#define MINUTE (SECOND * 60) /* minute epoch */
#define OFFSET 128 /* companded sample offset */
#define SIZE 256 /* decompanding table size */
-#define MAXSIG 6000. /* max signal level reference */
+#define MAXAMP 6000. /* max signal level reference */
#define MAXCLP 100 /* max clips above reference per s */
#define MAXSNR 40. /* max SNR reference */
#define MAXFREQ 1.5 /* max frequency tolerance (187 PPM) */
* only by timeout, upon which the driver starts over from scratch.
*
* DGATE is lit if the data bit amplitude or SNR is below thresholds and
- * BGATE is lit if a the pulse width amplitude or SNR is below
- * thresolds. LEPSEC is set during the last minute of the leap day At
- * the end of this minute the driver inserts second 60 in the seconds
- * state machine and the minute sync slips a second.
+ * BGATE is lit if the pulse width amplitude or SNR is below thresolds.
+ * LEPSEC is set during the last minute of the leap day. At the end of
+ * this minute the driver inserts second 60 in the seconds state machine
+ * and the minute sync slips a second.
*/
#define MSYNC 0x0001 /* minute epoch sync */
#define SSYNC 0x0002 /* second epoch sync */
#define MTHR 13. /* acquisition signal gate (percent) */
#define TTHR 50. /* tracking signal gate (percent) */
#define AWND 20 /* acquisition jitter threshold (ms) */
-#define ATHR 3000. /* QRZ minute sync threshold */
+#define ATHR 2500. /* QRZ minute sync threshold */
#define ASNR 20. /* QRZ minute sync SNR threshold (dB) */
-#define QTHR 3000. /* QSY minute sync threshold */
+#define QTHR 2500. /* QSY minute sync threshold */
#define QSNR 20. /* QSY minute sync SNR threshold (dB) */
-#define STHR 3000. /* second sync threshold */
+#define STHR 2500. /* second sync threshold */
#define SSNR 15. /* second sync SNR threshold (dB) */
#define SCMP 10 /* second sync compare threshold */
#define DTHR 1000. /* bit threshold */
#define BTHR 1000. /* digit threshold */
#define BSNR 3. /* digit likelihood threshold (dB) */
#define BCMP 3 /* digit compare threshold */
-#define MAXERR 20 /* maximum error alarm */
+#define MAXERR 40 /* maximum error alarm */
/*
* Tone frequency definitions. The increments are for 4.5-deg sine
* Variables used to establish basic system timing
*/
int avgint; /* master time constant */
- int tepoch; /* sync epoch median */
int yepoch; /* sync epoch */
int repoch; /* buffered sync epoch */
double epomax; /* second sync amplitude */
sample = up->comp[~*dpt++ & 0xff];
/*
- * Clip noise spikes greater than MAXSIG. If no clips,
+ * Clip noise spikes greater than MAXAMP. If no clips,
* increase the gain a tad; if the clips are too high,
* decrease a tad.
*/
- if (sample > MAXSIG) {
- sample = MAXSIG;
+ if (sample > MAXAMP) {
+ sample = MAXAMP;
up->clipcnt++;
- } else if (sample < -MAXSIG) {
- sample = -MAXSIG;
+ } else if (sample < -MAXAMP) {
+ sample = -MAXAMP;
up->clipcnt++;
}
* Little bit of class here.
*/
if (up->epomax > STHR && up->eposnr > SSNR) {
- fpoch = up->mphase % SECOND - up->tepoch;
+ fpoch = up->mphase % SECOND - up->yepoch;
if (fpoch < 0)
fpoch += SECOND;
} else {
"wwv8 %d %3d %s %d %5.0f %5.1f %5.0f %5ld %5d %ld",
up->port, up->gain, sp->refid, sp->count,
sp->synmax, sp->synsnr, sp->metric, sp->pos,
- up->tepoch, epoch);
+ up->yepoch, epoch);
record_clock_stats(&peer->srcadr, tbuf);
#ifdef DEBUG
if (debug)
struct refclockproc *pp;
struct wwvunit *up;
static int epoch_mf[3]; /* epoch median filter */
+ static int tepoch; /* current second epoch */
static int xepoch; /* last second epoch */
- static int zepoch; /* last averaging interval epoch */
+ static int zepoch; /* last run epoch */
+ static int zcount; /* last run end time */
+ static int scount; /* seconds counter */
static int syncnt; /* run length counter */
static int maxrun; /* longest run length */
- static int mepoch; /* longest run epoch */
+ static int mepoch; /* longest run end epoch */
+ static int mcount; /* longest run end time */
static int avgcnt; /* averaging interval counter */
static int avginc; /* averaging ratchet */
static int iniflg; /* initialization flag */
memset((char *)epoch_mf, 0, sizeof(epoch_mf));
}
+ /*
+ * If the signal amplitude or SNR fall below thresholds, dim the
+ * second sync lamp and wait for hotter ions. If no stations are
+ * heard we are either in a probe cycle or the ions are really
+ * dim.
