2755 lines
82 KiB
C
2755 lines
82 KiB
C
/*
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* refclock_wwv - clock driver for NIST WWV/H time/frequency station
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*/
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#ifdef HAVE_CONFIG_H
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#include <config.h>
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#endif
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#if defined(REFCLOCK) && defined(CLOCK_WWV)
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#include <stdio.h>
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#include <ctype.h>
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#include <sys/time.h>
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#include <math.h>
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#ifdef HAVE_SYS_IOCTL_H
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#include <sys/ioctl.h>
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#endif /* HAVE_SYS_IOCTL_H */
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#include "ntpd.h"
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#include "ntp_io.h"
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#include "ntp_refclock.h"
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#include "ntp_calendar.h"
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#include "ntp_stdlib.h"
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#include "audio.h"
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#define ICOM 1 /* undefine to suppress ICOM code */
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#ifdef ICOM
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#include "icom.h"
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#endif /* ICOM */
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/*
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* Audio WWV/H demodulator/decoder
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*
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* This driver synchronizes the computer time using data encoded in
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* radio transmissions from NIST time/frequency stations WWV in Boulder,
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* CO, and WWVH in Kauai, HI. Transmikssions are made continuously on
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* 2.5, 5, 10, 15 and 20 MHz in AM mode. An ordinary shortwave receiver
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* can be tuned manually to one of these frequencies or, in the case of
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* ICOM receivers, the receiver can be tuned automatically using this
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* program as propagation conditions change throughout the day and
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* night.
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*
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* The driver receives, demodulates and decodes the radio signals when
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* connected to the audio codec of a Sun workstation running SunOS or
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* Solaris, and with a little help, other workstations with similar
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* codecs or sound cards. In this implementation, only one audio driver
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* and codec can be supported on a single machine.
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*
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* The demodulation and decoding algorithms used in this driver are
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* based on those developed for the TAPR DSP93 development board and the
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* TI 320C25 digital signal processor described in: Mills, D.L. A
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* precision radio clock for WWV transmissions. Electrical Engineering
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* Report 97-8-1, University of Delaware, August 1997, 25 pp. Available
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* from www.eecis.udel.edu/~mills/reports.htm. The algorithms described
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* in this report have been modified somewhat to improve performance
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* under weak signal conditions and to provide an automatic station
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* identification feature.
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*
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* The ICOM code is normally compiled in the driver. It isn't used,
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* unless the mode keyword on the server configuration command specifies
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* a nonzero ICOM ID select code. The C-IV trace is turned on if the
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* debug level is greater than one.
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*/
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/*
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* Interface definitions
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*/
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#define PRECISION (-10) /* precision assumed (about 1 ms) */
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#define REFID "NONE" /* reference ID */
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#define DESCRIPTION "WWV/H Audio Demodulator/Decoder" /* WRU */
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#define SECOND 8000 /* second epoch (sample rate) (Hz) */
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#define MINUTE (SECOND * 60) /* minute epoch */
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#define OFFSET 128 /* companded sample offset */
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#define SIZE 256 /* decompanding table size */
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#define MAXSIG 6000. /* maximum signal level reference */
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#define MAXSNR 30. /* max SNR reference */
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#define DGAIN 20. /* data channel gain reference */
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#define SGAIN 10. /* sync channel gain reference */
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#define MAXFREQ (125e-6 * SECOND) /* freq tolerance (.0125%) */
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#define PI 3.1415926535 /* the real thing */
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#define DATSIZ (170 * MS) /* data matched filter size */
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#define SYNSIZ (800 * MS) /* minute sync matched filter size */
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#define UTCYEAR 72 /* the first UTC year */
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#define MAXERR 30 /* max data bit errors in minute */
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#define NCHAN 5 /* number of channels */
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/*
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* Macroni
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*/
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#define MOD(x, y) ((x) < 0 ? -(-(x) % (y)) : (x) % (y))
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/*
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* General purpose status bits (status)
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*
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* Notes: SELV and/or SELH are set when the minute sync pulse from
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* either or both WWV and/or WWVH stations has been heard. MSYNC is set
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* when the minute sync pulse has been acquired and never reset. SSYNC
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* is set when the second sync pulse has been acquired and cleared by
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* watchdog or signal loss. DSYNC is set when the minutes unit digit has
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* reached the threshold and INSYNC is set when if all nine digits have
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* reached the threshold and never cleared.
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*
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* DGATE is set if a data bit is invalid, BGATE is set if a BCD digit
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* bit is invalid. SFLAG is set when during seconds 59, 0 and 1 while
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* probing for alternate frequencies. LEPSEC is set when the SECWAR of
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* the timecode is set on the last second of 30 June or 31 December. At
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* the end of this minute both the receiver and transmitter insert
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* second 60 in the minute and the minute sync slips a second.
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*/
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#define MSYNC 0x0001 /* minute epoch sync */
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#define SSYNC 0x0002 /* second epoch sync */
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#define DSYNC 0x0004 /* minute units sync */
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#define INSYNC 0x0008 /* clock synchronized */
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#define DGATE 0x0010 /* data bit error */
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#define BGATE 0x0020 /* BCD digit bit error */
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#define SFLAG 0x1000 /* probe flag */
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#define LEPSEC 0x2000 /* leap second in progress */
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/*
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* Station scoreboard bits (select)
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*
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* These are used to establish the signal quality for each of the five
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* frequencies and two stations.
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*/
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#define JITRNG 0x0001 /* jitter above threshold */
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#define SYNCNG 0x0002 /* sync below threshold or SNR */
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#define DATANG 0x0004 /* data below threshold or SNR */
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#define SELV 0x0100 /* WWV station select */
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#define SELH 0x0200 /* WWVH station select */
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/*
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* Alarm status bits (alarm)
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*
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* These bits indicate various alarm conditions, which are decoded to
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* form the quality character included in the timecode. There are four
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* four-bit nibble fields in the word, each corresponding to a specific
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* alarm condition. At the end of each second, the word is shifted left
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* one position and the least significant bit of each nibble cleared.
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* This bit can be set during the next minute if the associated alarm
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* condition is raised. This provides a way to remember alarm conditions
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* up to four minutes.
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*
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* If not tracking both minute sync and second sync, the SYNERR alarm is
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* raised. The data error counter is incremented for each invalid data
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* bit. If too many data bit errors are encountered in one minute, the
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* MODERR alarm is raised. The DECERR alarm is raised if a maximum
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* likelihood digit fails to compare with the current clock digit. If
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* the probability of any miscellaneous bit or any digit falls below the
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* threshold, the SYMERR alarm is raised.
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*/
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#define DECERR 0 /* BCD digit compare error */
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#define SYMERR 4 /* low bit or digit probability */
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#define MODERR 8 /* too many data bit errors */
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#define SYNERR 12 /* not synchronized to station */
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/*
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* Watchdog timeouts (watch)
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*
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* If these timeouts expire, the status bits are mashed to zero and the
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* driver starts from scratch. Suitably more refined procedures may be
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* developed in future. All these are in minutes.
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*/
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#define ACQSN 5 /* acquisition timeout */
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#define HSPEC 15 /* second sync timeout */
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#define DIGIT 30 /* minute unit digit timeout */
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#define PANIC (4 * 1440) /* panic timeout */
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/*
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* Thresholds. These establish the minimum signal level, minimum SNR and
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* maximum jitter thresholds which establish the error and false alarm
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* rates of the receiver. The values defined here may be on the
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* adventurous side in the interest of the highest sensitivity.
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*/
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#define ATHR 2000 /* acquisition amplitude threshold */
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#define ASNR 6.0 /* acquisition SNR threshold (dB) */
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#define AWND 50 /* acquisition window threshold (ms) */
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#define AMIN 3 /* acquisition min compare count */
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#define AMAX 6 /* max compare count */
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#define QTHR 2000 /* QSY amplitude threshold */
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#define QSNR 20.0 /* QSY SNR threshold (dB) */
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#define STHR 500 /* second sync amplitude threshold */
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#define SCMP 10 /* second sync compare threshold */
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#define DTHR 1000 /* bit amplitude threshold */
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#define DSNR 10.0 /* bit SNR threshold (dB) */
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#define BTHR 1000 /* digit probability threshold */
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#define BSNR 3.0 /* digit likelihood threshold (dB) */
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#define BCMP 5 /* digit compare threshold (dB) */
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/*
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* Tone frequency definitions.
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*/
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#define MS 8 /* samples per millisecond */
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#define IN100 1 /* 100 Hz 4.5-deg sin table */
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#define IN1000 10 /* 1000 Hz 4.5-deg sin table */
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#define IN1200 12 /* 1200 Hz 4.5-deg sin table */
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/*
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* Acquisition and tracking time constants. Usually powers of 2.
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*/
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#define MINAVG 8 /* min time constant (s) */
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#define MAXAVG 7 /* max time constant (log2 s) */
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#define TCONST 16 /* minute time constant (s) */
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#define SYNCTC (1024 / (1 << MAXAVG)) /* FLL constant (s) */
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/*
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* Miscellaneous status bits (misc)
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*
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* These bits correspond to designated bits in the WWV/H timecode. The
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* bit probabilities are exponentially averaged over several minutes and
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* processed by a integrator and threshold.
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*/
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#define DUT1 0x01 /* 56 DUT .1 */
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#define DUT2 0x02 /* 57 DUT .2 */
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#define DUT4 0x04 /* 58 DUT .4 */
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#define DUTS 0x08 /* 50 DUT sign */
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#define DST1 0x10 /* 55 DST1 DST in progress */
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#define DST2 0x20 /* 2 DST2 DST change warning */
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#define SECWAR 0x40 /* 3 leap second warning */
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/*
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* The total system delay with the DSP93 program is at 22.5 ms,
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* including the propagation delay from Ft. Collins, CO, to Newark, DE
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* (8.9 ms), the communications receiver delay and the delay of the
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* DSP93 program itself. The DSP93 program delay is due mainly to the
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* 400-Hz FIR bandpass filter (5 ms) and second sync matched filter (5
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* ms), leaving about 3.6 ms for the receiver delay and strays.
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*
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* The total system delay with this program is estimated at 27.1 ms by
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* comparison with another PPS-synchronized NTP server over a 10-Mb/s
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* Ethernet. The propagation and receiver delays are the same as with
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* the DSP93 program. The program delay is due only to the 600-Hz
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* IIR bandpass filter (1.1 ms), since other delays have been removed.
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* Assuming 4.7 ms for the receiver, program and strays, this leaves
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* 13.5 ms for the audio codec and operating system latencies for a
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* total of 18.2 ms. as the systematic delay. The additional propagation
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* delay specific to each receiver location can be programmed in the
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* fudge time1 and time2 values for WWV and WWVH, respectively.
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*/
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#define PDELAY (.0036 + .0011 + .0135) /* net system delay (s) */
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/*
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* Table of sine values at 4.5-degree increments. This is used by the
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* synchronous matched filter demodulators. The integral of sine-squared
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* over one complete cycle is PI, so the table is normallized by 1 / PI.
