1: /*
2: * refclock_irig - audio IRIG-B/E demodulator/decoder
3: */
4: #ifdef HAVE_CONFIG_H
5: #include <config.h>
6: #endif
7:
8: #if defined(REFCLOCK) && defined(CLOCK_IRIG)
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: #ifdef HAVE_SYS_IOCTL_H
20: #include <sys/ioctl.h>
21: #endif /* HAVE_SYS_IOCTL_H */
22:
23: #include "audio.h"
24:
25: /*
26: * Audio IRIG-B/E demodulator/decoder
27: *
28: * This driver synchronizes the computer time using data encoded in
29: * IRIG-B/E signals commonly produced by GPS receivers and other timing
30: * devices. The IRIG signal is an amplitude-modulated carrier with
31: * pulse-width modulated data bits. For IRIG-B, the carrier frequency is
32: * 1000 Hz and bit rate 100 b/s; for IRIG-E, the carrier frequenchy is
33: * 100 Hz and bit rate 10 b/s. The driver automatically recognizes which
34: & format is in use.
35: *
36: * The driver requires an audio codec or sound card with sampling rate 8
37: * kHz and mu-law companding. This is the same standard as used by the
38: * telephone industry and is supported by most hardware and operating
39: * systems, including Solaris, SunOS, FreeBSD, NetBSD and Linux. In this
40: * implementation, only one audio driver and codec can be supported on a
41: * single machine.
42: *
43: * The program processes 8000-Hz mu-law companded samples using separate
44: * signal filters for IRIG-B and IRIG-E, a comb filter, envelope
45: * detector and automatic threshold corrector. Cycle crossings relative
46: * to the corrected slice level determine the width of each pulse and
47: * its value - zero, one or position identifier.
48: *
49: * The data encode 20 BCD digits which determine the second, minute,
50: * hour and day of the year and sometimes the year and synchronization
51: * condition. The comb filter exponentially averages the corresponding
52: * samples of successive baud intervals in order to reliably identify
53: * the reference carrier cycle. A type-II phase-lock loop (PLL) performs
54: * additional integration and interpolation to accurately determine the
55: * zero crossing of that cycle, which determines the reference
56: * timestamp. A pulse-width discriminator demodulates the data pulses,
57: * which are then encoded as the BCD digits of the timecode.
58: *
59: * The timecode and reference timestamp are updated once each second
60: * with IRIG-B (ten seconds with IRIG-E) and local clock offset samples
61: * saved for later processing. At poll intervals of 64 s, the saved
62: * samples are processed by a trimmed-mean filter and used to update the
63: * system clock.
64: *
65: * An automatic gain control feature provides protection against
66: * overdriven or underdriven input signal amplitudes. It is designed to
67: * maintain adequate demodulator signal amplitude while avoiding
68: * occasional noise spikes. In order to assure reliable capture, the
69: * decompanded input signal amplitude must be greater than 100 units and
70: * the codec sample frequency error less than 250 PPM (.025 percent).
71: *
72: * Monitor Data
73: *
74: * The timecode format used for debugging and data recording includes
75: * data helpful in diagnosing problems with the IRIG signal and codec
76: * connections. The driver produces one line for each timecode in the
77: * following format:
78: *
79: * 00 00 98 23 19:26:52 2782 143 0.694 10 0.3 66.5 3094572411.00027
80: *
81: * If clockstats is enabled, the most recent line is written to the
82: * clockstats file every 64 s. If verbose recording is enabled (fudge
83: * flag 4) each line is written as generated.
84: *
85: * The first field containes the error flags in hex, where the hex bits
86: * are interpreted as below. This is followed by the year of century,
87: * day of year and time of day. Note that the time of day is for the
88: * previous minute, not the current time. The status indicator and year
89: * are not produced by some IRIG devices and appear as zeros. Following
90: * these fields are the carrier amplitude (0-3000), codec gain (0-255),
91: * modulation index (0-1), time constant (4-10), carrier phase error
92: * +-.5) and carrier frequency error (PPM). The last field is the on-
93: * time timestamp in NTP format.
94: *
95: * The error flags are defined as follows in hex:
96: *
97: * x01 Low signal. The carrier amplitude is less than 100 units. This
98: * is usually the result of no signal or wrong input port.
99: * x02 Frequency error. The codec frequency error is greater than 250
100: * PPM. This may be due to wrong signal format or (rarely)
101: * defective codec.
102: * x04 Modulation error. The IRIG modulation index is less than 0.5.
103: * This is usually the result of an overdriven codec, wrong signal
104: * format or wrong input port.
105: * x08 Frame synch error. The decoder frame does not match the IRIG
106: * frame. This is usually the result of an overdriven codec, wrong
107: * signal format or noisy IRIG signal. It may also be the result of
108: * an IRIG signature check which indicates a failure of the IRIG
109: * signal synchronization source.
110: * x10 Data bit error. The data bit length is out of tolerance. This is
111: * usually the result of an overdriven codec, wrong signal format
112: * or noisy IRIG signal.
