2710 lines
80 KiB
C
2710 lines
80 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 "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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#include <stdio.h>
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#include <ctype.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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#define ICOM 1
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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. Transmissions are made continuously on
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* 2.5, 5, 10 and 15 MHz from WWV and WWVH, and 20 MHz from WWV. An
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* ordinary AM shortwave receiver can be tuned manually to one of these
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* frequencies or, in the case of ICOM receivers, the receiver can be
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* tuned automatically using this program as propagation conditions
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* change throughout the weasons, both day and 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 workstation running Solaris, SunOS
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* FreeBSD or Linux, and with a little help, other workstations with
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* similar codecs or sound cards. In this implementation, only one audio
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* driver 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.html. 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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* Fudge factors
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*
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* Fudge flag4 causes the dubugging output described above to be
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* recorded in the clockstats file. Fudge flag2 selects the audio input
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* port, where 0 is the mike port (default) and 1 is the line-in port.
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* It does not seem useful to select the compact disc player port. Fudge
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* flag3 enables audio monitoring of the input signal. For this purpose,
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* the monitor gain is set to a default value.
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*/
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/*
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* General definitions. These ordinarily do not need to be changed.
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*/
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#define DEVICE_AUDIO "/dev/audio" /* audio device name */
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#define AUDIO_BUFSIZ 320 /* audio buffer size (50 ms) */
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#define PRECISION (-10) /* precision assumed (about 1 ms) */
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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 MAXAMP 6000. /* max signal level reference */
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#define MAXCLP 100 /* max clips above reference per s */
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#define MAXSNR 40. /* max SNR reference */
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#define MAXFREQ 1.5 /* max frequency tolerance (187 PPM) */
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#define DATCYC 170 /* data filter cycles */
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#define DATSIZ (DATCYC * MS) /* data filter size */
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#define SYNCYC 800 /* minute filter cycles */
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#define SYNSIZ (SYNCYC * MS) /* minute filter size */
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#define TCKCYC 5 /* tick filter cycles */
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#define TCKSIZ (TCKCYC * MS) /* tick filter size */
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#define NCHAN 5 /* number of radio channels */
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#define AUDIO_PHI 5e-6 /* dispersion growth factor */
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/*
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* Tunable parameters. The DGAIN parameter can be changed to fit the
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* audio response of the radio at 100 Hz. The WWV/WWVH data subcarrier
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* is transmitted at about 20 percent percent modulation; the matched
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* filter boosts it by a factor of 17 and the receiver response does
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* what it does. The compromise value works for ICOM radios. If the
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* radio is not tunable, the DCHAN parameter can be changed to fit the
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* expected best propagation frequency: higher if further from the
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* transmitter, lower if nearer. The compromise value works for the US
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* right coast. The FREQ_OFFSET parameter can be used as a frequency
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* vernier to correct codec requency if greater than MAXFREQ.
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*/
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#define DCHAN 3 /* default radio channel (15 Mhz) */
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#define DGAIN 5. /* subcarrier gain */
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#define FREQ_OFFSET 0. /* codec frequency correction (PPM) */
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/*
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* General purpose status bits (status)
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*
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* SELV and/or SELH are set when WWV or WWVH have been heard and cleared
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* on signal loss. SSYNC is set when the second sync pulse has been
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* acquired and cleared by signal loss. MSYNC is set when the minute
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* sync pulse has been acquired. DSYNC is set when the units digit has
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* has reached the threshold and INSYNC is set when all nine digits have
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* reached the threshold. The MSYNC, DSYNC and INSYNC bits are cleared
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* only by timeout, upon which the driver starts over from scratch.
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*
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* DGATE is lit if the data bit amplitude or SNR is below thresholds and
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* BGATE is lit if the pulse width amplitude or SNR is below thresolds.
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* LEPSEC is set during the last minute of the leap day. At the end of
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* this minute the driver inserts second 60 in the seconds state machine
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* 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 FGATE 0x0010 /* frequency gate */
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#define DGATE 0x0020 /* data pulse amplitude error */
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#define BGATE 0x0040 /* data pulse width error */
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#define LEPSEC 0x1000 /* leap minute */
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/*
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* Station scoreboard bits
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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 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.
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*/
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#define CMPERR 1 /* digit or misc bit compare error */
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#define LOWERR 2 /* low bit or digit amplitude or SNR */
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#define NINERR 4 /* less than nine digits in minute */
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#define SYNERR 8 /* not tracking second sync */
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/*
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* Watchcat 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 6 /* station acquisition timeout */
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#define DATA 15 /* unit minutes timeout */
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#define SYNCH 40 /* station sync timeout */
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#define PANIC (2 * 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 driver. 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 MTHR 13. /* minute sync gate (percent) */
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#define TTHR 50. /* minute sync threshold (percent) */
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#define AWND 20 /* minute sync jitter threshold (ms) */
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#define ATHR 2500. /* QRZ minute sync threshold */
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#define ASNR 20. /* QRZ minute sync SNR threshold (dB) */
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#define QTHR 2500. /* QSY minute sync threshold */
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#define QSNR 20. /* QSY minute sync SNR threshold (dB) */
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#define STHR 2500. /* second sync threshold */
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#define SSNR 15. /* second sync SNR threshold (dB) */
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#define SCMP 10 /* second sync compare threshold */
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#define DTHR 1000. /* bit threshold */
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#define DSNR 10. /* bit SNR threshold (dB) */
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#define AMIN 3 /* min bit count */
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#define AMAX 6 /* max bit count */
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#define BTHR 1000. /* digit threshold */
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#define BSNR 3. /* digit likelihood threshold (dB) */
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#define BCMP 3 /* digit compare threshold */
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#define MAXERR 40 /* maximum error alarm */
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/*
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* Tone frequency definitions. The increments are for 4.5-deg sine
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* table.
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*/
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#define MS (SECOND / 1000) /* samples per millisecond */
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#define IN100 ((100 * 80) / SECOND) /* 100 Hz increment */
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#define IN1000 ((1000 * 80) / SECOND) /* 1000 Hz increment */
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#define IN1200 ((1200 * 80) / SECOND) /* 1200 Hz increment */
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/*
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* Acquisition and tracking time constants
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*/
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#define MINAVG 8 /* min averaging time */
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#define MAXAVG 1024 /* max averaging time */
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#define FCONST 3 /* frequency time constant */
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#define TCONST 16 /* data bit/digit time constant */
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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 leap warning */
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#define DST2 0x20 /* 2 DST2 DST1 delayed one day */
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#define SECWAR 0x40 /* 3 leap second warning */
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/*
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* The on-time synchronization point for the driver is the second epoch
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* sync pulse produced by the FIR matched filters. As the 5-ms delay of
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* these filters is compensated, the program delay is 1.1 ms due to the
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* 600-Hz IIR bandpass filter. The measured receiver delay is 4.7 ms and
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* the codec delay less than 0.2 ms. The additional propagation delay
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* specific to each receiver location can be programmed in the fudge
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* time1 and time2 values for WWV and WWVH, respectively.
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*/
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#define PDELAY (.0011 + .0047 + .0002) /* 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.
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*/
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double sintab[] = {
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0.000000e+00, 7.845910e-02, 1.564345e-01, 2.334454e-01, /* 0-3 */
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3.090170e-01, 3.826834e-01, 4.539905e-01, 5.224986e-01, /* 4-7 */
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5.877853e-01, 6.494480e-01, 7.071068e-01, 7.604060e-01, /* 8-11 */
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8.090170e-01, 8.526402e-01, 8.910065e-01, 9.238795e-01, /* 12-15 */
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9.510565e-01, 9.723699e-01, 9.876883e-01, 9.969173e-01, /* 16-19 */
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1.000000e+00, 9.969173e-01, 9.876883e-01, 9.723699e-01, /* 20-23 */
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9.510565e-01, 9.238795e-01, 8.910065e-01, 8.526402e-01, /* 24-27 */
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8.090170e-01, 7.604060e-01, 7.071068e-01, 6.494480e-01, /* 28-31 */
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5.877853e-01, 5.224986e-01, 4.539905e-01, 3.826834e-01, /* 32-35 */
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3.090170e-01, 2.334454e-01, 1.564345e-01, 7.845910e-02, /* 36-39 */
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-0.000000e+00, -7.845910e-02, -1.564345e-01, -2.334454e-01, /* 40-43 */
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-3.090170e-01, -3.826834e-01, -4.539905e-01, -5.224986e-01, /* 44-47 */
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-5.877853e-01, -6.494480e-01, -7.071068e-01, -7.604060e-01, /* 48-51 */
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-8.090170e-01, -8.526402e-01, -8.910065e-01, -9.238795e-01, /* 52-55 */
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-9.510565e-01, -9.723699e-01, -9.876883e-01, -9.969173e-01, /* 56-59 */
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-1.000000e+00, -9.969173e-01, -9.876883e-01, -9.723699e-01, /* 60-63 */
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-9.510565e-01, -9.238795e-01, -8.910065e-01, -8.526402e-01, /* 64-67 */
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-8.090170e-01, -7.604060e-01, -7.071068e-01, -6.494480e-01, /* 68-71 */
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-5.877853e-01, -5.224986e-01, -4.539905e-01, -3.826834e-01, /* 72-75 */
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-3.090170e-01, -2.334454e-01, -1.564345e-01, -7.845910e-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 */
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#define COEF1 2 /* BCD bit for minute unit */
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#define COEF2 3 /* BCD bit not used */
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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 /* latch time */
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#define MIN2 12 /* leap second */
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#define SYNC2 13 /* latch minute sync pulse */
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#define SYNC3 14 /* latch data pulse */
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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 minute sync pulse */
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{SYNC3, 0}, /* 1 latch data pulse */
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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) */
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{COEF2, 3}, /* 28 80 (not used) */
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{DECIM2, HR + 1}, /* 29 p3 */
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{COEF, 0}, /* 30 1 day units */
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{COEF, 1}, /* 31 2 */
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{COEF, 2}, /* 32 4 */
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{COEF, 3}, /* 33 8 */
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{DECIM9, DA}, /* 34 */
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{COEF, 0}, /* 35 10 day tens */
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{COEF, 1}, /* 36 20 */
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{COEF, 2}, /* 37 40 */
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{COEF, 3}, /* 38 80 */
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{DECIM9, DA + 1}, /* 39 p4 */
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{COEF, 0}, /* 40 100 day hundreds */
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{COEF, 1}, /* 41 200 */
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{COEF2, 2}, /* 42 400 (not used) */
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{COEF2, 3}, /* 43 800 (not used) */
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{DECIM3, DA + 2}, /* 44 */
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{IDLE, 0}, /* 45 */
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{IDLE, 0}, /* 46 */
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{IDLE, 0}, /* 47 */
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{IDLE, 0}, /* 48 */
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{IDLE, 0}, /* 49 p5 */
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{MSCBIT, DUTS}, /* 50 dut+- */
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{COEF, 0}, /* 51 10 year tens */
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{COEF, 1}, /* 52 20 */
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{COEF, 2}, /* 53 40 */
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{COEF, 3}, /* 54 80 */
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{MSC20, DST1}, /* 55 dst1 */
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{MSCBIT, DUT1}, /* 56 0.1 dut */
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{MSCBIT, DUT2}, /* 57 0.2 */
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{MSC21, DUT4}, /* 58 0.4 QSY probe channel */
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{MIN1, 0}, /* 59 p6 latch time */
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{MIN2, 0} /* 60 leap second */
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};
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/*
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* BCD coefficients for maximum likelihood digit decode
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*/
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#define P15 1. /* max positive number */
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#define N15 -1. /* max negative number */
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/*
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* Digits 0-9
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*/
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#define P9 (P15 / 4) /* mark (+1) */
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#define N9 (N15 / 4) /* space (-1) */
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double bcd9[][4] = {
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{N9, N9, N9, N9}, /* 0 */
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{P9, N9, N9, N9}, /* 1 */
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{N9, P9, N9, N9}, /* 2 */
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{P9, P9, N9, N9}, /* 3 */
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{N9, N9, P9, N9}, /* 4 */
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{P9, N9, P9, N9}, /* 5 */
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{N9, P9, P9, N9}, /* 6 */
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{P9, P9, P9, N9}, /* 7 */
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{N9, N9, N9, P9}, /* 8 */
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{P9, N9, N9, P9}, /* 9 */
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{0, 0, 0, 0} /* backstop */
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};
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/*
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* Digits 0-6 (minute tens)
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*/
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#define P6 (P15 / 3) /* mark (+1) */
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#define N6 (N15 / 3) /* space (-1) */
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double bcd6[][4] = {
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{N6, N6, N6, 0}, /* 0 */
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{P6, N6, N6, 0}, /* 1 */
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{N6, P6, N6, 0}, /* 2 */
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{P6, P6, N6, 0}, /* 3 */
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{N6, N6, P6, 0}, /* 4 */
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{P6, N6, P6, 0}, /* 5 */
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{N6, P6, P6, 0}, /* 6 */
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{0, 0, 0, 0} /* backstop */
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};
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/*
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* Digits 0-3 (day hundreds)
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*/
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#define P3 (P15 / 2) /* mark (+1) */
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#define N3 (N15 / 2) /* space (-1) */
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double bcd3[][4] = {
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{N3, N3, 0, 0}, /* 0 */
|
|
{P3, N3, 0, 0}, /* 1 */
|
|
{N3, P3, 0, 0}, /* 2 */
|
|
{P3, P3, 0, 0}, /* 3 */
|
|
{0, 0, 0, 0} /* backstop */
|
|
};
|
|
|
|
/*
|
|
* Digits 0-2 (hour tens)
|
|
*/
|
|
#define P2 (P15 / 2) /* mark (+1) */
|
|
#define N2 (N15 / 2) /* space (-1) */
|
|
|
|
double bcd2[][4] = {
|
|
{N2, N2, 0, 0}, /* 0 */
|
|
{P2, N2, 0, 0}, /* 1 */
|
|
{N2, P2, 0, 0}, /* 2 */
|
|
{0, 0, 0, 0} /* backstop */
|
|
};
|
|
|
|
/*
|
|
* DST decode (DST2 DST1) for prettyprint
|
|
*/
|
|
char dstcod[] = {
|
|
'S', /* 00 standard time */
|
|
'I', /* 01 set clock ahead at 0200 local */
|
|
'O', /* 10 set clock back at 0200 local */
|
|
'D' /* 11 daylight time */
|
|
};
|
|
|
|
/*
|
|
* The decoding matrix consists of nine row vectors, one for each digit
|
|
* of the timecode. The digits are stored from least to most significant
|
|
* order. The maximum likelihood timecode is formed from the digits
|
|
* corresponding to the maximum likelihood values reading in the
|
|
* opposite order: yy ddd hh:mm.