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*/
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double sintab[] = {
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0.000000e+00, 2.497431e-02, 4.979464e-02, 7.430797e-02, /* 0-3 */
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9.836316e-02, 1.218119e-01, 1.445097e-01, 1.663165e-01, /* 4-7 */
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1.870979e-01, 2.067257e-01, 2.250791e-01, 2.420447e-01, /* 8-11 */
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2.575181e-01, 2.714038e-01, 2.836162e-01, 2.940800e-01, /* 12-15 */
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3.027307e-01, 3.095150e-01, 3.143910e-01, 3.173286e-01, /* 16-19 */
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3.183099e-01, 3.173286e-01, 3.143910e-01, 3.095150e-01, /* 20-23 */
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3.027307e-01, 2.940800e-01, 2.836162e-01, 2.714038e-01, /* 24-27 */
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2.575181e-01, 2.420447e-01, 2.250791e-01, 2.067257e-01, /* 28-31 */
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1.870979e-01, 1.663165e-01, 1.445097e-01, 1.218119e-01, /* 32-35 */
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9.836316e-02, 7.430797e-02, 4.979464e-02, 2.497431e-02, /* 36-39 */
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-0.000000e+00, -2.497431e-02, -4.979464e-02, -7.430797e-02, /* 40-43 */
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-9.836316e-02, -1.218119e-01, -1.445097e-01, -1.663165e-01, /* 44-47 */
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-1.870979e-01, -2.067257e-01, -2.250791e-01, -2.420447e-01, /* 48-51 */
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-2.575181e-01, -2.714038e-01, -2.836162e-01, -2.940800e-01, /* 52-55 */
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-3.027307e-01, -3.095150e-01, -3.143910e-01, -3.173286e-01, /* 56-59 */
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-3.183099e-01, -3.173286e-01, -3.143910e-01, -3.095150e-01, /* 60-63 */
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-3.027307e-01, -2.940800e-01, -2.836162e-01, -2.714038e-01, /* 64-67 */
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-2.575181e-01, -2.420447e-01, -2.250791e-01, -2.067257e-01, /* 68-71 */
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-1.870979e-01, -1.663165e-01, -1.445097e-01, -1.218119e-01, /* 72-75 */
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-9.836316e-02, -7.430797e-02, -4.979464e-02, -2.497431e-02, /* 76-79 */
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0.000000e+00}; /* 80 */
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/*
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* Decoder operations at the end of each second are driven by a state
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* machine. The transition matrix consists of a dispatch table indexed
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* by second number. Each entry in the table contains a case switch
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* number and argument.
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*/
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struct progx {
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int sw; /* case switch number */
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int arg; /* argument */
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};
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/*
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* Case switch numbers
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*/
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#define IDLE 0 /* no operation */
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#define COEF 1 /* BCD bit conditioned on DSYNC */
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#define COEF1 2 /* BCD bit */
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#define COEF2 3 /* BCD bit ignored */
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#define DECIM9 4 /* BCD digit 0-9 */
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#define DECIM6 5 /* BCD digit 0-6 */
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#define DECIM3 6 /* BCD digit 0-3 */
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#define DECIM2 7 /* BCD digit 0-2 */
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#define MSCBIT 8 /* miscellaneous bit */
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#define MSC20 9 /* miscellaneous bit */
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#define MSC21 10 /* QSY probe channel */
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#define MIN1 11 /* minute */
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#define MIN2 12 /* leap second */
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#define SYNC2 13 /* QSY data channel */
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#define SYNC3 14 /* QSY data channel */
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||
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/*
|
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* Offsets in decoding matrix
|
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*/
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#define MN 0 /* minute digits (2) */
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#define HR 2 /* hour digits (2) */
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#define DA 4 /* day digits (3) */
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#define YR 7 /* year digits (2) */
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struct progx progx[] = {
|
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{SYNC2, 0}, /* 0 latch sync max */
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{SYNC3, 0}, /* 1 QSY data channel */
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{MSCBIT, DST2}, /* 2 dst2 */
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{MSCBIT, SECWAR}, /* 3 lw */
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{COEF, 0}, /* 4 1 year units */
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{COEF, 1}, /* 5 2 */
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{COEF, 2}, /* 6 4 */
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{COEF, 3}, /* 7 8 */
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{DECIM9, YR}, /* 8 */
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{IDLE, 0}, /* 9 p1 */
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{COEF1, 0}, /* 10 1 minute units */
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{COEF1, 1}, /* 11 2 */
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{COEF1, 2}, /* 12 4 */
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{COEF1, 3}, /* 13 8 */
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{DECIM9, MN}, /* 14 */
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{COEF, 0}, /* 15 10 minute tens */
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{COEF, 1}, /* 16 20 */
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{COEF, 2}, /* 17 40 */
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{COEF2, 3}, /* 18 80 (not used) */
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{DECIM6, MN + 1}, /* 19 p2 */
|
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{COEF, 0}, /* 20 1 hour units */
|
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{COEF, 1}, /* 21 2 */
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{COEF, 2}, /* 22 4 */
|
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{COEF, 3}, /* 23 8 */
|
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{DECIM9, HR}, /* 24 */
|
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{COEF, 0}, /* 25 10 hour tens */
|
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{COEF, 1}, /* 26 20 */
|
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{COEF2, 2}, /* 27 40 (not used) */
|
||
{COEF2, 3}, /* 28 80 (not used) */
|
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{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 */
|
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{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 sync min */
|
||
{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 daylight warning */
|
||
'O', /* 10 standard warning */
|
||
'D' /* 11 daylight time */
|
||
};
|
||
|
||
/*
|
||
* The decoding matrix consists of nine row vectors, one for each digit
|
||
* of the timecode. The digits are stored from least to most significant
|
||
* order. The maximum likelihood timecode is formed from the digits
|
||
* corresponding to the maximum likelihood values reading in the
|
||
* opposite order: yy ddd hh:mm.
|
||
*/
|
||
struct decvec {
|
||
int radix; /* radix (3, 4, 6, 10) */
|
||
int digit; /* current clock digit */
|
||
int mldigit; /* maximum likelihood digit */
|
||
int phase; /* maximum likelihood digit phase */
|
||
int count; /* match count */
|
||
double digprb; /* max digit probability */
|
||
double digsnr; /* likelihood function (dB) */
|
||
double like[10]; /* likelihood integrator 0-9 */
|
||
};
|
||
|
||
/*
|
||
* The station structure 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 amp; /* sync amplitude (I, Q square) */
|
||
double synamp; /* sync envelope at 800 ms */
|
||
double synmax; /* sync envelope at 0 s */
|
||
double synmin; /* avg sync envelope at 59 s, 1 s */
|
||
double synsnr; /* sync signal SNR */
|
||
double noise; /* max amplitude off pulse */
|
||
double sigmax; /* max amplitude on pulse */
|
||
double lastmax; /* last max amplitude on pulse */
|
||
long pos; /* position at maximum amplitude */
|
||
long lastpos; /* last position at maximum amplitude */
|
||
long jitter; /* shake, wiggle and waggle */
|
||
long mepoch; /* minute synch epoch */
|
||
int count; /* compare counter */
|
||
char refid[5]; /* reference identifier */
|
||
char ident[4]; /* station identifier */
|
||
int select; /* select bits */
|
||
};
|
||
|
||
/*
|
||
* The channel structure is used to mitigate between channels. At this
|
||
* point we have already decided which station to use.
|
||
*/
|
||
struct chan {
|
||
int gain; /* audio gain */
|
||
int errcnt; /* data bit error counter */
|
||
double noiamp; /* I-channel average noise amplitude */
|
||
struct sync wwv; /* wwv station */
|
||
struct sync wwvh; /* wwvh station */
|
||
};
|
||
|
||
/*
|
||
* WWV unit control structure
|
||
*/
|
||
struct wwvunit {
|
||
l_fp timestamp; /* audio sample timestamp */
|
||
l_fp tick; /* audio sample increment */
|
||
double comp[SIZE]; /* decompanding table */
|
||
double phase, freq; /* logical clock phase and frequency */
|
||
double monitor; /* audio monitor point */
|
||
int fd_icom; /* ICOM file descriptor */
|
||
int errflg; /* error flags */
|
||
int bufcnt; /* samples in buffer */
|
||
int bufptr; /* buffer index pointer */
|
||
int port; /* codec port */
|
||
int gain; /* codec gain */
|
||
int clipcnt; /* sample clipped count */
|
||
int seccnt; /* second countdown */
|
||
int minset; /* minutes since last clock set */
|
||
int watch; /* watchcat */
|
||
int swatch; /* second sync watchcat */
|
||
|
||
/*
|
||
* Variables used to establish basic system timing
|
||
*/
|
||
int avgint; /* log2 master time constant (s) */
|
||
int epoch; /* second epoch ramp */
|
||
int repoch; /* receiver sync epoch */
|
||
int yepoch; /* transmitter sync epoch */
|
||
double epomax; /* second sync amplitude */
|
||
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; /* receiver sample counter */
|
||
int rsec; /* receiver seconds counter */
|
||
long mphase; /* minute sample counter */
|
||
long nepoch; /* minute epoch index */
|
||
|
||
/*
|
||
* 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 cdelay; /* WWV propagation delay (samples) */
|
||
int hdelay; /* WVVH propagation delay (samples) */
|
||
int pdelay; /* propagation delay (samples) */
|
||
int tphase; /* transmitter sample counter */
|
||
int tsec; /* transmitter seconds counter */
|
||
int digcnt; /* count of digits synchronized */
|
||
|
||
/*
|
||
* Variables used to estimate signal levels and bit/digit
|
||
* probabilities
|
||
*/
|
||
double sigamp; /* I-channel peak signal amplitude */
|
||
double noiamp; /* I-channel average noise amplitude */
|
||
double datsnr; /* data SNR (dB) */
|
||
|
||
/*
|
||
* Variables used to establish status and alarm conditions
|
||
*/
|
||
int status; /* status bits */
|
||
int alarm; /* alarm flashers */
|
||
int misc; /* miscellaneous timecode bits */
|
||
int errcnt; /* data bit error counter */
|
||
};
|
||
|
||
/*
|
||
* Function prototypes
|
||
*/
|
||
static int wwv_start P((int, struct peer *));
|
||
static void wwv_shutdown P((int, struct peer *));
|
||
static void wwv_receive P((struct recvbuf *));
|
||
static void wwv_poll P((int, struct peer *));
|
||
|
||
/*
|
||
* More function prototypes
|
||
*/
|
||
static void wwv_epoch P((struct peer *));
|
||
static void wwv_rf P((struct peer *, double));
|
||
static void wwv_endpoc P((struct peer *, double, int));
|
||
static void wwv_rsec P((struct peer *, double));
|
||
static void wwv_qrz P((struct peer *, struct sync *,
|
||
double));
|
||
static void wwv_corr4 P((struct peer *, struct decvec *,
|
||
double [], double [][4]));
|
||
static void wwv_gain P((struct peer *));
|
||
static void wwv_tsec P((struct wwvunit *));
|
||
static double wwv_data P((struct wwvunit *, double));
|
||
static int timecode P((struct wwvunit *, char *));
|
||
static double wwv_snr P((double, double));
|
||
static int carry P((struct decvec *));
|
||
static void wwv_newchan P((struct peer *));
|
||
static int wwv_qsy P((struct peer *, int));
|
||
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 (not used) */
|
||
struct peer *peer /* peer structure pointer */
|
||
)
|
||
{
|
||
struct refclockproc *pp;
|
||
struct wwvunit *up;
|
||
struct chan *cp;
|
||
#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();
|
||
if (fd < 0)
|
||
return (0);
|
||
#ifdef DEBUG
|
||
if (debug)
|
||
audio_show();
|
||
#endif
|
||
|
||
/*
|
||
* Allocate and initialize unit structure
|
||
*/
|
||
if (!(up = (struct wwvunit *)
|
||
emalloc(sizeof(struct wwvunit)))) {
|
||
(void) close(fd);
|
||
return (0);
|
||
}
|
||
memset((char *)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)) {
|
||
(void)close(fd);
|
||
free(up);
|
||
return (0);
|
||
}
|
||
|
||
/*
|
||
* Initialize miscellaneous variables
|
||
*/
|
||
peer->precision = PRECISION;
|
||
pp->clockdesc = DESCRIPTION;
|
||
memcpy((char *)&pp->refid, REFID, 4);
|
||
DTOLFP(1. / SECOND, &up->tick);
|
||
|
||
/*
|
||
* 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.;
|
||
}
|
||
|
||
/*
|
||
* 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;
|
||
|
||
/*
|
||
* Initialize the station processes for audio gain, select bit,
|
||
* station/frequency identifier and reference identifier.