113: * x20 Seconds numbering discrepancy. The decoder second does not match
114: * the IRIG second. This is usually the result of an overdriven
115: * codec, wrong signal format or noisy IRIG signal.
116: * x40 Codec error (overrun). The machine is not fast enough to keep up
117: * with the codec.
118: * x80 Device status error (Spectracom).
119: *
120: *
121: * Once upon a time, an UltrSPARC 30 and Solaris 2.7 kept the clock
122: * within a few tens of microseconds relative to the IRIG-B signal.
123: * Accuracy with IRIG-E was about ten times worse. Unfortunately, Sun
124: * broke the 2.7 audio driver in 2.8, which has a 10-ms sawtooth
125: * modulation.
126: *
127: * Unlike other drivers, which can have multiple instantiations, this
128: * one supports only one. It does not seem likely that more than one
129: * audio codec would be useful in a single machine. More than one would
130: * probably chew up too much CPU time anyway.
131: *
132: * Fudge factors
133: *
134: * Fudge flag4 causes the dubugging output described above to be
135: * recorded in the clockstats file. Fudge flag2 selects the audio input
136: * port, where 0 is the mike port (default) and 1 is the line-in port.
137: * It does not seem useful to select the compact disc player port. Fudge
138: * flag3 enables audio monitoring of the input signal. For this purpose,
139: * the monitor gain is set t a default value. Fudgetime2 is used as a
140: * frequency vernier for broken codec sample frequency.
141: *
142: * Alarm codes
143: *
144: * CEVNT_BADTIME invalid date or time
145: * CEVNT_TIMEOUT no IRIG data since last poll
146: */
147: /*
148: * Interface definitions
149: */
150: #define DEVICE_AUDIO "/dev/audio" /* audio device name */
151: #define PRECISION (-17) /* precision assumed (about 10 us) */
152: #define REFID "IRIG" /* reference ID */
153: #define DESCRIPTION "Generic IRIG Audio Driver" /* WRU */
154: #define AUDIO_BUFSIZ 320 /* audio buffer size (40 ms) */
155: #define SECOND 8000 /* nominal sample rate (Hz) */
156: #define BAUD 80 /* samples per baud interval */
157: #define OFFSET 128 /* companded sample offset */
158: #define SIZE 256 /* decompanding table size */
159: #define CYCLE 8 /* samples per bit */
160: #define SUBFLD 10 /* bits per frame */
161: #define FIELD 100 /* bits per second */
162: #define MINTC 2 /* min PLL time constant */
163: #define MAXTC 10 /* max PLL time constant max */
164: #define MAXAMP 3000. /* maximum signal amplitude */
165: #define MINAMP 2000. /* minimum signal amplitude */
166: #define DRPOUT 100. /* dropout signal amplitude */
167: #define MODMIN 0.5 /* minimum modulation index */
168: #define MAXFREQ (250e-6 * SECOND) /* freq tolerance (.025%) */
169:
170: /*
171: * The on-time synchronization point is the positive-going zero crossing
172: * of the first cycle of the second. The IIR baseband filter phase delay
173: * is 1.03 ms for IRIG-B and 3.47 ms for IRIG-E. The fudge value 2.68 ms
174: * due to the codec and other causes was determined by calibrating to a
175: * PPS signal from a GPS receiver.
176: *
177: * The results with a 2.4-GHz P4 running FreeBSD 6.1 are generally
178: * within .02 ms short-term with .02 ms jitter. The processor load due
179: * to the driver is 0.51 percent.
