 4 */ {COEF, 3}, /* 7 8 */ {DECIM9, YR}, /* 8 */ {IDLE, 0}, /* 9 p1 */ {COEF1, 0}, /* 10 1 minute units */ {COEF1, 1}, /* 11 2 */ {COEF1, 2}, /* 12 4 */ {COEF1, 3}, /* 13 8 */ {DECIM9, MN}, /* 14 */ {COEF, 0}, /* 15 10 minute tens */ {COEF, 1}, /* 16 20 */ {COEF, 2}, /* 17 40 */ {COEF2, 3}, /* 18 80 (not used) */ {DECIM6, MN + 1}, /* 19 p2 */ {COEF, 0}, /* 20 1 hour units */ {COEF, 1}, /* 21 2 */ {COEF, 2}, /* 22 4 */ {COEF, 3}, /* 23 8 */ {DECIM9, HR}, /* 24 */ {COEF, 0}, /* 25 10 hour tens */ {COEF, 1}, /* 26 20 */ {COEF2, 2}, /* 27 40 (not used) */ {COEF2, 3}, /* 28 80 (not used) */ {DECIM2, HR + 1}, /* 29 p3 */ {COEF, 0}, /* 30 1 day units */ {COEF, 1}, /* 31 2 */ {COEF, 2}, /* 32 4 */ {COEF, 3}, /* 33 8 */ {DECIM9, DA}, /* 34 */ {COEF, 0}, /* 35 10 day tens */ {COEF, 1}, /* 36 20 */ {COEF, 2}, /* 37 40 */ {COEF, 3}, /* 38 80 */ {DECIM9, DA + 1}, /* 39 p4 */ {COEF, 0}, /* 40 100 day hundreds */ {COEF, 1}, /* 41 200 */ {COEF2, 2}, /* 42 400 (not used) */ {COEF2, 3}, /* 43 800 (not used) */ {DECIM3, DA + 2}, /* 44 */ {IDLE, 0}, /* 45 */ {IDLE, 0}, /* 46 */ {IDLE, 0}, /* 47 */ {IDLE, 0}, /* 48 */ {IDLE, 0}, /* 49 p5 */ {MSCBIT, DUTS}, /* 50 dut+- */ {COEF, 0}, /* 51 10 year tens */ {COEF, 1}, /* 52 20 */ {COEF, 2}, /* 53 40 */ {COEF, 3}, /* 54 80 */ {MSC20, DST1}, /* 55 dst1 */ {MSCBIT, DUT1}, /* 56 0.1 dut */ {MSCBIT, DUT2}, /* 57 0.2 */ {MSC21, DUT4}, /* 58 0.4 QSY probe channel */ {MIN1, 0}, /* 59 p6 latch time */ {MIN2, 0} /* 60 leap second */ }; /* * BCD coefficients for maximum-likelihood digit decode */ #define P15 1. /* max positive number */ #define N15 -1. /* max negative number */ /* * Digits 0-9 */ #define P9 (P15 / 4) /* mark (+1) */ #define N9 (N15 / 4) /* space (-1) */ double bcd9[][4] = { {N9, N9, N9, N9}, /* 0 */ {P9, N9, N9, N9}, /* 1 */ {N9, P9, N9, N9}, /* 2 */ {P9, P9, N9, N9}, /* 3 */ {N9, N9, P9, N9}, /* 4 */ {P9, N9, P9, N9}, /* 5 */ {N9, P9, P9, N9}, /* 6 */ {P9, P9, P9, N9}, /* 7 */ {N9, N9, N9, P9}, /* 8 */ {P9, N9, N9, P9}, /* 9 */ {0, 0, 0, 0} /* backstop */ }; /* * Digits 0-6 (minute tens) */ #define P6 (P15 / 3) /* mark (+1) */ #define N6 (N15 / 3) /* space (-1) */ double bcd6[][4] = { {N6, N6, N6, 0}, /* 0 */ {P6, N6, N6, 0}, /* 1 */ {N6, P6, N6, 0}, /* 2 */ {P6, P6, N6, 0}, /* 3 */ {N6, N6, P6, 0}, /* 4 */ {P6, N6, P6, 0}, /* 5 */ {N6, P6, P6, 0}, /* 6 */ {0, 0, 0, 0} /* backstop */ }; /* * Digits 0-3 (day hundreds) */ #define P3 (P15 / 2) /* mark (+1) */ #define N3 (N15 / 2) /* space (-1) */ double bcd3[][4] = { {N3, N3, 0, 0}, /* 0 */ {P3, N3, 0, 0}, /* 1 */ {N3, P3, 0, 0}, /* 2 */ {P3, P3, 0, 0}, /* 3 */ {0, 0, 0, 0} /* backstop */ }; /* * Digits 0-2 (hour tens) */ #define P2 (P15 / 2) /* mark (+1) */ #define N2 (N15 / 2) /* space (-1) */ double bcd2[][4] = { {N2, N2, 0, 0}, /* 0 */ {P2, N2, 0, 0}, /* 1 */ {N2, P2, 0, 0}, /* 2 */ {0, 0, 0, 0} /* backstop */ }; /* * DST decode (DST2 DST1) for prettyprint */ char dstcod[] = { 'S', /* 00 standard time */ 'I', /* 01 set clock ahead at 0200 local */ 'O', /* 10 set clock back at 0200 local */ 'D' /* 11 daylight time */ }; /* * The decoding matrix consists of nine row vectors, one for each digit * of the timecode. The digits are stored from least to most significant * order. The maximum-likelihood timecode is formed from the digits * corresponding to the maximum-likelihood values reading in the * opposite order: yy ddd hh:mm. */ struct decvec { int radix; /* radix (3, 4, 6, 10) */ int digit; /* current clock digit */ int count; /* match count */ double digprb; /* max digit probability */ double digsnr; /* likelihood function (dB) */ double like[10]; /* likelihood integrator 0-9 */ }; /* * The station structure (sp) is used to acquire the minute pulse from * WWV and/or WWVH. These stations are distinguished by the frequency * used for the second and minute sync pulses, 1000 Hz for WWV and 1200 * Hz for WWVH. Other than frequency, the format is the same. */ struct sync { double epoch; /* accumulated epoch differences */ double maxeng; /* sync max energy */ double noieng; /* sync noise energy */ long pos; /* max amplitude position */ long lastpos; /* last max position */ long mepoch; /* minute synch epoch */ double amp; /* sync signal */ double syneng; /* sync signal max */ double synmax; /* sync signal max latched at 0 s */ double synsnr; /* sync signal SNR */ double metric; /* signal quality metric */ int reach; /* reachability register */ int count; /* bit counter */ int select; /* select bits */ char refid[5]; /* reference identifier */ }; /* * The channel structure (cp) is used to mitigate between channels. */ struct chan { int gain; /* audio gain */ struct sync wwv; /* wwv station */ struct sync wwvh; /* wwvh station */ }; /* * WWV unit control structure (up) */ struct wwvunit { l_fp timestamp; /* audio sample timestamp */ l_fp tick; /* audio sample increment */ double phase, freq; /* logical clock phase and frequency */ double monitor; /* audio monitor point */ double pdelay; /* propagation delay (s) */ #ifdef ICOM int fd_icom; /* ICOM file descriptor */ #endif /* ICOM */ int errflg; /* error flags */ int watch; /* watchcat */ /* * Audio codec variables */ double comp[SIZE]; /* decompanding table */ int port; /* codec port */ int gain; /* codec gain */ int mongain; /* codec monitor gain */ int clipcnt; /* sample clipped count */ /* * Variables used to establish basic system timing */ int avgint; /* master time constant */ int yepoch; /* sync epoch */ int repoch; /* buffered sync epoch */ double epomax; /* second sync amplitude */ double eposnr; /* second sync SNR */ double irig; /* data I channel amplitude */ double qrig; /* data Q channel amplitude */ int datapt; /* 100 Hz ramp */ double datpha; /* 100 Hz VFO control */ int rphase; /* second sample counter */ long mphase; /* minute sample counter */ /* * Variables used to mitigate which channel to use */ struct chan mitig[NCHAN]; /* channel data */ struct sync *sptr; /* station pointer */ int dchan; /* data channel */ int schan; /* probe channel */ int achan; /* active channel */ /* * Variables used by the clock state machine */ struct decvec decvec[9]; /* decoding matrix */ int rsec; /* seconds counter */ int digcnt; /* count of digits synchronized */ /* * Variables used to estimate signal levels and bit/digit * probabilities */ double datsig; /* data signal max */ double datsnr; /* data signal SNR (dB) */ /* * Variables used to establish status and alarm conditions */ int status; /* status bits */ int alarm; /* alarm flashers */ int misc; /* miscellaneous timecode bits */ int errcnt; /* data bit error counter */ }; /* * Function prototypes */ static int wwv_start (int, struct peer *); static void wwv_shutdown (int, struct peer *); static void wwv_receive (struct recvbuf *); static void wwv_poll (int, struct peer *); /* * More function prototypes */ static void wwv_epoch (struct peer *); static void wwv_rf (struct peer *, double); static void wwv_endpoc (struct peer *, int); static void wwv_rsec (struct peer *, double); static void wwv_qrz (struct peer *, struct sync *, int); static void wwv_corr4 (struct peer *, struct decvec *, double [], double [][4]); static void wwv_gain (struct peer *); static void wwv_tsec (struct peer *); static int timecode (struct wwvunit *, char *); static double wwv_snr (double, double); static int carry (struct decvec *); static int wwv_newchan (struct peer *); static void wwv_newgame (struct peer *); static double wwv_metric (struct sync *); static void wwv_clock (struct peer *); #ifdef ICOM static int wwv_qsy (struct peer *, int); #endif /* ICOM */ static double qsy[NCHAN] = {2.5, 5, 10, 15, 20}; /* frequencies (MHz) */ /* * Transfer vector */ struct refclock refclock_wwv = { wwv_start, /* start up driver */ wwv_shutdown, /* shut down driver */ wwv_poll, /* transmit poll message */ noentry, /* not used (old wwv_control) */ noentry, /* initialize driver (not used) */ noentry, /* not used (old wwv_buginfo) */ NOFLAGS /* not used */ }; /* * wwv_start - open the devices and initialize data for processing */ static int wwv_start( int unit, /* instance number (used by PCM) */ struct peer *peer /* peer structure pointer */ ) { struct refclockproc *pp; struct wwvunit *up; #ifdef ICOM int temp; #endif /* ICOM */ /* * Local variables */ int fd; /* file descriptor */ int i; /* index */ double step; /* codec adjustment */ /* * Open audio device */ fd = audio_init(DEVICE_AUDIO, AUDIO_BUFSIZ, unit); if (fd < 0) return (0); #ifdef DEBUG if (debug) audio_show(); #endif /* DEBUG */ /* * Allocate and initialize unit structure */ if (!