+ */
+ scount++;
+ if (up->epomax < STHR || up->eposnr < SSNR) {
+ up->status &= ~(SSYNC | FGATE);
+ avgcnt = syncnt = maxrun = 0;
+ return;
+ }
+ if (!(up->status & (SELV | SELH)))
+ return;
+
/*
* A three-stage median filter is used to help denoise the
* second sync pulse. The median sample becomes the candidate
epoch_mf[0] = epopos;
if (epoch_mf[0] > epoch_mf[1]) {
if (epoch_mf[1] > epoch_mf[2])
- up->tepoch = epoch_mf[1]; /* 0 1 2 */
+ tepoch = epoch_mf[1]; /* 0 1 2 */
else if (epoch_mf[2] > epoch_mf[0])
- up->tepoch = epoch_mf[0]; /* 2 0 1 */
+ tepoch = epoch_mf[0]; /* 2 0 1 */
else
- up->tepoch = epoch_mf[2]; /* 0 2 1 */
+ tepoch = epoch_mf[2]; /* 0 2 1 */
} else {
if (epoch_mf[1] < epoch_mf[2])
- up->tepoch = epoch_mf[1]; /* 2 1 0 */
+ tepoch = epoch_mf[1]; /* 2 1 0 */
else if (epoch_mf[2] < epoch_mf[0])
- up->tepoch = epoch_mf[0]; /* 1 0 2 */
+ tepoch = epoch_mf[0]; /* 1 0 2 */
else
- up->tepoch = epoch_mf[2]; /* 1 2 0 */
+ tepoch = epoch_mf[2]; /* 1 2 0 */
}
- /*
- * If the signal amplitude or SNR fall below thresholds, dim the
- * second sync lamp and start over. If no stations are heard we
- * are either in a probe cycle or the ions are dim. In that case
- * allow the amplitude and SNR to discharge and go no further.
- */
- if (up->epomax < STHR || up->eposnr < SSNR) {
- up->status &= ~(SSYNC | FGATE);
- avgcnt = syncnt = maxrun = 0;
- return;
- }
- if (!(up->status & (SELV | SELH)))
- return;
-
- avgcnt++;
/*
* If the epoch candidate is the same as the last one, increment
- * the compare counter. If not, save the length and epoch of the
- * current run for use later and reset the counter.
+ * the run counter. If not, save the length, epoch and end
+ * time of the current run for use later and reset the counter.
+ * If the run is at least SCMP (10) s, the SSYNC bit is lit and
+ * the epoch considered valid for synchronization.
*/
- tmp2 = (up->tepoch - xepoch) % SECOND;
+ tmp2 = (tepoch - xepoch) % SECOND;
if (tmp2 == 0) {
syncnt++;
- } else {
- if (maxrun > 0 && mepoch == xepoch) {
- maxrun += syncnt;
- } else if (syncnt > maxrun) {
- maxrun = syncnt;
- mepoch = xepoch;
+ if (syncnt > SCMP) {
+ up->status |= SSYNC;
+ up->yepoch = tepoch;
}
+ } else if (syncnt >= maxrun) {
+ maxrun = syncnt;
+ mepoch = xepoch;
+ mcount = scount;
syncnt = 0;
}
- if ((pp->sloppyclockflag & CLK_FLAG4) && !(up->status & (SSYNC |
- MSYNC))) {
+ if ((pp->sloppyclockflag & CLK_FLAG4) && !(up->status & MSYNC))
+ {
sprintf(tbuf,
- "wwv1 %04x %5.0f %5.1f %5d %5d %4d %4d",
- up->status, up->epomax, up->eposnr, up->tepoch,
- tmp2, avgcnt, syncnt);
+ "wwv1 %04x %5.0f %5.1f %5d %5d %4d %4d %4d %5d",
+ up->status, up->epomax, up->eposnr, tepoch,
+ tmp2, avgcnt, syncnt, maxrun, mepoch);
record_clock_stats(&peer->srcadr, tbuf);
#ifdef DEBUG
if (debug)
printf("%s\n", tbuf);
#endif /* DEBUG */
}
-
- /*
- * The sample clock frequency is disciplined using a first order
- * feedback loop with time constant consistent with the Allan
- * intercept of typical computer clocks.