180: */
181: #define IRIG_B ((1.03 + 2.68) / 1000) /* IRIG-B system delay (s) */
182: #define IRIG_E ((3.47 + 2.68) / 1000) /* IRIG-E system delay (s) */
183:
184: /*
185: * Data bit definitions
186: */
187: #define BIT0 0 /* zero */
188: #define BIT1 1 /* one */
189: #define BITP 2 /* position identifier */
190:
191: /*
192: * Error flags
193: */
194: #define IRIG_ERR_AMP 0x01 /* low carrier amplitude */
195: #define IRIG_ERR_FREQ 0x02 /* frequency tolerance exceeded */
196: #define IRIG_ERR_MOD 0x04 /* low modulation index */
197: #define IRIG_ERR_SYNCH 0x08 /* frame synch error */
198: #define IRIG_ERR_DECODE 0x10 /* frame decoding error */
199: #define IRIG_ERR_CHECK 0x20 /* second numbering discrepancy */
200: #define IRIG_ERR_ERROR 0x40 /* codec error (overrun) */
201: #define IRIG_ERR_SIGERR 0x80 /* IRIG status error (Spectracom) */
202:
203: static char hexchar[] = "0123456789abcdef";
204:
205: /*
206: * IRIG unit control structure
207: */
208: struct irigunit {
209: u_char timecode[2 * SUBFLD + 1]; /* timecode string */
210: l_fp timestamp; /* audio sample timestamp */
211: l_fp tick; /* audio sample increment */
212: l_fp refstamp; /* reference timestamp */
213: l_fp chrstamp; /* baud timestamp */
214: l_fp prvstamp; /* previous baud timestamp */
215: double integ[BAUD]; /* baud integrator */
216: double phase, freq; /* logical clock phase and frequency */
217: double zxing; /* phase detector integrator */
218: double yxing; /* cycle phase */
219: double exing; /* envelope phase */
220: double modndx; /* modulation index */
221: double irig_b; /* IRIG-B signal amplitude */
222: double irig_e; /* IRIG-E signal amplitude */
223: int errflg; /* error flags */
224: /*
225: * Audio codec variables
226: */
227: double comp[SIZE]; /* decompanding table */
228: double signal; /* peak signal for AGC */
229: int port; /* codec port */
230: int gain; /* codec gain */
231: int mongain; /* codec monitor gain */
232: int seccnt; /* second interval counter */
233:
234: /*
235: * RF variables
236: */
237: double bpf[9]; /* IRIG-B filter shift register */
238: double lpf[5]; /* IRIG-E filter shift register */
239: double envmin, envmax; /* envelope min and max */
240: double slice; /* envelope slice level */
241: double intmin, intmax; /* integrated envelope min and max */
242: double maxsignal; /* integrated peak amplitude */
243: double noise; /* integrated noise amplitude */
244: double lastenv[CYCLE]; /* last cycle amplitudes */
245: double lastint[CYCLE]; /* last integrated cycle amplitudes */
246: double lastsig; /* last carrier sample */
247: double fdelay; /* filter delay */
248: int decim; /* sample decimation factor */
249: int envphase; /* envelope phase */
250: int envptr; /* envelope phase pointer */
251: int envsw; /* envelope state */
252: int envxing; /* envelope slice crossing */
253: int tc; /* time constant */
254: int tcount; /* time constant counter */
255: int badcnt; /* decimation interval counter */
256:
257: /*
258: * Decoder variables
259: */
260: int pulse; /* cycle counter */
261: int cycles; /* carrier cycles */
262: int dcycles; /* data cycles */
263: int lastbit; /* last code element */
264: int second; /* previous second */
265: int bitcnt; /* bit count in frame */
266: int frmcnt; /* bit count in second */
267: int xptr; /* timecode pointer */
268: int bits; /* demodulated bits */
269: };
270:
271: /*
272: * Function prototypes
273: */
274: static int irig_start (int, struct peer *);
275: static void irig_shutdown (int, struct peer *);
276: static void irig_receive (struct recvbuf *);
277: static void irig_poll (int, struct peer *);
278:
279: /*
280: * More function prototypes
281: */
282: static void irig_base (struct peer *, double);
283: static void irig_rf (struct peer *, double);
284: static void irig_baud (struct peer *, int);
285: static void irig_decode (struct peer *, int);
286: static void irig_gain (struct peer *);
287:
288: /*
289: * Transfer vector
290: */
291: struct refclock refclock_irig = {
292: irig_start, /* start up driver */
293: irig_shutdown, /* shut down driver */
294: irig_poll, /* transmit poll message */
295: noentry, /* not used (old irig_control) */
296: noentry, /* initialize driver (not used) */
297: noentry, /* not used (old irig_buginfo) */
298: NOFLAGS /* not used */
299: };
300:
301:
302: /*
303: * irig_start - open the devices and initialize data for processing
304: */
305: static int
306: irig_start(
307: int unit, /* instance number (used for PCM) */
308: struct peer *peer /* peer structure pointer */
309: )
310: {
311: struct refclockproc *pp;
312: struct irigunit *up;
313:
314: /*
315: * Local variables
316: */
317: int fd; /* file descriptor */
318: int i; /* index */
319: double step; /* codec adjustment */
320:
321: /*
322: * Open audio device
323: */
324: fd = audio_init(DEVICE_AUDIO, AUDIO_BUFSIZ, unit);
325: if (fd < 0)
326: return (0);
327: #ifdef DEBUG
328: if (debug)
329: audio_show();
330: #endif
331:
332: /*
333: * Allocate and initialize unit structure
334: */
335: up = emalloc(sizeof(*up));
336: memset(up, 0, sizeof(*up));
337: pp = peer->procptr;
338: pp->unitptr = (caddr_t)up;
339: pp->io.clock_recv = irig_receive;
340: pp->io.srcclock = (caddr_t)peer;
341: pp->io.datalen = 0;
342: pp->io.fd = fd;
343: if (!io_addclock(&pp->io)) {
344: close(fd);
345: pp->io.fd = -1;
346: free(up);
347: pp->unitptr = NULL;
348: return (0);
349: }
350:
351: /*
352: * Initialize miscellaneous variables
353: */
354: peer->precision = PRECISION;
355: pp->clockdesc = DESCRIPTION;
356: memcpy((char *)&pp->refid, REFID, 4);
357: up->tc = MINTC;
358: up->decim = 1;
359: up->gain = 127;
360:
361: /*
362: * The companded samples are encoded sign-magnitude. The table
363: * contains all the 256 values in the interest of speed.
