refclock_irig.c

网络时间协议NTP 源码 版本v4.2.0b 该源码用于linux平台下

	/*
	 * Pulse code demodulator and reference timestamp. The decoder
	 * looks for a sequence of ten bits; the first two bits must be
	 * one, the last two bits must be zero. Frame synch is asserted
	 * when three correct frames have been found.
	 */
	up->pulse = (up->pulse + 1) % 10;
	if (up->pulse == 1)
		up->envmax = env;
	else if (up->pulse == 9)
		up->envmin = env;
	up->dcycles <<= 1;
	if (env >= (up->envmax + up->envmin) / 2.)
		up->dcycles |= 1;
	up->cycles <<= 1;
	if (lope >= (up->maxsignal + up->noise) / 2.)
		up->cycles |= 1;
	if ((up->cycles & 0x303c0f03) == 0x300c0300) {
		l_fp ltemp;
		int bitz;

		/*
		 * The PLL time constant starts out small, in order to
		 * sustain a frequency tolerance of 250 PPM. It
		 * gradually increases as the loop settles down. Note
		 * that small wiggles are not believed, unless they
		 * persist for lots of samples.
		 */
		if (up->pulse != 9)
			up->errflg |= IRIG_ERR_SYNCH;
		up->pulse = 9;
		up->exing = -up->yxing;
		if (fabs(up->envxing - up->envphase) <= 1) {
			up->tcount++;
			if (up->tcount > 50 * up->tc) {
				up->tc++;
				if (up->tc > MAXTC)
					up->tc = MAXTC;
				up->tcount = 0;
				up->envxing = up->envphase;
			} else {
				up->exing -= up->envxing - up->envphase;
			}
		} else {
			up->tcount = 0;
			up->envxing = up->envphase;
		}

		/*
		 * Determine a reference timestamp, accounting for the
		 * codec delay and filter delay. Note the timestamp is
		 * for the previous frame, so we have to backtrack for
		 * this plus the delay since the last carrier positive
		 * zero crossing.
		 */
		dtemp = up->decim * ((up->exing + BAUD) / SECOND + 1.) +
		    up->fdelay;
		DTOLFP(dtemp, &ltemp);
		pp->lastrec = up->timestamp;
		L_SUB(&pp->lastrec, &ltemp);

		/*
		 * The data bits are collected in ten-bit frames. The
		 * first two and last two bits are determined by frame
		 * sync and ignored here; the resulting patterns
		 * represent zero (0-1 bits), one (2-4 bits) and
		 * position identifier (5-6 bits). The remaining
		 * patterns represent errors and are treated as zeros.
		 */
		bitz = up->dcycles & 0xfc;
		switch(bitz) {

		case 0x00:
		case 0x80:
			irig_decode(peer, BIT0);
			break;

		case 0xc0:
		case 0xe0:
		case 0xf0:
			irig_decode(peer, BIT1);
			break;

		case 0xf8:
		case 0xfc:
			irig_decode(peer, BITP);
			break;

		default:
			irig_decode(peer, 0);
			up->errflg |= IRIG_ERR_DECODE;
		}
	}
}


/*
 * irig_decode - decode the data
 *
 * This routine assembles bits into digits, digits into subfields and
 * subfields into the timecode field. Bits can have values of zero, one
 * or position identifier. There are four bits per digit, two digits per
 * subfield and ten subfields per field. The last bit in every subfield
 * and the first bit in the first subfield are position identifiers.
 */
static void
irig_decode(
	struct	peer *peer,	/* peer structure pointer */
	int	bit		/* data bit (0, 1 or 2) */
	)
{
	struct refclockproc *pp;
	struct irigunit *up;
#ifdef IRIG_SUCKS
	int	i;
#endif /* IRIG_SUCKS */

	/*
	 * Local variables
	 */
	char	syncchar;	/* sync character (Spectracom) */
	char	sbs[6];		/* binary seconds since 0h */
	char	spare[2];	/* mulligan digits */

        pp = peer->procptr;
	up = (struct irigunit *)pp->unitptr;

	/*
	 * Assemble subfield bits.
	 */
	up->bits <<= 1;
	if (bit == BIT1) {
		up->bits |= 1;
	} else if (bit == BITP && up->lastbit == BITP) {

		/*
		 * Frame sync - two adjacent position identifiers.
		 * Monitor the reference timestamp and wiggle the
		 * clock, but only if no errors have occurred.
		 */
		up->bitcnt = 1;
		up->fieldcnt = 0;
		up->lastbit = 0;
		if (up->errflg == 0) {
#ifdef IRIG_SUCKS
			l_fp	ltemp;

			/*
			 * You really don't wanna know what comes down
			 * here. Leave it to say Solaris 2.8 broke the
			 * nice clean audio stream, apparently affected
			 * by a 5-ms sawtooth jitter. Sundown on
			 * Solaris. This leaves a little twilight.
			 *
			 * The scheme involves differentiation, forward
			 * learning and integration. The sawtooth has a
			 * period of 11 seconds. The timestamp
			 * differences are integrated and subtracted
			 * from the signal.
			 */
			ltemp = pp->lastrec;
			L_SUB(&ltemp, &pp->lastref);
			if (ltemp.l_f < 0)
				ltemp.l_i = -1;
			else
				ltemp.l_i = 0;
			pp->lastref = pp->lastrec;
			if (!L_ISNEG(&ltemp))
				L_CLR(&up->wigwag);
			else
				L_ADD(&up->wigwag, &ltemp);
			L_SUB(&pp->lastrec, &up->wigwag);
			up->wiggle[up->wp] = ltemp;