(up = (struct wwvunit *)emalloc(sizeof(struct wwvunit)))) { close(fd); return (0); } memset(up, 0, sizeof(struct wwvunit)); pp = peer->procptr; pp->unitptr = (caddr_t)up; pp->io.clock_recv = wwv_receive; pp->io.srcclock = (caddr_t)peer; pp->io.datalen = 0; pp->io.fd = fd; if (!io_addclock(&pp->io)) { close(fd); free(up); return (0); } /* * Initialize miscellaneous variables */ peer->precision = PRECISION; pp->clockdesc = DESCRIPTION; /* * The companded samples are encoded sign-magnitude. The table * contains all the 256 values in the interest of speed. */ up->comp[0] = up->comp[OFFSET] = 0.; up->comp[1] = 1.; up->comp[OFFSET + 1] = -1.; up->comp[2] = 3.; up->comp[OFFSET + 2] = -3.; step = 2.; for (i = 3; i < OFFSET; i++) { up->comp[i] = up->comp[i - 1] + step; up->comp[OFFSET + i] = -up->comp[i]; if (i % 16 == 0) step *= 2.; } DTOLFP(1. / SECOND, &up->tick); /* * Initialize the decoding matrix with the radix for each digit * position. */ up->decvec[MN].radix = 10; /* minutes */ up->decvec[MN + 1].radix = 6; up->decvec[HR].radix = 10; /* hours */ up->decvec[HR + 1].radix = 3; up->decvec[DA].radix = 10; /* days */ up->decvec[DA + 1].radix = 10; up->decvec[DA + 2].radix = 4; up->decvec[YR].radix = 10; /* years */ up->decvec[YR + 1].radix = 10; #ifdef ICOM /* * Initialize autotune if available. Note that the ICOM select * code must be less than 128, so the high order bit can be used * to select the line speed 0 (9600 bps) or 1 (1200 bps). Note * we don't complain if the ICOM device is not there; but, if it * is, the radio better be working. */ temp = 0; #ifdef DEBUG if (debug > 1) temp = P_TRACE; #endif /* DEBUG */ if (peer->ttl != 0) { if (peer->ttl & 0x80) up->fd_icom = icom_init("/dev/icom", B1200, temp); else up->fd_icom = icom_init("/dev/icom", B9600, temp); } if (up->fd_icom > 0) { if (wwv_qsy(peer, DCHAN) != 0) { msyslog(LOG_NOTICE, "icom: radio not found"); close(up->fd_icom); up->fd_icom = 0; } else { msyslog(LOG_NOTICE, "icom: autotune enabled"); } } #endif /* ICOM */ /* * Let the games begin. */ wwv_newgame(peer); return (1); } /* * wwv_shutdown - shut down the clock */ static void wwv_shutdown( int unit, /* instance number (not used) */ struct peer *peer /* peer structure pointer */ ) { struct refclockproc *pp; struct wwvunit *up; pp = peer->procptr; up = (struct wwvunit *)pp->unitptr; if (up == NULL) return; io_closeclock(&pp->io); #ifdef ICOM if (up->fd_icom > 0) close(up->fd_icom); #endif /* ICOM */ free(up); } /* * wwv_receive - receive data from the audio device * * This routine reads input samples and adjusts the logical clock to * track the A/D sample clock by dropping or duplicating codec samples. * It also controls the A/D signal level with an AGC loop to mimimize * quantization noise and avoid overload. */ static void wwv_receive( struct recvbuf *rbufp /* receive buffer structure pointer */ ) { struct peer *peer; struct refclockproc *pp; struct wwvunit *up; /* * Local variables */ double sample; /* codec sample */ u_char *dpt; /* buffer pointer */ int bufcnt; /* buffer counter */ l_fp ltemp; peer = (struct peer *)rbufp->recv_srcclock; pp = peer->procptr; up = (struct wwvunit *)pp->unitptr; /* * Main loop - read until there ain't no more. Note codec * samples are bit-inverted. */ DTOLFP((double)rbufp->recv_length / SECOND, <emp); L_SUB(&rbufp->recv_time, <emp); up->timestamp = rbufp->recv_time; dpt = rbufp->recv_buffer; for (bufcnt = 0; bufcnt < rbufp->recv_length; bufcnt++) { sample = up->comp[~*dpt++ & 0xff]; /* * Clip noise spikes greater than MAXAMP (6000) and * record the number of clips to be used later by the * AGC. */ if (sample > MAXAMP) { sample = MAXAMP; up->clipcnt++; } else if (sample < -MAXAMP) { sample = -MAXAMP; up->clipcnt++; } /* * Variable frequency oscillator. The codec oscillator * runs at the nominal rate of 8000 samples per second, * or 125 us per sample. A frequency change of one unit * results in either duplicating or deleting one sample * per second, which results in a frequency change of * 125 PPM. */ up->phase += (up->freq + clock_codec) / SECOND; if (up->phase >= .5) { up->phase -= 1.; } else if (up->phase < -.5) { up->phase += 1.; wwv_rf(peer, sample); wwv_rf(peer, sample); } else { wwv_rf(peer, sample); } L_ADD(&up->timestamp, &up->tick); } /* * Set the input port and monitor gain for the next buffer. */ if (pp->sloppyclockflag & CLK_FLAG2) up->port = 2; else up->port = 1; if (pp->sloppyclockflag & CLK_FLAG3) up->mongain = MONGAIN; else up->mongain = 0; } /* * wwv_poll - called by the transmit procedure * * This routine keeps track of status. If no offset samples have been * processed during a poll interval, a timeout event is declared. If * errors have have occurred during the interval, they are reported as * well. */ static void wwv_poll( int unit, /* instance number (not used) */ struct peer *peer /* peer structure pointer */ ) { struct refclockproc *pp; struct wwvunit *up; pp = peer->procptr; up = (struct wwvunit *)pp->unitptr; if (up->errflg) refclock_report(peer, up->errflg); up->errflg = 0; pp->polls++; } /* * wwv_rf - process signals and demodulate to baseband * * This routine grooms and filters decompanded raw audio samples. The * output signal is the 100-Hz filtered baseband data signal in * quadrature phase. The routine also determines the minute synch epoch, * as well as certain signal maxima, minima and related values. * * There are two 1-s ramps used by this program. Both count the 8000 * logical clock samples spanning exactly one second. The epoch ramp * counts the samples starting at an arbitrary time. The rphase ramp * counts the samples starting at the 5-ms second sync pulse found * during the epoch ramp. * * There are two 1-m ramps used by this program. The mphase ramp counts * the 480,000 logical clock samples spanning exactly one minute and * starting at an arbitrary time. The rsec ramp counts the 60 seconds of * the minute starting at the 800-ms minute sync pulse found during the * mphase ramp. The rsec ramp drives the seconds state machine to * determine the bits and digits of the timecode. * * Demodulation operations are based on three synthesized quadrature * sinusoids: 100 Hz for the data signal, 1000 Hz for the WWV sync * signal and 1200 Hz for the WWVH sync signal. These drive synchronous * matched filters for the data signal (170 ms at 100 Hz), WWV minute * sync signal (800 ms at 1000 Hz) and WWVH minute sync signal (800 ms * at 1200 Hz). Two additional matched filters are switched in * as required for the WWV second sync signal (5 cycles at 1000 Hz) and * WWVH second sync signal (6 cycles at 1200 Hz). */ static void wwv_rf( struct peer *peer, /* peerstructure pointer */ double isig /* input signal */ ) { struct refclockproc *pp; struct wwvunit *up; struct sync *sp, *rp; static double lpf[5]; /* 150-Hz lpf delay line */ double data; /* lpf output */ static double bpf[9]; /* 1000/1200-Hz bpf delay line */ double syncx; /* bpf output */ static double mf[41]; /* 1000/1200-Hz mf delay line */ double mfsync; /* mf output */ static int iptr; /* data channel pointer */ static double ibuf[DATSIZ]; /* data I channel delay line */ static double qbuf[DATSIZ]; /* data Q channel delay line */ static int jptr; /* sync channel pointer */ static int kptr; /* tick channel pointer */ static int csinptr; /* wwv channel phase */ static double cibuf[SYNSIZ]; /* wwv I channel delay line */ static double cqbuf[SYNSIZ]; /* wwv Q channel delay line */ static double ciamp; /* wwv I