364: */
365: up->comp[0] = up->comp[OFFSET] = 0.;
366: up->comp[1] = 1; up->comp[OFFSET + 1] = -1.;
367: up->comp[2] = 3; up->comp[OFFSET + 2] = -3.;
368: step = 2.;
369: for (i = 3; i < OFFSET; i++) {
370: up->comp[i] = up->comp[i - 1] + step;
371: up->comp[OFFSET + i] = -up->comp[i];
372: if (i % 16 == 0)
373: step *= 2.;
374: }
375: DTOLFP(1. / SECOND, &up->tick);
376: return (1);
377: }
378:
379:
380: /*
381: * irig_shutdown - shut down the clock
382: */
383: static void
384: irig_shutdown(
385: int unit, /* instance number (not used) */
386: struct peer *peer /* peer structure pointer */
387: )
388: {
389: struct refclockproc *pp;
390: struct irigunit *up;
391:
392: pp = peer->procptr;
393: up = (struct irigunit *)pp->unitptr;
394: if (-1 != pp->io.fd)
395: io_closeclock(&pp->io);
396: if (NULL != up)
397: free(up);
398: }
399:
400:
401: /*
402: * irig_receive - receive data from the audio device
403: *
404: * This routine reads input samples and adjusts the logical clock to
405: * track the irig clock by dropping or duplicating codec samples.
406: */
407: static void
408: irig_receive(
409: struct recvbuf *rbufp /* receive buffer structure pointer */
410: )
411: {
412: struct peer *peer;
413: struct refclockproc *pp;
414: struct irigunit *up;
415:
416: /*
417: * Local variables
418: */
419: double sample; /* codec sample */
420: u_char *dpt; /* buffer pointer */
421: int bufcnt; /* buffer counter */
422: l_fp ltemp; /* l_fp temp */
423:
424: peer = (struct peer *)rbufp->recv_srcclock;
425: pp = peer->procptr;
426: up = (struct irigunit *)pp->unitptr;
427:
428: /*
429: * Main loop - read until there ain't no more. Note codec
430: * samples are bit-inverted.
431: */
432: DTOLFP((double)rbufp->recv_length / SECOND, <emp);
433: L_SUB(&rbufp->recv_time, <emp);
434: up->timestamp = rbufp->recv_time;
435: dpt = rbufp->recv_buffer;
436: for (bufcnt = 0; bufcnt < rbufp->recv_length; bufcnt++) {
437: sample = up->comp[~*dpt++ & 0xff];
438:
439: /*
440: * Variable frequency oscillator. The codec oscillator
441: * runs at the nominal rate of 8000 samples per second,
442: * or 125 us per sample. A frequency change of one unit
443: * results in either duplicating or deleting one sample
444: * per second, which results in a frequency change of
445: * 125 PPM.
446: */
447: up->phase += (up->freq + clock_codec) / SECOND;
448: up->phase += pp->fudgetime2 / 1e6;
449: if (up->phase >= .5) {
450: up->phase -= 1.;
451: } else if (up->phase < -.5) {
452: up->phase += 1.;
453: irig_rf(peer, sample);
454: irig_rf(peer, sample);
455: } else {
456: irig_rf(peer, sample);
457: }
458: L_ADD(&up->timestamp, &up->tick);
459: sample = fabs(sample);
460: if (sample > up->signal)
461: up->signal = sample;
462: up->signal += (sample - up->signal) /
463: 1000;
464:
465: /*
466: * Once each second, determine the IRIG format and gain.
467: */
468: up->seccnt = (up->seccnt + 1) % SECOND;
469: if (up->seccnt == 0) {
470: if (up->irig_b > up->irig_e) {
471: up->decim = 1;
472: up->fdelay = IRIG_B;
473: } else {
474: up->decim = 10;
475: up->fdelay = IRIG_E;
476: }
477: up->irig_b = up->irig_e = 0;
478: irig_gain(peer);
479:
480: }
481: }
482:
483: /*
484: * Set the input port and monitor gain for the next buffer.
485: */
486: if (pp->sloppyclockflag & CLK_FLAG2)
487: up->port = 2;
488: else
489: up->port = 1;
490: if (pp->sloppyclockflag & CLK_FLAG3)
491: up->mongain = MONGAIN;
492: else
493: up->mongain = 0;
494: }
495:
496:
497: /*
498: * irig_rf - RF processing
499: *
500: * This routine filters the RF signal using a bandass filter for IRIG-B
501: * and a lowpass filter for IRIG-E. In case of IRIG-E, the samples are
502: * decimated by a factor of ten. Note that the codec filters function as
503: * roofing filters to attenuate both the high and low ends of the
504: * passband. IIR filter coefficients were determined using Matlab Signal
505: * Processing Toolkit.