|
|
*/
|
|
struct decvec {
|
|
int radix; /* radix (3, 4, 6, 10) */
|
|
int digit; /* current clock digit */
|
|
int mldigit; /* maximum likelihood digit */
|
|
int count; /* match count */
|
|
double digprb; /* max digit probability */
|
|
double digsnr; /* likelihood function (dB) */
|
|
double like[10]; /* likelihood integrator 0-9 */
|
|
};
|
|
|
|
/*
|
|
* The station structure (sp) is used to acquire the minute pulse from
|
|
* WWV and/or WWVH. These stations are distinguished by the frequency
|
|
* used for the second and minute sync pulses, 1000 Hz for WWV and 1200
|
|
* Hz for WWVH. Other than frequency, the format is the same.
|
|
*/
|
|
struct sync {
|
|
double epoch; /* accumulated epoch differences */
|
|
double maxeng; /* sync max energy */
|
|
double noieng; /* sync noise energy */
|
|
long pos; /* max amplitude position */
|
|
long lastpos; /* last max position */
|
|
long mepoch; /* minute synch epoch */
|
|
|
|
double amp; /* sync signal */
|
|
double syneng; /* sync signal max */
|
|
double synmax; /* sync signal max latched at 0 s */
|
|
double synsnr; /* sync signal SNR */
|
|
double metric; /* signal quality metric */
|
|
int reach; /* reachability register */
|
|
int count; /* bit counter */
|
|
int select; /* select bits */
|
|
char refid[5]; /* reference identifier */
|
|
};
|
|
|
|
/*
|
|
* The channel structure (cp) is used to mitigate between channels.
|
|
*/
|
|
struct chan {
|
|
int gain; /* audio gain */
|
|
struct sync wwv; /* wwv station */
|
|
struct sync wwvh; /* wwvh station */
|
|
};
|
|
|
|
/*
|
|
* WWV unit control structure (up)
|
|
*/
|
|
struct wwvunit {
|
|
l_fp timestamp; /* audio sample timestamp */
|
|
l_fp tick; /* audio sample increment */
|
|
double phase, freq; /* logical clock phase and frequency */
|
|
double monitor; /* audio monitor point */
|
|
#ifdef ICOM
|
|
int fd_icom; /* ICOM file descriptor */
|
|
#endif /* ICOM */
|
|
int errflg; /* error flags */
|
|
int watch; /* watchcat */
|
|
|
|
/*
|
|
* Audio codec variables
|
|
*/
|
|
double comp[SIZE]; /* decompanding table */
|
|
int port; /* codec port */
|
|
int gain; /* codec gain */
|
|
int mongain; /* codec monitor gain */
|
|
int clipcnt; /* sample clipped count */
|
|
|
|
/*
|
|
* Variables used to establish basic system timing
|
|
*/
|
|
int avgint; /* master time constant */
|
|
int yepoch; /* sync epoch */
|
|
int repoch; /* buffered sync epoch */
|
|
double epomax; /* second sync amplitude */
|
|
double eposnr; /* second sync SNR */
|
|
double irig; /* data I channel amplitude */
|
|
double qrig; /* data Q channel amplitude */
|
|
int datapt; /* 100 Hz ramp */
|
|
double datpha; /* 100 Hz VFO control */
|
|
int rphase; /* second sample counter */
|
|
long mphase; /* minute sample counter */
|
|
|
|
/*
|
|
* Variables used to mitigate which channel to use
|
|
*/
|
|
struct chan mitig[NCHAN]; /* channel data */
|
|
struct sync *sptr; /* station pointer */
|
|
int dchan; /* data channel */
|
|
int schan; /* probe channel */
|
|
int achan; /* active channel */
|
|
|
|
/*
|
|
* Variables used by the clock state machine
|
|
*/
|
|
struct decvec decvec[9]; /* decoding matrix */
|
|
int rsec; /* seconds counter */
|
|
int digcnt; /* count of digits synchronized */
|
|
|
|
/*
|
|
* Variables used to estimate signal levels and bit/digit
|
|
* probabilities
|
|
*/
|
|
double datsig; /* data signal max */
|
|
double datsnr; /* data signal SNR (dB) */
|
|
|
|
/*
|
|
* Variables used to establish status and alarm conditions
|
|
*/
|
|
int status; /* status bits */
|
|
int alarm; /* alarm flashers */
|
|
int misc; /* miscellaneous timecode bits */
|
|
int errcnt; /* data bit error counter */
|
|
};
|
|
|
|
/*
|
|
* Function prototypes
|
|
*/
|
|
static int wwv_start P((int, struct peer *));
|
|
static void wwv_shutdown P((int, struct peer *));
|
|
static void wwv_receive P((struct recvbuf *));
|
|
static void wwv_poll P((int, struct peer *));
|
|
|
|
/*
|
|
* More function prototypes
|
|
*/
|
|
static void wwv_epoch P((struct peer *));
|
|
static void wwv_rf P((struct peer *, double));
|
|
static void wwv_endpoc P((struct peer *, int));
|
|
static void wwv_rsec P((struct peer *, double));
|
|
static void wwv_qrz P((struct peer *, struct sync *, int));
|
|
static void wwv_corr4 P((struct peer *, struct decvec *,
|
|
double [], double [][4]));
|
|
static void wwv_gain P((struct peer *));
|
|
static void wwv_tsec P((struct peer *));
|
|
static int timecode P((struct wwvunit *, char *));
|
|
static double wwv_snr P((double, double));
|
|
static int carry P((struct decvec *));
|
|
static int wwv_newchan P((struct peer *));
|
|
static void wwv_newgame P((struct peer *));
|
|
static double wwv_metric P((struct sync *));
|
|
static void wwv_clock P((struct peer *));
|
|
#ifdef ICOM
|
|
static int wwv_qsy P((struct peer *, int));
|
|
#endif /* ICOM */
|
|
|
|
static double qsy[NCHAN] = {2.5, 5, 10, 15, 20}; /* frequencies (MHz) */
|
|
|
|
/*
|
|
* Transfer vector
|
|
*/
|
|
struct refclock refclock_wwv = {
|
|
wwv_start, /* start up driver */
|
|
wwv_shutdown, /* shut down driver */
|
|
wwv_poll, /* transmit poll message */
|
|
noentry, /* not used (old wwv_control) */
|
|
noentry, /* initialize driver (not used) */
|
|
noentry, /* not used (old wwv_buginfo) */
|
|
NOFLAGS /* not used */
|
|
};
|
|
|
|
|
|
/*
|
|
* wwv_start - open the devices and initialize data for processing
|
|
*/
|
|
static int
|
|
wwv_start(
|
|
int unit, /* instance number (used by PCM) */
|
|
struct peer *peer /* peer structure pointer */
|
|
)
|
|
{
|
|
struct refclockproc *pp;
|
|
struct wwvunit *up;
|
|
#ifdef ICOM
|
|
int temp;
|
|
#endif /* ICOM */
|
|
|
|
/*
|
|
* Local variables
|
|
*/
|
|
int fd; /* file descriptor */
|
|
int i; /* index */
|
|
double step; /* codec adjustment */
|
|
|
|
/*
|
|
* Open audio device
|
|
*/
|
|
fd = audio_init(DEVICE_AUDIO, AUDIO_BUFSIZ, unit);
|
|
if (fd < 0)
|
|
return (0);
|
|
#ifdef DEBUG
|
|
if (debug)
|
|
audio_show();
|
|
#endif /* DEBUG */
|
|
|
|
/*
|
|
* Allocate and initialize unit structure
|
|
*/
|
|
if (!(up = (struct wwvunit *)emalloc(sizeof(struct wwvunit)))) {
|
|
close(fd);
|
|
return (0);
|
|
}
|
|
memset(up, 0, sizeof(struct wwvunit));
|
|
pp = peer->procptr;
|
|
pp->unitptr = (caddr_t)up;
|
|
pp->io.clock_recv = wwv_receive;
|
|
pp->io.srcclock = (caddr_t)peer;
|
|
pp->io.datalen = 0;
|
|
pp->io.fd = fd;
|
|
if (!io_addclock(&pp->io)) {
|
|
close(fd);
|
|
free(up);
|
|
return (0);
|
|
}
|
|
|
|
/*
|
|
* Initialize miscellaneous variables
|
|
*/
|
|
peer->precision = PRECISION;
|
|
pp->clockdesc = DESCRIPTION;
|
|
|
|
/*
|
|
* The companded samples are encoded sign-magnitude. The table
|
|
* contains all the 256 values in the interest of speed.
|
|
*/
|
|
up->comp[0] = up->comp[OFFSET] = 0.;
|
|
up->comp[1] = 1.; up->comp[OFFSET + 1] = -1.;
|
|
up->comp[2] = 3.; up->comp[OFFSET + 2] = -3.;
|
|
step = 2.;
|
|
for (i = 3; i < OFFSET; i++) {
|
|
up->comp[i] = up->comp[i - 1] + step;
|
|
up->comp[OFFSET + i] = -up->comp[i];
|
|
if (i % 16 == 0)
|
|
step *= 2.;
|
|
}
|
|
DTOLFP(1. / SECOND, &up->tick);
|
|
|
|
/*
|
|
* Initialize the decoding matrix with the radix for each digit
|
|
* position.
|
|
*/
|
|
up->decvec[MN].radix = 10; /* minutes */
|
|
up->decvec[MN + 1].radix = 6;
|
|
up->decvec[HR].radix = 10; /* hours */
|
|
up->decvec[HR + 1].radix = 3;
|
|
up->decvec[DA].radix = 10; /* days */
|
|
up->decvec[DA + 1].radix = 10;
|
|
up->decvec[DA + 2].radix = 4;
|
|
up->decvec[YR].radix = 10; /* years */
|
|
up->decvec[YR + 1].radix = 10;
|
|
|
|
#ifdef ICOM
|
|
/*
|
|
* Initialize autotune if available. Note that the ICOM select
|
|
* code must be less than 128, so the high order bit can be used
|
|
* to select the line speed 0 (9600 bps) or 1 (1200 bps).
|
|
*/
|
|
temp = 0;
|
|
#ifdef DEBUG
|
|
if (debug > 1)
|
|
temp = P_TRACE;
|
|
#endif /* DEBUG */
|
|
if (peer->ttl != 0) {
|
|
if (peer->ttl & 0x80)
|
|
up->fd_icom = icom_init("/dev/icom", B1200,
|
|
temp);
|
|
else
|
|
up->fd_icom = icom_init("/dev/icom", B9600,
|
|
temp);
|
|
if (up->fd_icom < 0) {
|
|
NLOG(NLOG_SYNCEVENT | NLOG_SYSEVENT)
|
|
msyslog(LOG_NOTICE,
|
|
"icom: %m");
|
|
up->errflg = CEVNT_FAULT;
|
|
}
|
|
}
|
|
if (up->fd_icom > 0) {
|
|
if (wwv_qsy(peer, DCHAN) != 0) {
|
|
NLOG(NLOG_SYNCEVENT | NLOG_SYSEVENT)
|
|
msyslog(LOG_NOTICE,
|
|
"icom: radio not found");
|
|
up->errflg = CEVNT_FAULT;
|
|
close(up->fd_icom);
|
|
up->fd_icom = 0;
|
|
} else {
|
|
NLOG(NLOG_SYNCEVENT | NLOG_SYSEVENT)
|
|
msyslog(LOG_NOTICE,
|
|
"icom: autotune enabled");
|
|
}
|
|
}
|
|
#endif /* ICOM */
|
|
|
|
/*
|
|
* Let the games begin.
|
|
*/
|
|
wwv_newgame(peer);
|
|
return (1);
|
|
}
|
|
|
|
|
|
/*
|
|
* wwv_shutdown - shut down the clock
|
|
*/
|
|
static void
|
|
wwv_shutdown(
|
|
int unit, /* instance number (not used) */
|
|
struct peer *peer /* peer structure pointer */
|
|
)
|
|
{
|
|
struct refclockproc *pp;
|
|
struct wwvunit *up;
|
|
|
|
pp = peer->procptr;
|
|
up = (struct wwvunit *)pp->unitptr;
|
|
if (up == NULL)
|
|
return;
|
|
|
|
io_closeclock(&pp->io);
|
|
#ifdef ICOM
|
|
if (up->fd_icom > 0)
|
|
close(up->fd_icom);
|
|
#endif /* ICOM */
|
|
free(up);
|
|
}
|
|
|
|
|
|
/*
|
|
* wwv_receive - receive data from the audio device
|
|
*
|
|
* This routine reads input samples and adjusts the logical clock to
|
|
* track the A/D sample clock by dropping or duplicating codec samples.