- *
- * The frequency update is calculated from the epoch change in
- * 125-us units divided by the averaging interval in seconds.
- * The averaging interval affects other receiver functions,
- * including the the 1000/1200-Hz comb filter and codec clock
- * loop. It also affects the 100-Hz subcarrier loop and the bit
- * and digit comparison counter thresholds.
- */
+ avgcnt++;
if (avgcnt < up->avgint) {
- xepoch = up->tepoch;
+ xepoch = tepoch;
return;
}
/*
- * During the averaging interval the longest run of identical
- * epoches is determined. If the longest run is at least 10
- * seconds, the SSYNC bit is lit and the value becomes the
- * reference epoch for the next interval. If not, the second
- * sync lamp is dark and flashers set.
- */
- if (maxrun > 0 && mepoch == xepoch) {
- maxrun += syncnt;
- } else if (syncnt > maxrun) {
+ * The sample clock frequency is disciplined using a first order
+ * feedback loop with time constant consistent with the Allan
+ * intercept of typical computer clocks. During each averaging
+ * interval the candidate epoch at the end of the longest run is
+ * determined. If the longest run is zero, all epoches in the
+ * interval are different, so the candidate epoch is the current
+ * epoch. The frequency update is computed from the candidate
+ * epoch difference (125-us units) and time difference (seconds)
+ * between updates.
+ */
+ if (syncnt >= maxrun) {
maxrun = syncnt;
mepoch = xepoch;
+ mcount = scount;
}
- xepoch = up->tepoch;
- if (maxrun > SCMP) {
- up->status |= SSYNC;
- up->yepoch = mepoch;
- } else {
- up->status &= ~SSYNC;
+ xepoch = tepoch;
+ if (maxrun == 0) {
+ mepoch = tepoch;
+ mcount = scount;
}
/*
- * If the epoch change over the averaging interval is less than
- * 1 ms, the frequency is adjusted, but clamped at +-125 PPM. If
- * greater than 1 ms, the counter is decremented. If the epoch
- * change is less than 0.5 ms, the counter is incremented. If
- * the counter increments to +3, the averaging interval is
- * doubled and the counter set to zero; if it decrements to -3,
- * the interval is halved and the counter set to zero.
+ * The master clock runs at the codec sample frequency of 8000
+ * Hz, so the intrinsic time resolution is 125 us. The frequency
+ * resolution ranges from 18 PPM at the minimum averaging
+ * interval to 0.12 PPM at the maximum averaging interval. If a
+ * frequency update is greater than the maximum MAXFREQ (1.5 or
+ * 187.5 PPM), the hysteresis counter is decremented and the
+ * update is ignored. Otherwise the frequency is adjusted, but
+ * clamped to the maximum. If the update is greater than half
+ * the maximum, the hysteresis counter is incremented. If the
+ * counter increments to +3, the averaging interval is doubled
+ * and the counter set to zero; if it decrements to -3, the
+ * interval is halved and the counter set to zero.
*/
- if (maxrun == 0)
- mepoch = up->tepoch;
dtemp = (mepoch - zepoch) % SECOND;
if (up->status & FGATE) {
if (abs(dtemp) < MAXFREQ * MINAVG) {
- up->freq += dtemp / (avgcnt * FCONST);
+ up->freq += (dtemp / 2) / ((mcount - zcount) *
+ FCONST);
if (up->freq > MAXFREQ)
up->freq = MAXFREQ;
else if (up->freq < -MAXFREQ)
}
if (pp->sloppyclockflag & CLK_FLAG4) {
sprintf(tbuf,
- "wwv2 %04x %4.0f %4d %4d %2d %4d %4.0f %7.2f",
- up->status, up->epomax, mepoch, maxrun, avginc,
- avgcnt, dtemp, up->freq * 1e6 / SECOND);
+ "wwv2 %04x %5.0f %5.1f %5d %4d %4d %4d %4.0f %7.2f",
+ up->status, up->epomax, up->eposnr, mepoch,
+ up->avgint, maxrun, mcount - zcount, dtemp,
+ up->freq * 1e6 / SECOND);
record_clock_stats(&peer->srcadr, tbuf);
#ifdef DEBUG
if (debug)
}
up->status |= FGATE;
zepoch = mepoch;
+ zcount = mcount;
avgcnt = syncnt = maxrun = 0;
}
*
* The WWV/H format contains data pulses in second 59 (position
* identifier) and second 1, but not in second 0. The minute
- * sync pulse is contained in second 0. second 0. At the end of
- * second 58 QSY to the probe channel, which rotates in turn
- * over all WWV/H frequencies. At the end of second 0 measure
- * the minute sync pulse. At the end of second 1 measure the
- * data pulse and QSY back to the data channel. Note that the
- * seconds numbering here applies to the end of the second, so
- * appears one second earlier than the clock displayed on the
- * radio itself.