506: */
507: static void
508: irig_rf(
509: struct peer *peer, /* peer structure pointer */
510: double sample /* current signal sample */
511: )
512: {
513: struct refclockproc *pp;
514: struct irigunit *up;
515:
516: /*
517: * Local variables
518: */
519: double irig_b, irig_e; /* irig filter outputs */
520:
521: pp = peer->procptr;
522: up = (struct irigunit *)pp->unitptr;
523:
524: /*
525: * IRIG-B filter. Matlab 4th-order IIR elliptic, 800-1200 Hz
526: * bandpass, 0.3 dB passband ripple, -50 dB stopband ripple,
527: * phase delay 1.03 ms.
528: */
529: irig_b = (up->bpf[8] = up->bpf[7]) * 6.505491e-001;
530: irig_b += (up->bpf[7] = up->bpf[6]) * -3.875180e+000;
531: irig_b += (up->bpf[6] = up->bpf[5]) * 1.151180e+001;
532: irig_b += (up->bpf[5] = up->bpf[4]) * -2.141264e+001;
533: irig_b += (up->bpf[4] = up->bpf[3]) * 2.712837e+001;
534: irig_b += (up->bpf[3] = up->bpf[2]) * -2.384486e+001;
535: irig_b += (up->bpf[2] = up->bpf[1]) * 1.427663e+001;
536: irig_b += (up->bpf[1] = up->bpf[0]) * -5.352734e+000;
537: up->bpf[0] = sample - irig_b;
538: irig_b = up->bpf[0] * 4.952157e-003
539: + up->bpf[1] * -2.055878e-002
540: + up->bpf[2] * 4.401413e-002
541: + up->bpf[3] * -6.558851e-002
542: + up->bpf[4] * 7.462108e-002
543: + up->bpf[5] * -6.558851e-002
544: + up->bpf[6] * 4.401413e-002
545: + up->bpf[7] * -2.055878e-002
546: + up->bpf[8] * 4.952157e-003;
547: up->irig_b += irig_b * irig_b;
548:
549: /*
550: * IRIG-E filter. Matlab 4th-order IIR elliptic, 130-Hz lowpass,
551: * 0.3 dB passband ripple, -50 dB stopband ripple, phase delay
552: * 3.47 ms.
553: */
554: irig_e = (up->lpf[4] = up->lpf[3]) * 8.694604e-001;
555: irig_e += (up->lpf[3] = up->lpf[2]) * -3.589893e+000;
556: irig_e += (up->lpf[2] = up->lpf[1]) * 5.570154e+000;
557: irig_e += (up->lpf[1] = up->lpf[0]) * -3.849667e+000;
558: up->lpf[0] = sample - irig_e;
559: irig_e = up->lpf[0] * 3.215696e-003
560: + up->lpf[1] * -1.174951e-002
561: + up->lpf[2] * 1.712074e-002
562: + up->lpf[3] * -1.174951e-002
563: + up->lpf[4] * 3.215696e-003;
564: up->irig_e += irig_e * irig_e;
565:
566: /*
567: * Decimate by a factor of either 1 (IRIG-B) or 10 (IRIG-E).
568: */
569: up->badcnt = (up->badcnt + 1) % up->decim;
570: if (up->badcnt == 0) {
571: if (up->decim == 1)
572: irig_base(peer, irig_b);
573: else
574: irig_base(peer, irig_e);
575: }
576: }
577:
578: /*
579: * irig_base - baseband processing
580: *
581: * This routine processes the baseband signal and demodulates the AM
582: * carrier using a synchronous detector. It then synchronizes to the
583: * data frame at the baud rate and decodes the width-modulated data
584: * pulses.
585: */
586: static void
587: irig_base(
588: struct peer *peer, /* peer structure pointer */
589: double sample /* current signal sample */
590: )
591: {
592: struct refclockproc *pp;
593: struct irigunit *up;
594:
595: /*
596: * Local variables
597: */
598: double lope; /* integrator output */
599: double env; /* envelope detector output */
600: double dtemp;
601: int carphase; /* carrier phase */
602:
603: pp = peer->procptr;
604: up = (struct irigunit *)pp->unitptr;
605:
606: /*
607: * Synchronous baud integrator. Corresponding samples of current
608: * and past baud intervals are integrated to refine the envelope
609: * amplitude and phase estimate. We keep one cycle (1 ms) of the
610: * raw data and one baud (10 ms) of the integrated data.
611: */
612: up->envphase = (up->envphase + 1) % BAUD;
613: up->integ[up->envphase] += (sample - up->integ[up->envphase]) /
614: (5 * up->tc);
615: lope = up->integ[up->envphase];
616: carphase = up->envphase % CYCLE;
617: up->lastenv[carphase] = sample;
618: up->lastint[carphase] = lope;
619:
620: /*
621: * Phase detector. Find the negative-going zero crossing
622: * relative to sample 4 in the 8-sample sycle. A phase change of
623: * 360 degrees produces an output change of one unit.