|
|
* It also controls the A/D signal level with an AGC loop to mimimize
|
|
* quantization noise and avoid overload.
|
|
*/
|
|
static void
|
|
wwv_receive(
|
|
struct recvbuf *rbufp /* receive buffer structure pointer */
|
|
)
|
|
{
|
|
struct peer *peer;
|
|
struct refclockproc *pp;
|
|
struct wwvunit *up;
|
|
|
|
/*
|
|
* Local variables
|
|
*/
|
|
double sample; /* codec sample */
|
|
u_char *dpt; /* buffer pointer */
|
|
int bufcnt; /* buffer counter */
|
|
l_fp ltemp;
|
|
|
|
peer = (struct peer *)rbufp->recv_srcclock;
|
|
pp = peer->procptr;
|
|
up = (struct wwvunit *)pp->unitptr;
|
|
|
|
/*
|
|
* Main loop - read until there ain't no more. Note codec
|
|
* samples are bit-inverted.
|
|
*/
|
|
DTOLFP((double)rbufp->recv_length / SECOND, <emp);
|
|
L_SUB(&rbufp->recv_time, <emp);
|
|
up->timestamp = rbufp->recv_time;
|
|
dpt = rbufp->recv_buffer;
|
|
for (bufcnt = 0; bufcnt < rbufp->recv_length; bufcnt++) {
|
|
sample = up->comp[~*dpt++ & 0xff];
|
|
|
|
/*
|
|
* Clip noise spikes greater than MAXAMP (6000) and
|
|
* record the number of clips to be used later by the
|
|
* AGC.
|
|
*/
|
|
if (sample > MAXAMP) {
|
|
sample = MAXAMP;
|
|
up->clipcnt++;
|
|
} else if (sample < -MAXAMP) {
|
|
sample = -MAXAMP;
|
|
up->clipcnt++;
|
|
}
|
|
|
|
/*
|
|
* Variable frequency oscillator. The codec oscillator
|
|
* runs at the nominal rate of 8000 samples per second,
|
|
* or 125 us per sample. A frequency change of one unit
|
|
* results in either duplicating or deleting one sample
|
|
* per second, which results in a frequency change of
|
|
* 125 PPM.
|
|
*/
|
|
up->phase += up->freq / SECOND;
|
|
up->phase += FREQ_OFFSET / 1e6;
|
|
if (up->phase >= .5) {
|
|
up->phase -= 1.;
|
|
} else if (up->phase < -.5) {
|
|
up->phase += 1.;
|
|
wwv_rf(peer, sample);
|
|
wwv_rf(peer, sample);
|
|
} else {
|
|
wwv_rf(peer, sample);
|
|
}
|
|
L_ADD(&up->timestamp, &up->tick);
|
|
}
|
|
|
|
/*
|
|
* Set the input port and monitor gain for the next buffer.
|
|
*/
|
|
if (pp->sloppyclockflag & CLK_FLAG2)
|
|
up->port = 2;
|
|
else
|
|
up->port = 1;
|
|
if (pp->sloppyclockflag & CLK_FLAG3)
|
|
up->mongain = MONGAIN;
|
|
else
|
|
up->mongain = 0;
|
|
}
|
|
|
|
|
|
/*
|
|
* wwv_poll - called by the transmit procedure
|
|
*
|
|
* This routine keeps track of status. If no offset samples have been
|
|
* processed during a poll interval, a timeout event is declared. If
|
|
* errors have have occurred during the interval, they are reported as
|
|
* well.
|
|
*/
|
|
static void
|
|
wwv_poll(
|
|
int unit, /* instance number (not used) */
|
|
struct peer *peer /* peer structure pointer */
|
|
)
|
|
{
|
|
struct refclockproc *pp;
|
|
struct wwvunit *up;
|
|
|
|
pp = peer->procptr;
|
|
up = (struct wwvunit *)pp->unitptr;
|
|
if (pp->coderecv == pp->codeproc)
|
|
up->errflg = CEVNT_TIMEOUT;
|
|
if (up->errflg)
|
|
refclock_report(peer, up->errflg);
|
|
up->errflg = 0;
|
|
pp->polls++;
|
|
}
|
|
|
|
|
|
/*
|
|
* wwv_rf - process signals and demodulate to baseband
|
|
*
|
|
* This routine grooms and filters decompanded raw audio samples. The
|
|
* output signal is the 100-Hz filtered baseband data signal in
|
|
* quadrature phase. The routine also determines the minute synch epoch,
|
|
* as well as certain signal maxima, minima and related values.
|
|
*
|
|
* There are two 1-s ramps used by this program. Both count the 8000
|
|
* logical clock samples spanning exactly one second. The epoch ramp
|
|
* counts the samples starting at an arbitrary time. The rphase ramp
|
|
* counts the samples starting at the 5-ms second sync pulse found
|
|
* during the epoch ramp.
|
|
*
|
|
* There are two 1-m ramps used by this program. The mphase ramp counts
|
|
* the 480,000 logical clock samples spanning exactly one minute and
|
|
* starting at an arbitrary time. The rsec ramp counts the 60 seconds of
|
|
* the minute starting at the 800-ms minute sync pulse found during the
|
|
* mphase ramp. The rsec ramp drives the seconds state machine to
|
|
* determine the bits and digits of the timecode.
|
|
*
|
|
* Demodulation operations are based on three synthesized quadrature
|
|
* sinusoids: 100 Hz for the data signal, 1000 Hz for the WWV sync
|
|
* signal and 1200 Hz for the WWVH sync signal. These drive synchronous
|
|
* matched filters for the data signal (170 ms at 100 Hz), WWV minute
|
|
* sync signal (800 ms at 1000 Hz) and WWVH minute sync signal (800 ms
|
|
* at 1200 Hz). Two additional matched filters are switched in
|
|
* as required for the WWV second sync signal (5 cycles at 1000 Hz) and
|
|
* WWVH second sync signal (6 cycles at 1200 Hz).
|
|
*/
|
|
static void
|
|
wwv_rf(
|
|
struct peer *peer, /* peerstructure pointer */
|
|
double isig /* input signal */
|
|
)
|
|
{
|
|
struct refclockproc *pp;
|
|
struct wwvunit *up;
|
|
struct sync *sp, *rp;
|
|
|
|
static double lpf[5]; /* 150-Hz lpf delay line */
|
|
double data; /* lpf output */
|
|
static double bpf[9]; /* 1000/1200-Hz bpf delay line */
|
|
double syncx; /* bpf output */
|
|
static double mf[41]; /* 1000/1200-Hz mf delay line */
|
|
double mfsync; /* mf output */
|
|
|
|
static int iptr; /* data channel pointer */
|
|
static double ibuf[DATSIZ]; /* data I channel delay line */
|
|
static double qbuf[DATSIZ]; /* data Q channel delay line */
|
|
|
|
static int jptr; /* sync channel pointer */
|
|
static int kptr; /* tick channel pointer */
|
|
|
|
static int csinptr; /* wwv channel phase */
|
|
static double cibuf[SYNSIZ]; /* wwv I channel delay line */
|
|
static double cqbuf[SYNSIZ]; /* wwv Q channel delay line */
|
|
static double ciamp; /* wwv I channel amplitude */
|
|
static double cqamp; /* wwv Q channel amplitude */
|
|
|
|
static double csibuf[TCKSIZ]; /* wwv I tick delay line */
|
|
static double csqbuf[TCKSIZ]; /* wwv Q tick delay line */
|
|
static double csiamp; /* wwv I tick amplitude */
|
|
static double csqamp; /* wwv Q tick amplitude */
|
|
|
|
static int hsinptr; /* wwvh channel phase */
|
|
static double hibuf[SYNSIZ]; /* wwvh I channel delay line */
|
|
static double hqbuf[SYNSIZ]; /* wwvh Q channel delay line */
|
|
static double hiamp; /* wwvh I channel amplitude */
|
|
static double hqamp; /* wwvh Q channel amplitude */
|
|
|
|
static double hsibuf[TCKSIZ]; /* wwvh I tick delay line */
|
|
static double hsqbuf[TCKSIZ]; /* wwvh Q tick delay line */
|
|
static double hsiamp; /* wwvh I tick amplitude */
|
|
static double hsqamp; /* wwvh Q tick amplitude */
|
|
|
|
static double epobuf[SECOND]; /* second sync comb filter */
|
|
static double epomax, nxtmax; /* second sync amplitude buffer */
|
|
static int epopos; /* epoch second sync position buffer */
|
|
|
|
static int iniflg; /* initialization flag */
|
|
int pdelay; /* propagation delay (samples) */
|
|
int epoch; /* comb filter index */
|
|
double dtemp;
|
|
int i;
|
|
|
|
pp = peer->procptr;
|
|
up = (struct wwvunit *)pp->unitptr;
|
|
|
|
if (!iniflg) {
|
|
iniflg = 1;
|
|
memset((char *)lpf, 0, sizeof(lpf));
|
|
memset((char *)bpf, 0, sizeof(bpf));
|
|
memset((char *)mf, 0, sizeof(mf));
|
|
memset((char *)ibuf, 0, sizeof(ibuf));
|
|
memset((char *)qbuf, 0, sizeof(qbuf));
|
|
memset((char *)cibuf, 0, sizeof(cibuf));
|
|
memset((char *)cqbuf, 0, sizeof(cqbuf));
|
|
memset((char *)csibuf, 0, sizeof(csibuf));
|
|
memset((char *)csqbuf, 0, sizeof(csqbuf));
|
|
memset((char *)hibuf, 0, sizeof(hibuf));
|
|
memset((char *)hqbuf, 0, sizeof(hqbuf));
|
|
memset((char *)hsibuf, 0, sizeof(hsibuf));
|
|
memset((char *)hsqbuf, 0, sizeof(hsqbuf));
|
|
memset((char *)epobuf, 0, sizeof(epobuf));
|
|
}
|
|
|
|
/*
|
|
* Baseband data demodulation. The 100-Hz subcarrier is
|
|
* extracted using a 150-Hz IIR lowpass filter. This attenuates
|
|
* the 1000/1200-Hz sync signals, as well as the 440-Hz and
|
|
* 600-Hz tones and most of the noise and voice modulation
|
|
* components.
|
|
*
|
|
* The subcarrier is transmitted 10 dB down from the carrier.
|
|
* The DGAIN parameter can be adjusted for this and to
|
|
* compensate for the radio audio response at 100 Hz.
|
|
*
|
|
* Matlab IIR 4th-order IIR elliptic, 150 Hz lowpass, 0.2 dB
|
|
* passband ripple, -50 dB stopband ripple.
|
|
*/
|
|
data = (lpf[4] = lpf[3]) * 8.360961e-01;
|
|
data += (lpf[3] = lpf[2]) * -3.481740e+00;
|
|
data += (lpf[2] = lpf[1]) * 5.452988e+00;
|
|
data += (lpf[1] = lpf[0]) * -3.807229e+00;
|
|
lpf[0] = isig * DGAIN - data;
|
|
data = lpf[0] * 3.281435e-03
|
|
+ lpf[1] * -1.149947e-02
|
|
+ lpf[2] * 1.654858e-02
|
|
+ lpf[3] * -1.149947e-02
|
|
+ lpf[4] * 3.281435e-03;
|
|
|
|
/*
|
|
* The 100-Hz data signal is demodulated using a pair of
|
|
* quadrature multipliers, matched filters and a phase lock
|
|
* loop. The I and Q quadrature data signals are produced by
|
|
* multiplying the filtered signal by 100-Hz sine and cosine
|
|
* signals, respectively. The signals are processed by 170-ms
|
|
* synchronous matched filters to produce the amplitude and
|
|
* phase signals used by the demodulator. The signals are scaled
|
|
* to produce unit energy at the maximum value.
|
|
*/
|
|
i = up->datapt;
|
|
up->datapt = (up->datapt + IN100) % 80;
|
|
dtemp = sintab[i] * data / (MS / 2. * DATCYC);
|
|
up->irig -= ibuf[iptr];
|
|
ibuf[iptr] = dtemp;
|
|
up->irig += dtemp;
|
|
|
|
i = (i + 20) % 80;
|
|
dtemp = sintab[i] * data / (MS / 2. * DATCYC);
|
|
up->qrig -= qbuf[iptr];
|
|
qbuf[iptr] = dtemp;
|
|
up->qrig += dtemp;
|
|
iptr = (iptr + 1) % DATSIZ;
|
|
|
|
/*
|
|
* Baseband sync demodulation. The 1000/1200 sync signals are
|
|
* extracted using a 600-Hz IIR bandpass filter. This removes
|
|
* the 100-Hz data subcarrier, as well as the 440-Hz and 600-Hz
|
|
* tones and most of the noise and voice modulation components.
|
|
*
|
|
* Matlab 4th-order IIR elliptic, 800-1400 Hz bandpass, 0.2 dB
|
|
* passband ripple, -50 dB stopband ripple.