|
||
*/
|
||
up->gain = 127;
|
||
for (i = 0; i < NCHAN; i++) {
|
||
cp = &up->mitig[i];
|
||
cp->gain = up->gain;
|
||
cp->wwv.select = SELV;
|
||
strcpy(cp->wwv.refid, "WWV ");
|
||
sprintf(cp->wwv.ident,"C%.0f", floor(qsy[i]));
|
||
cp->wwvh.select = SELH;
|
||
strcpy(cp->wwvh.refid, "WWVH");
|
||
sprintf(cp->wwvh.ident, "H%.0f", floor(qsy[i]));
|
||
}
|
||
|
||
/*
|
||
* Initialize autotune if available. Start out at 15 MHz. Note
|
||
* that the ICOM select code must be less than 128, so the high
|
||
* order bit can be used to select the line speed.
|
||
*/
|
||
#ifdef ICOM
|
||
temp = 0;
|
||
#ifdef DEBUG
|
||
if (debug > 1)
|
||
temp = P_TRACE;
|
||
#endif
|
||
if (peer->ttl != 0) {
|
||
if (peer->ttl & 0x80)
|
||
up->fd_icom = icom_init("/dev/icom", B1200,
|
||
temp);
|
||
else
|
||
up->fd_icom = icom_init("/dev/icom", B9600,
|
||
temp);
|
||
}
|
||
if (up->fd_icom > 0) {
|
||
up->schan = 3;
|
||
if ((temp = wwv_qsy(peer, up->schan)) < 0) {
|
||
NLOG(NLOG_SYNCEVENT | NLOG_SYSEVENT)
|
||
msyslog(LOG_ERR,
|
||
"ICOM bus error; autotune disabled");
|
||
up->errflg = CEVNT_FAULT;
|
||
close(up->fd_icom);
|
||
up->fd_icom = 0;
|
||
}
|
||
}
|
||
#endif /* ICOM */
|
||
return (1);
|
||
}
|
||
|
||
|
||
/*
|
||
* wwv_shutdown - shut down the clock
|
||
*/
|
||
static void
|
||
wwv_shutdown(
|
||
int unit, /* instance number (not used) */
|
||
struct peer *peer /* peer structure pointer */
|
||
)
|
||
{
|
||
struct refclockproc *pp;
|
||
struct wwvunit *up;
|
||
|
||
pp = peer->procptr;
|
||
up = (struct wwvunit *)pp->unitptr;
|
||
io_closeclock(&pp->io);
|
||
if (up->fd_icom > 0)
|
||
close(up->fd_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 */
|
||
l_fp ltemp;
|
||
int isneg;
|
||
double dtemp;
|
||
int i, j;
|
||
|
||
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.
|
||
*/
|
||
up->timestamp = rbufp->recv_time;
|
||
up->bufcnt = rbufp->recv_length;
|
||
DTOLFP((double)up->bufcnt / SECOND, <emp);
|
||
L_SUB(&up->timestamp, <emp);
|
||
dpt = rbufp->recv_buffer;
|
||
for (up->bufptr = 0; up->bufptr < up->bufcnt; up->bufptr++) {
|
||
sample = up->comp[~*dpt & 0xff];
|
||
|
||
/*
|
||
* Clip noise spikes greater than MAXSIG. If no clips,
|
||
* increase the gain a tad; if the clips are too high,
|
||
* decrease a tad.
|
||
*/
|
||
if (sample > MAXSIG) {
|
||
sample = MAXSIG;
|
||
up->clipcnt++;
|
||
} else if (sample < -MAXSIG) {
|
||
sample = -MAXSIG;
|
||
up->clipcnt++;
|
||
}
|
||
|
||
/*
|
||
* Variable frequency oscillator. A phase change of one
|
||
* unit produces a change of 360 degrees; a frequency
|
||
* change of one unit produces a change of 1 Hz.
|
||
*/
|
||
up->phase += up->freq / 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);
|
||
|
||
/*
|
||
* Once each second adjust the codec port and gain.
|
||
* While at it, initialize the propagation delay for
|
||
* both WWV and WWVH. Don't forget to correct for the
|
||
* receiver phase delay, mostly due to the 600-Hz
|
||
* IIR bandpass filter used for the sync signals.
|
||
*/
|
||
up->cdelay = (int)(SECOND * (pp->fudgetime1 + PDELAY));
|
||
up->hdelay = (int)(SECOND * (pp->fudgetime2 + PDELAY));
|
||
up->seccnt = (up->seccnt + 1) % SECOND;
|
||
if (up->seccnt == 0) {
|
||
if (pp->sloppyclockflag & CLK_FLAG2)
|
||
up->port = 2;
|
||
else
|
||
up->port = 1;
|
||
}
|
||
|
||
/*
|
||
* During development, it is handy to have an audio
|
||
* monitor that can be switched to various signals. This
|
||
* code converts the linear signal left in up->monitor
|
||
* to codec format.
|
||
*/
|
||
isneg = 0;
|
||
dtemp = up->monitor;
|
||
if (sample < 0) {
|
||
isneg = 1;
|
||
dtemp -= dtemp;
|
||
}
|
||
i = 0;
|
||
j = OFFSET >> 1;
|
||
while (j != 0) {
|
||
if (dtemp > up->comp[i])
|
||
i += j;
|
||
else if (dtemp < up->comp[i])
|
||
i -= j;
|
||
else
|
||
break;
|
||
j >>= 1;
|
||
}
|
||
if (isneg)
|
||
*dpt = ~(i + OFFSET);
|
||
else
|
||
*dpt = ~i;
|
||
dpt++;
|
||
}
|
||
|
||
/*
|
||
* Squawk to the monitor speaker if enabled.
|
||
*/
|
||
if (pp->sloppyclockflag & CLK_FLAG3)
|
||
if (write(pp->io.fd, (u_char *)&rbufp->recv_space,
|
||
(u_int)up->bufcnt) < 0)
|
||
perror("wwv:");
|
||
}
|
||
|
||
|
||
/*
|
||
* wwv_poll - called by the transmit procedure
|
||
*
|
||
* This routine keeps track of status. If nothing is heard for two
|
||
* successive poll intervals, a timeout event is declared and any
|
||
* orphaned timecode updates are sent to foster care. Once the clock is
|
||
* set, it always appears reachable, unless reset by watchdog timeout.
|
||
*/
|
||
static void
|
||
wwv_poll(
|
||
int unit, /* instance number (not used) */
|
||
struct peer *peer /* peer structure pointer */
|
||
)
|
||
{
|
||
struct refclockproc *pp;
|
||
struct wwvunit *up;
|
||
|
||
pp = peer->procptr;
|
||
up = (struct wwvunit *)pp->unitptr;
|
||
if (pp->coderecv == pp->codeproc)
|
||
up->errflg = CEVNT_TIMEOUT;
|
||
else
|
||
pp->polls++;
|
||
if (up->status & INSYNC)
|
||
peer->reach |= 1;
|
||
if (up->errflg)
|
||
refclock_report(peer, up->errflg);
|
||
up->errflg = 0;
|
||
}
|
||
|
||
|
||
/*
|
||
* wwv_rf - process signals and demodulate to baseband
|
||
*
|
||
* This routine grooms and filters decompanded raw audio samples. The
|
||
* output signals include the 100-Hz baseband data signal in quadrature
|
||
* form, plus the epoch index of the second sync signal and the second
|
||
* index of the minute sync signal.
|
||
*
|
||
* There are three 1-s ramps used by this program, all spanning the
|
||
* range 0-7999 logical samples for exactly one second, as determined by
|
||
* the logical clock. The first drives the second epoch and runs
|
||
* continuously. The second determines the receiver phase and the third
|
||
* the transmitter phase within the second. The receiver second begins
|
||
* upon arrival of the 5-ms second sync pulse which begins the second;
|
||
* while the transmitter second begins before it by the specified
|
||
* propagation delay.
|
||
*
|
||
* There are three 1-m ramps spanning the range 0-59 seconds. The first
|
||
* drives the minute epoch in samples and runs continuously. The second
|
||
* determines the receiver second and the third the transmitter second.
|
||
* The receiver second begins upon arrival of the 800-ms sync pulse sent
|
||
* during the first second of the minute; while the transmitter second
|
||
* begins before it by the specified propagation delay.
|
||
*
|
||
* The output signals include the epoch maximum and phase and second
|
||
* maximum and index. The epoch phase provides the master reference for
|
||
* all signal and timing functions, while the second index identifies
|
||
* the first second of the minute. The epoch and second maxima are used
|
||
* to calculate SNR for gating functions.
|
||
*
|
||
* Demodulation operations are based on three synthesized quadrature
|
||
* sinusoids: 100 Hz for the data subcarrier, 1000 Hz for the WWV sync
|
||
* signals and 1200 Hz for the WWVH sync signal. These drive synchronous
|
||
* matched filters for the data subcarrier (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 seconds sync signal (5 ms at 1000 Hz) and
|
||
* WWVH seconds sync signal (5 ms at 1200 Hz).
|
||
*/
|
||
static void
|
||
wwv_rf(
|
||
struct peer *peer, /* peerstructure pointer */
|
||
double isig /* input signal */
|
||
)
|
||
{
|
||
struct refclockproc *pp;
|
||
struct wwvunit *up;
|
||
|
||
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 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 int csinptr; /* wwv 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 int hsinptr; /* wwvh channels phase */
|
||
|
||
static double epobuf[SECOND]; /* epoch sync comb filter */
|
||
static double epomax; /* epoch sync amplitude buffer */
|
||
static int epopos; /* epoch sync position buffer */
|
||
|
||
static int iniflg; /* initialization flag */
|
||
struct sync *sp;
|
||
double dtemp;
|
||
long ltemp;
|
||
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 *)hibuf, 0, sizeof(hibuf));
|
||
memset((char *)hqbuf, 0, sizeof(hqbuf));
|
||
memset((char *)epobuf, 0, sizeof(epobuf));
|
||
}
|
||
up->monitor = isig; /* change for debug */
|
||
|
||
/*
|
||
* 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.
|
||
*
|
||
* Matlab IIR 4th-order IIR elliptic, 150 Hz lowpass, 0.2 dB
|
||
* passband ripple, -50 dB stopband ripple.
|
||
*/
|
||
data = (lpf[4] = lpf[3]) * 8.360961e-01;
|
||
data += (lpf[3] = lpf[2]) * -3.481740e+00;
|
||
data += (lpf[2] = lpf[1]) * 5.452988e+00;
|
||
data += (lpf[1] = lpf[0]) * -3.807229e+00;
|
||
lpf[0] = isig - 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 I and Q quadrature data signals are produced by
|
||
* multiplying the filtered signal by 100-Hz sine and cosine
|
||
* signals, respectively. The data signals are demodulated by
|
||
* 170-ms synchronous matched filters to produce the amplitude
|
||
* and phase signals used by the decoder. Note the correction
|
||
* due to the propagation delay is necessary for seamless
|
||
* handover between WWV and WWVH.
|
||
*/
|
||
i = up->datapt - up->pdelay % 80;
|
||
if (i < 0)
|
||
i += 80;
|
||
up->datapt = (up->datapt + IN100) % 80;
|
||
dtemp = sintab[i] * data / DATSIZ * DGAIN;
|
||
up->irig -= ibuf[iptr];
|
||
ibuf[iptr] = dtemp;
|
||
up->irig += dtemp;
|
||
i = (i + 20) % 80;
|
||
dtemp = sintab[i] * data / DATSIZ * DGAIN;
|
||
up->qrig -= qbuf[iptr];
|
||
qbuf[iptr] = dtemp;
|
||
up->qrig += dtemp;
|
||
iptr = (iptr + 1) % DATSIZ;
|
||
|
||
/*
|
||
* Baseband sync demodulation. The 1000/1200 sync signals are
|
||
* extracted using a 600-Hz IIR bandpass filter. This removes
|
||
* the 100-Hz data subcarrier, as well as the 440-Hz and 600-Hz
|
||
* tones and most of the noise and voice modulation components.