channel amplitude */ static double cqamp; /* wwv Q channel amplitude */ static double csibuf[TCKSIZ]; /* wwv I tick delay line */ static double csqbuf[TCKSIZ]; /* wwv Q tick delay line */ static double csiamp; /* wwv I tick amplitude */ static double csqamp; /* wwv Q tick amplitude */ static int hsinptr; /* wwvh channel phase */ static double hibuf[SYNSIZ]; /* wwvh I channel delay line */ static double hqbuf[SYNSIZ]; /* wwvh Q channel delay line */ static double hiamp; /* wwvh I channel amplitude */ static double hqamp; /* wwvh Q channel amplitude */ static double hsibuf[TCKSIZ]; /* wwvh I tick delay line */ static double hsqbuf[TCKSIZ]; /* wwvh Q tick delay line */ static double hsiamp; /* wwvh I tick amplitude */ static double hsqamp; /* wwvh Q tick amplitude */ static double epobuf[SECOND]; /* second sync comb filter */ static double epomax, nxtmax; /* second sync amplitude buffer */ static int epopos; /* epoch second sync position buffer */ static int iniflg; /* initialization flag */ int epoch; /* comb filter index */ double dtemp; int i; pp = peer->procptr; up = (struct wwvunit *)pp->unitptr; if (!iniflg) { iniflg = 1; memset((char *)lpf, 0, sizeof(lpf)); memset((char *)bpf, 0, sizeof(bpf)); memset((char *)mf, 0, sizeof(mf)); memset((char *)ibuf, 0, sizeof(ibuf)); memset((char *)qbuf, 0, sizeof(qbuf)); memset((char *)cibuf, 0, sizeof(cibuf)); memset((char *)cqbuf, 0, sizeof(cqbuf)); memset((char *)csibuf, 0, sizeof(csibuf)); memset((char *)csqbuf, 0, sizeof(csqbuf)); memset((char *)hibuf, 0, sizeof(hibuf)); memset((char *)hqbuf, 0, sizeof(hqbuf)); memset((char *)hsibuf, 0, sizeof(hsibuf)); memset((char *)hsqbuf, 0, sizeof(hsqbuf)); memset((char *)epobuf, 0, sizeof(epobuf)); } /* * Baseband data demodulation. The 100-Hz subcarrier is * extracted using a 150-Hz IIR lowpass filter. This attenuates * the 1000/1200-Hz sync signals, as well as the 440-Hz and * 600-Hz tones and most of the noise and voice modulation * components. * * The subcarrier is transmitted 10 dB down from the carrier. * The DGAIN parameter can be adjusted for this and to * compensate for the radio audio response at 100 Hz. * * Matlab IIR 4th-order IIR elliptic, 150 Hz lowpass, 0.2 dB * passband ripple, -50 dB stopband ripple, phase delay 0.97 ms. */ data = (lpf[4] = lpf[3]) * 8.360961e-01; data += (lpf[3] = lpf[2]) * -3.481740e+00; data += (lpf[2] = lpf[1]) * 5.452988e+00; data += (lpf[1] = lpf[0]) * -3.807229e+00; lpf[0] = isig * DGAIN - data; data = lpf[0] * 3.281435e-03 + lpf[1] * -1.149947e-02 + lpf[2] * 1.654858e-02 + lpf[3] * -1.149947e-02 + lpf[4] * 3.281435e-03; /* * The 100-Hz data signal is demodulated using a pair of * quadrature multipliers, matched filters and a phase lock * loop. The I and Q quadrature data signals are produced by * multiplying the filtered signal by 100-Hz sine and cosine * signals, respectively. The signals are processed by 170-ms * synchronous matched filters to produce the amplitude and * phase signals used by the demodulator. The signals are scaled * to produce unit energy at the maximum value. */ i = up->datapt; up->datapt = (up->datapt + IN100) % 80; dtemp = sintab[i] * data / (MS / 2. * DATCYC); up->irig -= ibuf[iptr]; ibuf[iptr] = dtemp; up->irig += dtemp; i = (i + 20) % 80; dtemp = sintab[i] * data / (MS / 2. * DATCYC); up->qrig -= qbuf[iptr]; qbuf[iptr] = dtemp; up->qrig += dtemp; iptr = (iptr + 1) % DATSIZ; /* * Baseband sync demodulation. The 1000/1200 sync signals are * extracted using a 600-Hz IIR bandpass filter. This removes * the 100-Hz data subcarrier, as well as the 440-Hz and 600-Hz * tones and most of the noise and voice modulation components. * * Matlab 4th-order IIR elliptic, 800-1400 Hz bandpass, 0.2 dB * passband ripple, -50 dB stopband ripple, phase delay 0.91 ms. */ syncx = (bpf[8] = bpf[7]) * 4.897278e-01; syncx += (bpf[7] = bpf[6]) * -2.765914e+00; syncx += (bpf[6] = bpf[5]) * 8.110921e+00; syncx += (bpf[5] = bpf[4]) * -1.517732e+01; syncx += (bpf[4] = bpf[3]) * 1.975197e+01; syncx += (bpf[3] = bpf[2]) * -1.814365e+01; syncx += (bpf[2] = bpf[1]) * 1.159783e+01; syncx += (bpf[1] = bpf[0]) * -4.735040e+00; bpf[0] = isig - syncx; syncx = bpf[0] * 8.203628e-03 + bpf[1] * -2.375732e-02 + bpf[2] * 3.353214e-02 + bpf[3] * -4.080258e-02 + bpf[4] * 4.605479e-02 + bpf[5] * -4.080258e-02 + bpf[6] * 3.353214e-02 + bpf[7] * -2.375732e-02 + bpf[8] * 8.203628e-03; /* * The 1000/1200 sync signals are demodulated using a pair of * quadrature multipliers and matched filters. However, * synchronous demodulation at these frequencies is impractical, * so only the signal amplitude is used. The I and Q quadrature * sync signals are produced by multiplying the filtered signal * by 1000-Hz (WWV) and 1200-Hz (WWVH) sine and cosine signals, * respectively. The WWV and WWVH signals are processed by 800- * ms synchronous matched filters and combined to produce the * minute sync signal and detect which one (or both) the WWV or * WWVH signal is present. The WWV and WWVH signals are also * processed by 5-ms synchronous matched filters and combined to * produce the second sync signal. The signals are scaled to * produce unit energy at the maximum value. * * Note the master timing ramps, which run continuously. The * minute counter (mphase) counts the samples in the minute, * while the second counter (epoch) counts the samples in the * second. */ up->mphase = (up->mphase + 1) % MINUTE; epoch = up->mphase % SECOND; /* * WWV */ i = csinptr; csinptr = (csinptr + IN1000) % 80; dtemp = sintab[i] * syncx / (MS / 2.); ciamp -= cibuf[jptr]; cibuf[jptr] = dtemp; ciamp += dtemp; csiamp -= csibuf[kptr]; csibuf[kptr] = dtemp; csiamp += dtemp; i = (i + 20) % 80; dtemp = sintab[i] * syncx / (MS / 2.); cqamp -= cqbuf[jptr]; cqbuf[jptr] = dtemp; cqamp += dtemp; csqamp -= csqbuf[kptr]; csqbuf[kptr] = dtemp; csqamp += dtemp; sp = &up->mitig[up->achan].wwv; sp->amp = sqrt(ciamp * ciamp + cqamp * cqamp) / SYNCYC; if (!(up->status & MSYNC)) wwv_qrz(peer, sp, (int)(pp->fudgetime1 * SECOND)); /* * WWVH */ i = hsinptr; hsinptr = (hsinptr + IN1200) % 80; dtemp = sintab[i] * syncx / (MS / 2.); hiamp -= hibuf[jptr]; hibuf[jptr] = dtemp; hiamp += dtemp; hsiamp -= hsibuf[kptr]; hsibuf[kptr] = dtemp; hsiamp += dtemp; i = (i + 20) % 80; dtemp = sintab[i] * syncx / (MS / 2.); hqamp -= hqbuf[jptr]; hqbuf[jptr] = dtemp; hqamp += dtemp; hsqamp -= hsqbuf[kptr]; hsqbuf[kptr] = dtemp; hsqamp += dtemp; rp = &up->mitig[up->achan].wwvh; rp->amp = sqrt(hiamp * hiamp + hqamp * hqamp) / SYNCYC; if (!(up->status & MSYNC)) wwv_qrz(peer, rp, (int)(pp->fudgetime2 * SECOND)); jptr = (jptr + 1) % SYNSIZ; kptr = (kptr + 1) % TCKSIZ; /* * The following section is called once per minute. It does * housekeeping and timeout functions and empties the dustbins. */ if (up->mphase == 0) { up->watch++; if (!(up->status & MSYNC)) { /* * If minute sync has not been acquired before * ACQSN timeout (6 min), or if no signal is * heard, the program cycles to the next * frequency and tries again. */ if (!wwv_newchan(peer)) up->watch = 0; } else { /* * If the leap bit is set, set the minute epoch * back one second so the station processes * don't miss a beat. */ if (up->status & LEPSEC) { up->mphase -= SECOND; if (up->mphase < 0) up->mphase += MINUTE; } } } /* * When the channel metric reaches threshold and the second * counter matches the minute epoch within the second, the * driver has synchronized to the station. The second number is * the remaining seconds until the next minute epoch, while the * sync epoch is zero. Watch out for the first second; if * already synchronized to the second, the buffered sync epoch * must be set. * * Note the guard interval is 200 ms; if for some reason the * clock drifts more than that, it might wind up in the wrong * second. If the maximum frequency error is not more than about * 1 PPM, the clock can go as much as two days while still in * the same second. */ if (up->status & MSYNC) { wwv_epoch(peer); } else if (up->sptr != NULL) { sp = up->sptr; if (sp->metric >= TTHR && epoch == sp->mepoch % SECOND) { up->rsec = (60 - sp->mepoch / SECOND) % 60; up->rphase = 0; up->status |= MSYNC; up->watch = 0; if (!