1: /*
2: * refclock_chu - clock driver for Canadian CHU time/frequency station
3: */
4: #ifdef HAVE_CONFIG_H
5: #include <config.h>
6: #endif
7:
8: #if defined(REFCLOCK) && defined(CLOCK_CHU)
9:
10: #include "ntpd.h"
11: #include "ntp_io.h"
12: #include "ntp_refclock.h"
13: #include "ntp_calendar.h"
14: #include "ntp_stdlib.h"
15:
16: #include <stdio.h>
17: #include <ctype.h>
18: #include <math.h>
19:
20: #ifdef HAVE_AUDIO
21: #include "audio.h"
22: #endif /* HAVE_AUDIO */
23:
24: #define ICOM 1 /* undefine to suppress ICOM code */
25:
26: #ifdef ICOM
27: #include "icom.h"
28: #endif /* ICOM */
29: /*
30: * Audio CHU demodulator/decoder
31: *
32: * This driver synchronizes the computer time using data encoded in
33: * radio transmissions from Canadian time/frequency station CHU in
34: * Ottawa, Ontario. Transmissions are made continuously on 3330 kHz,
35: * 7850 kHz and 14670 kHz in upper sideband, compatible AM mode. An
36: * ordinary shortwave receiver can be tuned manually to one of these
37: * frequencies or, in the case of ICOM receivers, the receiver can be
38: * tuned automatically as propagation conditions change throughout the
39: * day and season.
40: *
41: * The driver requires an audio codec or sound card with sampling rate 8
42: * kHz and mu-law companding. This is the same standard as used by the
43: * telephone industry and is supported by most hardware and operating
44: * systems, including Solaris, SunOS, FreeBSD, NetBSD and Linux. In this
45: * implementation, only one audio driver and codec can be supported on a
46: * single machine.
47: *
48: * The driver can be compiled to use a Bell 103 compatible modem or
49: * modem chip to receive the radio signal and demodulate the data.
50: * Alternatively, the driver can be compiled to use the audio codec of
51: * the workstation or another with compatible audio drivers. In the
52: * latter case, the driver implements the modem using DSP routines, so
53: * the radio can be connected directly to either the microphone on line
54: * input port. In either case, the driver decodes the data using a
55: * maximum-likelihood technique which exploits the considerable degree
56: * of redundancy available to maximize accuracy and minimize errors.
57: *
58: * The CHU time broadcast includes an audio signal compatible with the
59: * Bell 103 modem standard (mark = 2225 Hz, space = 2025 Hz). The signal
60: * consists of nine, ten-character bursts transmitted at 300 bps between
61: * seconds 31 and 39 of each minute. Each character consists of eight
62: * data bits plus one start bit and two stop bits to encode two hex
63: * digits. The burst data consist of five characters (ten hex digits)
64: * followed by a repeat of these characters. In format A, the characters
65: * are repeated in the same polarity; in format B, the characters are
66: * repeated in the opposite polarity.
67: *
68: * Format A bursts are sent at seconds 32 through 39 of the minute in
69: * hex digits (nibble swapped)
70: *
71: * 6dddhhmmss6dddhhmmss
72: *
73: * The first ten digits encode a frame marker (6) followed by the day
74: * (ddd), hour (hh in UTC), minute (mm) and the second (ss). Since
75: * format A bursts are sent during the third decade of seconds the tens
76: * digit of ss is always 3. The driver uses this to determine correct
77: * burst synchronization. These digits are then repeated with the same
78: * polarity.
79: *
80: * Format B bursts are sent at second 31 of the minute in hex digits
81: *
82: * xdyyyyttaaxdyyyyttaa
83: *
84: * The first ten digits encode a code (x described below) followed by
85: * the DUT1 (d in deciseconds), Gregorian year (yyyy), difference TAI -
86: * UTC (tt) and daylight time indicator (aa) peculiar to Canada. These
87: * digits are then repeated with inverted polarity.
88: *
89: * The x is coded
90: *
91: * 1 Sign of DUT (0 = +)
92: * 2 Leap second warning. One second will be added.
93: * 4 Leap second warning. One second will be subtracted.
94: * 8 Even parity bit for this nibble.
95: *
96: * By design, the last stop bit of the last character in the burst
97: * coincides with 0.5 second. Since characters have 11 bits and are
98: * transmitted at 300 bps, the last stop bit of the first character
99: * coincides with 0.5 - 9 * 11/300 = 0.170 second. Depending on the
100: * UART, character interrupts can vary somewhere between the end of bit
101: * 9 and end of bit 11. These eccentricities can be corrected along with
102: * the radio propagation delay using fudge time 1.
103: *
104: * Debugging aids
105: *
106: * The timecode format used for debugging and data recording includes
107: * data helpful in diagnosing problems with the radio signal and serial
108: * connections. With debugging enabled (-d on the ntpd command line),
109: * the driver produces one line for each burst in two formats
110: * corresponding to format A and B.Each line begins with the format code
111: * chuA or chuB followed by the status code and signal level (0-9999).
112: * The remainder of the line is as follows.
113: *
114: * Following is format A:
115: *
116: * n b f s m code
117: *
118: * where n is the number of characters in the burst (0-10), b the burst
119: * distance (0-40), f the field alignment (-1, 0, 1), s the
120: * synchronization distance (0-16), m the burst number (2-9) and code
121: * the burst characters as received. Note that the hex digits in each
122: * character are reversed, so the burst
123: *
124: * 10 38 0 16 9 06851292930685129293
125: *
126: * is interpreted as containing 10 characters with burst distance 38,
127: * field alignment 0, synchronization distance 16 and burst number 9.
128: * The nibble-swapped timecode shows day 58, hour 21, minute 29 and
129: * second 39.
130: *
131: * Following is format B:
132: *
133: * n b s code
134: *
135: * where n is the number of characters in the burst (0-10), b the burst
136: * distance (0-40), s the synchronization distance (0-40) and code the
137: * burst characters as received. Note that the hex digits in each
138: * character are reversed and the last ten digits inverted, so the burst
139: *
140: * 10 40 1091891300ef6e76ec
141: *
142: * is interpreted as containing 10 characters with burst distance 40.
143: * The nibble-swapped timecode shows DUT1 +0.1 second, year 1998 and TAI
144: * - UTC 31 seconds.
145: *
146: * Each line is preceeded by the code chuA or chuB, as appropriate. If
147: * the audio driver is compiled, the current gain (0-255) and relative
148: * signal level (0-9999) follow the code. The receiver volume control
149: * should be set so that the gain is somewhere near the middle of the
150: * range 0-255, which results in a signal level near 1000.
151: *
152: * In addition to the above, the reference timecode is updated and
153: * written to the clockstats file and debug score after the last burst
154: * received in the minute. The format is
155: *
156: * sq yyyy ddd hh:mm:ss l s dd t agc ident m b
157: *
158: * s '?' before first synchronized and ' ' after that
159: * q status code (see below)
160: * yyyy year
161: * ddd day of year
162: * hh:mm:ss time of day
163: * l leap second indicator (space, L or D)
164: * dst Canadian daylight code (opaque)
165: * t number of minutes since last synchronized
166: * agc audio gain (0 - 255)
167: * ident identifier (CHU0 3330 kHz, CHU1 7850 kHz, CHU2 14670 kHz)
168: * m signal metric (0 - 100)
169: * b number of timecodes for the previous minute (0 - 59)
170: *
171: * Fudge factors
172: *
173: * For accuracies better than the low millisceconds, fudge time1 can be
174: * set to the radio propagation delay from CHU to the receiver. This can
175: * be done conviently using the minimuf program.
176: *
177: * Fudge flag4 causes the dubugging output described above to be
178: * recorded in the clockstats file. When the audio driver is compiled,
179: * fudge flag2 selects the audio input port, where 0 is the mike port
180: * (default) and 1 is the line-in port. It does not seem useful to
181: * select the compact disc player port. Fudge flag3 enables audio
182: * monitoring of the input signal. For this purpose, the monitor gain is
183: * set to a default value.