|
||
*
|
||
* Matlab 4th-order IIR elliptic, 800-1400 Hz bandpass, 0.2 dB
|
||
* passband ripple, -50 dB stopband ripple.
|
||
*/
|
||
syncx = (bpf[8] = bpf[7]) * 4.897278e-01;
|
||
syncx += (bpf[7] = bpf[6]) * -2.765914e+00;
|
||
syncx += (bpf[6] = bpf[5]) * 8.110921e+00;
|
||
syncx += (bpf[5] = bpf[4]) * -1.517732e+01;
|
||
syncx += (bpf[4] = bpf[3]) * 1.975197e+01;
|
||
syncx += (bpf[3] = bpf[2]) * -1.814365e+01;
|
||
syncx += (bpf[2] = bpf[1]) * 1.159783e+01;
|
||
syncx += (bpf[1] = bpf[0]) * -4.735040e+00;
|
||
bpf[0] = isig - syncx;
|
||
syncx = bpf[0] * 8.203628e-03
|
||
+ bpf[1] * -2.375732e-02
|
||
+ bpf[2] * 3.353214e-02
|
||
+ bpf[3] * -4.080258e-02
|
||
+ bpf[4] * 4.605479e-02
|
||
+ bpf[5] * -4.080258e-02
|
||
+ bpf[6] * 3.353214e-02
|
||
+ bpf[7] * -2.375732e-02
|
||
+ bpf[8] * 8.203628e-03;
|
||
|
||
/*
|
||
* The I and Q quadrature minute sync signals are produced by
|
||
* multiplying the filtered signal by 1000-Hz (WWV) and 1200-Hz
|
||
* (WWVH) sine and cosine signals, respectively. The resulting
|
||
* signals are demodulated by 800-ms synchronous matched filters
|
||
* to synchronize the second and minute and to detect which one
|
||
* (or both) the WWV or WWVH signal is present.
|
||
*/
|
||
up->mphase = (up->mphase + 1) % MINUTE;
|
||
|
||
i = csinptr;
|
||
csinptr = (csinptr + IN1000) % 80;
|
||
dtemp = sintab[i] * syncx / SYNSIZ * SGAIN;
|
||
ciamp = ciamp - cibuf[jptr] + dtemp;
|
||
cibuf[jptr] = dtemp;
|
||
i = (i + 20) % 80;
|
||
dtemp = sintab[i] * syncx / SYNSIZ * SGAIN;
|
||
cqamp = cqamp - cqbuf[jptr] + dtemp;
|
||
cqbuf[jptr] = dtemp;
|
||
dtemp = ciamp * ciamp + cqamp * cqamp;
|
||
wwv_qrz(peer, &up->mitig[up->schan].wwv, dtemp);
|
||
|
||
i = hsinptr;
|
||
hsinptr = (hsinptr + IN1200) % 80;
|
||
dtemp = sintab[i] * syncx / SYNSIZ * SGAIN;
|
||
hiamp = hiamp - hibuf[jptr] + dtemp;
|
||
hibuf[jptr] = dtemp;
|
||
i = (i + 20) % 80;
|
||
dtemp = sintab[i] * syncx / SYNSIZ * SGAIN;
|
||
hqamp = hqamp - hqbuf[jptr] + dtemp;
|
||
hqbuf[jptr] = dtemp;
|
||
dtemp = hiamp * hiamp + hqamp * hqamp;
|
||
wwv_qrz(peer, &up->mitig[up->schan].wwvh, dtemp);
|
||
|
||
jptr = (jptr + 1) % SYNSIZ;
|
||
|
||
if (up->mphase == 0) {
|
||
|
||
/*
|
||
* This section is called once per minute at the minute
|
||
* epoch independently of the transmitter or receiver
|
||
* minute. If the leap bit is set, set the minute epoch
|
||
* back one second so the station processes don't miss a
|
||
* beat. Then, increment the watchdog counter and test
|
||
* for two sets of conditions depending on whether
|
||
* minute sync has been acquired or not.
|
||
*/
|
||
up->watch++;
|
||
if (up->rsec == 60) {
|
||
up->mphase -= SECOND;
|
||
if (up->mphase < 0)
|
||
up->mphase += MINUTE;
|
||
} else if (!(up->status & MSYNC)) {
|
||
|
||
/*
|
||
* If minute sync has not been acquired, the
|
||
* program listens for minute sync pulses from
|
||
* both WWV and WWVH. The station with the
|
||
* greater compare count is selected, with ties
|
||
* broken by WWV, but only if the count is at
|
||
* least three. Once a station has been
|
||
* acquired, it is initialized and begins
|
||
* tracking the signal.
|
||
*/
|
||
if (up->mitig[up->achan].wwv.count >=
|
||
up->mitig[up->achan].wwvh.count)
|
||
sp = &up->mitig[up->achan].wwv;
|
||
else
|
||
sp = &up->mitig[up->achan].wwvh;
|
||
if (sp->count >= AMIN) {
|
||
up->watch = up->swatch = 0;
|
||
up->status |= MSYNC;
|
||
ltemp = sp->mepoch - SYNSIZ;
|
||
if (ltemp < 0)
|
||
ltemp += MINUTE;
|
||
up->rsec = (MINUTE - ltemp) / SECOND;
|
||
if (!(up->status & SSYNC)) {
|
||
up->repoch = ltemp % SECOND;
|
||
up->yepoch = up->repoch -
|
||
up->pdelay;
|
||
if (up->yepoch < 0)
|
||
up->yepoch += SECOND;
|
||
}
|
||
wwv_newchan(peer);
|
||
} else if (sp->count == 0 || up->watch >= ACQSN)
|
||
{
|
||
up->watch = sp->count = 0;
|
||
up->schan = (up->schan + 1) % NCHAN;
|
||
wwv_qsy(peer, up->schan);
|
||
}
|
||
} else {
|
||
|
||
/*
|
||
* If minute sync has been acquired, the program
|
||
* watches for timeout. The timeout is reset
|
||
* when the clock is set or verified. If a
|
||
* timeout occurs and the minute units digit has
|
||
* not synchronized, reset the program and start
|
||
* over.
|
||
*/
|
||
if (up->watch > DIGIT && !(up->status & DSYNC))
|
||
up->watch = up->status = 0;
|
||
|
||
/*
|
||
* If the second sync times out, dim the sync
|
||
* lamp and raise an alarm.
|
||
*/
|
||
up->swatch++;
|
||
if (up->swatch > HSPEC)
|
||
up->status &= ~SSYNC;
|
||
if (!(up->status & SSYNC))
|
||
up->alarm |= 1 << SYNERR;
|
||
}
|
||
}
|
||
|
||
/*
|
||
* The second sync pulse is extracted using 5-ms 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).
|
||
*/
|
||
if (up->status & SELV) {
|
||
up->pdelay = up->cdelay;
|
||
|
||
/*
|
||
* WWV FIR matched filter, five cycles of 1000-Hz
|
||
* sinewave.
|
||
*/
|
||
mf[40] = mf[39];
|
||
mfsync = (mf[39] = mf[38]) * 4.224514e-02;
|
||
mfsync += (mf[38] = mf[37]) * 5.974365e-02;
|
||
mfsync += (mf[37] = mf[36]) * 4.224514e-02;
|
||
mf[36] = mf[35];
|
||
mfsync += (mf[35] = mf[34]) * -4.224514e-02;
|
||
mfsync += (mf[34] = mf[33]) * -5.974365e-02;
|
||
mfsync += (mf[33] = mf[32]) * -4.224514e-02;
|
||
mf[32] = mf[31];
|
||
mfsync += (mf[31] = mf[30]) * 4.224514e-02;
|
||
mfsync += (mf[30] = mf[29]) * 5.974365e-02;
|
||
mfsync += (mf[29] = mf[28]) * 4.224514e-02;
|
||
mf[28] = mf[27];
|
||
mfsync += (mf[27] = mf[26]) * -4.224514e-02;
|
||
mfsync += (mf[26] = mf[25]) * -5.974365e-02;
|
||
mfsync += (mf[25] = mf[24]) * -4.224514e-02;
|
||
mf[24] = mf[23];
|
||
mfsync += (mf[23] = mf[22]) * 4.224514e-02;
|
||
mfsync += (mf[22] = mf[21]) * 5.974365e-02;
|
||
mfsync += (mf[21] = mf[20]) * 4.224514e-02;
|
||
mf[20] = mf[19];
|
||
mfsync += (mf[19] = mf[18]) * -4.224514e-02;
|
||
mfsync += (mf[18] = mf[17]) * -5.974365e-02;
|
||
mfsync += (mf[17] = mf[16]) * -4.224514e-02;
|
||
mf[16] = mf[15];
|
||
mfsync += (mf[15] = mf[14]) * 4.224514e-02;
|
||
mfsync += (mf[14] = mf[13]) * 5.974365e-02;
|
||
mfsync += (mf[13] = mf[12]) * 4.224514e-02;
|
||
mf[12] = mf[11];
|
||
mfsync += (mf[11] = mf[10]) * -4.224514e-02;
|
||
mfsync += (mf[10] = mf[9]) * -5.974365e-02;
|
||
mfsync += (mf[9] = mf[8]) * -4.224514e-02;
|
||
mf[8] = mf[7];
|
||
mfsync += (mf[7] = mf[6]) * 4.224514e-02;
|
||
mfsync += (mf[6] = mf[5]) * 5.974365e-02;
|
||
mfsync += (mf[5] = mf[4]) * 4.224514e-02;
|
||
mf[4] = mf[3];
|
||
mfsync += (mf[3] = mf[2]) * -4.224514e-02;
|
||
mfsync += (mf[2] = mf[1]) * -5.974365e-02;
|
||
mfsync += (mf[1] = mf[0]) * -4.224514e-02;
|
||
mf[0] = syncx;
|
||
} else if (up->status & SELH) {
|
||
up->pdelay = up->hdelay;
|
||
|
||
/*
|
||
* WWVH FIR matched filter, six cycles of 1200-Hz
|
||
* sinewave.