(up->status & SSYNC)) up->repoch = up->yepoch = epoch; else up->repoch = up->yepoch; } } /* * The second sync pulse is extracted using 5-ms (40 sample) FIR * matched filters at 1000 Hz for WWV or 1200 Hz for WWVH. This * pulse is used for the most precise synchronization, since if * provides a resolution of one sample (125 us). The filters run * only if the station has been reliably determined. */ if (up->status & SELV) mfsync = sqrt(csiamp * csiamp + csqamp * csqamp) / TCKCYC; else if (up->status & SELH) mfsync = sqrt(hsiamp * hsiamp + hsqamp * hsqamp) / TCKCYC; else mfsync = 0; /* * Enhance the seconds sync pulse using a 1-s (8000-sample) comb * filter. Correct for the FIR matched filter delay, which is 5 * ms for both the WWV and WWVH filters, and also for the * propagation delay. Once each second look for second sync. If * not in minute sync, fiddle the codec gain. Note the SNR is * computed from the maximum sample and the envelope of the * sample 6 ms before it, so if we slip more than a cycle the * SNR should plummet. The signal is scaled to produce unit * energy at the maximum value. */ dtemp = (epobuf[epoch] += (mfsync - epobuf[epoch]) / up->avgint); if (dtemp > epomax) { int j; epomax = dtemp; epopos = epoch; j = epoch - 6 * MS; if (j < 0) j += SECOND; nxtmax = fabs(epobuf[j]); } if (epoch == 0) { up->epomax = epomax; up->eposnr = wwv_snr(epomax, nxtmax); epopos -= TCKCYC * MS; if (epopos < 0) epopos += SECOND; wwv_endpoc(peer, epopos); if (!(up->status & SSYNC)) up->alarm |= SYNERR; epomax = 0; if (!(up->status & MSYNC)) wwv_gain(peer); } } /* * wwv_qrz - identify and acquire WWV/WWVH minute sync pulse * * This routine implements a virtual station process used to acquire * minute sync and to mitigate among the ten frequency and station * combinations. During minute sync acquisition the process probes each * frequency and station in turn for the minute pulse, which * involves searching through the entire 480,000-sample minute. The * process finds the maximum signal and RMS noise plus signal. Then, the * actual noise is determined by subtracting the energy of the matched * filter. * * Students of radar receiver technology will discover this algorithm * amounts to a range-gate discriminator. A valid pulse must have peak * amplitude at least QTHR (2500) and SNR at least QSNR (20) dB and the * difference between the current and previous epoch must be less than * AWND (20 ms). Note that the discriminator peak occurs about 800 ms * into the second, so the timing is retarded to the previous second * epoch. */ static void wwv_qrz( struct peer *peer, /* peer structure pointer */ struct sync *sp, /* sync channel structure */ int pdelay /* propagation delay (samples) */ ) { struct refclockproc *pp; struct wwvunit *up; char tbuf[TBUF]; /* monitor buffer */ long epoch; pp = peer->procptr; up = (struct wwvunit *)pp->unitptr; /* * Find the sample with peak amplitude, which defines the minute * epoch. Accumulate all samples to determine the total noise * energy. */ epoch = up->mphase - pdelay - SYNSIZ; if (epoch < 0) epoch += MINUTE; if (sp->amp > sp->maxeng) { sp->maxeng = sp->amp; sp->pos = epoch; } sp->noieng += sp->amp; /* * At the end of the minute, determine the epoch of the minute * sync pulse, as well as the difference between the current and * previous epoches due to the intrinsic frequency error plus * jitter. When calculating the SNR, subtract the pulse energy * from the total noise energy and then normalize. */ if (up->mphase == 0) { sp->synmax = sp->maxeng; sp->synsnr = wwv_snr(sp->synmax, (sp->noieng - sp->synmax) / MINUTE); if (sp->count == 0) sp->lastpos = sp->pos; epoch = (sp->pos - sp->lastpos) % MINUTE; sp->reach <<= 1; if (sp->reach & (1 << AMAX)) sp->count--; if (sp->synmax > ATHR && sp->synsnr > ASNR) { if (abs(epoch) < AWND * MS) { sp->reach |= 1; sp->count++; sp->mepoch = sp->lastpos = sp->pos; } else if (sp->count == 1) { sp->lastpos = sp->pos; } } if (up->watch > ACQSN) sp->metric = 0; else sp->metric = wwv_metric(sp); if (pp->sloppyclockflag & CLK_FLAG4) { sprintf(tbuf, "wwv8 %04x %3d %s %04x %.0f %.0f/%.1f %ld %ld", up->status, up->gain, sp->refid, sp->reach & 0xffff, sp->metric, sp->synmax, sp->synsnr, sp->pos % SECOND, epoch); record_clock_stats(&peer->srcadr, tbuf); #ifdef DEBUG if (debug) printf("%s\n", tbuf); #endif /* DEBUG */ } sp->maxeng = sp->noieng = 0; } } /* * wwv_endpoc - identify and acquire second sync pulse * * This routine is called at the end of the second sync interval. It * determines the second sync epoch position within the second and * disciplines the sample clock using a frequency-lock loop (FLL). * * Second sync is determined in the RF input routine as the maximum * over all 8000 samples in the second comb filter. To assure accurate * and reliable time and frequency discipline, this routine performs a * great deal of heavy-handed heuristic data filtering and grooming. */ static void wwv_endpoc( struct peer *peer, /* peer structure pointer */ int epopos /* epoch max position */ ) { struct refclockproc *pp; struct wwvunit *up; static int epoch_mf[3]; /* epoch median filter */ static int tepoch; /* current second epoch */ static int xepoch; /* last second epoch */ static int zepoch; /* last run epoch */ static int zcount; /* last run end time */ static int scount; /* seconds counter */ static int syncnt; /* run length counter */ static int maxrun; /* longest run length */ static int mepoch; /* longest run end epoch */ static int mcount; /* longest run end time */ static int avgcnt; /* averaging interval counter */ static int avginc; /* averaging ratchet */ static int iniflg; /* initialization flag */ char tbuf[TBUF]; /* monitor buffer */ double dtemp; int tmp2; pp = peer->procptr; up = (struct wwvunit *)pp->unitptr; if (!iniflg) { iniflg = 1; memset((char *)epoch_mf, 0, sizeof(epoch_mf)); } /* * If the signal amplitude or SNR fall below thresholds, dim the * second sync lamp and wait for hotter ions. If no stations are * heard, we are either in a probe cycle or the ions are really * cold. */ scount++; if (up->epomax < STHR || up->eposnr < SSNR) { up->status &= ~(SSYNC | FGATE); avgcnt = syncnt = maxrun = 0; return; } if (!(up->status & (SELV | SELH))) return; /* * A three-stage median filter is used to help denoise the * second sync pulse. The median sample becomes the candidate * epoch. */ epoch_mf[2] = epoch_mf[1]; epoch_mf[1] = epoch_mf[0]; epoch_mf[0] = epopos; if (epoch_mf[0] > epoch_mf[1]) { if (epoch_mf[1] > epoch_mf[2]) tepoch = epoch_mf[1]; /* 0 1 2 */ else if (epoch_mf[2] > epoch_mf[0]) tepoch = epoch_mf[0]; /* 2 0 1 */ else tepoch = epoch_mf[2]; /* 0 2 1 */ } else { if (epoch_mf[1] < epoch_mf[2]) tepoch = epoch_mf[1]; /* 2 1 0 */ else if (epoch_mf[2] < epoch_mf[0]) tepoch = epoch_mf[0]; /* 1 0 2 */ else tepoch = epoch_mf[2]; /* 1 2 0 */ } /* * If the epoch candidate is the same as the last one, increment * the run counter. If not, save the length, epoch and end * time of the current run for use later and reset the counter. * The epoch is considered valid if the run is at least SCMP * (10) s, the minute is synchronized and the interval since the * last epoch is not greater than the averaging interval. Thus, * after a long absence, the program will wait a full averaging * interval while the comb filter charges up and noise * dissapates.. */ tmp2 = (tepoch - xepoch) % SECOND; if (tmp2 == 0) { syncnt++; if (syncnt > SCMP && up->status & MSYNC && (up->status & FGATE || scount - zcount <= up->avgint)) { up->status |= SSYNC; up->yepoch = tepoch; } } else if (syncnt >= maxrun) { maxrun = syncnt; mcount = scount; mepoch = xepoch; syncnt = 0; } if ((pp->sloppyclockflag & CLK_FLAG4) && !