184: *
185: * The audio codec code is normally compiled in the driver if the
186: * architecture supports it (HAVE_AUDIO defined), but is used only if
187: * the link /dev/chu_audio is defined and valid. The serial port code is
188: * always compiled in the driver, but is used only if the autdio codec
189: * is not available and the link /dev/chu%d is defined and valid.
190: *
191: * The ICOM code is normally compiled in the driver if selected (ICOM
192: * defined), but is used only if the link /dev/icom%d is defined and
193: * valid and the mode keyword on the server configuration command
194: * specifies a nonzero mode (ICOM ID select code). The C-IV speed is
195: * 9600 bps if the high order 0x80 bit of the mode is zero and 1200 bps
196: * if one. The C-IV trace is turned on if the debug level is greater
197: * than one.
198: *
199: * Alarm codes
200: *
201: * CEVNT_BADTIME invalid date or time
202: * CEVNT_PROP propagation failure - no stations heard
203: */
204: /*
205: * Interface definitions
206: */
207: #define SPEED232 B300 /* uart speed (300 baud) */
208: #define PRECISION (-10) /* precision assumed (about 1 ms) */
209: #define REFID "CHU" /* reference ID */
210: #define DEVICE "/dev/chu%d" /* device name and unit */
211: #define SPEED232 B300 /* UART speed (300 baud) */
212: #ifdef ICOM
213: #define TUNE .001 /* offset for narrow filter (MHz) */
214: #define DWELL 5 /* minutes in a dwell */
215: #define NCHAN 3 /* number of channels */
216: #define ISTAGE 3 /* number of integrator stages */
217: #endif /* ICOM */
218:
219: #ifdef HAVE_AUDIO
220: /*
221: * Audio demodulator definitions
222: */
223: #define SECOND 8000 /* nominal sample rate (Hz) */
224: #define BAUD 300 /* modulation rate (bps) */
225: #define OFFSET 128 /* companded sample offset */
226: #define SIZE 256 /* decompanding table size */
227: #define MAXAMP 6000. /* maximum signal level */
228: #define MAXCLP 100 /* max clips above reference per s */
229: #define SPAN 800. /* min envelope span */
230: #define LIMIT 1000. /* soft limiter threshold */
231: #define AGAIN 6. /* baseband gain */
232: #define LAG 10 /* discriminator lag */
233: #define DEVICE_AUDIO "/dev/audio" /* device name */
234: #define DESCRIPTION "CHU Audio/Modem Receiver" /* WRU */
235: #define AUDIO_BUFSIZ 240 /* audio buffer size (30 ms) */
236: #else
237: #define DESCRIPTION "CHU Modem Receiver" /* WRU */
238: #endif /* HAVE_AUDIO */
239:
240: /*
241: * Decoder definitions
242: */
243: #define CHAR (11. / 300.) /* character time (s) */
244: #define BURST 11 /* max characters per burst */
245: #define MINCHAR 9 /* min characters per burst */
246: #define MINDIST 28 /* min burst distance (of 40) */
247: #define MINSYNC 8 /* min sync distance (of 16) */
248: #define MINSTAMP 20 /* min timestamps (of 60) */
249: #define MINMETRIC 50 /* min channel metric (of 160) */
250:
251: /*
252: * The on-time synchronization point for the driver is the last stop bit
253: * of the first character 170 ms. The modem delay is 0.8 ms, while the
254: * receiver delay is approxmately 4.7 ms at 2125 Hz. The fudge value 1.3
255: * ms due to the codec and other causes was determined by calibrating to
256: * a PPS signal from a GPS receiver. The additional propagation delay
257: * specific to each receiver location can be programmed in the fudge
258: * time1.
259: *
260: * The resulting offsets with a 2.4-GHz P4 running FreeBSD 6.1 are
261: * generally within 0.5 ms short term with 0.3 ms jitter. The long-term
262: * offsets vary up to 0.3 ms due to ionospheric layer height variations.
263: * The processor load due to the driver is 0.4 percent.
264: */
265: #define PDELAY ((170 + .8 + 4.7 + 1.3) / 1000) /* system delay (s) */
266:
267: /*
268: * Status bits (status)
269: */
270: #define RUNT 0x0001 /* runt burst */
271: #define NOISE 0x0002 /* noise burst */
272: #define BFRAME 0x0004 /* invalid format B frame sync */
273: #define BFORMAT 0x0008 /* invalid format B data */
274: #define AFRAME 0x0010 /* invalid format A frame sync */
275: #define AFORMAT 0x0020 /* invalid format A data */
276: #define DECODE 0x0040 /* invalid data decode */
277: #define STAMP 0x0080 /* too few timestamps */
278: #define AVALID 0x0100 /* valid A frame */
279: #define BVALID 0x0200 /* valid B frame */
280: #define INSYNC 0x0400 /* clock synchronized */
281: #define METRIC 0x0800 /* one or more stations heard */
282:
283: /*
284: * Alarm status bits (alarm)
285: *
286: * These alarms are set at the end of a minute in which at least one
287: * burst was received. SYNERR is raised if the AFRAME or BFRAME status
288: * bits are set during the minute, FMTERR is raised if the AFORMAT or
289: * BFORMAT status bits are set, DECERR is raised if the DECODE status
290: * bit is set and TSPERR is raised if the STAMP status bit is set.
291: */
292: #define SYNERR 0x01 /* frame sync error */
293: #define FMTERR 0x02 /* data format error */
294: #define DECERR 0x04 /* data decoding error */
295: #define TSPERR 0x08 /* insufficient data */
296:
297: #ifdef HAVE_AUDIO
298: /*
299: * Maximum-likelihood UART structure. There are eight of these
300: * corresponding to the number of phases.
301: */
302: struct surv {
303: l_fp cstamp; /* last bit timestamp */
304: double shift[12]; /* sample shift register */
305: double span; /* shift register envelope span */
306: double dist; /* sample distance */
307: int uart; /* decoded character */
308: };
309: #endif /* HAVE_AUDIO */
310:
311: #ifdef ICOM
312: /*
313: * CHU station structure. There are three of these corresponding to the
314: * three frequencies.