|
||
*/
|
||
mf[40] = mf[39];
|
||
mfsync = (mf[39] = mf[38]) * 4.833363e-02;
|
||
mfsync += (mf[38] = mf[37]) * 5.681959e-02;
|
||
mfsync += (mf[37] = mf[36]) * 1.846180e-02;
|
||
mfsync += (mf[36] = mf[35]) * -3.511644e-02;
|
||
mfsync += (mf[35] = mf[34]) * -5.974365e-02;
|
||
mfsync += (mf[34] = mf[33]) * -3.511644e-02;
|
||
mfsync += (mf[33] = mf[32]) * 1.846180e-02;
|
||
mfsync += (mf[32] = mf[31]) * 5.681959e-02;
|
||
mfsync += (mf[31] = mf[30]) * 4.833363e-02;
|
||
mf[30] = mf[29];
|
||
mfsync += (mf[29] = mf[28]) * -4.833363e-02;
|
||
mfsync += (mf[28] = mf[27]) * -5.681959e-02;
|
||
mfsync += (mf[27] = mf[26]) * -1.846180e-02;
|
||
mfsync += (mf[26] = mf[25]) * 3.511644e-02;
|
||
mfsync += (mf[25] = mf[24]) * 5.974365e-02;
|
||
mfsync += (mf[24] = mf[23]) * 3.511644e-02;
|
||
mfsync += (mf[23] = mf[22]) * -1.846180e-02;
|
||
mfsync += (mf[22] = mf[21]) * -5.681959e-02;
|
||
mfsync += (mf[21] = mf[20]) * -4.833363e-02;
|
||
mf[20] = mf[19];
|
||
mfsync += (mf[19] = mf[18]) * 4.833363e-02;
|
||
mfsync += (mf[18] = mf[17]) * 5.681959e-02;
|
||
mfsync += (mf[17] = mf[16]) * 1.846180e-02;
|
||
mfsync += (mf[16] = mf[15]) * -3.511644e-02;
|
||
mfsync += (mf[15] = mf[14]) * -5.974365e-02;
|
||
mfsync += (mf[14] = mf[13]) * -3.511644e-02;
|
||
mfsync += (mf[13] = mf[12]) * 1.846180e-02;
|
||
mfsync += (mf[12] = mf[11]) * 5.681959e-02;
|
||
mfsync += (mf[11] = mf[10]) * 4.833363e-02;
|
||
mf[10] = mf[9];
|
||
mfsync += (mf[9] = mf[8]) * -4.833363e-02;
|
||
mfsync += (mf[8] = mf[7]) * -5.681959e-02;
|
||
mfsync += (mf[7] = mf[6]) * -1.846180e-02;
|
||
mfsync += (mf[6] = mf[5]) * 3.511644e-02;
|
||
mfsync += (mf[5] = mf[4]) * 5.974365e-02;
|
||
mfsync += (mf[4] = mf[3]) * 3.511644e-02;
|
||
mfsync += (mf[3] = mf[2]) * -1.846180e-02;
|
||
mfsync += (mf[2] = mf[1]) * -5.681959e-02;
|
||
mfsync += (mf[1] = mf[0]) * -4.833363e-02;
|
||
mf[0] = syncx;
|
||
} else {
|
||
mfsync = 0;
|
||
}
|
||
|
||
/*
|
||
* Extract the seconds sync pulse using a 1-s comb filter at
|
||
* baseband. Correct for the FIR matched filter delay, which is
|
||
* 5 ms for both the WWV and WWVH filters. Blank the signal when
|
||
* probing.
|
||
*/
|
||
up->epoch = (up->epoch + 1) % SECOND;
|
||
if (up->epoch == 0) {
|
||
wwv_endpoc(peer, epomax, epopos);
|
||
up->epomax = epomax;
|
||
epomax = 0;
|
||
if (!(up->status & MSYNC))
|
||
wwv_gain(peer);
|
||
}
|
||
dtemp = (epobuf[up->epoch] += (mfsync - epobuf[up->epoch]) /
|
||
(MINAVG << up->avgint));
|
||
if (dtemp > epomax) {
|
||
epomax = dtemp;
|
||
epopos = up->epoch - up->pdelay - 5 * MS;
|
||
if (epopos < 0)
|
||
epopos += SECOND;
|
||
}
|
||
if (up->status & MSYNC)
|
||
wwv_epoch(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 in turn for the minute pulse from either station, which
|
||
* involves searching through the entire epoch minute of samples. After
|
||
* minute sync acquisition, the process searches only during the probe
|
||
* window, which occupies seconds 59, 0 and 1, to construct a metric
|
||
* used to determine which frequency and station provides the best
|
||
* signal.
|
||
*
|
||
* The pulse discriminator requires that (a) the peak on-pulse sample
|
||
* amplitude must be above 2000, (b) the SNR relative to the peak
|
||
* off-pulse sample amplitude must be reduced 6 dB or more below the
|
||
* peak and (c) the maximum difference between the current and previous
|
||
* epoch indices must be less than 50 ms. A compare counter keeps track
|
||
* of the number of successive intervals which satisfy these criteria.
|
||
*
|
||
* Students of radar receiver technology will discover this algorithm
|
||
* amounts to a range gate discriminator. In practice, the performance
|
||
* of this gadget is amazing. Once setting teeth in a station, it hangs
|
||
* on until the minute beep can barely be heard and long after the
|
||
* second tick and comb filter have given up.
|
||
*/
|
||
static void
|
||
wwv_qrz(
|
||
struct peer *peer, /* peerstructure pointer */
|
||
struct sync *sp, /* sync channel structure */
|
||
double syncx /* bandpass filtered sync signal */
|
||
)
|
||
{
|
||
struct refclockproc *pp;
|
||
struct wwvunit *up;
|
||
char tbuf[80]; /* monitor buffer */
|
||
double snr; /* on-pulse/off-pulse ratio (dB) */
|
||
long epoch;
|
||
int isgood;
|
||
|
||
pp = peer->procptr;
|
||
up = (struct wwvunit *)pp->unitptr;
|
||
|
||
/*
|
||
* Find the sample with peak energy, which defines the minute
|
||
* epoch. If minute sync has been acquired, search only the
|
||
* probe window; otherwise, search the entire minute. If a
|
||
* maximum has been found with good amplitude, search only the
|
||
* second before and after that position for the next maximum
|
||
* and the rest of the window for the noise.
|
||
*/
|
||
if (!(up->status & MSYNC) || up->status & SFLAG) {
|
||
sp->amp = syncx;
|
||
if (up->status & MSYNC)
|
||
epoch = up->nepoch;
|
||
else if (sp->count > 1)
|
||
epoch = sp->mepoch;
|
||
else
|
||
epoch = sp->lastpos;
|
||
if (syncx > sp->sigmax) {
|
||
sp->sigmax = syncx;
|
||
sp->pos = up->mphase;
|
||
}
|
||
if (abs(MOD(up->mphase - epoch, MINUTE)) > SYNSIZ &&
|
||
syncx > sp->noise) {
|
||
sp->noise = syncx;
|
||
}
|
||
}
|
||
if (up->mphase == 0) {
|
||
|
||
/*
|
||
* At the end of the minute, determine the epoch of the
|
||
* sync pulse, as well as the SNR and difference between
|
||
* the current and previous epoch (jitter).
|
||
*/
|
||
sp->jitter = MOD(sp->pos - sp->lastpos, MINUTE);
|
||
sp->select &= ~JITRNG;
|
||
if (abs(sp->jitter) > AWND * MS)
|
||
sp->select |= JITRNG;
|
||
sp->sigmax = sqrt(sp->sigmax);
|
||
sp->noise = sqrt(sp->noise);
|
||
if (up->status & MSYNC) {
|
||
|
||
/*
|
||
* If in minute sync, just count the runs up and
|
||
* down.
|
||
*/
|
||
if (sp->select & (DATANG | SYNCNG | JITRNG)) {
|
||
if (sp->count > 0)
|
||
sp->count--;
|
||
} else {
|
||
if (sp->count < AMAX)
|
||
sp->count++;
|
||
}
|
||
} else {
|
||
|
||
/*
|
||
* If not yet in minute sync, we have to do a
|
||
* little dance to find a valid minute sync
|
||
* pulse, emphasis valid.
|
||
*/
|
||
snr = wwv_snr(sp->sigmax, sp->noise);
|
||
isgood = sp->sigmax > ATHR && snr > ASNR &&
|
||
!(sp->select & JITRNG);
|
||
switch (sp->count) {
|
||
|
||
/*
|
||
* In state 0 the station was not heard during
|
||
* the previous probe. Look for the biggest blip
|
||
* greater than the amplitude threshold in the
|
||
* minute and assume that the minute sync pulse.
|
||
* If found, bump to state 1.
|
||
*/
|
||
case 0:
|
||
if (sp->sigmax >= ATHR)
|
||
sp->count++;
|
||
break;
|
||
|
||
/*
|
||
* In state 1 a candidate blip has been found
|
||
* and the next minute has been searched for
|
||
* another blip. If none are found greater than
|
||
* the threshold, or if the biggest blip outside
|
||
* the candidate pulse is less than 6 dB below
|
||
* the biggest blip, drop back to state 0 and
|
||
* hunt some more. Otherwise, a legitimate
|
||
* minute pulse may have been found, so bump to
|
||
* state 2.
|
||
*/
|
||
case 1:
|
||
if (sp->sigmax < ATHR) {
|
||
sp->count--;
|
||
break;
|
||
} else if (!isgood) {
|
||
break;
|
||
}
|
||
/* fall through */
|
||
|
||
/*
|
||
* In states 2 and above, continue to groom
|
||
* samples as before and drop back to the
|
||
* previous state if the groom fails. If it
|
||
* succeeds, bump to the next state until
|
||
* reaching the clamp, if ever.
|
||
*/
|
||
default:
|
||
if (!isgood) {
|
||
sp->count--;
|
||
break;
|
||
}
|
||
sp->mepoch = sp->pos;
|
||
if (sp->count < AMAX)
|
||
sp->count++;
|
||
break;
|
||
}
|
||
sprintf(tbuf,
|
||
"wwv8 %d %3d %-3s %d %5.0f %5.1f %7ld %7ld %7ld",
|
||
up->port, up->gain, sp->ident, sp->count,
|
||
sp->sigmax, snr, sp->pos, sp->jitter,
|
||
MOD(sp->pos - up->nepoch - SYNSIZ, MINUTE));
|
||
if (pp->sloppyclockflag & CLK_FLAG4)
|
||
record_clock_stats(&peer->srcadr, tbuf);
|
||
#ifdef DEBUG
|
||
if (debug)
|
||
printf("%s\n", tbuf);
|
||
#endif
|
||
}
|
||
sp->lastmax = sp->sigmax;
|
||
sp->lastpos = sp->pos;
|
||
sp->sigmax = sp->noise = 0;
|
||
}
|
||
}
|
||
|
||
|
||
/*
|
||
* wwv_endpoc - process receiver epoch
|
||
*
|
||
* This routine is called at the end of the receiver epoch. It
|
||
* determines the epoch position within the second and disciplines the
|
||
* sample clock using a frequency-lock loop (FLL).
|
||
*
|
||
* Seconds 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 data filtering and grooming.
|
||
*/
|
||
static void
|
||
wwv_endpoc(
|
||
struct peer *peer, /* peer structure pointer */
|
||
double epomax, /* epoch max */
|
||
int epopos /* epoch max position */
|
||
)
|
||
{
|
||
struct refclockproc *pp;
|
||
struct wwvunit *up;
|
||
|
||
static int epoch_mf[3]; /* epoch median filter */
|
||
static int tepoch; /* median filter epoch */
|
||
static int tspan; /* median filter span */
|
||
static int xepoch; /* last second epoch */
|
||
static int zepoch; /* last averaging interval epoch */
|
||
static int syncnt; /* second epoch run length counter */
|
||
static int jitcnt; /* jitter holdoff counter */
|
||
static int avgcnt; /* averaging interval counter */
|
||
static int avginc; /* averaging ratchet */
|
||
|
||
static int iniflg; /* initialization flag */
|
||
char tbuf[80]; /* monitor buffer */
|
||
double dtemp;
|
||
int tmp2, tmp3;
|
||
|
||
pp = peer->procptr;
|
||
up = (struct wwvunit *)pp->unitptr;
|
||
if (!iniflg) {
|
||
iniflg = 1;
|
||
memset((char *)epoch_mf, 0, sizeof(epoch_mf));
|
||
}
|
||
|
||
/*
|
||
* A three-stage median filter is used to help denoise the
|
||
* seconds sync pulse. The median sample becomes the candidate
|
||
* epoch; the difference between the other two samples becomes
|
||
* the span, which is used currently only for debugging.