			/*
			 * Bottom fisher. To understand this, you have
			 * to know about velocity microphones and AM
			 * transmitters. No further explanation is
			 * offered, as this is truly a black art.
			 */
			up->wigbot[up->wp] = pp->lastrec;
			for (i = 0; i < WIGGLE; i++) {
				if (i != up->wp)
					up->wigbot[i].l_ui++;
				L_SUB(&pp->lastrec, &up->wigbot[i]);
				if (L_ISNEG(&pp->lastrec))
					L_ADD(&pp->lastrec,
					    &up->wigbot[i]);
				else
					pp->lastrec = up->wigbot[i];
			}
			up->wp++;
			up->wp %= WIGGLE;
			up->wuggle = pp->lastrec;
			refclock_process(pp);
#else /* IRIG_SUCKS */
			pp->lastref = pp->lastrec;
			up->wuggle = pp->lastrec;
			refclock_process(pp);
#endif /* IRIG_SUCKS */
		}
		up->errflg = 0;
	}
	up->bitcnt = (up->bitcnt + 1) % SUBFLD;
	if (up->bitcnt == 0) {

		/*
		 * End of subfield. Encode two hexadecimal digits in
		 * little-endian timecode field.
		 */
		if (up->fieldcnt == 0)
		    up->bits <<= 1;
		if (up->xptr < 2)
		    up->xptr = 2 * FIELD;
		up->timecode[--up->xptr] = hexchar[(up->bits >> 5) &
		    0xf];
		up->timecode[--up->xptr] = hexchar[up->bits & 0xf];
		up->fieldcnt = (up->fieldcnt + 1) % FIELD;
		if (up->fieldcnt == 0) {

			/*
			 * End of field. Decode the timecode and wind
			 * the clock. Not all IRIG generators have the
			 * year; if so, it is nonzero after year 2000.
			 * Not all have the hardware status bit; if so,
			 * it is lit when the source is okay and dim
			 * when bad. We watch this only if the year is
			 * nonzero. Not all are configured for signature
			 * control. If so, all BCD digits are set to
			 * zero if the source is bad. In this case the
			 * refclock_process() will reject the timecode
			 * as invalid.
			 */
			up->xptr = 2 * FIELD;
			if (sscanf((char *)up->timecode,
			   "%6s%2d%c%2s%3d%2d%2d%2d", sbs, &pp->year,
			    &syncchar, spare, &pp->day, &pp->hour,
			    &pp->minute, &pp->second) != 8)
				pp->leap = LEAP_NOTINSYNC;
			else
				pp->leap = LEAP_NOWARNING;
			up->second = (up->second + up->decim) % 60;
			if (pp->year > 0)
				pp->year += 2000;
			if (pp->second != up->second)
				up->errflg |= IRIG_ERR_CHECK;
			up->second = pp->second;
			sprintf(pp->a_lastcode,
			    "%02x %c %2d %3d %02d:%02d:%02d %4.0f %3d %6.3f %2d %6.1f %6.1f %s",
			    up->errflg, syncchar, pp->year, pp->day,
			    pp->hour, pp->minute, pp->second,
			    up->maxsignal, up->gain, up->modndx,
			    up->tc, up->exing * 1e6 / SECOND, up->freq *
			    1e6 / SECOND, ulfptoa(&up->wuggle, 6));
			pp->lencode = strlen(pp->a_lastcode);
			if (pp->sloppyclockflag & CLK_FLAG4) {
				record_clock_stats(&peer->srcadr,
				    pp->a_lastcode);
#ifdef DEBUG
				if (debug)
					printf("irig: %s\n",
					    pp->a_lastcode);
#endif /* DEBUG */
			}
		}
	}
	up->lastbit = bit;
}


/*
 * irig_poll - called by the transmit procedure
 *
 * This routine sweeps up the timecode updates since the last poll. For
 * IRIG-B there should be at least 60 updates; for IRIG-E there should
 * be at least 6. If nothing is heard, a timeout event is declared and
 * any orphaned timecode updates are sent to foster care. 
 */
static void
irig_poll(
	int	unit,		/* instance number (not used) */
	struct peer *peer	/* peer structure pointer */
	)
{
	struct refclockproc *pp;
	struct irigunit *up;

	pp = peer->procptr;
	up = (struct irigunit *)pp->unitptr;

	if (pp->coderecv == pp->codeproc) {
		refclock_report(peer, CEVNT_TIMEOUT);
		return;

	} else {
		refclock_receive(peer);
		record_clock_stats(&peer->srcadr, pp->a_lastcode);
#ifdef DEBUG
		if (debug)
			printf("irig: %s\n", pp->a_lastcode);
#endif /* DEBUG */
	}
	pp->polls++;
	
}


/*
 * irig_gain - adjust codec gain
 *
 * This routine is called once each second. If the signal envelope
 * amplitude is too low, the codec gain is bumped up by four units; if
 * too high, it is bumped down. The decoder is relatively insensitive to
 * amplitude, so this crudity works just fine. The input port is set and
 * the error flag is cleared, mostly to be ornery.
 */
static void
irig_gain(
	struct peer *peer	/* peer structure pointer */
	)
{
	struct refclockproc *pp;
	struct irigunit *up;

	pp = peer->procptr;
	up = (struct irigunit *)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;
}

#else
int refclock_irig_bs;
#endif /* REFCLOCK */