315: */
316: struct xmtr {
317: double integ[ISTAGE]; /* circular integrator */
318: double metric; /* integrator sum */
319: int iptr; /* integrator pointer */
320: int probe; /* dwells since last probe */
321: };
322: #endif /* ICOM */
323:
324: /*
325: * CHU unit control structure
326: */
327: struct chuunit {
328: u_char decode[20][16]; /* maximum-likelihood decoding matrix */
329: l_fp cstamp[BURST]; /* character timestamps */
330: l_fp tstamp[MAXSTAGE]; /* timestamp samples */
331: l_fp timestamp; /* current buffer timestamp */
332: l_fp laststamp; /* last buffer timestamp */
333: l_fp charstamp; /* character time as a l_fp */
334: int second; /* counts the seconds of the minute */
335: int errflg; /* error flags */
336: int status; /* status bits */
337: char ident[5]; /* station ID and channel */
338: #ifdef ICOM
339: int fd_icom; /* ICOM file descriptor */
340: int chan; /* radio channel */
341: int dwell; /* dwell cycle */
342: struct xmtr xmtr[NCHAN]; /* station metric */
343: #endif /* ICOM */
344:
345: /*
346: * Character burst variables
347: */
348: int cbuf[BURST]; /* character buffer */
349: int ntstamp; /* number of timestamp samples */
350: int ndx; /* buffer start index */
351: int prevsec; /* previous burst second */
352: int burdist; /* burst distance */
353: int syndist; /* sync distance */
354: int burstcnt; /* format A bursts this minute */
355: double maxsignal; /* signal level (modem only) */
356: int gain; /* codec gain (modem only) */
357:
358: /*
359: * Format particulars
360: */
361: int leap; /* leap/dut code */
362: int dut; /* UTC1 correction */
363: int tai; /* TAI - UTC correction */
364: int dst; /* Canadian DST code */
365:
366: #ifdef HAVE_AUDIO
367: /*
368: * Audio codec variables
369: */
370: int fd_audio; /* audio port file descriptor */
371: double comp[SIZE]; /* decompanding table */
372: int port; /* codec port */
373: int mongain; /* codec monitor gain */
374: int clipcnt; /* sample clip count */
375: int seccnt; /* second interval counter */
376:
377: /*
378: * Modem variables
379: */
380: l_fp tick; /* audio sample increment */
381: double bpf[9]; /* IIR bandpass filter */
382: double disc[LAG]; /* discriminator shift register */
383: double lpf[27]; /* FIR lowpass filter */
384: double monitor; /* audio monitor */
385: int discptr; /* discriminator pointer */
386:
387: /*
388: * Maximum-likelihood UART variables
389: */
390: double baud; /* baud interval */
391: struct surv surv[8]; /* UART survivor structures */
392: int decptr; /* decode pointer */
393: int decpha; /* decode phase */
394: int dbrk; /* holdoff counter */
395: #endif /* HAVE_AUDIO */
396: };
397:
398: /*
399: * Function prototypes
400: */
401: static int chu_start (int, struct peer *);
402: static void chu_shutdown (int, struct peer *);
403: static void chu_receive (struct recvbuf *);
404: static void chu_second (int, struct peer *);
405: static void chu_poll (int, struct peer *);
406:
407: /*
408: * More function prototypes
409: */
410: static void chu_decode (struct peer *, int, l_fp);
411: static void chu_burst (struct peer *);
412: static void chu_clear (struct peer *);
413: static void chu_a (struct peer *, int);
414: static void chu_b (struct peer *, int);
415: static int chu_dist (int, int);
416: static double chu_major (struct peer *);
417: #ifdef HAVE_AUDIO
418: static void chu_uart (struct surv *, double);
419: static void chu_rf (struct peer *, double);
420: static void chu_gain (struct peer *);
421: static void chu_audio_receive (struct recvbuf *rbufp);
422: #endif /* HAVE_AUDIO */
423: #ifdef ICOM
424: static int chu_newchan (struct peer *, double);
425: #endif /* ICOM */
426: static void chu_serial_receive (struct recvbuf *rbufp);
427:
428: /*
429: * Global variables
430: */
431: static char hexchar[] = "0123456789abcdef_*=";
432:
433: #ifdef ICOM
434: /*
435: * Note the tuned frequencies are 1 kHz higher than the carrier. CHU
436: * transmits on USB with carrier so we can use AM and the narrow SSB
437: * filter.
438: */
439: static double qsy[NCHAN] = {3.330, 7.850, 14.670}; /* freq (MHz) */
440: #endif /* ICOM */
441:
442: /*
443: * Transfer vector
444: */
445: struct refclock refclock_chu = {
446: chu_start, /* start up driver */
447: chu_shutdown, /* shut down driver */
448: chu_poll, /* transmit poll message */
449: noentry, /* not used (old chu_control) */
450: noentry, /* initialize driver (not used) */
451: noentry, /* not used (old chu_buginfo) */
452: chu_second /* housekeeping timer */
453: };
454:
455:
456: /*
457: * chu_start - open the devices and initialize data for processing
458: */
459: static int
460: chu_start(
461: int unit, /* instance number (not used) */
462: struct peer *peer /* peer structure pointer */
463: )
464: {
465: struct chuunit *up;
466: struct refclockproc *pp;
467: char device[20]; /* device name */
468: int fd; /* file descriptor */
469: #ifdef ICOM
470: int temp;
471: #endif /* ICOM */
472: #ifdef HAVE_AUDIO
473: int fd_audio; /* audio port file descriptor */
474: int i; /* index */
475: double step; /* codec adjustment */
476:
477: /*
478: * Open audio device. Don't complain if not there.
479: */
480: fd_audio = audio_init(DEVICE_AUDIO, AUDIO_BUFSIZ, unit);
481: #ifdef DEBUG
482: if (fd_audio > 0 && debug)
483: audio_show();
484: #endif
485:
486: /*
487: * If audio is unavailable, Open serial port in raw mode.
488: */
489: if (fd_audio > 0) {
490: fd = fd_audio;
491: } else {
492: snprintf(device, sizeof(device), DEVICE, unit);
493: fd = refclock_open(device, SPEED232, LDISC_RAW);
494: }
495: #else /* HAVE_AUDIO */
496:
497: /*
498: * Open serial port in raw mode.
499: */
500: snprintf(device, sizeof(device), DEVICE, unit);
501: fd = refclock_open(device, SPEED232, LDISC_RAW);
502: #endif /* HAVE_AUDIO */
503: if (fd <= 0)
504: return (0);
505:
506: /*
507: * Allocate and initialize unit structure
508: */
509: up = emalloc(sizeof(*up));
510: memset(up, 0, sizeof(*up));
511: pp = peer->procptr;
512: pp->unitptr = (caddr_t)up;
513: pp->io.clock_recv = chu_receive;
514: pp->io.srcclock = (caddr_t)peer;
515: pp->io.datalen = 0;
516: pp->io.fd = fd;
517: if (!io_addclock(&pp->io)) {
518: close(fd);
519: pp->io.fd = -1;
520: free(up);
521: pp->unitptr = NULL;
522: return (0);
523: }
524:
525: /*
526: * Initialize miscellaneous variables
527: */
528: peer->precision = PRECISION;
529: pp->clockdesc = DESCRIPTION;
530: strcpy(up->ident, "CHU");
531: memcpy(&pp->refid, up->ident, 4);
532: DTOLFP(CHAR, &up->charstamp);
533: #ifdef HAVE_AUDIO
534:
535: /*
536: * The companded samples are encoded sign-magnitude. The table
537: * contains all the 256 values in the interest of speed. We do
538: * this even if the audio codec is not available. C'est la lazy.
539: */
540: up->fd_audio = fd_audio;
541: up->gain = 127;
542: up->comp[0] = up->comp[OFFSET] = 0.;
543: up->comp[1] = 1; up->comp[OFFSET + 1] = -1.;
544: up->comp[2] = 3; up->comp[OFFSET + 2] = -3.;
545: step = 2.;
546: for (i = 3; i < OFFSET; i++) {
547: up->comp[i] = up->comp[i - 1] + step;
548: up->comp[OFFSET + i] = -up->comp[i];
549: if (i % 16 == 0)
550: step *= 2.;
551: }
552: DTOLFP(1. / SECOND, &up->tick);
553: #endif /* HAVE_AUDIO */
554: #ifdef ICOM
555: temp = 0;
556: #ifdef DEBUG
557: if (debug > 1)
558: temp = P_TRACE;
559: #endif
560: if (peer->ttl > 0) {
561: if (peer->ttl & 0x80)
562: up->fd_icom = icom_init("/dev/icom", B1200,
563: temp);
564: else
565: up->fd_icom = icom_init("/dev/icom", B9600,
566: temp);
567: }
568: if (up->fd_icom > 0) {
569: if (chu_newchan(peer, 0) != 0) {
570: msyslog(LOG_NOTICE, "icom: radio not found");
571: close(up->fd_icom);
572: up->fd_icom = 0;
573: } else {
574: msyslog(LOG_NOTICE, "icom: autotune enabled");
575: }
576: }
577: #endif /* ICOM */
578: return (1);
579: }
580:
581:
582: /*
583: * chu_shutdown - shut down the clock
584: */
585: static void
586: chu_shutdown(
587: int unit, /* instance number (not used) */
588: struct peer *peer /* peer structure pointer */
589: )
590: {
591: struct chuunit *up;
592: struct refclockproc *pp;
593:
594: pp = peer->procptr;
595: up = (struct chuunit *)pp->unitptr;
596: if (up == NULL)
597: return;
598:
599: io_closeclock(&pp->io);
600: #ifdef ICOM
601: if (up->fd_icom > 0)
602: close(up->fd_icom);
603: #endif /* ICOM */
604: free(up);
605: }
606:
607:
608: /*
609: * chu_receive - receive data from the audio or serial device
610: */
611: static void
612: chu_receive(
613: struct recvbuf *rbufp /* receive buffer structure pointer */
614: )
615: {
616: #ifdef HAVE_AUDIO
617: struct chuunit *up;
618: struct refclockproc *pp;
619: struct peer *peer;
620:
621: peer = (struct peer *)rbufp->recv_srcclock;
622: pp = peer->procptr;
623: up = (struct chuunit *)pp->unitptr;
624:
625: /*
626: * If the audio codec is warmed up, the buffer contains codec
627: * samples which need to be demodulated and decoded into CHU
628: * characters using the software UART. Otherwise, the buffer
629: * contains CHU characters from the serial port, so the software
630: * UART is bypassed. In this case the CPU will probably run a
631: * few degrees cooler.