|
|
*/
|
|
syncx = (bpf[8] = bpf[7]) * 4.897278e-01;
|
|
syncx += (bpf[7] = bpf[6]) * -2.765914e+00;
|
|
syncx += (bpf[6] = bpf[5]) * 8.110921e+00;
|
|
syncx += (bpf[5] = bpf[4]) * -1.517732e+01;
|
|
syncx += (bpf[4] = bpf[3]) * 1.975197e+01;
|
|
syncx += (bpf[3] = bpf[2]) * -1.814365e+01;
|
|
syncx += (bpf[2] = bpf[1]) * 1.159783e+01;
|
|
syncx += (bpf[1] = bpf[0]) * -4.735040e+00;
|
|
bpf[0] = isig - syncx;
|
|
syncx = bpf[0] * 8.203628e-03
|
|
+ bpf[1] * -2.375732e-02
|
|
+ bpf[2] * 3.353214e-02
|
|
+ bpf[3] * -4.080258e-02
|
|
+ bpf[4] * 4.605479e-02
|
|
+ bpf[5] * -4.080258e-02
|
|
+ bpf[6] * 3.353214e-02
|
|
+ bpf[7] * -2.375732e-02
|
|
+ bpf[8] * 8.203628e-03;
|
|
|
|
/*
|
|
* The 1000/1200 sync signals are demodulated using a pair of
|
|
* quadrature multipliers and matched filters. However,
|
|
* synchronous demodulation at these frequencies is impractical,
|
|
* so only the signal amplitude is used. The I and Q quadrature
|
|
* sync signals are produced by multiplying the filtered signal
|
|
* by 1000-Hz (WWV) and 1200-Hz (WWVH) sine and cosine signals,
|
|
* respectively. The WWV and WWVH signals are processed by 800-
|
|
* ms synchronous matched filters and combined to produce the
|
|
* minute sync signal and detect which one (or both) the WWV or
|
|
* WWVH signal is present. The WWV and WWVH signals are also
|
|
* processed by 5-ms synchronous matched filters and combined to
|
|
* produce the second sync signal. The signals are scaled to
|
|
* produce unit energy at the maximum value.
|
|
*
|
|
* Note the master timing ramps, which run continuously. The
|
|
* minute counter (mphase) counts the samples in the minute,
|
|
* while the second counter (epoch) counts the samples in the
|
|
* second.
|
|
*/
|
|
up->mphase = (up->mphase + 1) % MINUTE;
|
|
epoch = up->mphase % SECOND;
|
|
|
|
/*
|
|
* WWV
|
|
*/
|
|
i = csinptr;
|
|
csinptr = (csinptr + IN1000) % 80;
|
|
|
|
dtemp = sintab[i] * syncx / (MS / 2.);
|
|
ciamp -= cibuf[jptr];
|
|
cibuf[jptr] = dtemp;
|
|
ciamp += dtemp;
|
|
csiamp -= csibuf[kptr];
|
|
csibuf[kptr] = dtemp;
|
|
csiamp += dtemp;
|
|
|
|
i = (i + 20) % 80;
|
|
dtemp = sintab[i] * syncx / (MS / 2.);
|
|
cqamp -= cqbuf[jptr];
|
|
cqbuf[jptr] = dtemp;
|
|
cqamp += dtemp;
|
|
csqamp -= csqbuf[kptr];
|
|
csqbuf[kptr] = dtemp;
|
|
csqamp += dtemp;
|
|
|
|
sp = &up->mitig[up->achan].wwv;
|
|
sp->amp = sqrt(ciamp * ciamp + cqamp * cqamp) / SYNCYC;
|
|
if (!(up->status & MSYNC))
|
|
wwv_qrz(peer, sp, (int)(pp->fudgetime1 * SECOND));
|
|
|
|
/*
|
|
* WWVH
|
|
*/
|
|
i = hsinptr;
|
|
hsinptr = (hsinptr + IN1200) % 80;
|
|
|
|
dtemp = sintab[i] * syncx / (MS / 2.);
|
|
hiamp -= hibuf[jptr];
|
|
hibuf[jptr] = dtemp;
|
|
hiamp += dtemp;
|
|
hsiamp -= hsibuf[kptr];
|
|
hsibuf[kptr] = dtemp;
|
|
hsiamp += dtemp;
|
|
|
|
i = (i + 20) % 80;
|
|
dtemp = sintab[i] * syncx / (MS / 2.);
|
|
hqamp -= hqbuf[jptr];
|
|
hqbuf[jptr] = dtemp;
|
|
hqamp += dtemp;
|
|
hsqamp -= hsqbuf[kptr];
|
|
hsqbuf[kptr] = dtemp;
|
|
hsqamp += dtemp;
|
|
|
|
rp = &up->mitig[up->achan].wwvh;
|
|
rp->amp = sqrt(hiamp * hiamp + hqamp * hqamp) / SYNCYC;
|
|
if (!(up->status & MSYNC))
|
|
wwv_qrz(peer, rp, (int)(pp->fudgetime2 * SECOND));
|
|
jptr = (jptr + 1) % SYNSIZ;
|
|
kptr = (kptr + 1) % TCKSIZ;
|
|
|
|
/*
|
|
* The following section is called once per minute. It does
|
|
* housekeeping and timeout functions and empties the dustbins.
|
|
*/
|
|
if (up->mphase == 0) {
|
|
up->watch++;
|
|
if (!(up->status & MSYNC)) {
|
|
|
|
/*
|
|
* If minute sync has not been acquired before
|
|
* ACQSN timeout (6 min), or if no signal is
|
|
* heard, the program cycles to the next
|
|
* frequency and tries again.
|
|
*/
|
|
if (!wwv_newchan(peer))
|
|
up->watch = 0;
|
|
#ifdef ICOM
|
|
if (up->fd_icom > 0)
|
|
wwv_qsy(peer, up->dchan);
|
|
#endif /* ICOM */
|
|
} else {
|
|
|
|
/*
|
|
* If the leap bit is set, set the minute epoch
|
|
* back one second so the station processes
|
|
* don't miss a beat.
|
|
*/
|
|
if (up->status & LEPSEC) {
|
|
up->mphase -= SECOND;
|
|
if (up->mphase < 0)
|
|
up->mphase += MINUTE;
|
|
}
|
|
}
|
|
}
|
|
|
|
/*
|
|
* When the channel metric reaches threshold and the second
|
|
* counter matches the minute epoch within the second, the
|
|
* driver has synchronized to the station. The second number is
|
|
* the remaining seconds until the next minute epoch, while the
|
|
* sync epoch is zero. Watch out for the first second; if
|
|
* already synchronized to the second, the buffered sync epoch
|
|
* must be set.
|
|
*
|
|
* Note the guard interval is 200 ms; if for some reason the
|
|
* clock drifts more than that, it might wind up in the wrong
|
|
* second. If the maximum frequency error is not more than about
|
|
* 1 PPM, the clock can go as much as two days while still in
|
|
* the same second.
|
|
*/
|
|
if (up->status & MSYNC) {
|
|
wwv_epoch(peer);
|
|
} else if (up->sptr != NULL) {
|
|
sp = up->sptr;
|
|
if (sp->metric >= TTHR && epoch == sp->mepoch % SECOND) {
|
|
up->rsec = (60 - sp->mepoch / SECOND) % 60;
|
|
up->rphase = 0;
|
|
up->status |= MSYNC;
|
|
up->watch = 0;
|
|
if (!(up->status & SSYNC))
|
|
up->repoch = up->yepoch = epoch;
|
|
else
|
|
up->repoch = up->yepoch;
|
|
|
|
}
|
|
}
|
|
|
|
/*
|
|
* The second sync pulse is extracted using 5-ms (40 sample) FIR
|
|
* matched filters at 1000 Hz for WWV or 1200 Hz for WWVH. This
|
|
* pulse is used for the most precise synchronization, since if
|
|
* provides a resolution of one sample (125 us). The filters run
|
|
* only if the station has been reliably determined.
|
|
*/
|
|
if (up->status & SELV) {
|
|
pdelay = (int)(pp->fudgetime1 * SECOND);
|
|
mfsync = sqrt(csiamp * csiamp + csqamp * csqamp) /
|
|
TCKCYC;
|
|
} else if (up->status & SELH) {
|
|
pdelay = (int)(pp->fudgetime2 * SECOND);
|
|
mfsync = sqrt(hsiamp * hsiamp + hsqamp * hsqamp) /
|
|
TCKCYC;
|
|
} else {
|
|
pdelay = 0;
|
|
mfsync = 0;
|
|
}
|
|
|
|
/*
|
|
* Enhance the seconds sync pulse using a 1-s (8000-sample) comb
|
|
* filter. Correct for the FIR matched filter delay, which is 5
|
|
* ms for both the WWV and WWVH filters, and also for the
|
|
* propagation delay. Once each second look for second sync. If
|
|
* not in minute sync, fiddle the codec gain. Note the SNR is
|
|
* computed from the maximum sample and the envelope of the
|
|
* sample 6 ms before it, so if we slip more than a cycle the
|
|
* SNR should plummet. The signal is scaled to produce unit
|
|
* energy at the maximum value.
|
|
*/
|
|
dtemp = (epobuf[epoch] += (mfsync - epobuf[epoch]) /
|
|
up->avgint);
|
|
if (dtemp > epomax) {
|
|
int j;
|
|
|
|
epomax = dtemp;
|
|
epopos = epoch;
|
|
j = epoch - 6 * MS;
|
|
if (j < 0)
|
|
j += SECOND;
|
|
nxtmax = fabs(epobuf[j]);
|
|
}
|
|
if (epoch == 0) {
|
|
up->epomax = epomax;
|
|
up->eposnr = wwv_snr(epomax, nxtmax);
|
|
epopos -= pdelay + TCKCYC * MS;
|
|
if (epopos < 0)
|
|
epopos += SECOND;
|
|
wwv_endpoc(peer, epopos);
|
|
if (!(up->status & SSYNC))
|
|
up->alarm |= SYNERR;
|
|
epomax = 0;
|
|
if (!(up->status & MSYNC))
|
|
wwv_gain(peer);
|
|
}
|
|
}
|
|
|
|
|
|
/*
|
|
* wwv_qrz - identify and acquire WWV/WWVH minute sync pulse
|
|
*
|
|
* This routine implements a virtual station process used to acquire
|
|
* minute sync and to mitigate among the ten frequency and station
|
|
* combinations. During minute sync acquisition the process probes each
|
|
* frequency and station in turn for the minute pulse, which
|
|
* involves searching through the entire 480,000-sample minute. The
|
|
* process finds the maximum signal and RMS noise plus signal. Then, the
|
|
* actual noise is determined by subtracting the energy of the matched
|
|
* filter.
|
|
*
|
|
* Students of radar receiver technology will discover this algorithm
|
|
* amounts to a range-gate discriminator. A valid pulse must have peak
|
|
* amplitude at least QTHR (2500) and SNR at least QSNR (20) dB and the
|
|
* difference between the current and previous epoch must be less than
|
|
* AWND (20 ms). Note that the discriminator peak occurs about 800 ms
|
|
* into the second, so the timing is retarded to the previous second
|
|
* epoch.
|
|
*/
|
|
static void
|
|
wwv_qrz(
|
|
struct peer *peer, /* peer structure pointer */
|
|
struct sync *sp, /* sync channel structure */
|
|
int pdelay /* propagation delay (samples) */
|
|
)
|
|
{
|
|
struct refclockproc *pp;
|
|
struct wwvunit *up;
|
|
char tbuf[80]; /* monitor buffer */
|
|
long epoch;
|
|
|
|
pp = peer->procptr;
|
|
up = (struct wwvunit *)pp->unitptr;
|
|
|
|
/*
|
|
* Find the sample with peak amplitude, which defines the minute
|
|
* epoch. Accumulate all samples to determine the total noise
|
|
* energy.
|
|
*/
|
|
epoch = up->mphase - pdelay - SYNSIZ;
|
|
if (epoch < 0)
|
|
epoch += MINUTE;
|
|
if (sp->amp > sp->maxeng) {
|
|
sp->maxeng = sp->amp;
|
|
sp->pos = epoch;
|
|
}
|
|
sp->noieng += sp->amp;
|
|
|
|
/*
|
|
* At the end of the minute, determine the epoch of the minute
|
|
* sync pulse, as well as the difference between the current and
|
|
* previous epoches due to the intrinsic frequency error plus
|
|
* jitter. When calculating the SNR, subtract the pulse energy
|
|
* from the total noise energy and then normalize.