624: */
625: if (up->lastsig > 0 && lope <= 0)
626: up->zxing += (double)(carphase - 4) / CYCLE;
627: up->lastsig = lope;
628:
629: /*
630: * End of the baud. Update signal/noise estimates and PLL
631: * phase, frequency and time constant.
632: */
633: if (up->envphase == 0) {
634: up->maxsignal = up->intmax; up->noise = up->intmin;
635: up->intmin = 1e6; up->intmax = -1e6;
636: if (up->maxsignal < DRPOUT)
637: up->errflg |= IRIG_ERR_AMP;
638: if (up->maxsignal > 0)
639: up->modndx = (up->maxsignal - up->noise) /
640: up->maxsignal;
641: else
642: up->modndx = 0;
643: if (up->modndx < MODMIN)
644: up->errflg |= IRIG_ERR_MOD;
645: if (up->errflg & (IRIG_ERR_AMP | IRIG_ERR_FREQ |
646: IRIG_ERR_MOD | IRIG_ERR_SYNCH)) {
647: up->tc = MINTC;
648: up->tcount = 0;
649: }
650:
651: /*
652: * Update PLL phase and frequency. The PLL time constant
653: * is set initially to stabilize the frequency within a
654: * minute or two, then increases to the maximum. The
655: * frequency is clamped so that the PLL capture range
656: * cannot be exceeded.
657: */
658: dtemp = up->zxing * up->decim / BAUD;
659: up->yxing = dtemp;
660: up->zxing = 0.;
661: up->phase += dtemp / up->tc;
662: up->freq += dtemp / (4. * up->tc * up->tc);
663: if (up->freq > MAXFREQ) {
664: up->freq = MAXFREQ;
665: up->errflg |= IRIG_ERR_FREQ;
666: } else if (up->freq < -MAXFREQ) {
667: up->freq = -MAXFREQ;
668: up->errflg |= IRIG_ERR_FREQ;
669: }
670: }
671:
672: /*
673: * Synchronous demodulator. There are eight samples in the cycle
674: * and ten cycles in the baud. Since the PLL has aligned the
675: * negative-going zero crossing at sample 4, the maximum
676: * amplitude is at sample 2 and minimum at sample 6. The
677: * beginning of the data pulse is determined from the integrated
678: * samples, while the end of the pulse is determined from the
679: * raw samples. The raw data bits are demodulated relative to
680: * the slice level and left-shifted in the decoding register.
681: */
682: if (carphase != 7)
683: return;
684:
685: lope = (up->lastint[2] - up->lastint[6]) / 2.;
686: if (lope > up->intmax)
687: up->intmax = lope;
688: if (lope < up->intmin)
689: up->intmin = lope;
690:
691: /*
692: * Pulse code demodulator and reference timestamp. The decoder
693: * looks for a sequence of ten bits; the first two bits must be
694: * one, the last two bits must be zero. Frame synch is asserted
695: * when three correct frames have been found.
696: */
697: up->pulse = (up->pulse + 1) % 10;
698: up->cycles <<= 1;
699: if (lope >= (up->maxsignal + up->noise) / 2.)
700: up->cycles |= 1;
701: if ((up->cycles & 0x303c0f03) == 0x300c0300) {
702: if (up->pulse != 0)
703: up->errflg |= IRIG_ERR_SYNCH;
704: up->pulse = 0;
705: }
706:
707: /*
708: * Assemble the baud and max/min to get the slice level for the
709: * next baud. The slice level is based on the maximum over the
710: * first two bits and the minimum over the last two bits, with
711: * the slice level halfway between the maximum and minimum.
712: */
713: env = (up->lastenv[2] - up->lastenv[6]) / 2.;
714: up->dcycles <<= 1;
715: if (env >= up->slice)
716: up->dcycles |= 1;
717: switch(up->pulse) {
718:
719: case 0:
720: irig_baud(peer, up->dcycles);
721: if (env < up->envmin)
722: up->envmin = env;
723: up->slice = (up->envmax + up->envmin) / 2;
724: up->envmin = 1e6; up->envmax = -1e6;
725: break;
726:
727: case 1:
728: up->envmax = env;
729: break;
730:
731: case 2:
732: if (env > up->envmax)
733: up->envmax = env;
734: break;
735:
736: case 9:
737: up->envmin = env;
738: break;
739: }
740: }
741:
742: /*
743: * irig_baud - update the PLL and decode the pulse-width signal
744: */
745: static void
746: irig_baud(
747: struct peer *peer, /* peer structure pointer */
748: int bits /* decoded bits */
749: )
750: {
751: struct refclockproc *pp;
752: struct irigunit *up;
753: double dtemp;
754: l_fp ltemp;
755:
756: pp = peer->procptr;
757: up = (struct irigunit *)pp->unitptr;
758:
759: /*
760: * The PLL time constant starts out small, in order to
761: * sustain a frequency tolerance of 250 PPM. It
762: * gradually increases as the loop settles down. Note
763: * that small wiggles are not believed, unless they
764: * persist for lots of samples.