632: */
633: if (up->fd_audio > 0)
634: chu_audio_receive(rbufp);
635: else
636: chu_serial_receive(rbufp);
637: #else
638: chu_serial_receive(rbufp);
639: #endif /* HAVE_AUDIO */
640: }
641:
642:
643: #ifdef HAVE_AUDIO
644: /*
645: * chu_audio_receive - receive data from the audio device
646: */
647: static void
648: chu_audio_receive(
649: struct recvbuf *rbufp /* receive buffer structure pointer */
650: )
651: {
652: struct chuunit *up;
653: struct refclockproc *pp;
654: struct peer *peer;
655:
656: double sample; /* codec sample */
657: u_char *dpt; /* buffer pointer */
658: int bufcnt; /* buffer counter */
659: l_fp ltemp; /* l_fp temp */
660:
661: peer = (struct peer *)rbufp->recv_srcclock;
662: pp = peer->procptr;
663: up = (struct chuunit *)pp->unitptr;
664:
665: /*
666: * Main loop - read until there ain't no more. Note codec
667: * samples are bit-inverted.
668: */
669: DTOLFP((double)rbufp->recv_length / SECOND, <emp);
670: L_SUB(&rbufp->recv_time, <emp);
671: up->timestamp = rbufp->recv_time;
672: dpt = rbufp->recv_buffer;
673: for (bufcnt = 0; bufcnt < rbufp->recv_length; bufcnt++) {
674: sample = up->comp[~*dpt++ & 0xff];
675:
676: /*
677: * Clip noise spikes greater than MAXAMP. If no clips,
678: * increase the gain a tad; if the clips are too high,
679: * decrease a tad.
680: */
681: if (sample > MAXAMP) {
682: sample = MAXAMP;
683: up->clipcnt++;
684: } else if (sample < -MAXAMP) {
685: sample = -MAXAMP;
686: up->clipcnt++;
687: }
688: chu_rf(peer, sample);
689: L_ADD(&up->timestamp, &up->tick);
690:
691: /*
692: * Once each second ride gain.
693: */
694: up->seccnt = (up->seccnt + 1) % SECOND;
695: if (up->seccnt == 0) {
696: chu_gain(peer);
697: }
698: }
699:
700: /*
701: * Set the input port and monitor gain for the next buffer.
702: */
703: if (pp->sloppyclockflag & CLK_FLAG2)
704: up->port = 2;
705: else
706: up->port = 1;
707: if (pp->sloppyclockflag & CLK_FLAG3)
708: up->mongain = MONGAIN;
709: else
710: up->mongain = 0;
711: }
712:
713:
714: /*
715: * chu_rf - filter and demodulate the FSK signal
716: *
717: * This routine implements a 300-baud Bell 103 modem with mark 2225 Hz
718: * and space 2025 Hz. It uses a bandpass filter followed by a soft
719: * limiter, FM discriminator and lowpass filter. A maximum-likelihood
720: * decoder samples the baseband signal at eight times the baud rate and
721: * detects the start bit of each character.
722: *
723: * The filters are built for speed, which explains the rather clumsy
724: * code. Hopefully, the compiler will efficiently implement the move-
725: * and-muiltiply-and-add operations.
726: */
727: static void
728: chu_rf(
729: struct peer *peer, /* peer structure pointer */
730: double sample /* analog sample */
731: )
732: {
733: struct refclockproc *pp;
734: struct chuunit *up;
735: struct surv *sp;
736:
737: /*
738: * Local variables
739: */
740: double signal; /* bandpass signal */
741: double limit; /* limiter signal */
742: double disc; /* discriminator signal */
743: double lpf; /* lowpass signal */
744: double dist; /* UART signal distance */
745: int i, j;
746:
747: pp = peer->procptr;
748: up = (struct chuunit *)pp->unitptr;
749:
750: /*
751: * Bandpass filter. 4th-order elliptic, 500-Hz bandpass centered
752: * at 2125 Hz. Passband ripple 0.3 dB, stopband ripple 50 dB,
753: * phase delay 0.24 ms.
754: */
755: signal = (up->bpf[8] = up->bpf[7]) * 5.844676e-01;
756: signal += (up->bpf[7] = up->bpf[6]) * 4.884860e-01;
757: signal += (up->bpf[6] = up->bpf[5]) * 2.704384e+00;
758: signal += (up->bpf[5] = up->bpf[4]) * 1.645032e+00;
759: signal += (up->bpf[4] = up->bpf[3]) * 4.644557e+00;
760: signal += (up->bpf[3] = up->bpf[2]) * 1.879165e+00;
761: signal += (up->bpf[2] = up->bpf[1]) * 3.522634e+00;
762: signal += (up->bpf[1] = up->bpf[0]) * 7.315738e-01;
763: up->bpf[0] = sample - signal;
764: signal = up->bpf[0] * 6.176213e-03
765: + up->bpf[1] * 3.156599e-03
766: + up->bpf[2] * 7.567487e-03
767: + up->bpf[3] * 4.344580e-03
768: + up->bpf[4] * 1.190128e-02
769: + up->bpf[5] * 4.344580e-03
770: + up->bpf[6] * 7.567487e-03
771: + up->bpf[7] * 3.156599e-03
772: + up->bpf[8] * 6.176213e-03;
773:
774: up->monitor = signal / 4.; /* note monitor after filter */
775:
776: /*
777: * Soft limiter/discriminator. The 11-sample discriminator lag
778: * interval corresponds to three cycles of 2125 Hz, which
779: * requires the sample frequency to be 2125 * 11 / 3 = 7791.7
780: * Hz. The discriminator output varies +-0.5 interval for input
781: * frequency 2025-2225 Hz. However, we don't get to sample at
782: * this frequency, so the discriminator output is biased. Life
783: * at 8000 Hz sucks.
784: */
785: limit = signal;
786: if (limit > LIMIT)
787: limit = LIMIT;
788: else if (limit < -LIMIT)
789: limit = -LIMIT;
790: disc = up->disc[up->discptr] * -limit;
791: up->disc[up->discptr] = limit;
792: up->discptr = (up->discptr + 1 ) % LAG;
793: if (disc >= 0)
794: disc = SQRT(disc);
795: else
796: disc = -SQRT(-disc);
797:
798: /*
799: * Lowpass filter. Raised cosine FIR, Ts = 1 / 300, beta = 0.1.