(up->status & MSYNC)) { sprintf(tbuf, "wwv1 %04x %3d %4d %5.0f %5.1f %5d %4d %4d %4d", up->status, up->gain, tepoch, up->epomax, up->eposnr, tmp2, avgcnt, syncnt, maxrun); record_clock_stats(&peer->srcadr, tbuf); #ifdef DEBUG if (debug) printf("%s\n", tbuf); #endif /* DEBUG */ } avgcnt++; if (avgcnt < up->avgint) { xepoch = tepoch; return; } /* * The sample clock frequency is disciplined using a first-order * feedback loop with time constant consistent with the Allan * intercept of typical computer clocks. During each averaging * interval the candidate epoch at the end of the longest run is * determined. If the longest run is zero, all epoches in the * interval are different, so the candidate epoch is the current * epoch. The frequency update is computed from the candidate * epoch difference (125-us units) and time difference (seconds) * between updates. */ if (syncnt >= maxrun) { maxrun = syncnt; mcount = scount; mepoch = xepoch; } xepoch = tepoch; if (maxrun == 0) { mepoch = tepoch; mcount = scount; } /* * The master clock runs at the codec sample frequency of 8000 * Hz, so the intrinsic time resolution is 125 us. The frequency * resolution ranges from 18 PPM at the minimum averaging * interval of 8 s to 0.12 PPM at the maximum interval of 1024 * s. An offset update is determined at the end of the longest * run in each averaging interval. The frequency adjustment is * computed from the difference between offset updates and the * interval between them. * * The maximum frequency adjustment ranges from 187 PPM at the * minimum interval to 1.5 PPM at the maximum. If the adjustment * exceeds the maximum, the update is discarded and the * hysteresis counter is decremented. Otherwise, the frequency * is incremented by the adjustment, but clamped to the maximum * 187.5 PPM. If the update is less than half the maximum, the * hysteresis counter is incremented. If the counter increments * to +3, the averaging interval is doubled and the counter set * to zero; if it decrements to -3, the interval is halved and * the counter set to zero. */ dtemp = (mepoch - zepoch) % SECOND; if (up->status & FGATE) { if (abs(dtemp) < MAXFREQ * MINAVG) { up->freq += (dtemp / 2.) / ((mcount - zcount) * FCONST); if (up->freq > MAXFREQ) up->freq = MAXFREQ; else if (up->freq < -MAXFREQ) up->freq = -MAXFREQ; if (abs(dtemp) < MAXFREQ * MINAVG / 2.) { if (avginc < 3) { avginc++; } else { if (up->avgint < MAXAVG) { up->avgint <<= 1; avginc = 0; } } } } else { if (avginc > -3) { avginc--; } else { if (up->avgint > MINAVG) { up->avgint >>= 1; avginc = 0; } } } } if (pp->sloppyclockflag & CLK_FLAG4) { sprintf(tbuf, "wwv2 %04x %5.0f %5.1f %5d %4d %4d %4d %4.0f %7.2f", up->status, up->epomax, up->eposnr, mepoch, up->avgint, maxrun, mcount - zcount, dtemp, up->freq * 1e6 / SECOND); record_clock_stats(&peer->srcadr, tbuf); #ifdef DEBUG if (debug) printf("%s\n", tbuf); #endif /* DEBUG */ } /* * This is a valid update; set up for the next interval. */ up->status |= FGATE; zepoch = mepoch; zcount = mcount; avgcnt = syncnt = maxrun = 0; } /* * wwv_epoch - epoch scanner * * This routine extracts data signals from the 100-Hz subcarrier. It * scans the receiver second epoch to determine the signal amplitudes * and pulse timings. Receiver synchronization is determined by the * minute sync pulse detected in the wwv_rf() routine and the second * sync pulse detected in the wwv_epoch() routine. The transmitted * signals are delayed by the propagation delay, receiver delay and * filter delay of this program. Delay corrections are introduced * separately for WWV and WWVH. * * Most communications radios use a highpass filter in the audio stages, * which can do nasty things to the subcarrier phase relative to the * sync pulses. Therefore, the data subcarrier reference phase is * disciplined using the hardlimited quadrature-phase signal sampled at * the same time as the in-phase signal. The phase tracking loop uses * phase adjustments of plus-minus one sample (125 us). */ static void wwv_epoch( struct peer *peer /* peer structure pointer */ ) { struct refclockproc *pp; struct wwvunit *up; struct chan *cp; static double sigmin, sigzer, sigone, engmax, engmin; pp = peer->procptr; up = (struct wwvunit *)pp->unitptr; /* * Find the maximum minute sync pulse energy for both the * WWV and WWVH stations. This will be used later for channel * and station mitigation. Also set the seconds epoch at 800 ms * well before the end of the second to make sure we never set * the epoch backwards. */ cp = &up->mitig[up->achan]; if (cp->wwv.amp > cp->wwv.syneng) cp->wwv.syneng = cp->wwv.amp; if (cp->wwvh.amp > cp->wwvh.syneng) cp->wwvh.syneng = cp->wwvh.amp; if (up->rphase == 800 * MS) up->repoch = up->yepoch; /* * Use the signal amplitude at epoch 15 ms as the noise floor. * This gives a guard time of +-15 ms from the beginning of the * second until the second pulse rises at 30 ms. There is a * compromise here; we want to delay the sample as long as * possible to give the radio time to change frequency and the * AGC to stabilize, but as early as possible if the second * epoch is not exact. */ if (up->rphase == 15 * MS) sigmin = sigzer = sigone = up->irig; /* * Latch the data signal at 200 ms. Keep this around until the * end of the second. Use the signal energy as the peak to * compute the SNR. Use the Q sample to adjust the 100-Hz * reference oscillator phase. */ if (up->rphase == 200 * MS) { sigzer = up->irig; engmax = sqrt(up->irig * up->irig + up->qrig * up->qrig); up->datpha = up->qrig / up->avgint; if (up->datpha >= 0) { up->datapt++; if (up->datapt >= 80) up->datapt -= 80; } else { up->datapt--; if (up->datapt < 0) up->datapt += 80; } } /* * Latch the data signal at 500 ms. Keep this around until the * end of the second. */ else if (up->rphase == 500 * MS) sigone = up->irig; /* * At the end of the second crank the clock state machine and * adjust the codec gain. Note the epoch is buffered from the * center of the second in order to avoid jitter while the * seconds synch is diddling the epoch. Then, determine the true * offset and update the median filter in the driver interface. * * Use the energy at the end of the second as the noise to * compute the SNR for the data pulse. This gives a better * measurement than the beginning of the second, especially when * returning from the probe channel. This gives a guard time of * 30 ms from the decay of the longest pulse to the rise of the * next pulse. */ up->rphase++; if (up->mphase % SECOND == up->repoch) { up->status &= ~(DGATE | BGATE); engmin = sqrt(up->irig * up->irig + up->qrig * up->qrig); up->datsig = engmax; up->datsnr = wwv_snr(engmax, engmin); /* * If the amplitude or SNR is below threshold, average a * 0 in the the integrators; otherwise, average the * bipolar signal. This is done to avoid noise polution. */ if (engmax < DTHR || up->datsnr < DSNR) { up->status |= DGATE; wwv_rsec(peer, 0); } else { sigzer -= sigone; sigone -= sigmin; wwv_rsec(peer, sigone - sigzer); } if (up->status & (DGATE | BGATE)) up->errcnt++; if (up->errcnt > MAXERR) up->alarm |= LOWERR; wwv_gain(peer); cp = &up->mitig[up->achan]; cp->wwv.syneng = 0; cp->wwvh.syneng = 0; up->rphase = 0; } } /* * wwv_rsec - process receiver second * * This routine is called at the end of each receiver second to * implement the per-second state machine. The machine assembles BCD * digit bits, decodes miscellaneous bits and dances the leap seconds. * * Normally, the minute has 60 seconds numbered 0-59. If the leap * warning bit is set, the last minute (1439) of 30 June (day 181 or 182 * for leap years) or 31 December (day 365 or 366 for leap years) is * augmented by one second numbered 60. This is accomplished by * extending the minute interval by one second and teaching the state * machine to ignore it. */ static void wwv_rsec( struct peer *peer, /* peer structure pointer */ double bit ) { static int iniflg; /* initialization flag */ static double bcddld[4]; /* BCD data bits */ static double bitvec[61]; /* bit integrator for misc bits */ struct refclockproc *pp; struct wwvunit *up; struct chan *cp; struct sync *sp, *rp; char tbuf[TBUF]; /* monitor buffer */ int sw, arg, nsec; pp = peer->procptr; up = (struct wwvunit *)pp->unitptr; if (!iniflg) { iniflg = 1; memset((char *)bitvec, 0, sizeof(bitvec)); } /* * The bit represents the probability of a hit on zero (negative * values), a hit on one (positive values) or a miss (zero * value). The likelihood vector is the exponential average of * these probabilities. Only the bits of this vector * corresponding to the miscellaneous bits of the timecode are * used, but it's easier to do them all. After that, crank the * seconds state machine. */ nsec = up->rsec; up->rsec++; bitvec[nsec] += (bit - bitvec[nsec]) / TCONST; sw = progx[nsec].sw; arg = progx[nsec].arg; /* * The minute state machine. Fly off to a particular section as * directed by the transition matrix and second number. */ switch (sw) { /* * Ignore this second. */ case IDLE: /* 9, 45-49 */ break; /* * Probe channel stuff * * The WWV/H format contains data pulses in second 59 (position * identifier) and second 1, but not in second 0. The minute * sync pulse is contained in second 0. At the end of second 58 * QSY to the probe channel, which rotates in turn over all * WWV/H frequencies. At the end of second 0 measure the minute * sync pulse. At the end of second 1 measure the data pulse and * QSY back to the data channel. Note that the actions commented * here happen at the end of the second numbered as shown. * * At the end of second 0 save the minute sync amplitude latched * at 800 ms as the signal later used to calculate the SNR. */ case SYNC2: /* 0 */ cp = &up->mitig[up->achan]; cp->wwv.synmax = cp->wwv.syneng; cp->wwvh.synmax = cp->wwvh.syneng; break; /* * At the end of second 1 use the minute sync amplitude latched * at 800 ms as the noise to calculate the SNR. If the minute * sync pulse and SNR are above thresholds and the data pulse * amplitude and SNR are above thresolds, shift a 1 into the * station reachability register; otherwise, shift a 0. The * number of 1 bits in the last six intervals is a component of * the channel metric computed by the wwv_metric() routine. * Finally, QSY back to the data channel. */ case SYNC3: /* 1 */ cp = &up->mitig[up->achan]; /* * WWV station */ sp = &cp->wwv; sp->synsnr = wwv_snr(sp->synmax, sp->amp); sp->reach <<= 1; if (sp->reach & (1 << AMAX)) sp->count--; if (sp->synmax >= QTHR && sp->synsnr >= QSNR && !(up->status & (DGATE | BGATE))) { sp->reach |= 1; sp->count++; } sp->metric = wwv_metric(sp); /* * WWVH station */ rp = &cp->wwvh; rp->synsnr = wwv_snr(rp->synmax, rp->amp); rp->reach <<= 1; if (rp->reach & (1 << AMAX)) rp->count--; if (rp->synmax >= QTHR && rp->synsnr >= QSNR && !(up->status & (DGATE | BGATE))) { rp->reach |= 1; rp->count++; } rp->metric = wwv_metric(rp); if (pp->sloppyclockflag & CLK_FLAG4) { sprintf(tbuf, "wwv5 %04x %3d %4d %.0f/%.1f %.0f/%.1f %s %04x %.0f %.0f/%.1f %s %04x %.0f %.0f/%.1f", up->status, up->gain, up->yepoch, up->epomax, up->eposnr, up->datsig, up->datsnr, sp->refid, sp->reach & 0xffff, sp->metric, sp->synmax, sp->synsnr, rp->refid, rp->reach & 0xffff, rp->metric, rp->synmax, rp->synsnr); record_clock_stats(&peer->srcadr, tbuf); #ifdef DEBUG if (debug) printf("%s\n", tbuf); #endif /* DEBUG */ } up->errcnt = up->digcnt = up->alarm = 0; /* * If synchronized to a station, restart if no stations * have been heard within the PANIC timeout (2 days). If * not and the minute digit has been found, restart if * not synchronized withing the SYNCH timeout (40 m). If * not, restart if the unit digit has not been found * within the DATA timeout (15 m). */ if (up->status & INSYNC) { if (up->watch > PANIC) { wwv_newgame(peer); return; } } else if (up->status & DSYNC) { if (up->watch > SYNCH) { wwv_newgame(peer); return; } } else if (up->watch > DATA) { wwv_newgame(peer); return; } wwv_newchan(peer); break; /* * Save the bit probability in the BCD data vector at the index * given by the argument. Bits not used in the digit are forced * to zero. */ case COEF1: /* 4-7 */ bcddld[arg] = bit; break; case COEF: /* 10-13, 15-17, 20-23, 25-26, 30-33, 35-38, 40-41, 51-54 */ if (up->status & DSYNC) bcddld[arg] = bit; else bcddld[arg] = 0; break; case COEF2: /* 18, 27-28, 42-43 */ bcddld[arg] = 0; break; /* * Correlate coefficient vector with each valid digit vector and * save in decoding matrix. We step through the decoding matrix * digits correlating each with the coefficients and saving the * greatest and the next lower for later SNR calculation. */ case DECIM2: /* 29 */ wwv_corr4(peer, &up->decvec[arg], bcddld, bcd2); break; case DECIM3: /* 44 */ wwv_corr4(peer, &up->decvec[arg], bcddld, bcd3); break; case DECIM6: /* 19 */ wwv_corr4(peer, &up->decvec[arg], bcddld, bcd6); break; case DECIM9: /* 8, 14, 24, 34, 39 */ wwv_corr4(peer, &up->decvec[arg], bcddld, bcd9); break; /* * Miscellaneous bits. If above the positive threshold, declare * 1; if below the negative threshold, declare 0; otherwise * raise the BGATE bit. The design is intended to avoid * integrating noise under low SNR conditions. */ case MSC20: /* 55 */ wwv_corr4(peer, &up->decvec[YR + 1], bcddld, bcd9); /* fall through */ case MSCBIT: /* 2-3, 50, 56-57 */ if (bitvec[nsec] > BTHR) { if (!(up->misc & arg)) up->alarm |= CMPERR; up->misc |= arg; } else if (bitvec[nsec] < -BTHR) { if (up->misc & arg) up->alarm |= CMPERR; up->misc &= ~arg; } else { up->status |= BGATE; } break; /* * Save the data channel gain, then QSY to the probe channel and * dim the seconds comb filters. The www_newchan() routine will * light them back up. */ case MSC21: /* 58 */ if (bitvec[nsec] > BTHR) { if (!(up->misc & arg)) up->alarm |= CMPERR; up->misc |= arg; } else if (bitvec[nsec] < -BTHR) { if (up->misc & arg) up->alarm |= CMPERR; up->misc &= ~arg; } else { up->status |= BGATE; } up->status &= ~(SELV | SELH); #ifdef ICOM if (up->fd_icom > 0) { up->schan = (up->schan + 1) % NCHAN; wwv_qsy(peer, up->schan); } else { up->mitig[up->achan].gain = up->gain; } #else up->mitig[up->achan].gain = up->gain; #endif /* ICOM */ break; /* * The endgames * * During second 59 the receiver and codec AGC are settling * down, so the data pulse is unusable as quality metric. If * LEPSEC is set on the last minute of 30 June or 31 December, * the transmitter and receiver insert an extra second (60) in * the timescale and the minute sync repeats the second. Once * leaps occurred at intervals of about 18 months, but the last * leap before the most recent leap in 1995 was in 1998. */ case MIN1: /* 59 */ if (up->status & LEPSEC) break; /* fall through */ case MIN2: /* 60 */ up->status &= ~LEPSEC; wwv_tsec(peer); up->rsec = 0; wwv_clock(peer); break; } if ((pp->sloppyclockflag & CLK_FLAG4) && !(up->status & DSYNC)) { sprintf(tbuf, "wwv3 %2d %04x %3d %4d %5.0f %5.1f %5.0f %5.1f %5.0f", nsec, up->status, up->gain, up->yepoch, up->epomax, up->eposnr, up->datsig, up->datsnr, bit); record_clock_stats(&peer->srcadr, tbuf); #ifdef DEBUG if (debug) printf("%s\n", tbuf); #endif /* DEBUG */ } pp->disp += AUDIO_PHI; } /* * The radio clock is set if the alarm bits are all zero. After that, * the time is considered valid if the second sync bit is lit. It should * not be a surprise, especially if the radio is not tunable, that * sometimes no stations are above the noise and the integrators * discharge below the thresholds. We assume that, after a day of signal * loss, the minute sync epoch will be in the same second. This requires * the codec frequency be accurate within 6 PPM. Practical experience * shows the frequency typically within 0.1 PPM, so after a day of * signal loss, the time should be within 8.6 ms.. */ static void wwv_clock( struct peer *peer /* peer unit pointer */ ) { struct refclockproc *pp; struct wwvunit *up; l_fp offset; /* offset in NTP seconds */ pp = peer->procptr; up = (struct wwvunit *)pp->unitptr; if (!(up->status & SSYNC)) up->alarm |= SYNERR; if (up->digcnt < 9) up->alarm |= NINERR; if (!