765: */
766: up->exing = -up->yxing;
767: if (fabs(up->envxing - up->envphase) <= 1) {
768: up->tcount++;
769: if (up->tcount > 20 * up->tc) {
770: up->tc++;
771: if (up->tc > MAXTC)
772: up->tc = MAXTC;
773: up->tcount = 0;
774: up->envxing = up->envphase;
775: } else {
776: up->exing -= up->envxing - up->envphase;
777: }
778: } else {
779: up->tcount = 0;
780: up->envxing = up->envphase;
781: }
782:
783: /*
784: * Strike the baud timestamp as the positive zero crossing of
785: * the first bit, accounting for the codec delay and filter
786: * delay.
787: */
788: up->prvstamp = up->chrstamp;
789: dtemp = up->decim * (up->exing / SECOND) + up->fdelay;
790: DTOLFP(dtemp, <emp);
791: up->chrstamp = up->timestamp;
792: L_SUB(&up->chrstamp, <emp);
793:
794: /*
795: * The data bits are collected in ten-bit bauds. The first two
796: * bits are not used. The resulting patterns represent runs of
797: * 0-1 bits (0), 2-4 bits (1) and 5-7 bits (PI). The remaining
798: * 8-bit run represents a soft error and is treated as 0.
799: */
800: switch (up->dcycles & 0xff) {
801:
802: case 0x00: /* 0-1 bits (0) */
803: case 0x80:
804: irig_decode(peer, BIT0);
805: break;
806:
807: case 0xc0: /* 2-4 bits (1) */
808: case 0xe0:
809: case 0xf0:
810: irig_decode(peer, BIT1);
811: break;
812:
813: case 0xf8: /* (5-7 bits (PI) */
814: case 0xfc:
815: case 0xfe:
816: irig_decode(peer, BITP);
817: break;
818:
819: default: /* 8 bits (error) */
820: irig_decode(peer, BIT0);
821: up->errflg |= IRIG_ERR_DECODE;
822: }
823: }
824:
825:
826: /*
827: * irig_decode - decode the data
828: *
829: * This routine assembles bauds into digits, digits into frames and
830: * frames into the timecode fields. Bits can have values of zero, one
831: * or position identifier. There are four bits per digit, ten digits per
832: * frame and ten frames per second.
833: */
834: static void
835: irig_decode(
836: struct peer *peer, /* peer structure pointer */
837: int bit /* data bit (0, 1 or 2) */
838: )
839: {
840: struct refclockproc *pp;
841: struct irigunit *up;
842:
843: /*
844: * Local variables
845: */
846: int syncdig; /* sync digit (Spectracom) */
847: char sbs[6 + 1]; /* binary seconds since 0h */
848: char spare[2 + 1]; /* mulligan digits */
849: int temp;
850:
851: pp = peer->procptr;
852: up = (struct irigunit *)pp->unitptr;
853:
854: /*
855: * Assemble frame bits.
856: */
857: up->bits >>= 1;
858: if (bit == BIT1) {
859: up->bits |= 0x200;
860: } else if (bit == BITP && up->lastbit == BITP) {
861:
862: /*
863: * Frame sync - two adjacent position identifiers, which
864: * mark the beginning of the second. The reference time
865: * is the beginning of the second position identifier,
866: * so copy the character timestamp to the reference
867: * timestamp.
868: */
869: if (up->frmcnt != 1)
870: up->errflg |= IRIG_ERR_SYNCH;
871: up->frmcnt = 1;
872: up->refstamp = up->prvstamp;
873: }
874: up->lastbit = bit;
875: if (up->frmcnt % SUBFLD == 0) {
876:
877: /*
878: * End of frame. Encode two hexadecimal digits in
879: * little-endian timecode field. Note frame 1 is shifted
880: * right one bit to account for the marker PI.
881: */
882: temp = up->bits;
883: if (up->frmcnt == 10)
884: temp >>= 1;
885: if (up->xptr >= 2) {
886: up->timecode[--up->xptr] = hexchar[temp & 0xf];
887: up->timecode[--up->xptr] = hexchar[(temp >> 5) &
888: 0xf];
889: }
890: if (up->frmcnt == 0) {
891:
892: /*
893: * End of second. Decode the timecode and wind
894: * the clock. Not all IRIG generators have the
895: * year; if so, it is nonzero after year 2000.
896: * Not all have the hardware status bit; if so,
897: * it is lit when the source is okay and dim
898: * when bad. We watch this only if the year is
899: * nonzero. Not all are configured for signature
900: * control. If so, all BCD digits are set to
901: * zero if the source is bad. In this case the
902: * refclock_process() will reject the timecode
903: * as invalid.