800: */
801: lpf = (up->lpf[26] = up->lpf[25]) * 2.538771e-02;
802: lpf += (up->lpf[25] = up->lpf[24]) * 1.084671e-01;
803: lpf += (up->lpf[24] = up->lpf[23]) * 2.003159e-01;
804: lpf += (up->lpf[23] = up->lpf[22]) * 2.985303e-01;
805: lpf += (up->lpf[22] = up->lpf[21]) * 4.003697e-01;
806: lpf += (up->lpf[21] = up->lpf[20]) * 5.028552e-01;
807: lpf += (up->lpf[20] = up->lpf[19]) * 6.028795e-01;
808: lpf += (up->lpf[19] = up->lpf[18]) * 6.973249e-01;
809: lpf += (up->lpf[18] = up->lpf[17]) * 7.831828e-01;
810: lpf += (up->lpf[17] = up->lpf[16]) * 8.576717e-01;
811: lpf += (up->lpf[16] = up->lpf[15]) * 9.183463e-01;
812: lpf += (up->lpf[15] = up->lpf[14]) * 9.631951e-01;
813: lpf += (up->lpf[14] = up->lpf[13]) * 9.907208e-01;
814: lpf += (up->lpf[13] = up->lpf[12]) * 1.000000e+00;
815: lpf += (up->lpf[12] = up->lpf[11]) * 9.907208e-01;
816: lpf += (up->lpf[11] = up->lpf[10]) * 9.631951e-01;
817: lpf += (up->lpf[10] = up->lpf[9]) * 9.183463e-01;
818: lpf += (up->lpf[9] = up->lpf[8]) * 8.576717e-01;
819: lpf += (up->lpf[8] = up->lpf[7]) * 7.831828e-01;
820: lpf += (up->lpf[7] = up->lpf[6]) * 6.973249e-01;
821: lpf += (up->lpf[6] = up->lpf[5]) * 6.028795e-01;
822: lpf += (up->lpf[5] = up->lpf[4]) * 5.028552e-01;
823: lpf += (up->lpf[4] = up->lpf[3]) * 4.003697e-01;
824: lpf += (up->lpf[3] = up->lpf[2]) * 2.985303e-01;
825: lpf += (up->lpf[2] = up->lpf[1]) * 2.003159e-01;
826: lpf += (up->lpf[1] = up->lpf[0]) * 1.084671e-01;
827: lpf += up->lpf[0] = disc * 2.538771e-02;
828:
829: /*
830: * Maximum-likelihood decoder. The UART updates each of the
831: * eight survivors and determines the span, slice level and
832: * tentative decoded character. Valid 11-bit characters are
833: * framed so that bit 10 and bit 11 (stop bits) are mark and bit
834: * 1 (start bit) is space. When a valid character is found, the
835: * survivor with maximum distance determines the final decoded
836: * character.
837: */
838: up->baud += 1. / SECOND;
839: if (up->baud > 1. / (BAUD * 8.)) {
840: up->baud -= 1. / (BAUD * 8.);
841: up->decptr = (up->decptr + 1) % 8;
842: sp = &up->surv[up->decptr];
843: sp->cstamp = up->timestamp;
844: chu_uart(sp, -lpf * AGAIN);
845: if (up->dbrk > 0) {
846: up->dbrk--;
847: if (up->dbrk > 0)
848: return;
849:
850: up->decpha = up->decptr;
851: }
852: if (up->decptr != up->decpha)
853: return;
854:
855: dist = 0;
856: j = -1;
857: for (i = 0; i < 8; i++) {
858:
859: /*
860: * The timestamp is taken at the last bit, so
861: * for correct decoding we reqire sufficient
862: * span and correct start bit and two stop bits.
863: */
864: if ((up->surv[i].uart & 0x601) != 0x600 ||
865: up->surv[i].span < SPAN)
866: continue;
867:
868: if (up->surv[i].dist > dist) {
869: dist = up->surv[i].dist;
870: j = i;
871: }
872: }
873: if (j < 0)
874: return;
875:
876: /*
877: * Process the character, then blank the decoder until
878: * the end of the next character.This sets the decoding
879: * phase of the entire burst from the phase of the first
880: * character.
881: */
882: up->maxsignal = up->surv[j].span;
883: chu_decode(peer, (up->surv[j].uart >> 1) & 0xff,
884: up->surv[j].cstamp);
885: up->dbrk = 88;
886: }
887: }
888:
889:
890: /*
891: * chu_uart - maximum-likelihood UART
892: *
893: * This routine updates a shift register holding the last 11 envelope
894: * samples. It then computes the slice level and span over these samples
895: * and determines the tentative data bits and distance. The calling
896: * program selects over the last eight survivors the one with maximum
897: * distance to determine the decoded character.
898: */
899: static void
900: chu_uart(
901: struct surv *sp, /* survivor structure pointer */
902: double sample /* baseband signal */
903: )
904: {
905: double es_max, es_min; /* max/min envelope */
906: double slice; /* slice level */
907: double dist; /* distance */
908: double dtemp;
909: int i;
910:
911: /*
912: * Save the sample and shift right. At the same time, measure
913: * the maximum and minimum over all eleven samples.
914: */
915: es_max = -1e6;
916: es_min = 1e6;
917: sp->shift[0] = sample;
918: for (i = 11; i > 0; i--) {
919: sp->shift[i] = sp->shift[i - 1];
920: if (sp->shift[i] > es_max)
921: es_max = sp->shift[i];
922: if (sp->shift[i] < es_min)
923: es_min = sp->shift[i];
924: }
925:
926: /*
927: * Determine the span as the maximum less the minimum and the
928: * slice level as the minimum plus a fraction of the span. Note
929: * the slight bias toward mark to correct for the modem tendency
930: * to make more mark than space errors. Compute the distance on
931: * the assumption the last two bits must be mark, the first
932: * space and the rest either mark or space.
933: */
934: sp->span = es_max - es_min;
935: slice = es_min + .45 * sp->span;
936: dist = 0;
937: sp->uart = 0;
938: for (i = 1; i < 12; i++) {
939: sp->uart <<= 1;
940: dtemp = sp->shift[i];
941: if (dtemp > slice)
942: sp->uart |= 0x1;
943: if (i == 1 || i == 2) {
944: dist += dtemp - es_min;
945: } else if (i == 11) {
946: dist += es_max - dtemp;
947: } else {
948: if (dtemp > slice)
949: dist += dtemp - es_min;
950: else
951: dist += es_max - dtemp;
952: }
953: }
954: sp->dist = dist / (11 * sp->span);
955: }
956: #endif /* HAVE_AUDIO */
957:
958:
959: /*
960: * chu_serial_receive - receive data from the serial device
961: */
962: static void
963: chu_serial_receive(
964: struct recvbuf *rbufp /* receive buffer structure pointer */
965: )
966: {
967: struct chuunit *up;
968: struct refclockproc *pp;
969: struct peer *peer;
970:
971: u_char *dpt; /* receive buffer pointer */
972:
973: peer = (struct peer *)rbufp->recv_srcclock;
974: pp = peer->procptr;
975: up = (struct chuunit *)pp->unitptr;
976:
977: dpt = (u_char *)&rbufp->recv_space;
978: chu_decode(peer, *dpt, rbufp->recv_time);
979: }
980:
981:
982: /*
983: * chu_decode - decode the character data
984: */
985: static void
986: chu_decode(
987: struct peer *peer, /* peer structure pointer */
988: int hexhex, /* data character */
989: l_fp cstamp /* data character timestamp */
990: )
991: {
992: struct refclockproc *pp;
993: struct chuunit *up;
994:
995: l_fp tstmp; /* timestamp temp */
996: double dtemp;
997:
998: pp = peer->procptr;
999: up = (struct chuunit *)pp->unitptr;
1000:
1001: /*
1002: * If the interval since the last character is greater than the
1003: * longest burst, process the last burst and start a new one. If
1004: * the interval is less than this but greater than two
1005: * characters, consider this a noise burst and reject it.