(up->alarm)) up->status |= INSYNC; if (up->status & INSYNC && up->status & SSYNC) { if (up->misc & SECWAR) pp->leap = LEAP_ADDSECOND; else pp->leap = LEAP_NOWARNING; pp->second = up->rsec; pp->minute = up->decvec[MN].digit + up->decvec[MN + 1].digit * 10; pp->hour = up->decvec[HR].digit + up->decvec[HR + 1].digit * 10; pp->day = up->decvec[DA].digit + up->decvec[DA + 1].digit * 10 + up->decvec[DA + 2].digit * 100; pp->year = up->decvec[YR].digit + up->decvec[YR + 1].digit * 10; pp->year += 2000; L_CLR(&offset); if (!clocktime(pp->day, pp->hour, pp->minute, pp->second, GMT, up->timestamp.l_ui, &pp->yearstart, &offset.l_ui)) { up->errflg = CEVNT_BADTIME; } else { up->watch = 0; pp->disp = 0; pp->lastref = up->timestamp; refclock_process_offset(pp, offset, up->timestamp, PDELAY + up->pdelay); refclock_receive(peer); } } pp->lencode = timecode(up, pp->a_lastcode); record_clock_stats(&peer->srcadr, pp->a_lastcode); #ifdef DEBUG if (debug) printf("wwv: timecode %d %s\n", pp->lencode, pp->a_lastcode); #endif /* DEBUG */ } /* * wwv_corr4 - determine maximum-likelihood digit * * This routine correlates the received digit vector with the BCD * coefficient vectors corresponding to all valid digits at the given * position in the decoding matrix. The maximum value corresponds to the * maximum-likelihood digit, while the ratio of this value to the next * lower value determines the likelihood function. Note that, if the * digit is invalid, the likelihood vector is averaged toward a miss. */ static void wwv_corr4( struct peer *peer, /* peer unit pointer */ struct decvec *vp, /* decoding table pointer */ double data[], /* received data vector */ double tab[][4] /* correlation vector array */ ) { struct refclockproc *pp; struct wwvunit *up; double topmax, nxtmax; /* metrics */ double acc; /* accumulator */ char tbuf[TBUF]; /* monitor buffer */ int mldigit; /* max likelihood digit */ int i, j; pp = peer->procptr; up = (struct wwvunit *)pp->unitptr; /* * Correlate digit vector with each BCD coefficient vector. If * any BCD digit bit is bad, consider all bits a miss. Until the * minute units digit has been resolved, don't to anything else. * Note the SNR is calculated as the ratio of the largest * likelihood value to the next largest likelihood value. */ mldigit = 0; topmax = nxtmax = -MAXAMP; for (i = 0; tab[i][0] != 0; i++) { acc = 0; for (j = 0; j < 4; j++) acc += data[j] * tab[i][j]; acc = (vp->like[i] += (acc - vp->like[i]) / TCONST); if (acc > topmax) { nxtmax = topmax; topmax = acc; mldigit = i; } else if (acc > nxtmax) { nxtmax = acc; } } vp->digprb = topmax; vp->digsnr = wwv_snr(topmax, nxtmax); /* * The current maximum-likelihood digit is compared to the last * maximum-likelihood digit. If different, the compare counter * and maximum-likelihood digit are reset. When the compare * counter reaches the BCMP threshold (3), the digit is assumed * correct. When the compare counter of all nine digits have * reached threshold, the clock is assumed correct. * * Note that the clock display digit is set before the compare * counter has reached threshold; however, the clock display is * not considered correct until all nine clock digits have * reached threshold. This is intended as eye candy, but avoids * mistakes when the signal is low and the SNR is very marginal. */ if (vp->digprb < BTHR || vp->digsnr < BSNR) { up->status |= BGATE; } else { if (vp->digit != mldigit) { up->alarm |= CMPERR; if (vp->count > 0) vp->count--; if (vp->count == 0) vp->digit = mldigit; } else { if (vp->count < BCMP) vp->count++; if (vp->count == BCMP) { up->status |= DSYNC; up->digcnt++; } } } if ((pp->sloppyclockflag & CLK_FLAG4) && !(up->status & INSYNC)) { sprintf(tbuf, "wwv4 %2d %04x %3d %4d %5.0f %2d %d %d %d %5.0f %5.1f", up->rsec - 1, up->status, up->gain, up->yepoch, up->epomax, vp->radix, vp->digit, mldigit, vp->count, vp->digprb, vp->digsnr); record_clock_stats(&peer->srcadr, tbuf); #ifdef DEBUG if (debug) printf("%s\n", tbuf); #endif /* DEBUG */ } } /* * wwv_tsec - transmitter minute processing * * This routine is called at the end of the transmitter minute. It * implements a state machine that advances the logical clock subject to * the funny rules that govern the conventional clock and calendar. */ static void wwv_tsec( struct peer *peer /* driver structure pointer */ ) { struct refclockproc *pp; struct wwvunit *up; int minute, day, isleap; int temp; pp = peer->procptr; up = (struct wwvunit *)pp->unitptr; /* * Advance minute unit of the day. Don't propagate carries until * the unit minute digit has been found. */ temp = carry(&up->decvec[MN]); /* minute units */ if (!(up->status & DSYNC)) return; /* * Propagate carries through the day. */ if (temp == 0) /* carry minutes */ temp = carry(&up->decvec[MN + 1]); if (temp == 0) /* carry hours */ temp = carry(&up->decvec[HR]); if (temp == 0) temp = carry(&up->decvec[HR + 1]); /* * Decode the current minute and day. Set leap day if the * timecode leap bit is set on 30 June or 31 December. Set leap * minute if the last minute on leap day, but only if the clock * is syncrhronized. This code fails in 2400 AD. */ minute = up->decvec[MN].digit + up->decvec[MN + 1].digit * 10 + up->decvec[HR].digit * 60 + up->decvec[HR + 1].digit * 600; day = up->decvec[DA].digit + up->decvec[DA + 1].digit * 10 + up->decvec[DA + 2].digit * 100; /* * Set the leap bit on the last minute of the leap day. */ isleap = up->decvec[YR].digit & 0x3; if (up->misc & SECWAR && up->status & INSYNC) { if ((day == (isleap ? 182 : 183) || day == (isleap ? 365 : 366)) && minute == 1439) up->status |= LEPSEC; } /* * Roll the day if this the first minute and propagate carries * through the year. */ if (minute != 1440) return; minute = 0; while (carry(&up->decvec[HR]) != 0); /* advance to minute 0 */ while (carry(&up->decvec[HR + 1]) != 0); day++; temp = carry(&up->decvec[DA]); /* carry days */ if (temp == 0) temp = carry(&up->decvec[DA + 1]); if (temp == 0) temp = carry(&up->decvec[DA + 2]); /* * Roll the year if this the first day and propagate carries * through the century. */ if (day != (isleap ? 365 : 366)) return; day = 1; while (carry(&up->decvec[DA]) != 1); /* advance to day 1 */ while (carry(&up->decvec[DA + 1]) != 0); while (carry(&up->decvec[DA + 2]) != 0); temp = carry(&up->decvec[YR]); /* carry years */ if (temp == 0) carry(&up->decvec[YR + 1]); } /* * carry - process digit * * This routine rotates a likelihood vector one position and increments * the clock digit modulo the radix. It returns the new clock digit or * zero if a carry occurred. Once synchronized, the clock digit will * match the maximum-likelihood digit corresponding to that position. */ static int carry( struct decvec *dp /* decoding table pointer */ ) { int temp; int j; dp->digit++; if (dp->digit == dp->radix) dp->digit = 0; temp = dp->like[dp->radix - 1]; for (j = dp->radix - 1; j > 0; j--) dp->like[j] = dp->like[j - 1]; dp->like[0] = temp; return (dp->digit); } /* * wwv_snr - compute SNR or likelihood function */ static double wwv_snr( double signal, /* signal */ double noise /* noise */ ) { double rval; /* * This is a little tricky. Due to the way things are measured, * either or both the signal or noise amplitude can be negative * or zero. The intent is that, if the signal is negative or * zero, the SNR must always be zero. This can happen with the * subcarrier SNR before the phase has been aligned. On the * other hand, in the likelihood function the "noise" is the * next maximum down from the peak and this could be negative. * However, in this case the SNR is truly stupendous, so we * simply cap at MAXSNR dB (40). */ if (signal <= 0) { rval = 0; } else if (noise <= 0) { rval = MAXSNR; } else { rval = 20. * log10(signal / noise); if (rval > MAXSNR) rval = MAXSNR; } return (rval); } /* * wwv_newchan - change to new data channel * * The radio actually appears to have ten channels, one channel for each * of five frequencies and each of two stations (WWV and WWVH), although * if not tunable only the DCHAN channel appears live. While the radio * is tuned to the working data channel frequency and station for most * of the minute, during seconds 59, 0 and 1 the radio is tuned to a * probe frequency in order to search for minute sync pulse and data * subcarrier from other transmitters. * * The search for WWV and WWVH operates simultaneously, with WWV minute * sync pulse at 1000 Hz and WWVH at 1200 Hz. The probe frequency * rotates each minute over 2.5, 5, 10, 15 and 20 MHz in order and yes, * we all know WWVH is dark on 20 MHz, but few remember when WWV was lit * on 25 MHz. * * This routine selects the best channel using a metric computed from * the reachability register and minute pulse amplitude. Normally, the * award goes to the the channel with the highest metric; but, in case * of ties, the award goes to the channel with the highest minute sync * pulse amplitude and then to the highest frequency. * * The routine performs an important squelch function to keep dirty data * from polluting the integrators. In order to consider a station valid, * the metric must be at least MTHR (13); otherwise, the station select * bits are cleared so the second sync is disabled and the data bit * integrators averaged to a miss. */ static int wwv_newchan( struct peer *peer /* peer structure pointer */ ) { struct refclockproc *pp; struct wwvunit *up; struct sync *sp, *rp; double rank, dtemp; int i, j, rval; pp = peer->procptr; up = (struct wwvunit *)pp->unitptr; /* * Search all five station pairs looking for the channel with * maximum metric. */ sp = NULL; j = 0; rank = 0; for (i = 0; i < NCHAN; i++) { rp = &up->mitig[i].wwvh; dtemp = rp->metric; if (dtemp >= rank) { rank = dtemp; sp = rp; j = i; } rp = &up->mitig[i].wwv; dtemp = rp->metric; if (dtemp >= rank) { rank = dtemp; sp = rp; j = i; } } /* * If the strongest signal is less than the MTHR threshold (13), * we are beneath the waves, so squelch the second sync and * advance to the next station. This makes sure all stations are * scanned when the ions grow dim. If the strongest signal is * greater than the threshold, tune to that frequency and * transmitter QTH. */ up->status &= ~(SELV | SELH); if (rank < MTHR) { up->dchan = (up->dchan + 1) % NCHAN; if (up->status & METRIC) { up->status &= ~METRIC; refclock_report(peer, CEVNT_PROP); } rval = FALSE; } else { up->dchan = j; up->sptr = sp; memcpy(&pp->refid, sp->refid, 4); peer->refid = pp->refid; up->status |= METRIC; if (sp->select & SELV) { up->status |= SELV; up->pdelay = pp->fudgetime1; } else if (sp->select & SELH) { up->status |= SELH; up->pdelay = pp->fudgetime2; } else { up->pdelay = 0; } rval = TRUE; } #ifdef ICOM if (up->fd_icom > 0) wwv_qsy(peer, up->dchan); #endif /* ICOM */ return (rval); } /* * wwv_newgame - reset and start over * * There are three conditions resulting in a new game: * * 1 After finding the minute pulse (MSYNC lit), going 15 minutes * (DATA) without finding the unit seconds digit. * * 2 After finding good data (DSYNC lit), going more than 40 minutes * (SYNCH) without finding station sync (INSYNC lit). * * 3 After finding station sync (INSYNC lit), going more than 2 days * (PANIC) without finding any station. */ static void wwv_newgame( struct peer *peer /* peer structure pointer */ ) { struct refclockproc *pp; struct wwvunit *up; struct chan *cp; int i; pp = peer->procptr; up = (struct wwvunit *)pp->unitptr; /* * Initialize strategic values. Note we set the leap bits * NOTINSYNC and the refid "NONE". */ if (up->status) up->errflg = CEVNT_TIMEOUT; peer->leap = LEAP_NOTINSYNC; up->watch = up->status = up->alarm = 0; up->avgint = MINAVG; up->freq = 0; up->gain = MAXGAIN / 2; /* * Initialize the station processes for audio gain, select bit, * station/frequency identifier and reference identifier. Start * probing at the strongest channel or the default channel if * nothing heard. */ memset(up->mitig, 0, sizeof(up->mitig)); for (i = 0; i < NCHAN; i++) { cp = &up->mitig[i]; cp->gain = up->gain; cp->wwv.select = SELV; sprintf(cp->wwv.refid, "WV%.0f", floor(qsy[i])); cp->wwvh.select = SELH; sprintf(cp->wwvh.refid, "WH%.0f", floor(qsy[i])); } up->dchan = (DCHAN + NCHAN - 1) % NCHAN; wwv_newchan(peer); up->schan = up->dchan; } /* * wwv_metric - compute station metric * * The most significant bits represent the number of ones in the * station reachability register. The least significant bits represent * the minute sync pulse amplitude. The combined value is scaled 0-100. */ double wwv_metric( struct sync *sp /* station pointer */ ) { double dtemp; dtemp = sp->count * MAXAMP; if (sp->synmax < MAXAMP) dtemp += sp->synmax; else dtemp += MAXAMP - 1; dtemp /= (AMAX + 1) * MAXAMP; return (dtemp * 100.); } #ifdef ICOM /* * wwv_qsy - Tune ICOM receiver * * This routine saves the AGC for the current channel, switches to a new * channel and restores the AGC for that channel. If a tunable receiver * is not available, just fake it. */ static int wwv_qsy( struct peer *peer, /* peer structure pointer */ int chan /* channel */ ) { int rval = 0; struct refclockproc *pp; struct wwvunit *up; pp = peer->procptr; up = (struct wwvunit *)pp->unitptr; if (up->fd_icom > 0) { up->mitig[up->achan].gain = up->gain; rval = icom_freq(up->fd_icom, peer->ttl & 0x7f, qsy[chan]); up->achan = chan; up->gain = up->mitig[up->achan].gain; } return (rval); } #endif /* ICOM */ /* * timecode - assemble timecode string and length * * Prettytime format - similar to Spectracom * * sq yy ddd hh:mm:ss ld dut lset agc iden sig errs freq avgt * * s sync indicator ('?' or ' ') * q error bits (hex 0-F) * yyyy year of century * ddd day of year * hh hour of day * mm minute of hour * ss second of minute) * l leap second warning (' ' or 'L') * d DST state ('S', 'D', 'I', or 'O') * dut DUT sign and magnitude (0.1 s) * lset minutes since last clock update * agc audio gain (0-255) * iden reference identifier (station and frequency) * sig signal quality (0-100) * errs bit errors in last minute * freq frequency offset (PPM) * avgt averaging time (s) */ static int timecode( struct wwvunit *up, /* driver structure pointer */ char *ptr /* target string */ ) { struct sync *sp; int year, day, hour, minute, second, dut; char synchar, leapchar, dst; char cptr[50]; /* * Common fixed-format fields */ synchar = (up->status & INSYNC) ? ' ' : '?'; year = up->decvec[YR].digit + up->decvec[YR + 1].digit * 10 + 2000; day = up->decvec[DA].digit + up->decvec[DA + 1].digit * 10 + up->decvec[DA + 2].digit * 100; hour = up->decvec[HR].digit + up->decvec[HR + 1].digit * 10; minute = up->decvec[MN].digit + up->decvec[MN + 1].digit * 10; second = 0; leapchar = (up->misc & SECWAR) ? 'L' : ' '; dst = dstcod[(up->misc >> 4) & 0x3]; dut = up->misc & 0x7; if (!(up->misc & DUTS)) dut = -dut; sprintf(ptr, "%c%1X", synchar, up->alarm); sprintf(cptr, " %4d %03d %02d:%02d:%02d %c%c %+d", year, day, hour, minute, second, leapchar, dst, dut); strcat(ptr, cptr); /* * Specific variable-format fields */ sp = up->sptr; sprintf(cptr, " %d %d %s %.0f %d %.1f %d", up->watch, up->mitig[up->dchan].gain, sp->refid, sp->metric, up->errcnt, up->freq / SECOND * 1e6, up->avgint); strcat(ptr, cptr); return (strlen(ptr)); } /* * wwv_gain - adjust codec gain * * This routine is called at the end of each second. During the second * the number of signal clips above the MAXAMP threshold (6000). If * there are no clips, the gain is bumped up; if there are more than * MAXCLP clips (100), it is bumped down. The decoder is relatively * insensitive to amplitude, so this crudity works just peachy. The * routine also jiggles the input port and selectively mutes the * monitor. */ static void wwv_gain( struct peer *peer /* peer structure pointer */ ) { struct refclockproc *pp; struct wwvunit *up; pp = peer->procptr; up = (struct wwvunit *)pp->unitptr; /* * Apparently, the codec uses only the high order bits of the * gain control field. Thus, it may take awhile for changes to * wiggle the hardware bits. */ if (up->clipcnt == 0) { up->gain += 4; if (up->gain > MAXGAIN) up->gain = MAXGAIN; } else if (up->clipcnt > MAXCLP) { up->gain -= 4; if (up->gain < 0) up->gain = 0; } audio_gain(up->gain, up->mongain, up->port); up->clipcnt = 0; #if DEBUG if (debug > 1) audio_show(); #endif } #else int refclock_wwv_bs; #endif /* REFCLOCK */