904: */
905: up->xptr = 2 * SUBFLD;
906: if (sscanf((char *)up->timecode,
907: "%6s%2d%1d%2s%3d%2d%2d%2d", sbs, &pp->year,
908: &syncdig, spare, &pp->day, &pp->hour,
909: &pp->minute, &pp->second) != 8)
910: pp->leap = LEAP_NOTINSYNC;
911: else
912: pp->leap = LEAP_NOWARNING;
913: up->second = (up->second + up->decim) % 60;
914:
915: /*
916: * Raise an alarm if the day field is zero,
917: * which happens when signature control is
918: * enabled and the device has lost
919: * synchronization. Raise an alarm if the year
920: * field is nonzero and the sync indicator is
921: * zero, which happens when a Spectracom radio
922: * has lost synchronization. Raise an alarm if
923: * the expected second does not agree with the
924: * decoded second, which happens with a garbled
925: * IRIG signal. We are very particular.
926: */
927: if (pp->day == 0 || (pp->year != 0 && syncdig ==
928: 0))
929: up->errflg |= IRIG_ERR_SIGERR;
930: if (pp->second != up->second)
931: up->errflg |= IRIG_ERR_CHECK;
932: up->second = pp->second;
933:
934: /*
935: * Wind the clock only if there are no errors
936: * and the time constant has reached the
937: * maximum.
938: */
939: if (up->errflg == 0 && up->tc == MAXTC) {
940: pp->lastref = pp->lastrec;
941: pp->lastrec = up->refstamp;
942: if (!refclock_process(pp))
943: refclock_report(peer,
944: CEVNT_BADTIME);
945: }
946: snprintf(pp->a_lastcode, sizeof(pp->a_lastcode),
947: "%02x %02d %03d %02d:%02d:%02d %4.0f %3d %6.3f %2d %6.2f %6.1f %s",
948: up->errflg, pp->year, pp->day,
949: pp->hour, pp->minute, pp->second,
950: up->maxsignal, up->gain, up->modndx,
951: up->tc, up->exing * 1e6 / SECOND, up->freq *
952: 1e6 / SECOND, ulfptoa(&pp->lastrec, 6));
953: pp->lencode = strlen(pp->a_lastcode);
954: up->errflg = 0;
955: if (pp->sloppyclockflag & CLK_FLAG4) {
956: record_clock_stats(&peer->srcadr,
957: pp->a_lastcode);
958: #ifdef DEBUG
959: if (debug)
960: printf("irig %s\n",
961: pp->a_lastcode);
962: #endif /* DEBUG */
963: }
964: }
965: }
966: up->frmcnt = (up->frmcnt + 1) % FIELD;
967: }
968:
969:
970: /*
971: * irig_poll - called by the transmit procedure
972: *
973: * This routine sweeps up the timecode updates since the last poll. For
974: * IRIG-B there should be at least 60 updates; for IRIG-E there should
975: * be at least 6. If nothing is heard, a timeout event is declared.
976: */
977: static void
978: irig_poll(
979: int unit, /* instance number (not used) */
980: struct peer *peer /* peer structure pointer */
981: )
982: {
983: struct refclockproc *pp;
984: struct irigunit *up;
985:
986: pp = peer->procptr;
987: up = (struct irigunit *)pp->unitptr;
988:
989: if (pp->coderecv == pp->codeproc) {
990: refclock_report(peer, CEVNT_TIMEOUT);
991: return;
992:
993: }
994: refclock_receive(peer);
995: if (!(pp->sloppyclockflag & CLK_FLAG4)) {
996: record_clock_stats(&peer->srcadr, pp->a_lastcode);
997: #ifdef DEBUG
998: if (debug)
999: printf("irig %s\n", pp->a_lastcode);
1000: #endif /* DEBUG */
1001: }
1002: pp->polls++;
1003:
1004: }
1005:
1006:
1007: /*
1008: * irig_gain - adjust codec gain
1009: *
1010: * This routine is called at the end of each second. It uses the AGC to
1011: * bradket the maximum signal level between MINAMP and MAXAMP to avoid
1012: * hunting. The routine also jiggles the input port and selectively
1013: * mutes the monitor.
1014: */
1015: static void
1016: irig_gain(
1017: struct peer *peer /* peer structure pointer */
1018: )
1019: {
1020: struct refclockproc *pp;
1021: struct irigunit *up;
1022:
1023: pp = peer->procptr;
1024: up = (struct irigunit *)pp->unitptr;
1025:
1026: /*
1027: * Apparently, the codec uses only the high order bits of the
1028: * gain control field. Thus, it may take awhile for changes to
1029: * wiggle the hardware bits.
1030: */
1031: if (up->maxsignal < MINAMP) {
1032: up->gain += 4;
1033: if (up->gain > MAXGAIN)
1034: up->gain = MAXGAIN;
1035: } else if (up->maxsignal > MAXAMP) {
1036: up->gain -= 4;
1037: if (up->gain < 0)
1038: up->gain = 0;
1039: }
1040: audio_gain(up->gain, up->mongain, up->port);
1041: }
1042:
1043:
1044: #else
1045: int refclock_irig_bs;
1046: #endif /* REFCLOCK */
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