|
|
*/
|
|
if (up->mphase == 0) {
|
|
sp->synmax = sp->maxeng;
|
|
sp->synsnr = wwv_snr(sp->synmax, (sp->noieng -
|
|
sp->synmax) / MINUTE);
|
|
if (sp->count == 0)
|
|
sp->lastpos = sp->pos;
|
|
epoch = (sp->pos - sp->lastpos) % MINUTE;
|
|
sp->reach <<= 1;
|
|
if (sp->reach & (1 << AMAX))
|
|
sp->count--;
|
|
if (sp->synmax > ATHR && sp->synsnr > ASNR) {
|
|
if (abs(epoch) < AWND * MS) {
|
|
sp->reach |= 1;
|
|
sp->count++;
|
|
sp->mepoch = sp->lastpos = sp->pos;
|
|
} else if (sp->count == 1) {
|
|
sp->lastpos = sp->pos;
|
|
}
|
|
}
|
|
if (up->watch > ACQSN)
|
|
sp->metric = 0;
|
|
else
|
|
sp->metric = wwv_metric(sp);
|
|
if (pp->sloppyclockflag & CLK_FLAG4) {
|
|
sprintf(tbuf,
|
|
"wwv8 %04x %3d %s %04x %.0f %.0f/%.1f %4ld %4ld",
|
|
up->status, up->gain, sp->refid,
|
|
sp->reach & 0xffff, sp->metric, sp->synmax,
|
|
sp->synsnr, sp->pos % SECOND, epoch);
|
|
record_clock_stats(&peer->srcadr, tbuf);
|
|
#ifdef DEBUG
|
|
if (debug)
|
|
printf("%s\n", tbuf);
|
|
#endif /* DEBUG */
|
|
}
|
|
sp->maxeng = sp->noieng = 0;
|
|
}
|
|
}
|
|
|
|
|
|
/*
|
|
* wwv_endpoc - identify and acquire second sync pulse
|
|
*
|
|
* This routine is called at the end of the second sync interval. It
|
|
* determines the second sync epoch position within the second and
|
|
* disciplines the sample clock using a frequency-lock loop (FLL).
|
|
*
|
|
* Second sync is determined in the RF input routine as the maximum
|
|
* over all 8000 samples in the second comb filter. To assure accurate
|
|
* and reliable time and frequency discipline, this routine performs a
|
|
* great deal of heavy-handed heuristic data filtering and grooming.
|
|
*/
|
|
static void
|
|
wwv_endpoc(
|
|
struct peer *peer, /* peer structure pointer */
|
|
int epopos /* epoch max position */
|
|
)
|
|
{
|
|
struct refclockproc *pp;
|
|
struct wwvunit *up;
|
|
static int epoch_mf[3]; /* epoch median filter */
|
|
static int tepoch; /* current second epoch */
|
|
static int xepoch; /* last second epoch */
|
|
static int zepoch; /* last run epoch */
|
|
static int zcount; /* last run end time */
|
|
static int scount; /* seconds counter */
|
|
static int syncnt; /* run length counter */
|
|
static int maxrun; /* longest run length */
|
|
static int mepoch; /* longest run end epoch */
|
|
static int mcount; /* longest run end time */
|
|
static int avgcnt; /* averaging interval counter */
|
|
static int avginc; /* averaging ratchet */
|
|
static int iniflg; /* initialization flag */
|
|
char tbuf[80]; /* monitor buffer */
|
|
double dtemp;
|
|
int tmp2;
|
|
|
|
pp = peer->procptr;
|
|
up = (struct wwvunit *)pp->unitptr;
|
|
if (!iniflg) {
|
|
iniflg = 1;
|
|
memset((char *)epoch_mf, 0, sizeof(epoch_mf));
|
|
}
|
|
|
|
/*
|
|
* If the signal amplitude or SNR fall below thresholds, dim the
|
|
* second sync lamp and wait for hotter ions. If no stations are
|
|
* heard, we are either in a probe cycle or the ions are really
|
|
* cold.
|
|
*/
|
|
scount++;
|
|
if (up->epomax < STHR || up->eposnr < SSNR) {
|
|
up->status &= ~(SSYNC | FGATE);
|
|
avgcnt = syncnt = maxrun = 0;
|
|
return;
|
|
}
|
|
if (!(up->status & (SELV | SELH)))
|
|
return;
|
|
|
|
/*
|
|
* A three-stage median filter is used to help denoise the
|
|
* second sync pulse. The median sample becomes the candidate
|
|
* epoch.
|
|
*/
|
|
epoch_mf[2] = epoch_mf[1];
|
|
epoch_mf[1] = epoch_mf[0];
|
|
epoch_mf[0] = epopos;
|
|
if (epoch_mf[0] > epoch_mf[1]) {
|
|
if (epoch_mf[1] > epoch_mf[2])
|
|
tepoch = epoch_mf[1]; /* 0 1 2 */
|
|
else if (epoch_mf[2] > epoch_mf[0])
|
|
tepoch = epoch_mf[0]; /* 2 0 1 */
|
|
else
|
|
tepoch = epoch_mf[2]; /* 0 2 1 */
|
|
} else {
|
|
if (epoch_mf[1] < epoch_mf[2])
|
|
tepoch = epoch_mf[1]; /* 2 1 0 */
|
|
else if (epoch_mf[2] < epoch_mf[0])
|
|
tepoch = epoch_mf[0]; /* 1 0 2 */
|
|
else
|
|
tepoch = epoch_mf[2]; /* 1 2 0 */
|
|
}
|
|
|
|
|
|
/*
|
|
* If the epoch candidate is the same as the last one, increment
|
|
* the run counter. If not, save the length, epoch and end
|
|
* time of the current run for use later and reset the counter.
|
|
* The epoch is considered valid if the run is at least SCMP
|
|
* (10) s, the minute is synchronized and the interval since the
|
|
* last epoch is not greater than the averaging interval. Thus,
|
|
* after a long absence, the program will wait a full averaging
|
|
* interval while the comb filter charges up and noise
|
|
* dissapates..
|
|
*/
|
|
tmp2 = (tepoch - xepoch) % SECOND;
|
|
if (tmp2 == 0) {
|
|
syncnt++;
|
|
if (syncnt > SCMP && up->status & MSYNC && (up->status &
|
|
FGATE || scount - zcount <= up->avgint)) {
|
|
up->status |= SSYNC;
|
|
up->yepoch = tepoch;
|
|
}
|
|
} else if (syncnt >= maxrun) {
|
|
maxrun = syncnt;
|
|
mcount = scount;
|
|
mepoch = xepoch;
|
|
syncnt = 0;
|
|
}
|
|
if ((pp->sloppyclockflag & CLK_FLAG4) && !(up->status & MSYNC))
|
|
{
|
|
sprintf(tbuf,
|
|
"wwv1 %04x %3d %4d %5.0f %5.1f %5d %4d %4d %4d",
|
|
up->status, up->gain, tepoch, up->epomax,
|
|
up->eposnr, tmp2, avgcnt, syncnt,
|
|
maxrun);
|
|
record_clock_stats(&peer->srcadr, tbuf);
|
|
#ifdef DEBUG
|
|
if (debug)
|
|
printf("%s\n", tbuf);
|
|
#endif /* DEBUG */
|
|
}
|
|
avgcnt++;
|
|
if (avgcnt < up->avgint) {
|
|
xepoch = tepoch;
|
|
return;
|
|
}
|
|
|
|
/*
|
|
* The sample clock frequency is disciplined using a first-order
|
|
* feedback loop with time constant consistent with the Allan
|
|
* intercept of typical computer clocks. During each averaging
|
|
* interval the candidate epoch at the end of the longest run is
|
|
* determined. If the longest run is zero, all epoches in the
|
|
* interval are different, so the candidate epoch is the current
|
|
* epoch. The frequency update is computed from the candidate
|
|
* epoch difference (125-us units) and time difference (seconds)
|
|
* between updates.
|
|
*/
|
|
if (syncnt >= maxrun) {
|
|
maxrun = syncnt;
|
|
mcount = scount;
|
|
mepoch = xepoch;
|
|
}
|
|
xepoch = tepoch;
|
|
if (maxrun == 0) {
|
|
mepoch = tepoch;
|
|
mcount = scount;
|
|
}
|
|
|
|
/*
|
|
* The master clock runs at the codec sample frequency of 8000
|
|
* Hz, so the intrinsic time resolution is 125 us. The frequency
|
|
* resolution ranges from 18 PPM at the minimum averaging
|
|
* interval of 8 s to 0.12 PPM at the maximum interval of 1024
|
|
* s. An offset update is determined at the end of the longest
|
|
* run in each averaging interval. The frequency adjustment is
|
|
* computed from the difference between offset updates and the
|
|
* interval between them.
|
|
*
|
|
* The maximum frequency adjustment ranges from 187 PPM at the
|
|
* minimum interval to 1.5 PPM at the maximum. If the adjustment
|
|
* exceeds the maximum, the update is discarded and the
|
|
* hysteresis counter is decremented. Otherwise, the frequency
|
|
* is incremented by the adjustment, but clamped to the maximum
|
|
* 187.5 PPM. If the update is less than half the maximum, the
|
|
* hysteresis counter is incremented. If the counter increments
|
|
* to +3, the averaging interval is doubled and the counter set
|
|
* to zero; if it decrements to -3, the interval is halved and
|
|
* the counter set to zero.
|
|
*/
|
|
dtemp = (mepoch - zepoch) % SECOND;
|
|
if (up->status & FGATE) {
|
|
if (abs(dtemp) < MAXFREQ * MINAVG) {
|
|
up->freq += (dtemp / 2.) / ((mcount - zcount) *
|
|
FCONST);
|
|
if (up->freq > MAXFREQ)
|
|
up->freq = MAXFREQ;
|
|
else if (up->freq < -MAXFREQ)
|
|
up->freq = -MAXFREQ;
|
|
if (abs(dtemp) < MAXFREQ * MINAVG / 2.) {
|
|
if (avginc < 3) {
|
|
avginc++;
|
|
} else {
|
|
if (up->avgint < MAXAVG) {
|
|
up->avgint <<= 1;
|
|
avginc = 0;
|
|
}
|
|
}
|
|
}
|
|
} else {
|
|
if (avginc > -3) {
|
|
avginc--;
|
|
} else {
|
|
if (up->avgint > MINAVG) {
|
|
up->avgint >>= 1;
|
|
avginc = 0;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
if (pp->sloppyclockflag & CLK_FLAG4) {
|
|
sprintf(tbuf,
|
|
"wwv2 %04x %5.0f %5.1f %5d %4d %4d %4d %4.0f %7.2f",
|
|
up->status, up->epomax, up->eposnr, mepoch,
|
|
up->avgint, maxrun, mcount - zcount, dtemp,
|
|
up->freq * 1e6 / SECOND);
|
|
record_clock_stats(&peer->srcadr, tbuf);
|
|
#ifdef DEBUG
|
|
if (debug)
|
|
printf("%s\n", tbuf);
|
|
#endif /* DEBUG */
|
|
}
|
|
|
|
/*
|
|
* This is a valid update; set up for the next interval.
|
|
*/
|
|
up->status |= FGATE;
|
|
zepoch = mepoch;
|
|
zcount = mcount;
|
|
avgcnt = syncnt = maxrun = 0;
|
|
}
|
|
|
|
|
|
/*
|
|
* wwv_epoch - epoch scanner
|
|
*
|
|
* This routine extracts data signals from the 100-Hz subcarrier. It
|
|
* scans the receiver second epoch to determine the signal amplitudes
|
|
* and pulse timings. Receiver synchronization is determined by the
|
|
* minute sync pulse detected in the wwv_rf() routine and the second
|
|
* sync pulse detected in the wwv_epoch() routine. The transmitted
|
|
* signals are delayed by the propagation delay, receiver delay and
|
|
* filter delay of this program. Delay corrections are introduced
|
|
* separately for WWV and WWVH.
|
|
*
|
|
* Most communications radios use a highpass filter in the audio stages,
|
|
* which can do nasty things to the subcarrier phase relative to the
|
|
* sync pulses. Therefore, the data subcarrier reference phase is
|
|
* disciplined using the hardlimited quadrature-phase signal sampled at
|
|
* the same time as the in-phase signal. The phase tracking loop uses
|
|
* phase adjustments of plus-minus one sample (125 us).
|
|
*/
|
|
static void
|
|
wwv_epoch(
|
|
struct peer *peer /* peer structure pointer */
|
|
)
|
|
{
|
|
struct refclockproc *pp;
|
|
struct wwvunit *up;
|
|
struct chan *cp;
|
|
static double sigmin, sigzer, sigone, engmax, engmin;
|
|
|
|
pp = peer->procptr;
|
|
up = (struct wwvunit *)pp->unitptr;
|
|
|
|
/*
|
|
* Find the maximum minute sync pulse energy for both the
|
|
* WWV and WWVH stations. This will be used later for channel
|
|
* and station mitigation. Also set the seconds epoch at 800 ms
|
|
* well before the end of the second to make sure we never set
|
|
* the epoch backwards.
|
|
*/
|
|
cp = &up->mitig[up->achan];
|
|
if (cp->wwv.amp > cp->wwv.syneng)
|
|
cp->wwv.syneng = cp->wwv.amp;
|
|
if (cp->wwvh.amp > cp->wwvh.syneng)
|
|
cp->wwvh.syneng = cp->wwvh.amp;
|
|
if (up->rphase == 800 * MS)
|
|
up->repoch = up->yepoch;
|
|
|
|
/*
|
|
* Use the signal amplitude at epoch 15 ms as the noise floor.
|
|
* This gives a guard time of +-15 ms from the beginning of the
|
|
* second until the second pulse rises at 30 ms. There is a
|
|
* compromise here; we want to delay the sample as long as
|
|
* possible to give the radio time to change frequency and the
|
|
* AGC to stabilize, but as early as possible if the second
|
|
* epoch is not exact.
|
|
*/
|
|
if (up->rphase == 15 * MS)
|
|
sigmin = sigzer = sigone = up->irig;
|
|
|
|
/*
|
|
* Latch the data signal at 200 ms. Keep this around until the
|
|
* end of the second. Use the signal energy as the peak to
|
|
* compute the SNR. Use the Q sample to adjust the 100-Hz
|
|
* reference oscillator phase.