|
||
*/
|
||
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 */
|
||
tspan = epoch_mf[0] - epoch_mf[2];
|
||
} else if (epoch_mf[2] > epoch_mf[0]) {
|
||
tepoch = epoch_mf[0]; /* 2 0 1 */
|
||
tspan = epoch_mf[2] - epoch_mf[1];
|
||
} else {
|
||
tepoch = epoch_mf[2]; /* 0 2 1 */
|
||
tspan = epoch_mf[0] - epoch_mf[1];
|
||
}
|
||
} else {
|
||
if (epoch_mf[1] < epoch_mf[2]) {
|
||
tepoch = epoch_mf[1]; /* 2 1 0 */
|
||
tspan = epoch_mf[2] - epoch_mf[0];
|
||
} else if (epoch_mf[2] < epoch_mf[0]) {
|
||
tepoch = epoch_mf[0]; /* 1 0 2 */
|
||
tspan = epoch_mf[1] - epoch_mf[2];
|
||
} else {
|
||
tepoch = epoch_mf[2]; /* 1 2 0 */
|
||
tspan = epoch_mf[1] - epoch_mf[0];
|
||
}
|
||
}
|
||
|
||
/*
|
||
* If the epoch candidate is within 1 ms of the last one, the
|
||
* new candidate replaces the last one and the jitter counter is
|
||
* reset; otherwise, the candidate is ignored and the jitter
|
||
* counter is incremented. If the jitter counter exceeds the
|
||
* frequency averaging interval, the new candidate replaces the
|
||
* old one anyway. The compare counter is incremented if the new
|
||
* candidate is identical to the last one; otherwise, it is
|
||
* forced to zero. If the compare counter increments to 10, the
|
||
* epoch is reset and the receiver second epoch is set.
|
||
*
|
||
* Careful attention to detail here. If the signal amplitude
|
||
* falls below the threshold or if no stations are heard, we
|
||
* certainly cannot be in sync.
|
||
*/
|
||
tmp2 = MOD(tepoch - xepoch, SECOND);
|
||
if (up->epomax < STHR || !(up->status & (SELV | SELH))) {
|
||
up->status &= ~SSYNC;
|
||
jitcnt = syncnt = avgcnt = 0;
|
||
} else if (abs(tmp2) <= MS || jitcnt >= (MINAVG << up->avgint))
|
||
{
|
||
jitcnt = 0;
|
||
if (tmp2 != 0) {
|
||
xepoch = tepoch;
|
||
syncnt = 0;
|
||
} else {
|
||
if (syncnt < SCMP) {
|
||
syncnt++;
|
||
} else {
|
||
up->status |= SSYNC;
|
||
up->swatch = 0;
|
||
up->repoch = tepoch;
|
||
up->yepoch = up->repoch;
|
||
if (up->yepoch < 0)
|
||
up->yepoch += SECOND;
|
||
}
|
||
}
|
||
avgcnt++;
|
||
} else {
|
||
jitcnt++;
|
||
syncnt = avgcnt = 0;
|
||
}
|
||
if (!(up->status & SSYNC) && 0) {
|
||
sprintf(tbuf,
|
||
"wwv1 %2d %04x %5.0f %2d %5.0f %5d %5d %5d %2d %4d",
|
||
up->rsec, up->status, up->epomax, avgcnt, epomax,
|
||
tepoch, tspan, tmp2, syncnt, jitcnt);
|
||
if (pp->sloppyclockflag & CLK_FLAG4)
|
||
record_clock_stats(&peer->srcadr, tbuf);
|
||
#ifdef DEBUG
|
||
if (debug)
|
||
printf("%s\n", tbuf);
|
||
#endif /* DEBUG */
|
||
}
|
||
|
||
/*
|
||
* The sample clock frequency is disciplined using a first-order
|
||
* feedback loop with time constant consistent with the Allan
|
||
* intercept of typical computer clocks. The loop update is
|
||
* calculated each averaging interval from the epoch change in
|
||
* 125-us units and interval length in seconds. The interval is
|
||
* doubled after four intervals where epoch change is not more
|
||
* than one sample.
|
||
*
|
||
* The averaging interval affects other receiver functions,
|
||
* including the the 1000/1200-Hz comb filter and sample clock
|
||
* loop. It also affects the 100-Hz subcarrier loop and the bit
|
||
* and digit comparison counter thresholds.
|
||
*/
|
||
tmp3 = MOD(tepoch - zepoch, SECOND);
|
||
if (avgcnt >= (MINAVG << up->avgint)) {
|
||
if (abs(tmp3) < MS) {
|
||
dtemp = (double)tmp3 / avgcnt;
|
||
up->freq += dtemp / SYNCTC;
|
||
if (up->freq > MAXFREQ)
|
||
up->freq = MAXFREQ;
|
||
else if (up->freq < -MAXFREQ)
|
||
up->freq = -MAXFREQ;
|
||
if (abs(tmp3) <= 1 && up->avgint < MAXAVG) {
|
||
if (avginc < 4) {
|
||
avginc++;
|
||
} else {
|
||
avginc = 0;
|
||
up->avgint++;
|
||
}
|
||
}
|
||
if (up->avgint < MAXAVG) {
|
||
sprintf(tbuf,
|
||
"wwv2 %2d %04x %5.0f %5d %5d %2d %2d %6.1f %6.1f",
|
||
up->rsec, up->status, up->epomax,
|
||
MINAVG << up->avgint, avgcnt,
|
||
avginc, tmp3, dtemp / SECOND * 1e6,
|
||
up->freq / SECOND * 1e6);
|
||
if (pp->sloppyclockflag & CLK_FLAG4)
|
||
record_clock_stats(
|
||
&peer->srcadr, tbuf);
|
||
#ifdef DEBUG
|
||
if (debug)
|
||
printf("%s\n", tbuf);
|
||
#endif /* DEBUG */
|
||
}
|
||
}
|
||
zepoch = tepoch;
|
||
avgcnt = 0;
|
||
}
|
||
}
|
||
|
||
|
||
/*
|
||
* wwv_epoch - main loop
|
||
*
|
||
* This routine establishes receiver and transmitter epoch
|
||
* synchronization and determines the data subcarrier pulse length.
|
||
* 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. This establishes when to sample the data
|
||
* subcarrier in-phase signal for the maximum level and noise level and
|
||
* when to determine the pulse length. The transmitter second leads the
|
||
* receiver second by the propagation delay, receiver delay and filter
|
||
* delay of this program. It establishes the clock time and implements
|
||
* the sometimes idiosyncratic conventional clock time and civil
|
||
* calendar.
|
||
*
|
||
* 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 */
|
||
)
|
||
{
|
||
static double dpulse; /* data pulse length */
|
||
struct refclockproc *pp;
|
||
struct wwvunit *up;
|
||
struct chan *cp;
|
||
struct sync *sp;
|
||
l_fp offset; /* NTP format offset */
|
||
double dtemp;
|
||
|
||
pp = peer->procptr;
|
||
up = (struct wwvunit *)pp->unitptr;
|
||
|
||
/*
|
||
* Sample the minute sync pulse amplitude at epoch 800 for both
|
||
* the WWV and WWVH stations. This will be used later for
|
||
* channel mitigation.
|
||
*/
|
||
cp = &up->mitig[up->achan];
|
||
if (up->rphase == 800 * MS) {
|
||
sp = &cp->wwv;
|
||
sp->synamp = sqrt(sp->amp);
|
||
sp = &cp->wwvh;
|
||
sp->synamp = sqrt(sp->amp);
|
||
}
|
||
|
||
if (up->rsec == 0) {
|
||
up->sigamp = up->datsnr = 0;
|
||
} else {
|
||
|
||
/*
|
||
* Estimate the noise level by integrating the I-channel
|
||
* energy at epoch 30 ms.
|
||
*/
|
||
if (up->rphase == 30 * MS) {
|
||
if (!(up->status & SFLAG))
|
||
up->noiamp += (up->irig - up->noiamp) /
|
||
(MINAVG << up->avgint);
|
||
else
|
||
cp->noiamp += (sqrt(up->irig *
|
||
up->irig + up->qrig * up->qrig) -
|
||
cp->noiamp) / 8;
|
||
|
||
/*
|
||
* Strobe the peak I-channel data signal at epoch 200
|
||
* ms. Compute the SNR and adjust the 100-Hz reference
|
||
* oscillator phase using the Q-channel data signal at
|
||
* that epoch. Save the envelope amplitude for the probe
|
||
* channel.
|
||
*/
|
||
} else if (up->rphase == 200 * MS) {
|
||
if (!(up->status & SFLAG)) {
|
||
up->sigamp = up->irig;
|
||
if (up->sigamp < 0)
|
||
up->sigamp = 0;
|
||
up->datsnr = wwv_snr(up->sigamp,
|
||
up->noiamp);
|
||
up->datpha = up->qrig / (MINAVG <<
|
||
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;
|
||
}
|
||
} else {
|
||
up->sigamp = sqrt(up->irig * up->irig +
|
||
up->qrig * up->qrig);
|
||
up->datsnr = wwv_snr(up->sigamp,
|
||
cp->noiamp);
|
||
}
|
||
|
||
/*
|
||
* The slice level is set half way between the peak
|
||
* signal and noise levels. Strobe the negative zero
|
||
* crossing after epoch 200 ms and record the epoch at
|
||
* that time. This defines the length of the data pulse,
|
||
* which will later be converted into scaled bit
|
||
* probabilities.
|
||
*/
|
||
} else if (up->rphase > 200 * MS) {
|
||
dtemp = (up->sigamp + up->noiamp) / 2;
|
||
if (up->irig < dtemp && dpulse == 0)
|
||
dpulse = up->rphase;
|
||
}
|
||
}
|
||
|
||
/*
|
||
* At the end of the transmitter second, crank the clock state
|
||
* machine. Note we have to be careful to set the transmitter
|
||
* epoch at the same time as the receiver epoch to be sure the
|
||
* right propagation delay is used. We don't bother the heavy
|
||
* machinery unless the clock is set.
|
||
*/
|
||
up->tphase++;
|
||
if (up->epoch == up->yepoch) {
|
||
wwv_tsec(up);
|
||
up->tphase = 0;
|
||
|
||
/*
|
||
* Determine the current offset from the time of century
|
||
* and the sample timestamp, but only if the SYNERR
|
||
* alarm has not been raised in the present or previous
|
||
* minute.
|
||
*/
|
||
if (!(up->status & SFLAG) && up->status & INSYNC &&
|
||
(up->alarm & (3 << SYNERR)) == 0) {
|
||
pp->second = up->tsec;
|
||
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;
|
||
if (pp->year < UTCYEAR)
|
||
pp->year += 2000;
|
||
else
|
||
pp->year += 1900;
|
||
|
||
/*
|
||
* We have to simulate refclock_process() here,
|
||
* since the fudgetime gets added much earlier
|
||
* than this.
|
||
*/
|
||
pp->lastrec = up->timestamp;
|
||
L_CLR(&offset);
|
||
if (!clocktime(pp->day, pp->hour, pp->minute,
|
||
pp->second, GMT, pp->lastrec.l_ui,
|
||
&pp->yearstart, &offset.l_ui))
|
||
up->errflg = CEVNT_BADTIME;
|
||
else
|
||
refclock_process_offset(pp, offset,
|
||
pp->lastrec, 0.);
|
||
}
|
||
}
|
||
|
||
/*
|
||
* At the end of the receiver second, process the data bit and
|
||
* update the decoding matrix probabilities.
|
||
*/
|
||
up->rphase++;
|
||
if (up->epoch == up->repoch) {
|
||
wwv_rsec(peer, dpulse);
|
||
wwv_gain(peer);
|
||
up->rphase = dpulse = 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. BTW, stations WWV/WWVH cowardly kill the
|
||
* transmitter carrier for a few seconds around the leap to avoid icky
|
||
* details of transmission format during the leap.