1006: */
1007: tstmp = up->timestamp;
1008: if (L_ISZERO(&up->laststamp))
1009: up->laststamp = up->timestamp;
1010: L_SUB(&tstmp, &up->laststamp);
1011: up->laststamp = up->timestamp;
1012: LFPTOD(&tstmp, dtemp);
1013: if (dtemp > BURST * CHAR) {
1014: chu_burst(peer);
1015: up->ndx = 0;
1016: } else if (dtemp > 2.5 * CHAR) {
1017: up->ndx = 0;
1018: }
1019:
1020: /*
1021: * Append the character to the current burst and append the
1022: * character timestamp to the timestamp list.
1023: */
1024: if (up->ndx < BURST) {
1025: up->cbuf[up->ndx] = hexhex & 0xff;
1026: up->cstamp[up->ndx] = cstamp;
1027: up->ndx++;
1028:
1029: }
1030: }
1031:
1032:
1033: /*
1034: * chu_burst - search for valid burst format
1035: */
1036: static void
1037: chu_burst(
1038: struct peer *peer
1039: )
1040: {
1041: struct chuunit *up;
1042: struct refclockproc *pp;
1043:
1044: int i;
1045:
1046: pp = peer->procptr;
1047: up = (struct chuunit *)pp->unitptr;
1048:
1049: /*
1050: * Correlate a block of five characters with the next block of
1051: * five characters. The burst distance is defined as the number
1052: * of bits that match in the two blocks for format A and that
1053: * match the inverse for format B.
1054: */
1055: if (up->ndx < MINCHAR) {
1056: up->status |= RUNT;
1057: return;
1058: }
1059: up->burdist = 0;
1060: for (i = 0; i < 5 && i < up->ndx - 5; i++)
1061: up->burdist += chu_dist(up->cbuf[i], up->cbuf[i + 5]);
1062:
1063: /*
1064: * If the burst distance is at least MINDIST, this must be a
1065: * format A burst; if the value is not greater than -MINDIST, it
1066: * must be a format B burst. If the B burst is perfect, we
1067: * believe it; otherwise, it is a noise burst and of no use to
1068: * anybody.
1069: */
1070: if (up->burdist >= MINDIST) {
1071: chu_a(peer, up->ndx);
1072: } else if (up->burdist <= -MINDIST) {
1073: chu_b(peer, up->ndx);
1074: } else {
1075: up->status |= NOISE;
1076: return;
1077: }
1078:
1079: /*
1080: * If this is a valid burst, wait a guard time of ten seconds to
1081: * allow for more bursts, then arm the poll update routine to
1082: * process the minute. Don't do this if this is called from the
1083: * timer interrupt routine.
1084: */
1085: if (peer->outdate != current_time)
1086: peer->nextdate = current_time + 10;
1087: }
1088:
1089:
1090: /*
1091: * chu_b - decode format B burst
1092: */
1093: static void
1094: chu_b(
1095: struct peer *peer,
1096: int nchar
1097: )
1098: {
1099: struct refclockproc *pp;
1100: struct chuunit *up;
1101:
1102: u_char code[11]; /* decoded timecode */
1103: char tbuf[80]; /* trace buffer */
1104: char * p;
1105: size_t chars;
1106: size_t cb;
1107: int i;
1108:
1109: pp = peer->procptr;
1110: up = (struct chuunit *)pp->unitptr;
1111:
1112: /*
1113: * In a format B burst, a character is considered valid only if
1114: * the first occurence matches the last occurence. The burst is
1115: * considered valid only if all characters are valid; that is,
1116: * only if the distance is 40. Note that once a valid frame has
1117: * been found errors are ignored.
1118: */
1119: snprintf(tbuf, sizeof(tbuf), "chuB %04x %4.0f %2d %2d ",
1120: up->status, up->maxsignal, nchar, -up->burdist);
1121: cb = sizeof(tbuf);
1122: p = tbuf;
1123: for (i = 0; i < nchar; i++) {
1124: chars = strlen(p);
1125: if (cb < chars + 1) {
1126: msyslog(LOG_ERR, "chu_b() fatal out buffer");
1127: exit(1);
1128: }
1129: cb -= chars;
1130: p += chars;
1131: snprintf(p, cb, "%02x", up->cbuf[i]);
1132: }
1133: if (pp->sloppyclockflag & CLK_FLAG4)
1134: record_clock_stats(&peer->srcadr, tbuf);
1135: #ifdef DEBUG
1136: if (debug)
1137: printf("%s\n", tbuf);
1138: #endif
1139: if (up->burdist > -40) {
1140: up->status |= BFRAME;
1141: return;
1142: }
1143:
1144: /*
1145: * Convert the burst data to internal format. Don't bother with
1146: * the timestamps.
1147: */
1148: for (i = 0; i < 5; i++) {
1149: code[2 * i] = hexchar[up->cbuf[i] & 0xf];
1150: code[2 * i + 1] = hexchar[(up->cbuf[i] >>
1151: 4) & 0xf];
1152: }
1153: if (sscanf((char *)code, "%1x%1d%4d%2d%2x", &up->leap, &up->dut,
1154: &pp->year, &up->tai, &up->dst) != 5) {
1155: up->status |= BFORMAT;
1156: return;
1157: }
1158: up->status |= BVALID;
1159: if (up->leap & 0x8)
1160: up->dut = -up->dut;
1161: }
1162:
1163:
1164: /*
1165: * chu_a - decode format A burst
1166: */
1167: static void
1168: chu_a(
1169: struct peer *peer,
1170: int nchar
1171: )
1172: {
1173: struct refclockproc *pp;
1174: struct chuunit *up;
1175:
1176: char tbuf[80]; /* trace buffer */
1177: char * p;
1178: size_t chars;
1179: size_t cb;
1180: l_fp offset; /* timestamp offset */
1181: int val; /* distance */
1182: int temp;
1183: int i, j, k;
1184:
1185: pp = peer->procptr;
1186: up = (struct chuunit *)pp->unitptr;
1187:
1188: /*
1189: * Determine correct burst phase. There are three cases
1190: * corresponding to in-phase, one character early or one
1191: * character late. These cases are distinguished by the position
1192: * of the framing digits 0x6 at positions 0 and 5 and 0x3 at
1193: * positions 4 and 9. The correct phase is when the distance
1194: * relative to the framing digits is maximum. The burst is valid
1195: * only if the maximum distance is at least MINSYNC.
1196: */
1197: up->syndist = k = 0;
1198: val = -16;
1199: for (i = -1; i < 2; i++) {
1200: temp = up->cbuf[i + 4] & 0xf;
1201: if (i >= 0)
1202: temp |= (up->cbuf[i] & 0xf) << 4;
1203: val = chu_dist(temp, 0x63);
1204: temp = (up->cbuf[i + 5] & 0xf) << 4;
1205: if (i + 9 < nchar)
1206: temp |= up->cbuf[i + 9] & 0xf;
1207: val += chu_dist(temp, 0x63);
1208: if (val > up->syndist) {
1209: up->syndist = val;
1210: k = i;
1211: }
1212: }
1213:
1214: /*
1215: * Extract the second number; it must be in the range 2 through
1216: * 9 and the two repititions must be the same.