|
|
*/
|
|
if (up->rphase == 200 * MS) {
|
|
sigzer = up->irig;
|
|
engmax = sqrt(up->irig * up->irig + up->qrig *
|
|
up->qrig);
|
|
up->datpha = up->qrig / up->avgint;
|
|
if (up->datpha >= 0) {
|
|
up->datapt++;
|
|
if (up->datapt >= 80)
|
|
up->datapt -= 80;
|
|
} else {
|
|
up->datapt--;
|
|
if (up->datapt < 0)
|
|
up->datapt += 80;
|
|
}
|
|
}
|
|
|
|
|
|
/*
|
|
* Latch the data signal at 500 ms. Keep this around until the
|
|
* end of the second.
|
|
*/
|
|
else if (up->rphase == 500 * MS)
|
|
sigone = up->irig;
|
|
|
|
/*
|
|
* At the end of the second crank the clock state machine and
|
|
* adjust the codec gain. Note the epoch is buffered from the
|
|
* center of the second in order to avoid jitter while the
|
|
* seconds synch is diddling the epoch. Then, determine the true
|
|
* offset and update the median filter in the driver interface.
|
|
*
|
|
* Use the energy at the end of the second as the noise to
|
|
* compute the SNR for the data pulse. This gives a better
|
|
* measurement than the beginning of the second, especially when
|
|
* returning from the probe channel. This gives a guard time of
|
|
* 30 ms from the decay of the longest pulse to the rise of the
|
|
* next pulse.
|
|
*/
|
|
up->rphase++;
|
|
if (up->mphase % SECOND == up->repoch) {
|
|
up->status &= ~(DGATE | BGATE);
|
|
engmin = sqrt(up->irig * up->irig + up->qrig *
|
|
up->qrig);
|
|
up->datsig = engmax;
|
|
up->datsnr = wwv_snr(engmax, engmin);
|
|
|
|
/*
|
|
* If the amplitude or SNR is below threshold, average a
|
|
* 0 in the the integrators; otherwise, average the
|
|
* bipolar signal. This is done to avoid noise polution.
|
|
*/
|
|
if (engmax < DTHR || up->datsnr < DSNR) {
|
|
up->status |= DGATE;
|
|
wwv_rsec(peer, 0);
|
|
} else {
|
|
sigzer -= sigone;
|
|
sigone -= sigmin;
|
|
wwv_rsec(peer, sigone - sigzer);
|
|
}
|
|
if (up->status & (DGATE | BGATE))
|
|
up->errcnt++;
|
|
if (up->errcnt > MAXERR)
|
|
up->alarm |= LOWERR;
|
|
wwv_gain(peer);
|
|
cp = &up->mitig[up->achan];
|
|
cp->wwv.syneng = 0;
|
|
cp->wwvh.syneng = 0;
|
|
up->rphase = 0;
|
|
}
|
|
}
|
|
|
|
|
|
/*
|
|
* wwv_rsec - process receiver second
|
|
*
|
|
* This routine is called at the end of each receiver second to
|
|
* implement the per-second state machine. The machine assembles BCD
|
|
* digit bits, decodes miscellaneous bits and dances the leap seconds.
|
|
*
|
|
* Normally, the minute has 60 seconds numbered 0-59. If the leap
|
|
* warning bit is set, the last minute (1439) of 30 June (day 181 or 182
|
|
* for leap years) or 31 December (day 365 or 366 for leap years) is
|
|
* augmented by one second numbered 60. This is accomplished by
|
|
* extending the minute interval by one second and teaching the state
|
|
* machine to ignore it.
|
|
*/
|
|
static void
|
|
wwv_rsec(
|
|
struct peer *peer, /* peer structure pointer */
|
|
double bit
|
|
)
|
|
{
|
|
static int iniflg; /* initialization flag */
|
|
static double bcddld[4]; /* BCD data bits */
|
|
static double bitvec[61]; /* bit integrator for misc bits */
|
|
struct refclockproc *pp;
|
|
struct wwvunit *up;
|
|
struct chan *cp;
|
|
struct sync *sp, *rp;
|
|
char tbuf[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;
|
|
up->rsec++;
|
|
bitvec[nsec] += (bit - bitvec[nsec]) / TCONST;
|
|
sw = progx[nsec].sw;
|
|
arg = progx[nsec].arg;
|
|
|
|
/*
|
|
* The minute state machine. Fly off to a particular section as
|
|
* directed by the transition matrix and second number.
|
|
*/
|
|
switch (sw) {
|
|
|
|
/*
|
|
* Ignore this second.
|
|
*/
|
|
case IDLE: /* 9, 45-49 */
|
|
break;
|
|
|
|
/*
|
|
* Probe channel stuff
|
|
*
|
|
* The WWV/H format contains data pulses in second 59 (position
|
|
* identifier) and second 1, but not in second 0. The minute
|
|
* sync pulse is contained in second 0. At the end of second 58
|
|
* QSY to the probe channel, which rotates in turn over all
|
|
* WWV/H frequencies. At the end of second 0 measure the minute
|
|
* sync pulse. At the end of second 1 measure the data pulse and
|
|
* QSY back to the data channel. Note that the actions commented
|
|
* here happen at the end of the second numbered as shown.
|
|
*
|
|
* At the end of second 0 save the minute sync amplitude latched
|
|
* at 800 ms as the signal later used to calculate the SNR.
|
|
*/
|
|
case SYNC2: /* 0 */
|
|
cp = &up->mitig[up->achan];
|
|
cp->wwv.synmax = cp->wwv.syneng;
|
|
cp->wwvh.synmax = cp->wwvh.syneng;
|
|
break;
|
|
|
|
/*
|
|
* At the end of second 1 use the minute sync amplitude latched
|
|
* at 800 ms as the noise to calculate the SNR. If the minute
|
|
* sync pulse and SNR are above thresholds and the data pulse
|
|
* amplitude and SNR are above thresolds, shift a 1 into the
|
|
* station reachability register; otherwise, shift a 0. The
|
|
* number of 1 bits in the last six intervals is a component of
|
|
* the channel metric computed by the wwv_metric() routine.
|
|
* Finally, QSY back to the data channel.
|
|
*/
|
|
case SYNC3: /* 1 */
|
|
cp = &up->mitig[up->achan];
|
|
|
|
/*
|
|
* WWV station
|
|
*/
|
|
sp = &cp->wwv;
|
|
sp->synsnr = wwv_snr(sp->synmax, sp->amp);
|
|
sp->reach <<= 1;
|
|
if (sp->reach & (1 << AMAX))
|
|
sp->count--;
|
|
if (sp->synmax >= QTHR && sp->synsnr >= QSNR &&
|
|
!(up->status & (DGATE | BGATE))) {
|
|
sp->reach |= 1;
|
|
sp->count++;
|
|
}
|
|
sp->metric = wwv_metric(sp);
|
|
|
|
/*
|
|
* WWVH station
|
|
*/
|
|
rp = &cp->wwvh;
|
|
rp->synsnr = wwv_snr(rp->synmax, rp->amp);
|
|
rp->reach <<= 1;
|
|
if (rp->reach & (1 << AMAX))
|
|
rp->count--;
|
|
if (rp->synmax >= QTHR && rp->synsnr >= QSNR &&
|
|
!(up->status & (DGATE | BGATE))) {
|
|
rp->reach |= 1;
|
|
rp->count++;
|
|
}
|
|
rp->metric = wwv_metric(rp);
|
|
if (pp->sloppyclockflag & CLK_FLAG4) {
|
|
sprintf(tbuf,
|
|
"wwv5 %04x %3d %4d %.0f/%.1f %.0f/%.1f %s %04x %.0f %.0f/%.1f %s %04x %.0f %.0f/%.1f",
|
|
up->status, up->gain, up->yepoch,
|
|
up->epomax, up->eposnr, up->datsig,
|
|
up->datsnr,
|
|
sp->refid, sp->reach & 0xffff,
|
|
sp->metric, sp->synmax, sp->synsnr,
|
|
rp->refid, rp->reach & 0xffff,
|
|
rp->metric, rp->synmax, rp->synsnr);
|
|
record_clock_stats(&peer->srcadr, tbuf);
|
|
#ifdef DEBUG
|
|
if (debug)
|
|
printf("%s\n", tbuf);
|
|
#endif /* DEBUG */
|
|
}
|
|
up->errcnt = up->digcnt = up->alarm = 0;
|
|
|
|
/*
|
|
* We now begin the minute scan. If not yet synchronized
|
|
* to a station, restart if the units digit has not been
|
|
* found within the DATA timeout (15 m) or if not
|
|
* synchronized within the SYNCH timeout (40 m). After
|
|
* synchronizing to a station, restart if no stations
|
|
* are found within the PANIC timeout (2 days).
|
|
*/
|
|
if (up->status & INSYNC) {
|
|
if (up->watch > PANIC) {
|
|
wwv_newgame(peer);
|
|
return;
|
|
}
|
|
} else {
|
|
if (!(up->status & DSYNC)) {
|
|
if (up->watch > DATA) {
|
|
wwv_newgame(peer);
|
|
return;
|
|
}
|
|
}
|
|
if (up->watch > SYNCH) {
|
|
wwv_newgame(peer);
|
|
return;
|
|
}
|
|
}
|
|
wwv_newchan(peer);
|
|
#ifdef ICOM
|
|
if (up->fd_icom > 0)
|
|
wwv_qsy(peer, up->dchan);
|
|
#endif /* ICOM */
|
|
break;
|
|
|
|
/*
|
|
* Save the bit probability in the BCD data vector at the index
|
|
* given by the argument. Bits not used in the digit are forced
|
|
* to zero.
|
|
*/
|
|
case COEF1: /* 4-7 */
|
|
bcddld[arg] = bit;
|
|
break;
|
|
|
|
case COEF: /* 10-13, 15-17, 20-23, 25-26,
|
|
30-33, 35-38, 40-41, 51-54 */
|
|
if (up->status & DSYNC)
|
|
bcddld[arg] = bit;
|
|
else
|
|
bcddld[arg] = 0;
|
|
break;
|
|
|
|
case COEF2: /* 18, 27-28, 42-43 */
|
|
bcddld[arg] = 0;
|
|
break;
|
|
|
|
/*
|
|
* Correlate coefficient vector with each valid digit vector and
|
|
* save in decoding matrix. We step through the decoding matrix
|
|
* digits correlating each with the coefficients and saving the
|
|
* greatest and the next lower for later SNR calculation.
|
|
*/
|
|
case DECIM2: /* 29 */
|
|
wwv_corr4(peer, &up->decvec[arg], bcddld, bcd2);
|
|
break;
|
|
|
|
case DECIM3: /* 44 */
|
|
wwv_corr4(peer, &up->decvec[arg], bcddld, bcd3);
|
|
break;
|
|
|
|
case DECIM6: /* 19 */
|
|
wwv_corr4(peer, &up->decvec[arg], bcddld, bcd6);
|
|
break;
|
|
|
|
case DECIM9: /* 8, 14, 24, 34, 39 */
|
|
wwv_corr4(peer, &up->decvec[arg], bcddld, bcd9);
|
|
break;
|
|
|
|
/*
|
|
* Miscellaneous bits. If above the positive threshold, declare
|
|
* 1; if below the negative threshold, declare 0; otherwise
|
|
* raise the BGATE bit. The design is intended to avoid
|
|
* integrating noise under low SNR conditions.
|
|
*/
|
|
case MSC20: /* 55 */
|
|
wwv_corr4(peer, &up->decvec[YR + 1], bcddld, bcd9);
|
|
/* fall through */
|
|
|
|
case MSCBIT: /* 2-3, 50, 56-57 */
|
|
if (bitvec[nsec] > BTHR) {
|
|
if (!(up->misc & arg))
|
|
up->alarm |= CMPERR;
|
|
up->misc |= arg;
|
|
} else if (bitvec[nsec] < -BTHR) {
|
|
if (up->misc & arg)
|
|
up->alarm |= CMPERR;
|
|
up->misc &= ~arg;
|
|
} else {
|
|
up->status |= BGATE;
|
|
}
|
|
break;
|
|
|
|
/*
|
|
* Save the data channel gain, then QSY to the probe channel and
|
|
* dim the seconds comb filters. The newchan() routine will
|
|
* light them back up.
|
|
*/
|
|
case MSC21: /* 58 */
|
|
if (bitvec[nsec] > BTHR) {
|
|
if (!(up->misc & arg))
|
|
up->alarm |= CMPERR;
|
|
up->misc |= arg;
|
|
} else if (bitvec[nsec] < -BTHR) {
|
|
if (up->misc & arg)
|
|
up->alarm |= CMPERR;
|
|
up->misc &= ~arg;
|
|
} else {
|
|
up->status |= BGATE;
|
|
}
|
|
up->status &= ~(SELV | SELH);
|
|
#ifdef ICOM
|
|
if (up->fd_icom > 0) {
|
|
up->schan = (up->schan + 1) % NCHAN;
|
|
wwv_qsy(peer, up->schan);
|
|
} else {
|
|
up->mitig[up->achan].gain = up->gain;
|
|
}
|
|
#else
|
|
up->mitig[up->achan].gain = up->gain;
|
|
#endif /* ICOM */
|
|
break;
|
|
|
|
/*
|
|
* The endgames
|
|
*
|
|
* During second 59 the receiver and codec AGC are settling
|
|
* down, so the data pulse is unusable as quality metric. If
|
|
* LEPSEC is set on the last minute of 30 June or 31 December,
|
|
* the transmitter and receiver insert an extra second (60) in
|
|
* the timescale and the minute sync repeats the second. Once
|
|
* leaps occurred at intervals of about 18 months, but the last
|
|
* leap before the most recent leap in 1995 was in 1998.