|
||
*/
|
||
static void
|
||
wwv_rsec(
|
||
struct peer *peer, /* peer structure pointer */
|
||
double dpulse
|
||
)
|
||
{
|
||
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;
|
||
double bit; /* bit likelihood */
|
||
char tbuf[80]; /* 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 + 1;
|
||
bit = wwv_data(up, dpulse);
|
||
bitvec[up->rsec] += (bit - bitvec[up->rsec]) / TCONST;
|
||
sw = progx[up->rsec].sw;
|
||
arg = progx[up->rsec].arg;
|
||
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 (not used), and the minute sync
|
||
* pulse in second 0. At the end of second 58, we QSYed to the
|
||
* probe channel, which rotates over all WWV/H frequencies. At
|
||
* the end of second 59, we latched the sync noise and tested
|
||
* for data bit error. At the end of second 0, we now latch the
|
||
* sync peak.
|
||
*/
|
||
case SYNC2: /* 0 */
|
||
cp = &up->mitig[up->achan];
|
||
sp = &cp->wwv;
|
||
sp->synmax = sp->synamp;
|
||
sp = &cp->wwvh;
|
||
sp->synmax = sp->synamp;
|
||
break;
|
||
|
||
/*
|
||
* At the end of second 1, latch and average the sync noise and
|
||
* test for data bit error. Set SYNCNG if the sync pulse
|
||
* amplitude and SNR are not above thresholds. Set DATANG if
|
||
* data error occured on both second 59 and second 1. Finally,
|
||
* QSY back to the data channel.
|
||
*/
|
||
case SYNC3: /* 1 */
|
||
cp = &up->mitig[up->achan];
|
||
if (up->sigamp < DTHR || up->datsnr < DSNR)
|
||
cp->errcnt++;
|
||
|
||
sp = &cp->wwv;
|
||
sp->synmin = (sp->synmin + sp->synamp) / 2;
|
||
sp->synsnr = wwv_snr(sp->synmax, sp->synmin);
|
||
sp->select &= ~(DATANG | SYNCNG);
|
||
if (sp->synmax < QTHR || sp->synsnr < QSNR)
|
||
sp->select |= SYNCNG;
|
||
if (cp->errcnt > 1)
|
||
sp->select |= DATANG;
|
||
|
||
rp = &cp->wwvh;
|
||
rp->synmin = (rp->synmin + rp->synamp) / 2;
|
||
rp->synsnr = wwv_snr(rp->synmax, rp->synmin);
|
||
rp->select &= ~(DATANG | SYNCNG);
|
||
if (rp->synmax < QTHR || rp->synsnr < QSNR)
|
||
rp->select |= SYNCNG;
|
||
if (cp->errcnt > 1)
|
||
rp->select |= DATANG;
|
||
|
||
cp->errcnt = 0;
|
||
sprintf(tbuf,
|
||
"wwv5 %d %3d %-3s %04x %d %.0f/%.1f/%ld %s %04x %d %.0f/%.1f/%ld",
|
||
up->port, up->gain, sp->ident, sp->select,
|
||
sp->count, sp->synmax, sp->synsnr, sp->jitter,
|
||
rp->ident, rp->select, rp->count, rp->synmax,
|
||
rp->synsnr, rp->jitter);
|
||
if (pp->sloppyclockflag & CLK_FLAG4)
|
||
record_clock_stats(&peer->srcadr, tbuf);
|
||
#ifdef DEBUG
|
||
if (debug)
|
||
printf("%s\n", tbuf);
|
||
#endif /* DEBUG */
|
||
up->status &= ~SFLAG;
|
||
wwv_newchan(peer);
|
||
break;
|
||
|
||
/*
|
||
* Save the bit probability in the BCD data vector at the index
|
||
* given by the argument. Note that all bits of the vector have
|
||
* to be above the data gate threshold for the digit to be
|
||
* considered valid. Bits not used in the digit are forced to
|
||
* zero and not checked for errors.
|
||
*/
|
||
case COEF1: /* 10-13 */
|
||
if (up->status & DGATE)
|
||
up->status |= BGATE;
|
||
bcddld[arg] = bit;
|
||
break;
|
||
|
||
case COEF2: /* 18, 27-28, 42-43 */
|
||
bcddld[arg] = 0;
|
||
break;
|
||
|
||
case COEF: /* 4-7, 15-17, 20-23, 25-26,
|
||
30-33, 35-38, 40-41, 51-54 */
|
||
if (up->status & DGATE || !(up->status & DSYNC))
|
||
up->status |= BGATE;
|
||
bcddld[arg] = bit;
|
||
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 SYMERR alarm. At the end of second 58, QSY to the
|
||
* probe channel.
|
||
*/
|
||
case MSC20: /* 55 */
|
||
wwv_corr4(peer, &up->decvec[YR + 1], bcddld, bcd9);
|
||
/* fall through */
|
||
|
||
case MSCBIT: /* 2, 3, 50, 56-57 */
|
||
if (bitvec[up->rsec] > BTHR)
|
||
up->misc |= arg;
|
||
else if (bitvec[up->rsec] < -BTHR)
|
||
up->misc &= ~arg;
|
||
else
|
||
up->alarm |= 1 << SYMERR;
|
||
break;
|
||
|
||
case MSC21: /* 58 */
|
||
if (bitvec[up->rsec] > BTHR)
|
||
up->misc |= arg;
|
||
else if (bitvec[up->rsec] < -BTHR)
|
||
up->misc &= ~arg;
|
||
else
|
||
up->alarm |= 1 << SYMERR;
|
||
up->schan = (up->schan + 1) % NCHAN;
|
||
wwv_qsy(peer, up->schan);
|
||
up->status |= SFLAG;
|
||
break;
|
||
|
||
/*
|
||
* The endgames
|
||
*
|
||
* Second 59 contains the first data pulse of the probe
|
||
* sequence. Check it for validity and establish the noise floor
|
||
* for the minute sync SNR.
|
||
*/
|
||
case MIN1: /* 59 */
|
||
cp = &up->mitig[up->achan];
|
||
if (up->sigamp < DTHR || up->datsnr < DSNR)
|
||
cp->errcnt++;
|
||
sp = &cp->wwv;
|
||
sp->synmin = sp->synamp;
|
||
sp = &cp->wwvh;
|
||
sp->synmin = sp->synamp;
|
||
|
||
/*
|
||
* If SECWARN is set on the last minute of 30 June or 31
|
||
* December, LEPSEC bit is set. At the end of the minute
|
||
* in which LEPSEC is set the transmitter and receiver
|
||
* insert an extra second (60) in the timescale and the
|
||
* minute sync skips a second. We only get to test this
|
||
* wrinkle at intervals of about 18 months, the actual
|
||
* mileage may vary.
|
||
*/
|
||
if (up->tsec == 60) {
|
||
up->status &= ~LEPSEC;
|
||
break;
|
||
}
|
||
/* fall through */
|
||
|
||
/*
|
||
* If all nine clock digits are valid and the SYNERR alarm is
|
||
* not raised in the current or previous second, the clock is
|
||
* set or validated. If at least one digit is set, which by
|
||
* design must be the minute units digit, the clock state
|
||
* machine begins to count the minutes.
|
||
*/
|
||
case MIN2: /* 59/60 */
|
||
up->minset = ((current_time - peer->update) + 30) / 60;
|
||
if (up->digcnt > 0)
|
||
up->status |= DSYNC;
|
||
if (up->digcnt >= 9 && (up->alarm & (3 << SYNERR)) == 0)
|
||
{
|
||
up->status |= INSYNC;
|
||
up->watch = 0;
|
||
}
|
||
pp->lencode = timecode(up, pp->a_lastcode);
|
||
if (up->misc & SECWAR)
|
||
pp->leap = LEAP_ADDSECOND;
|
||
else
|
||
pp->leap = LEAP_NOWARNING;
|
||
refclock_receive(peer);
|
||
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 */
|
||
|
||
/*
|
||
* The ultimate watchdog is the interval since the
|
||
* reference clock interface code last received an
|
||
* update from this driver. If the interval is greater
|
||
* than a couple of days, manual intervention is
|
||
* probably required, so the program resets and tries to
|
||
* resynchronized from scratch.
|
||
*/
|
||
if (up->minset > PANIC)
|
||
up->status = 0;
|
||
up->alarm = (up->alarm & ~0x8888) << 1;
|
||
up->nepoch = (up->mphase + SYNSIZ) % MINUTE;
|
||
up->errcnt = up->digcnt = nsec = 0;
|
||
break;
|
||
}
|
||
if (!(up->status & DSYNC)) {
|
||
sprintf(tbuf,
|
||
"wwv3 %2d %04x %5.0f %5.0f %5.0f %5.1f %5.0f %5.0f",
|
||
up->rsec, up->status, up->epomax, up->sigamp,
|
||
up->datpha, up->datsnr, bit, bitvec[up->rsec]);
|
||
if (pp->sloppyclockflag & CLK_FLAG4)
|
||
record_clock_stats(&peer->srcadr, tbuf);
|
||
#ifdef DEBUG
|
||
if (debug)
|
||
printf("%s\n", tbuf);
|
||
#endif /* DEBUG */
|
||
}
|
||
up->rsec = up->tsec = nsec;
|
||
return;
|
||
}
|
||
|
||
|
||
/*
|
||
* wwv_data - calculate bit probability
|
||
*
|
||
* This routine is called at the end of the receiver second to calculate
|
||
* the probabilities that the previous second contained a zero (P0), one
|
||
* (P1) or position indicator (P2) pulse. If not in sync or if the data
|
||
* bit is bad, a bit error is declared and the probabilities are forced
|
||
* to zero. Otherwise, the data gate is enabled and the probabilities
|
||
* are calculated. Note that the data matched filter contributes half
|
||
* the pulse width, or 85 ms..
|
||
*/
|
||
static double
|
||
wwv_data(
|
||
struct wwvunit *up, /* driver unit pointer */
|
||
double pulse /* pulse length (sample units) */
|
||
)
|
||
{
|
||
double p0, p1, p2; /* probabilities */
|
||
double dpulse; /* pulse length in ms */
|
||
|
||
p0 = p1 = p2 = 0;
|
||
dpulse = pulse - DATSIZ / 2;
|
||
|
||
/*
|
||
* If the data amplitude or SNR are below threshold or if the
|
||
* pulse length is less than 170 ms, declare an erasure.
|
||
*/
|
||
if (up->sigamp < DTHR || up->datsnr < DSNR || dpulse < DATSIZ) {
|
||
up->status |= DGATE;
|
||
up->errcnt++;
|
||
if (up->errcnt > MAXERR)
|
||
up->alarm |= 1 << MODERR;
|
||
return (0);
|
||
}
|
||
|
||
/*
|
||
* The probability of P0 is one below 200 ms falling to zero at
|
||
* 500 ms. The probability of P1 is zero below 200 ms rising to
|
||
* one at 500 ms and falling to zero at 800 ms. The probability
|
||
* of P2 is zero below 500 ms, rising to one above 800 ms.
|
||
*/
|
||
up->status &= ~DGATE;
|
||
if (dpulse < (200 * MS)) {
|
||
p0 = 1;
|
||
} else if (dpulse < 500 * MS) {
|
||
dpulse -= 200 * MS;
|
||
p1 = dpulse / (300 * MS);
|
||
p0 = 1 - p1;
|
||
} else if (dpulse < 800 * MS) {
|
||
dpulse -= 500 * MS;
|
||
p2 = dpulse / (300 * MS);
|
||
p1 = 1 - p2;
|
||
} else {
|
||
p2 = 1;
|
||
}
|
||
|
||
/*
|
||
* The ouput is a metric that ranges from -1 (P0), to +1 (P1)
|
||
* scaled for convenience. An output of zero represents an
|
||
* erasure, either because of a data error or pulse length
|
||
* greater than 500 ms. At the moment, we don't use P2.