1217: */
1218: temp = (up->cbuf[k + 4] >> 4) & 0xf;
1219: if (temp < 2 || temp > 9 || k + 9 >= nchar || temp !=
1220: ((up->cbuf[k + 9] >> 4) & 0xf))
1221: temp = 0;
1222: snprintf(tbuf, sizeof(tbuf),
1223: "chuA %04x %4.0f %2d %2d %2d %2d %1d ", up->status,
1224: up->maxsignal, nchar, up->burdist, k, up->syndist,
1225: temp);
1226: cb = sizeof(tbuf);
1227: p = tbuf;
1228: for (i = 0; i < nchar; i++) {
1229: chars = strlen(p);
1230: if (cb < chars + 1) {
1231: msyslog(LOG_ERR, "chu_a() fatal out buffer");
1232: exit(1);
1233: }
1234: cb -= chars;
1235: p += chars;
1236: snprintf(p, cb, "%02x", up->cbuf[i]);
1237: }
1238: if (pp->sloppyclockflag & CLK_FLAG4)
1239: record_clock_stats(&peer->srcadr, tbuf);
1240: #ifdef DEBUG
1241: if (debug)
1242: printf("%s\n", tbuf);
1243: #endif
1244: if (up->syndist < MINSYNC) {
1245: up->status |= AFRAME;
1246: return;
1247: }
1248:
1249: /*
1250: * A valid burst requires the first seconds number to match the
1251: * last seconds number. If so, the burst timestamps are
1252: * corrected to the current minute and saved for later
1253: * processing. In addition, the seconds decode is advanced from
1254: * the previous burst to the current one.
1255: */
1256: if (temp == 0) {
1257: up->status |= AFORMAT;
1258: } else {
1259: up->status |= AVALID;
1260: up->second = pp->second = 30 + temp;
1261: offset.l_ui = 30 + temp;
1262: offset.l_f = 0;
1263: i = 0;
1264: if (k < 0)
1265: offset = up->charstamp;
1266: else if (k > 0)
1267: i = 1;
1268: for (; i < nchar && i < k + 10; i++) {
1269: up->tstamp[up->ntstamp] = up->cstamp[i];
1270: L_SUB(&up->tstamp[up->ntstamp], &offset);
1271: L_ADD(&offset, &up->charstamp);
1272: if (up->ntstamp < MAXSTAGE - 1)
1273: up->ntstamp++;
1274: }
1275: while (temp > up->prevsec) {
1276: for (j = 15; j > 0; j--) {
1277: up->decode[9][j] = up->decode[9][j - 1];
1278: up->decode[19][j] =
1279: up->decode[19][j - 1];
1280: }
1281: up->decode[9][j] = up->decode[19][j] = 0;
1282: up->prevsec++;
1283: }
1284: }
1285:
1286: /*
1287: * Stash the data in the decoding matrix.
1288: */
1289: i = -(2 * k);
1290: for (j = 0; j < nchar; j++) {
1291: if (i < 0 || i > 18) {
1292: i += 2;
1293: continue;
1294: }
1295: up->decode[i][up->cbuf[j] & 0xf]++;
1296: i++;
1297: up->decode[i][(up->cbuf[j] >> 4) & 0xf]++;
1298: i++;
1299: }
1300: up->burstcnt++;
1301: }
1302:
1303:
1304: /*
1305: * chu_poll - called by the transmit procedure
1306: */
1307: static void
1308: chu_poll(
1309: int unit,
1310: struct peer *peer /* peer structure pointer */
1311: )
1312: {
1313: struct refclockproc *pp;
1314:
1315: pp = peer->procptr;
1316: pp->polls++;
1317: }
1318:
1319:
1320: /*
1321: * chu_second - process minute data
1322: */
1323: static void
1324: chu_second(
1325: int unit,
1326: struct peer *peer /* peer structure pointer */
1327: )
1328: {
1329: struct refclockproc *pp;
1330: struct chuunit *up;
1331: l_fp offset;
1332: char synchar, qual, leapchar;
1333: int minset, i;
1334: double dtemp;
1335:
1336: pp = peer->procptr;
1337: up = (struct chuunit *)pp->unitptr;
1338:
1339: /*
1340: * This routine is called once per minute to process the
1341: * accumulated burst data. We do a bit of fancy footwork so that
1342: * this doesn't run while burst data are being accumulated.
1343: */
1344: up->second = (up->second + 1) % 60;
1345: if (up->second != 0)
1346: return;
1347:
1348: /*
1349: * Process the last burst, if still in the burst buffer.
1350: * If the minute contains a valid B frame with sufficient A
1351: * frame metric, it is considered valid. However, the timecode
1352: * is sent to clockstats even if invalid.
1353: */
1354: chu_burst(peer);
1355: minset = ((current_time - peer->update) + 30) / 60;
1356: dtemp = chu_major(peer);
1357: qual = 0;
1358: if (up->status & (BFRAME | AFRAME))
1359: qual |= SYNERR;
1360: if (up->status & (BFORMAT | AFORMAT))
1361: qual |= FMTERR;
1362: if (up->status & DECODE)
1363: qual |= DECERR;
1364: if (up->status & STAMP)
1365: qual |= TSPERR;
1366: if (up->status & BVALID && dtemp >= MINMETRIC)
1367: up->status |= INSYNC;
1368: synchar = leapchar = ' ';
1369: if (!(up->status & INSYNC)) {
1370: pp->leap = LEAP_NOTINSYNC;
1371: synchar = '?';
1372: } else if (up->leap & 0x2) {
1373: pp->leap = LEAP_ADDSECOND;
1374: leapchar = 'L';
1375: } else if (up->leap & 0x4) {
1376: pp->leap = LEAP_DELSECOND;
1377: leapchar = 'l';
1378: } else {
1379: pp->leap = LEAP_NOWARNING;
1380: }
1381: snprintf(pp->a_lastcode, sizeof(pp->a_lastcode),
1382: "%c%1X %04d %03d %02d:%02d:%02d %c%x %+d %d %d %s %.0f %d",
1383: synchar, qual, pp->year, pp->day, pp->hour, pp->minute,
1384: pp->second, leapchar, up->dst, up->dut, minset, up->gain,
1385: up->ident, dtemp, up->ntstamp);
1386: pp->lencode = strlen(pp->a_lastcode);
1387:
1388: /*
1389: * If in sync and the signal metric is above threshold, the
1390: * timecode is ipso fatso valid and can be selected to
1391: * discipline the clock.
1392: */
1393: if (up->status & INSYNC && !(up->status & (DECODE | STAMP)) &&
1394: dtemp > MINMETRIC) {
1395: if (!clocktime(pp->day, pp->hour, pp->minute, 0, GMT,
1396: up->tstamp[0].l_ui, &pp->yearstart, &offset.l_ui)) {
1397: up->errflg = CEVNT_BADTIME;
1398: } else {
1399: offset.l_uf = 0;
1400: for (i = 0; i < up->ntstamp; i++)
1401: refclock_process_offset(pp, offset,
1402: up->tstamp[i], PDELAY +
1403: pp->fudgetime1);
1404: pp->lastref = up->timestamp;
1405: refclock_receive(peer);
1406: }
1407: }
1408: if (dtemp > 0)
1409: record_clock_stats(&peer->srcadr, pp->a_lastcode);
1410: #ifdef DEBUG
1411: if (debug)
1412: printf("chu: timecode %d %s\n", pp->lencode,
1413: pp->a_lastcode);
1414: #endif
1415: #ifdef ICOM
1416: chu_newchan(peer, dtemp);
1417: #endif /* ICOM */
1418: chu_clear(peer);
1419: if (up->errflg)
1420: refclock_report(peer, up->errflg);
1421: up->errflg = 0;
1422: }
1423:
1424:
1425: /*
1426: * chu_major - majority decoder
1427: */
1428: static double
1429: chu_major(
1430: struct peer *peer /* peer structure pointer */
1431: )
1432: {
1433: struct refclockproc *pp;
1434: struct chuunit *up;
1435:
1436: u_char code[11]; /* decoded timecode */
1437: int metric; /* distance metric */
1438: int val1; /* maximum distance */
1439: int synchar; /* stray cat */
1440: int temp;
1441: int i, j, k;
1442:
1443: pp = peer->procptr;
1444: up = (struct chuunit *)pp->unitptr;
1445:
1446: /*
1447: * Majority decoder. Each burst encodes two replications at each
1448: * digit position in the timecode. Each row of the decoding
1449: * matrix encodes the number of occurences of each digit found
1450: * at the corresponding position. The maximum over all
1451: * occurrences at each position is the distance for this
1452: * position and the corresponding digit is the maximum-
1453: * likelihood candidate. If the distance is not more than half
1454: * the total number of occurences, a majority has not been found
1455: * and the data are discarded. The decoding distance is defined
1456: * as the sum of the distances over the first nine digits. The
1457: * tenth digit varies over the seconds, so we don't count it.