|
|
*/
|
|
case MIN1: /* 59 */
|
|
if (up->status & LEPSEC)
|
|
break;
|
|
|
|
/* fall through */
|
|
|
|
case MIN2: /* 60 */
|
|
up->status &= ~LEPSEC;
|
|
wwv_tsec(peer);
|
|
up->rsec = 0;
|
|
wwv_clock(peer);
|
|
break;
|
|
}
|
|
if ((pp->sloppyclockflag & CLK_FLAG4) && !(up->status &
|
|
DSYNC)) {
|
|
sprintf(tbuf,
|
|
"wwv3 %2d %04x %3d %4d %5.0f %5.1f %5.0f %5.1f %5.0f",
|
|
nsec, up->status, up->gain, up->yepoch, up->epomax,
|
|
up->eposnr, up->datsig, up->datsnr, bit);
|
|
record_clock_stats(&peer->srcadr, tbuf);
|
|
#ifdef DEBUG
|
|
if (debug)
|
|
printf("%s\n", tbuf);
|
|
#endif /* DEBUG */
|
|
}
|
|
pp->disp += AUDIO_PHI;
|
|
}
|
|
|
|
/*
|
|
* The radio clock is set if the alarm bits are all zero. After that,
|
|
* the time is considered valid if the second sync bit is lit. It should
|
|
* not be a surprise, especially if the radio is not tunable, that
|
|
* sometimes no stations are above the noise and the integrators
|
|
* discharge below the thresholds. We assume that, after a day of signal
|
|
* loss, the minute sync epoch will be in the same second. This requires
|
|
* the codec frequency be accurate within 6 PPM. Practical experience
|
|
* shows the frequency typically within 0.1 PPM, so after a day of
|
|
* signal loss, the time should be within 8.6 ms..
|
|
*/
|
|
static void
|
|
wwv_clock(
|
|
struct peer *peer /* peer unit pointer */
|
|
)
|
|
{
|
|
struct refclockproc *pp;
|
|
struct wwvunit *up;
|
|
l_fp offset; /* offset in NTP seconds */
|
|
|
|
pp = peer->procptr;
|
|
up = (struct wwvunit *)pp->unitptr;
|
|
if (!(up->status & SSYNC))
|
|
up->alarm |= SYNERR;
|
|
if (up->digcnt < 9)
|
|
up->alarm |= NINERR;
|
|
if (!(up->alarm))
|
|
up->status |= INSYNC;
|
|
if (up->status & INSYNC && up->status & SSYNC) {
|
|
if (up->misc & SECWAR)
|
|
pp->leap = LEAP_ADDSECOND;
|
|
else
|
|
pp->leap = LEAP_NOWARNING;
|
|
pp->second = up->rsec;
|
|
pp->minute = up->decvec[MN].digit + up->decvec[MN +
|
|
1].digit * 10;
|
|
pp->hour = up->decvec[HR].digit + up->decvec[HR +
|
|
1].digit * 10;
|
|
pp->day = up->decvec[DA].digit + up->decvec[DA +
|
|
1].digit * 10 + up->decvec[DA + 2].digit * 100;
|
|
pp->year = up->decvec[YR].digit + up->decvec[YR +
|
|
1].digit * 10;
|
|
pp->year += 2000;
|
|
L_CLR(&offset);
|
|
if (!clocktime(pp->day, pp->hour, pp->minute,
|
|
pp->second, GMT, up->timestamp.l_ui,
|
|
&pp->yearstart, &offset.l_ui)) {
|
|
up->errflg = CEVNT_BADTIME;
|
|
} else {
|
|
up->watch = 0;
|
|
pp->disp = 0;
|
|
pp->lastref = up->timestamp;
|
|
refclock_process_offset(pp, offset,
|
|
up->timestamp, PDELAY);
|
|
refclock_receive(peer);
|
|
}
|
|
}
|
|
pp->lencode = timecode(up, pp->a_lastcode);
|
|
record_clock_stats(&peer->srcadr, pp->a_lastcode);
|
|
#ifdef DEBUG
|
|
if (debug)
|
|
printf("wwv: timecode %d %s\n", pp->lencode,
|
|
pp->a_lastcode);
|
|
#endif /* DEBUG */
|
|
}
|
|
|
|
|
|
/*
|
|
* wwv_corr4 - determine maximum likelihood digit
|
|
*
|
|
* This routine correlates the received digit vector with the BCD
|
|
* coefficient vectors corresponding to all valid digits at the given
|
|
* position in the decoding matrix. The maximum value corresponds to the
|
|
* maximum likelihood digit, while the ratio of this value to the next
|
|
* lower value determines the likelihood function. Note that, if the
|
|
* digit is invalid, the likelihood vector is averaged toward a miss.
|
|
*/
|
|
static void
|
|
wwv_corr4(
|
|
struct peer *peer, /* peer unit pointer */
|
|
struct decvec *vp, /* decoding table pointer */
|
|
double data[], /* received data vector */
|
|
double tab[][4] /* correlation vector array */
|
|
)
|
|
{
|
|
struct refclockproc *pp;
|
|
struct wwvunit *up;
|
|
double topmax, nxtmax; /* metrics */
|
|
double acc; /* accumulator */
|
|
char tbuf[80]; /* monitor buffer */
|
|
int mldigit; /* max likelihood digit */
|
|
int i, j;
|
|
|
|
pp = peer->procptr;
|
|
up = (struct wwvunit *)pp->unitptr;
|
|
|
|
/*
|
|
* Correlate digit vector with each BCD coefficient vector. If
|
|
* any BCD digit bit is bad, consider all bits a miss. Until the
|
|
* minute units digit has been resolved, don't to anything else.
|
|
* Note the SNR is calculated as the ratio of the largest
|
|
* likelihood value to the next largest likelihood value.
|
|
*/
|
|
mldigit = 0;
|
|
topmax = nxtmax = -MAXAMP;
|
|
for (i = 0; tab[i][0] != 0; i++) {
|
|
acc = 0;
|
|
for (j = 0; j < 4; j++)
|
|
acc += data[j] * tab[i][j];
|
|
acc = (vp->like[i] += (acc - vp->like[i]) / TCONST);
|
|
if (acc > topmax) {
|
|
nxtmax = topmax;
|
|
topmax = acc;
|
|
mldigit = i;
|
|
} else if (acc > nxtmax) {
|
|
nxtmax = acc;
|
|
}
|
|
}
|
|
vp->digprb = topmax;
|
|
vp->digsnr = wwv_snr(topmax, nxtmax);
|
|
|
|
/*
|
|
* The current maximum likelihood digit is compared to the last
|
|
* maximum likelihood digit. If different, the compare counter
|
|
* and maximum likelihood digit are reset. When the compare
|
|
* counter reaches the BCMP threshold (3), the digit is assumed
|
|
* correct. When the compare counter of all nine digits have
|
|
* reached threshold, the clock is assumed correct.
|
|
*
|
|
* Note that the clock display digit is set before the compare
|
|
* counter has reached threshold; however, the clock display is
|
|
* not considered correct until all nine clock digits have
|
|
* reached threshold. This is intended as eye candy, but avoids
|
|
* mistakes when the signal is low and the SNR is very marginal.
|
|
* once correctly set, the maximum likelihood digit is ignored
|
|
* on the assumption the clock will always be correct unless for
|
|
* some reason it drifts to a different second.
|
|
*/
|
|
vp->mldigit = mldigit;
|
|
if (vp->digprb < BTHR || vp->digsnr < BSNR) {
|
|
vp->count = 0;
|
|
up->status |= BGATE;
|
|
} else {
|
|
up->status |= DSYNC;
|
|
if (vp->digit != mldigit) {
|
|
vp->count = 0;
|
|
up->alarm |= CMPERR;
|
|
if (!(up->status & INSYNC))
|
|
vp->digit = mldigit;
|
|
} else {
|
|
if (vp->count < BCMP)
|
|
vp->count++;
|
|
else
|
|
up->digcnt++;
|
|
}
|
|
}
|
|
if ((pp->sloppyclockflag & CLK_FLAG4) && !(up->status &
|
|
INSYNC)) {
|
|
sprintf(tbuf,
|
|
"wwv4 %2d %04x %3d %4d %5.0f %2d %d %d %d %5.0f %5.1f",
|
|
up->rsec - 1, up->status, up->gain, up->yepoch,
|
|
up->epomax, vp->radix, vp->digit, vp->mldigit,
|
|
vp->count, vp->digprb, vp->digsnr);
|
|
record_clock_stats(&peer->srcadr, tbuf);
|
|
#ifdef DEBUG
|
|
if (debug)
|
|
printf("%s\n", tbuf);
|
|
#endif /* DEBUG */
|
|
}
|
|
}
|
|
|
|
|
|
/*
|
|
* wwv_tsec - transmitter minute processing
|
|
*
|
|
* This routine is called at the end of the transmitter minute. It
|
|
* implements a state machine that advances the logical clock subject to
|
|
* the funny rules that govern the conventional clock and calendar.
|
|
*/
|
|
static void
|
|
wwv_tsec(
|
|
struct peer *peer /* driver structure pointer */
|
|
)
|
|
{
|
|
struct refclockproc *pp;
|
|
struct wwvunit *up;
|
|
int minute, day, isleap;
|
|
int temp;
|
|
|
|
pp = peer->procptr;
|
|
up = (struct wwvunit *)pp->unitptr;
|
|
|
|
/*
|
|
* Advance minute unit of the day. Don't propagate carries until
|
|
* the unit minute digit has been found.
|
|
*/
|
|
temp = carry(&up->decvec[MN]); /* minute units */
|
|
if (!(up->status & DSYNC))
|
|
return;
|
|
|
|
/*
|
|
* Propagate carries through the day.
|
|
*/
|
|
if (temp == 0) /* carry minutes */
|
|
temp = carry(&up->decvec[MN + 1]);
|
|
if (temp == 0) /* carry hours */
|
|
temp = carry(&up->decvec[HR]);
|
|
if (temp == 0)
|
|
temp = carry(&up->decvec[HR + 1]);
|
|
|
|
/*
|
|
* Decode the current minute and day. Set leap day if the
|
|
* timecode leap bit is set on 30 June or 31 December. Set leap
|
|
* minute if the last minute on leap day, but only if the clock
|
|
* is syncrhronized. This code fails in 2400 AD.
|
|
*/
|
|
minute = up->decvec[MN].digit + up->decvec[MN + 1].digit *
|
|
10 + up->decvec[HR].digit * 60 + up->decvec[HR +
|
|
1].digit * 600;
|
|
day = up->decvec[DA].digit + up->decvec[DA + 1].digit * 10 +
|
|
up->decvec[DA + 2].digit * 100;
|
|
|
|
/*
|
|
* Set the leap bit on the last minute of the leap day.
|
|
*/
|
|
isleap = up->decvec[YR].digit & 0x3;
|
|
if (up->misc & SECWAR && up->status & INSYNC) {
|
|
if ((day == (isleap ? 182 : 183) || day == (isleap ?
|
|
365 : 366)) && minute == 1439)
|
|
up->status |= LEPSEC;
|
|
}
|
|
|
|
/*
|
|
* Roll the day if this the first minute and propagate carries
|
|
* through the year.
|
|
*/
|
|
if (minute != 1440)
|
|
return;
|
|
|
|
minute = 0;
|
|
while (carry(&up->decvec[HR]) != 0); /* advance to minute 0 */
|
|
while (carry(&up->decvec[HR + 1]) != 0);
|
|
day++;
|
|
temp = carry(&up->decvec[DA]); /* carry days */
|
|
if (temp == 0)
|
|
temp = carry(&up->decvec[DA + 1]);
|
|
if (temp == 0)
|
|
temp = carry(&up->decvec[DA + 2]);
|
|
|
|
/*
|
|
* Roll the year if this the first day and propagate carries
|
|
* through the century.
|
|
*/
|
|
if (day != (isleap ? 365 : 366))
|
|
return;
|
|
|
|
day = 1;
|
|
while (carry(&up->decvec[DA]) != 1); /* advance to day 1 */
|
|
while (carry(&up->decvec[DA + 1]) != 0);
|
|
while (carry(&up->decvec[DA + 2]) != 0);
|
|
temp = carry(&up->decvec[YR]); /* carry years */
|
|
if (temp == 0)
|
|
carry(&up->decvec[YR + 1]);
|
|
}
|
|
|
|
|
|
/*
|
|
* carry - process digit
|
|
*
|
|
* This routine rotates a likelihood vector one position and increments
|
|
* the clock digit modulo the radix. It returns the new clock digit or
|
|
* zero if a carry occurred. Once synchronized, the clock digit will
|
|
* match the maximum likelihood digit corresponding to that position.