|
||
*/
|
||
return ((p1 - p0) * MAXSIG);
|
||
}
|
||
|
||
|
||
/*
|
||
* 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[80]; /* monitor buffer */
|
||
int mldigit; /* max likelihood digit */
|
||
int diff; /* decoding difference */
|
||
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.
|
||
*/
|
||
mldigit = 0;
|
||
topmax = nxtmax = -MAXSIG;
|
||
for (i = 0; tab[i][0] != 0; i++) {
|
||
acc = 0;
|
||
for (j = 0; j < 4; j++) {
|
||
if (!(up->status & BGATE))
|
||
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->mldigit = mldigit;
|
||
vp->digprb = topmax;
|
||
vp->digsnr = wwv_snr(topmax, nxtmax);
|
||
|
||
/*
|
||
* The maximum likelihood digit is compared with the current
|
||
* clock digit. The difference represents the decoding phase
|
||
* error. If the digit probability and likelihood are good and
|
||
* the difference stays the same for a number of comparisons,
|
||
* the clock digit is reset to the maximum likelihood digit.
|
||
*/
|
||
diff = mldigit - vp->digit;
|
||
if (diff < 0)
|
||
diff += vp->radix;
|
||
if (diff != vp->phase) {
|
||
vp->phase = diff;
|
||
vp->count = 0;
|
||
}
|
||
if (vp->digprb < BTHR || vp->digsnr < BSNR) {
|
||
vp->count = 0;
|
||
up->alarm |= 1 << SYMERR;
|
||
} else if (vp->count < BCMP) {
|
||
if (!(up->status & INSYNC)) {
|
||
vp->phase = 0;
|
||
vp->digit = mldigit;
|
||
}
|
||
vp->count++;
|
||
} else {
|
||
vp->phase = 0;
|
||
vp->digit = mldigit;
|
||
up->digcnt++;
|
||
}
|
||
if (vp->digit != mldigit)
|
||
up->alarm |= 1 << DECERR;
|
||
if (!(up->status & INSYNC)) {
|
||
sprintf(tbuf,
|
||
"wwv4 %2d %04x %5.0f %2d %d %d %d %d %5.0f %5.1f",
|
||
up->rsec, up->status, up->epomax, vp->radix,
|
||
vp->digit, vp->mldigit, vp->phase, vp->count,
|
||
vp->digprb, vp->digsnr);
|
||
if (pp->sloppyclockflag & CLK_FLAG4)
|
||
record_clock_stats(&peer->srcadr, tbuf);
|
||
#ifdef DEBUG
|
||
if (debug)
|
||
printf("%s\n", tbuf);
|
||
#endif /* DEBUG */
|
||
}
|
||
up->status &= ~BGATE;
|
||
}
|
||
|
||
|
||
/*
|
||
* wwv_tsec - transmitter second processing
|
||
*
|
||
* This routine is called at the end of the transmitter second. It
|
||
* implements a state machine that advances the logical clock subject to
|
||
* the funny rules that govern the conventional clock and calendar. Note
|
||
* that carries from the least significant (minutes) digit are inhibited
|
||
* until that digit is synchronized.
|
||
*/
|
||
static void
|
||
wwv_tsec(
|
||
struct wwvunit *up /* driver structure pointer */
|
||
)
|
||
{
|
||
int minute, day, isleap;
|
||
int temp;
|
||
|
||
up->tsec++;
|
||
if (up->tsec < 60 || up->status & LEPSEC)
|
||
return;
|
||
up->tsec = 0;
|
||
|
||
/*
|
||
* Advance minute unit of the day. If the minute unit is not
|
||
* synchronized, go no further.
|
||
*/
|
||
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 the leap second enable
|
||
* bit on the last minute of 30 June and 31 December.
|
||
*/
|
||
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;
|
||
isleap = (up->decvec[YR].digit & 0x3) == 0;
|
||
if (minute == 1439 && (day == (isleap ? 182 : 183) || day ==
|
||
(isleap ? 365 : 366)) && up->misc & SECWAR)
|
||
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)
|
||
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 -
|
||
* zero if a carry occured. 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++; /* advance clock digit */
|
||
if (dp->digit == dp->radix) { /* modulo radix */
|
||
dp->digit = 0;
|
||
}
|
||
temp = dp->like[dp->radix - 1]; /* rotate likelihood vector */
|
||
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.
|
||
*/
|
||
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
|
||
*
|
||
* Assuming the radio can be tuned by this program, it actually appears
|
||
* as a 10-channel receiver, one channel for each of WWV and WWVH on
|
||
* each of five frequencies. 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 channel, in order
|
||
* to pick up minute sync and data pulses. The search for WWV and WWVH
|
||
* stations operates simultaneously, with WWV on 1000 Hz and WWVH on
|
||
* 1200 Hz. The probe channel rotates for each minute over the five
|
||
* frequencies. At the end of each rotation, this routine mitigates over
|
||
* all channels and chooses the best frequency and station.
|
||
*/
|
||
static void
|
||
wwv_newchan(
|
||
struct peer *peer /* peer structure pointer */
|
||
)
|
||
{
|
||
struct refclockproc *pp;
|
||
struct wwvunit *up;
|
||
struct chan *cp;
|
||
struct sync *sp, *rp;
|
||
int rank;
|
||
int i, j;
|
||
|
||
pp = peer->procptr;
|
||
up = (struct wwvunit *)pp->unitptr;
|
||
|
||
/*
|
||
* Reset the matched filter selector and station pointer to
|
||
* avoid fooling around should we lose this game.
|
||
*/
|
||
up->sptr = 0;
|
||
up->status &= ~(SELV | SELH);
|
||
|
||
/*
|
||
* Search all five station pairs looking for the station with
|
||
* the maximum compare counter. Ties go to the highest frequency
|
||
* and then to WWV.
|
||
*/
|
||
j = 0;
|
||
sp = (struct sync *)0;
|
||
rank = 0;
|
||
for (i = 0; i < NCHAN; i++) {
|
||
cp = &up->mitig[i];
|
||
rp = &cp->wwvh;
|
||
if (rp->count >= rank) {
|
||
sp = rp;
|
||
rank = rp->count;
|
||
j = i;
|
||
}
|
||
rp = &cp->wwv;
|
||
if (rp->count >= rank) {
|
||
sp = rp;
|
||
rank = rp->count;
|
||
j = i;
|
||
}
|
||
}
|
||
|
||
/*
|
||
* If we find a station, continue to track it. If not, X marks
|
||
* the spot and we wait for better ions.
|
||
*/
|
||
if (rank > 0) {
|
||
up->dchan = j;
|
||
up->sptr = sp;
|
||
up->status |= sp->select & (SELV | SELH);
|
||
memcpy((char *)&pp->refid, sp->refid, 4);
|
||
memcpy((char *)&peer->refid, sp->refid, 4);
|
||
wwv_qsy(peer, up->dchan);
|
||
}
|
||
}
|
||
|
||
|
||
/*
|
||
* 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 */
|
||
)
|
||
{
|
||
struct refclockproc *pp;
|
||
struct wwvunit *up;
|
||
int rval = 0;
|
||
|
||
pp = peer->procptr;
|
||
up = (struct wwvunit *)pp->unitptr;
|
||
up->mitig[up->achan].gain = up->gain;
|
||
#ifdef ICOM
|
||
if (up->fd_icom > 0)
|
||
rval = icom_freq(up->fd_icom, peer->ttl & 0x7f,
|
||
qsy[chan]);
|
||
#endif /* ICOM */
|
||
up->achan = chan;
|
||
up->gain = up->mitig[up->achan].gain;
|
||
return (rval);
|
||
}
|
||
|
||
|
||
/*
|
||
* timecode - assemble timecode string and length
|
||
*
|
||
* Prettytime format - similar to Spectracom
|
||
*
|
||
* sq yy ddd hh:mm:ss.fff ld dut lset agc stn comp errs freq avgt
|
||
*
|
||
* s sync indicator ('?' or ' ')
|
||
* q quality character (hex 0-F)
|
||
* yyyy year of century
|
||
* ddd day of year
|
||
* hh hour of day
|
||
* mm minute of hour
|
||
* ss minute of hour
|
||
* fff millisecond of second
|
||
* l leap second warning ' ' or 'L'
|
||
* d DST state 'S', 'D', 'I', or 'O'
|
||
* dut DUT sign and magnitude in deciseconds
|
||
* lset minutes since last clock update
|
||
* agc audio gain (0-255)
|
||
* iden station identifier (station and frequency)
|
||
* comp minute sync compare counter
|
||
* 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, frac, dut;
|
||
char synchar, qual, leapchar, dst;
|
||
char cptr[50];
|
||
|
||
|
||
/*
|
||
* Common fixed-format fields
|
||
*/
|
||
synchar = (up->status & INSYNC) ? ' ' : '?';
|
||
qual = 0;
|
||
if (up->alarm & (3 << DECERR))
|
||
qual |= 0x1;
|
||
if (up->alarm & (3 << SYMERR))
|
||
qual |= 0x2;
|
||
if (up->alarm & (3 << MODERR))
|
||
qual |= 0x4;
|
||
if (up->alarm & (3 << SYNERR))
|
||
qual |= 0x8;
|
||
year = up->decvec[7].digit + up->decvec[7].digit * 10;
|
||
if (year < UTCYEAR)
|
||
year += 2000;
|
||
else
|
||
year += 1900;
|
||
day = up->decvec[4].digit + up->decvec[5].digit * 10 +
|
||
up->decvec[6].digit * 100;
|
||
hour = up->decvec[2].digit + up->decvec[3].digit * 10;
|
||
minute = up->decvec[0].digit + up->decvec[1].digit * 10;
|
||
second = up->tsec;
|
||
frac = (up->tphase * 1000) / SECOND;
|
||
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, qual);
|
||
sprintf(cptr, " %4d %03d %02d:%02d:%02d.%.03d %c%c %+d",
|
||
year, day, hour, minute, second, frac, leapchar, dst, dut);
|
||
strcat(ptr, cptr);
|
||
|
||
/*
|
||
* Specific variable-format fields
|
||
*/
|
||
sp = up->sptr;
|
||
if (sp != 0)
|
||
sprintf(cptr, " %d %d %s %d %d %.1f %d", up->minset,
|
||
up->mitig[up->dchan].gain, sp->ident, sp->count,
|
||
up->errcnt, up->freq / SECOND * 1e6, MINAVG <<
|
||
up->avgint);
|
||
else
|
||
sprintf(cptr, " %d %d X 0 %d %.1f %d", up->minset,
|
||
up->mitig[up->dchan].gain, up->errcnt, up->freq /
|
||
SECOND * 1e6, MINAVG << up->avgint);
|
||
strcat(ptr, cptr);
|
||
return (strlen(ptr));
|
||
}
|
||
|
||
|
||
/*
|
||
* wwv_gain - adjust codec gain
|
||
*
|
||
* This routine is called once each second. If the signal envelope
|
||
* amplitude is too low, the codec gain is bumped up by four units; if
|
||
* too high, it is bumped down. The decoder is relatively insensitive to
|
||
* amplitude, so this crudity works just fine. The input port is set and
|
||
* the error flag is cleared, mostly to be ornery.
|
||
*/
|
||
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 > 255)
|
||
up->gain = 255;
|
||
} else if (up->clipcnt > SECOND / 100) {
|
||
up->gain -= 4;
|
||
if (up->gain < 0)
|
||
up->gain = 0;
|
||
}
|
||
audio_gain(up->gain, up->port);
|
||
up->clipcnt = 0;
|
||
}
|
||
|
||
|
||
#else
|
||
int refclock_wwv_bs;
|
||
#endif /* REFCLOCK */
|