1458: */
1459: metric = 0;
1460: for (i = 0; i < 9; i++) {
1461: val1 = 0;
1462: k = 0;
1463: for (j = 0; j < 16; j++) {
1464: temp = up->decode[i][j] + up->decode[i + 10][j];
1465: if (temp > val1) {
1466: val1 = temp;
1467: k = j;
1468: }
1469: }
1470: if (val1 <= up->burstcnt)
1471: up->status |= DECODE;
1472: metric += val1;
1473: code[i] = hexchar[k];
1474: }
1475:
1476: /*
1477: * Compute the timecode timestamp from the days, hours and
1478: * minutes of the timecode. Use clocktime() for the aggregate
1479: * minutes and the minute offset computed from the burst
1480: * seconds. Note that this code relies on the filesystem time
1481: * for the years and does not use the years of the timecode.
1482: */
1483: if (sscanf((char *)code, "%1x%3d%2d%2d", &synchar, &pp->day,
1484: &pp->hour, &pp->minute) != 4)
1485: up->status |= DECODE;
1486: if (up->ntstamp < MINSTAMP)
1487: up->status |= STAMP;
1488: return (metric);
1489: }
1490:
1491:
1492: /*
1493: * chu_clear - clear decoding matrix
1494: */
1495: static void
1496: chu_clear(
1497: struct peer *peer /* peer structure pointer */
1498: )
1499: {
1500: struct refclockproc *pp;
1501: struct chuunit *up;
1502: int i, j;
1503:
1504: pp = peer->procptr;
1505: up = (struct chuunit *)pp->unitptr;
1506:
1507: /*
1508: * Clear stuff for the minute.
1509: */
1510: up->ndx = up->prevsec = 0;
1511: up->burstcnt = up->ntstamp = 0;
1512: up->status &= INSYNC | METRIC;
1513: for (i = 0; i < 20; i++) {
1514: for (j = 0; j < 16; j++)
1515: up->decode[i][j] = 0;
1516: }
1517: }
1518:
1519: #ifdef ICOM
1520: /*
1521: * chu_newchan - called once per minute to find the best channel;
1522: * returns zero on success, nonzero if ICOM error.
1523: */
1524: static int
1525: chu_newchan(
1526: struct peer *peer,
1527: double met
1528: )
1529: {
1530: struct chuunit *up;
1531: struct refclockproc *pp;
1532: struct xmtr *sp;
1533: int rval;
1534: double metric;
1535: int i;
1536:
1537: pp = peer->procptr;
1538: up = (struct chuunit *)pp->unitptr;
1539:
1540: /*
1541: * The radio can be tuned to three channels: 0 (3330 kHz), 1
1542: * (7850 kHz) and 2 (14670 kHz). There are five one-minute
1543: * dwells in each cycle. During the first dwell the radio is
1544: * tuned to one of the three channels to measure the channel
1545: * metric. The channel is selected as the one least recently
1546: * measured. During the remaining four dwells the radio is tuned
1547: * to the channel with the highest channel metric.
1548: */
1549: if (up->fd_icom <= 0)
1550: return (0);
1551:
1552: /*
1553: * Update the current channel metric and age of all channels.
1554: * Scan all channels for the highest metric.
1555: */
1556: sp = &up->xmtr[up->chan];
1557: sp->metric -= sp->integ[sp->iptr];
1558: sp->integ[sp->iptr] = met;
1559: sp->metric += sp->integ[sp->iptr];
1560: sp->probe = 0;
1561: sp->iptr = (sp->iptr + 1) % ISTAGE;
1562: metric = 0;
1563: for (i = 0; i < NCHAN; i++) {
1564: up->xmtr[i].probe++;
1565: if (up->xmtr[i].metric > metric) {
1566: up->status |= METRIC;
1567: metric = up->xmtr[i].metric;
1568: up->chan = i;
1569: }
1570: }
1571:
1572: /*
1573: * Start the next dwell. If the first dwell or no stations have
1574: * been heard, continue round-robin scan.
1575: */
1576: up->dwell = (up->dwell + 1) % DWELL;
1577: if (up->dwell == 0 || metric == 0) {
1578: rval = 0;
1579: for (i = 0; i < NCHAN; i++) {
1580: if (up->xmtr[i].probe > rval) {
1581: rval = up->xmtr[i].probe;
1582: up->chan = i;
1583: }
1584: }
1585: }
1586:
1587: /* Retune the radio at each dwell in case somebody nudges the
1588: * tuning knob.
1589: */
1590: rval = icom_freq(up->fd_icom, peer->ttl & 0x7f, qsy[up->chan] +
1591: TUNE);
1592: snprintf(up->ident, sizeof(up->ident), "CHU%d", up->chan);
1593: memcpy(&pp->refid, up->ident, 4);
1594: memcpy(&peer->refid, up->ident, 4);
1595: if (metric == 0 && up->status & METRIC) {
1596: up->status &= ~METRIC;
1597: refclock_report(peer, CEVNT_PROP);
1598: }
1599: return (rval);
1600: }
1601: #endif /* ICOM */
1602:
1603:
1604: /*
1605: * chu_dist - determine the distance of two octet arguments
1606: */
1607: static int
1608: chu_dist(
1609: int x, /* an octet of bits */
1610: int y /* another octet of bits */
1611: )
1612: {
1613: int val; /* bit count */
1614: int temp;
1615: int i;
1616:
1617: /*
1618: * The distance is determined as the weight of the exclusive OR
1619: * of the two arguments. The weight is determined by the number
1620: * of one bits in the result. Each one bit increases the weight,
1621: * while each zero bit decreases it.
1622: */
1623: temp = x ^ y;
1624: val = 0;
1625: for (i = 0; i < 8; i++) {
1626: if ((temp & 0x1) == 0)
1627: val++;
1628: else
1629: val--;
1630: temp >>= 1;
1631: }
1632: return (val);
1633: }
1634:
1635:
1636: #ifdef HAVE_AUDIO
1637: /*
1638: * chu_gain - adjust codec gain
1639: *
1640: * This routine is called at the end of each second. During the second
1641: * the number of signal clips above the MAXAMP threshold (6000). If
1642: * there are no clips, the gain is bumped up; if there are more than
1643: * MAXCLP clips (100), it is bumped down. The decoder is relatively
1644: * insensitive to amplitude, so this crudity works just peachy. The
1645: * routine also jiggles the input port and selectively mutes the
1646: */
1647: static void
1648: chu_gain(
1649: struct peer *peer /* peer structure pointer */
1650: )
1651: {
1652: struct refclockproc *pp;
1653: struct chuunit *up;
1654:
1655: pp = peer->procptr;
1656: up = (struct chuunit *)pp->unitptr;
1657:
1658: /*
1659: * Apparently, the codec uses only the high order bits of the
1660: * gain control field. Thus, it may take awhile for changes to
1661: * wiggle the hardware bits.
1662: */
1663: if (up->clipcnt == 0) {
1664: up->gain += 4;
1665: if (up->gain > MAXGAIN)
1666: up->gain = MAXGAIN;
1667: } else if (up->clipcnt > MAXCLP) {
1668: up->gain -= 4;
1669: if (up->gain < 0)
1670: up->gain = 0;
1671: }
1672: audio_gain(up->gain, up->mongain, up->port);
1673: up->clipcnt = 0;
1674: }
1675: #endif /* HAVE_AUDIO */
1676:
1677:
1678: #else
1679: int refclock_chu_bs;
1680: #endif /* REFCLOCK */
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