|
|
*/
|
|
static int
|
|
carry(
|
|
struct decvec *dp /* decoding table pointer */
|
|
)
|
|
{
|
|
int temp;
|
|
int j;
|
|
|
|
dp->digit++;
|
|
if (dp->digit == dp->radix)
|
|
dp->digit = 0;
|
|
temp = dp->like[dp->radix - 1];
|
|
for (j = dp->radix - 1; j > 0; j--)
|
|
dp->like[j] = dp->like[j - 1];
|
|
dp->like[0] = temp;
|
|
return (dp->digit);
|
|
}
|
|
|
|
|
|
/*
|
|
* wwv_snr - compute SNR or likelihood function
|
|
*/
|
|
static double
|
|
wwv_snr(
|
|
double signal, /* signal */
|
|
double noise /* noise */
|
|
)
|
|
{
|
|
double rval;
|
|
|
|
/*
|
|
* This is a little tricky. Due to the way things are measured,
|
|
* either or both the signal or noise amplitude can be negative
|
|
* or zero. The intent is that, if the signal is negative or
|
|
* zero, the SNR must always be zero. This can happen with the
|
|
* subcarrier SNR before the phase has been aligned. On the
|
|
* other hand, in the likelihood function the "noise" is the
|
|
* next maximum down from the peak and this could be negative.
|
|
* However, in this case the SNR is truly stupendous, so we
|
|
* simply cap at MAXSNR dB (40).
|
|
*/
|
|
if (signal <= 0) {
|
|
rval = 0;
|
|
} else if (noise <= 0) {
|
|
rval = MAXSNR;
|
|
} else {
|
|
rval = 20. * log10(signal / noise);
|
|
if (rval > MAXSNR)
|
|
rval = MAXSNR;
|
|
}
|
|
return (rval);
|
|
}
|
|
|
|
|
|
/*
|
|
* wwv_newchan - change to new data channel
|
|
*
|
|
* The radio actually appears to have ten channels, one channel for each
|
|
* of five frequencies and each of two stations (WWV and WWVH), although
|
|
* if not tunable only the DCHAN channel appears live. While the radio
|
|
* is tuned to the working data channel frequency and station for most
|
|
* of the minute, during seconds 59, 0 and 1 the radio is tuned to a
|
|
* probe frequency in order to search for minute sync pulse and data
|
|
* subcarrier from other transmitters.
|
|
*
|
|
* The search for WWV and WWVH operates simultaneously, with WWV minute
|
|
* sync pulse at 1000 Hz and WWVH at 1200 Hz. The probe frequency
|
|
* rotates each minute over 2.5, 5, 10, 15 and 20 MHz in order and yes,
|
|
* we all know WWVH is dark on 20 MHz, but few remember when WWV was lit
|
|
* on 25 MHz.
|
|
*
|
|
* This routine selects the best channel using a metric computed from
|
|
* the reachability register and minute pulse amplitude. Normally, the
|
|
* award goes to the the channel with the highest metric; but, in case
|
|
* of ties, the award goes to the channel with the highest minute sync
|
|
* pulse amplitude and then to the highest frequency.
|
|
*
|
|
* The routine performs an important squelch function to keep dirty data
|
|
* from polluting the integrators. In order to consider a station valid,
|
|
* the metric must be at least MTHR (13); otherwise, the station select
|
|
* bits are cleared so the second sync is disabled and the data bit
|
|
* integrators averaged to a miss.
|
|
*/
|
|
static int
|
|
wwv_newchan(
|
|
struct peer *peer /* peer structure pointer */
|
|
)
|
|
{
|
|
struct refclockproc *pp;
|
|
struct wwvunit *up;
|
|
struct sync *sp, *rp;
|
|
double rank, dtemp;
|
|
int i, j;
|
|
|
|
pp = peer->procptr;
|
|
up = (struct wwvunit *)pp->unitptr;
|
|
|
|
/*
|
|
* Search all five station pairs looking for the channel with
|
|
* maximum metric. If no station is found above thresholds, tune
|
|
* to WWV on 15 MHz, set the reference ID to NONE and wait for
|
|
* hotter ions.
|
|
*/
|
|
sp = NULL;
|
|
j = 0;
|
|
rank = 0;
|
|
for (i = 0; i < NCHAN; i++) {
|
|
rp = &up->mitig[i].wwvh;
|
|
dtemp = rp->metric;
|
|
if (dtemp >= rank) {
|
|
rank = dtemp;
|
|
sp = rp;
|
|
j = i;
|
|
}
|
|
rp = &up->mitig[i].wwv;
|
|
dtemp = rp->metric;
|
|
if (dtemp >= rank) {
|
|
rank = dtemp;
|
|
sp = rp;
|
|
j = i;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* If the strongest signal is less than the MTHR threshold (13),
|
|
* we are beneath the waves, so squelch the second sync. If the
|
|
* strongest signal is greater than the threshold, tune to that
|
|
* frequency and transmitter QTH.
|
|
*/
|
|
if (rank < MTHR) {
|
|
up->dchan = (up->dchan + 1) % NCHAN;
|
|
up->status &= ~(SELV | SELH);
|
|
return (FALSE);
|
|
}
|
|
up->dchan = j;
|
|
up->status |= SELV | SELH;
|
|
up->sptr = sp;
|
|
memcpy(&pp->refid, sp->refid, 4);
|
|
peer->refid = pp->refid;
|
|
return (TRUE);
|
|
}
|
|
|
|
|
|
/*
|
|
* wwv_newgame - reset and start over
|
|
*
|
|
* There are four conditions resulting in a new game:
|
|
*
|
|
* 1 During initial acquisition (MSYNC dark) going 6 minutes (ACQSN)
|
|
* without reliably finding the minute pulse (MSYNC lit).
|
|
*
|
|
* 2 After finding the minute pulse (MSYNC lit), going 15 minutes
|
|
* (DATA) without finding the unit seconds digit.
|
|
*
|
|
* 3 After finding good data (DATA lit), going more than 40 minutes
|
|
* (SYNCH) without finding station sync (INSYNC lit).
|
|
*
|
|
* 4 After finding station sync (INSYNC lit), going more than 2 days
|
|
* (PANIC) without finding any station.
|
|
*/
|
|
static void
|
|
wwv_newgame(
|
|
struct peer *peer /* peer structure pointer */
|
|
)
|
|
{
|
|
struct refclockproc *pp;
|
|
struct wwvunit *up;
|
|
struct chan *cp;
|
|
int i;
|
|
|
|
pp = peer->procptr;
|
|
up = (struct wwvunit *)pp->unitptr;
|
|
|
|
/*
|
|
* Initialize strategic values. Note we set the leap bits
|
|
* NOTINSYNC and the refid "NONE".
|
|
*/
|
|
peer->leap = LEAP_NOTINSYNC;
|
|
up->watch = up->status = up->alarm = 0;
|
|
up->avgint = MINAVG;
|
|
up->freq = 0;
|
|
up->gain = MAXGAIN / 2;
|
|
|
|
/*
|
|
* Initialize the station processes for audio gain, select bit,
|
|
* station/frequency identifier and reference identifier. Start
|
|
* probing at the next channel after the data channel.
|
|
*/
|
|
memset(up->mitig, 0, sizeof(up->mitig));
|
|
for (i = 0; i < NCHAN; i++) {
|
|
cp = &up->mitig[i];
|
|
cp->gain = up->gain;
|
|
cp->wwv.select = SELV;
|
|
sprintf(cp->wwv.refid, "WV%.0f", floor(qsy[i]));
|
|
cp->wwvh.select = SELH;
|
|
sprintf(cp->wwvh.refid, "WH%.0f", floor(qsy[i]));
|
|
}
|
|
up->dchan = (DCHAN + NCHAN - 1) % NCHAN;;
|
|
wwv_newchan(peer);
|
|
up->achan = up->schan = up->dchan;
|
|
#ifdef ICOM
|
|
if (up->fd_icom > 0)
|
|
wwv_qsy(peer, up->dchan);
|
|
#endif /* ICOM */
|
|
}
|
|
|
|
/*
|
|
* wwv_metric - compute station metric
|
|
*
|
|
* The most significant bits represent the number of ones in the
|
|
* station reachability register. The least significant bits represent
|
|
* the minute sync pulse amplitude. The combined value is scaled 0-100.
|
|
*/
|
|
double
|
|
wwv_metric(
|
|
struct sync *sp /* station pointer */
|
|
)
|
|
{
|
|
double dtemp;
|
|
|
|
dtemp = sp->count * MAXAMP;
|
|
if (sp->synmax < MAXAMP)
|
|
dtemp += sp->synmax;
|
|
else
|
|
dtemp += MAXAMP - 1;
|
|
dtemp /= (AMAX + 1) * MAXAMP;
|
|
return (dtemp * 100.);
|
|
}
|
|
|
|
|
|
#ifdef ICOM
|
|
/*
|
|
* wwv_qsy - Tune ICOM receiver
|
|
*
|
|
* This routine saves the AGC for the current channel, switches to a new
|
|
* channel and restores the AGC for that channel. If a tunable receiver
|
|
* is not available, just fake it.
|
|
*/
|
|
static int
|
|
wwv_qsy(
|
|
struct peer *peer, /* peer structure pointer */
|
|
int chan /* channel */
|
|
)
|
|
{
|
|
int rval = 0;
|
|
struct refclockproc *pp;
|
|
struct wwvunit *up;
|
|
|
|
pp = peer->procptr;
|
|
up = (struct wwvunit *)pp->unitptr;
|
|
if (up->fd_icom > 0) {
|
|
up->mitig[up->achan].gain = up->gain;
|
|
rval = icom_freq(up->fd_icom, peer->ttl & 0x7f,
|
|
qsy[chan]);
|
|
up->achan = chan;
|
|
up->gain = up->mitig[up->achan].gain;
|
|
}
|
|
return (rval);
|
|
}
|
|
#endif /* ICOM */
|
|
|
|
|
|
/*
|
|
* timecode - assemble timecode string and length
|
|
*
|
|
* Prettytime format - similar to Spectracom
|
|
*
|
|
* sq yy ddd hh:mm:ss ld dut lset agc iden sig errs freq avgt
|
|
*
|
|
* s sync indicator ('?' or ' ')
|
|
* q error bits (hex 0-F)
|
|
* yyyy year of century
|
|
* ddd day of year
|
|
* hh hour of day
|
|
* mm minute of hour
|
|
* ss second of minute)
|
|
* l leap second warning (' ' or 'L')
|
|
* d DST state ('S', 'D', 'I', or 'O')
|
|
* dut DUT sign and magnitude (0.1 s)
|
|
* lset minutes since last clock update
|
|
* agc audio gain (0-255)
|
|
* iden reference identifier (station and frequency)
|
|
* sig signal quality (0-100)
|
|
* errs bit errors in last minute
|
|
* freq frequency offset (PPM)
|
|
* avgt averaging time (s)
|
|
*/
|
|
static int
|
|
timecode(
|
|
struct wwvunit *up, /* driver structure pointer */
|
|
char *ptr /* target string */
|
|
)
|
|
{
|
|
struct sync *sp;
|
|
int year, day, hour, minute, second, dut;
|
|
char synchar, leapchar, dst;
|
|
char cptr[50];
|
|
|
|
|
|
/*
|
|
* Common fixed-format fields
|
|
*/
|
|
synchar = (up->status & INSYNC) ? ' ' : '?';
|
|
year = up->decvec[YR].digit + up->decvec[YR + 1].digit * 10 +
|
|
2000;
|
|
day = up->decvec[DA].digit + up->decvec[DA + 1].digit * 10 +
|
|
up->decvec[DA + 2].digit * 100;
|
|
hour = up->decvec[HR].digit + up->decvec[HR + 1].digit * 10;
|
|
minute = up->decvec[MN].digit + up->decvec[MN + 1].digit * 10;
|
|
second = 0;
|
|
leapchar = (up->misc & SECWAR) ? 'L' : ' ';
|
|
dst = dstcod[(up->misc >> 4) & 0x3];
|
|
dut = up->misc & 0x7;
|
|
if (!(up->misc & DUTS))
|
|
dut = -dut;
|
|
sprintf(ptr, "%c%1X", synchar, up->alarm);
|
|
sprintf(cptr, " %4d %03d %02d:%02d:%02d %c%c %+d",
|
|
year, day, hour, minute, second, leapchar, dst, dut);
|
|
strcat(ptr, cptr);
|
|
|
|
/*
|
|
* Specific variable-format fields
|
|
*/
|
|
sp = up->sptr;
|
|
sprintf(cptr, " %d %d %s %.0f %d %.1f %d", up->watch,
|
|
up->mitig[up->dchan].gain, sp->refid, sp->metric,
|
|
up->errcnt, up->freq / SECOND * 1e6, up->avgint);
|
|
strcat(ptr, cptr);
|
|
return (strlen(ptr));
|
|
}
|
|
|
|
|
|
/*
|
|
* wwv_gain - adjust codec gain
|
|
*
|
|
* This routine is called at the end of each second. During the second
|
|
* the number of signal clips above the MAXAMP threshold (6000). If
|
|
* there are no clips, the gain is bumped up; if there are more than
|
|
* MAXCLP clips (100), it is bumped down. The decoder is relatively
|
|
* insensitive to amplitude, so this crudity works just peachy. The
|
|
* 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 > MAXGAIN)
|
|
up->gain = MAXGAIN;
|
|
} else if (up->clipcnt > MAXCLP) {
|
|
up->gain -= 4;
|
|
if (up->gain < 0)
|
|
up->gain = 0;
|
|
}
|
|
audio_gain(up->gain, up->mongain, up->port);
|
|
up->clipcnt = 0;
|
|
#if DEBUG
|
|
if (debug > 1)
|
|
audio_show();
|
|
#endif
|
|
}
|
|
|
|
|
|
#else
|
|
int refclock_wwv_bs;
|
|
#endif /* REFCLOCK */
|