+ * sync pulse is contained in second 0. At the end of second 58
+ * QSY to the probe channel, which rotates in turn over all
+ * WWV/H frequencies. At the end of second 0 measure the minute
+ * sync pulse. At the end of second 1 measure the data pulse and
+ * QSY back to the data channel. Note that the actions commented
+ * here happen at the end of the second numbered as shown.
*
- * At the end of second 0 save the minute sync pulse peak
+ * At the end of second 0 save the minute sync pulse maximum
* amplitude previously latched at 800 ms.
*/
case SYNC2: /* 0 */
* At the end of second 1 measure the minute sync pulse
* minimum amplitude and calculate the SNR. If the minute sync
* pulse and SNR are above threshold and the data pulse
- * amplitude and SNR are above thresold and, shift a 1 into the
+ * amplitude and SNR are above thresold, shift a 1 into the
* station reachability register; otherwise, shift a 0. The
* number of 1 bits in the last six intervals is a component of
* the channel metric computed by the mitigation routine.
if (sp->reach & (1 << AMAX))
sp->count--;
if (sp->synmax >= QTHR && sp->synsnr >= QSNR &&
- ~(up->status & (DGATE | BGATE))) {
+ !(up->status & (DGATE | BGATE))) {
sp->reach |= 1;
sp->count++;
}
if (rp->reach & (1 << AMAX))
rp->count--;
if (rp->synmax >= QTHR && rp->synsnr >= QSNR &&
- ~(up->status & (DGATE | BGATE))) {
+ !(up->status & (DGATE | BGATE))) {
rp->reach |= 1;
rp->count++;
}
}
/*
- * If victory has been declared and seconds sync is lit, strike
- * a timestamp. It should not be a surprise, especially if the
- * radio is not tunable, that sometimes no stations are above
- * the noise and the reference ID set to NONE.
+ * The radio clock is set if the alarm bits are all zero. After that,
+ * the time is considered valid if the second sync bit is lit. It should
+ * not be a surprise, especially if the radio is not tunable, that
+ * sometimes no stations are above the noise and the integrators
+ * discharge below the thresholds. We assume that, after a day of signal
+ * loss, the minute sync epoch will be in the same second. This requires
+ * the codec frequency be accurate within 6 PPM. Practical experience
+ * shows the frequency typically within 0.1 PPM, so after a day of
+ * signal loss, the time should be within 8.6 ms..
*/
static void
wwv_clock(
up->alarm |= SYNERR;
if (up->digcnt < 9)
up->alarm |= NINERR;
- if (!(up->alarm)) {
+ if (!(up->alarm))
up->status |= INSYNC;
+ if (up->status & INSYNC && up->status & SSYNC) {
if (up->misc & SECWAR)
pp->leap = LEAP_ADDSECOND;
else
* minute units digit has been resolved, don't to anything else.
*/
mldigit = 0;
- topmax = nxtmax = -MAXSIG;
+ topmax = nxtmax = -MAXAMP;
for (i = 0; tab[i][0] != 0; i++) {
acc = 0;
for (j = 0; j < 4; j++)
{
double dtemp;
- dtemp = sp->count * MAXSIG;
- if (sp->synmax < MAXSIG)
+ dtemp = sp->count * MAXAMP;
+ if (sp->synmax < MAXAMP)
dtemp += sp->synmax;
else
- dtemp += MAXSIG - 1;
- dtemp /= (AMAX + 1) * MAXSIG;
+ dtemp += MAXAMP - 1;
+ dtemp /= (AMAX + 1) * MAXAMP;
return (dtemp * 100.);
}
* wwv_gain - adjust codec gain
*
* This routine is called at the end of each second. It counts the
- * number of signal clips above the MAXSIG threshold during the previous
+ * number of signal clips above the MAXAMP threshold during the previous
* second. If there are no clips, the gain is bumped up; if too many
* clips, it is bumped down. The decoder is relatively insensitive to
* amplitude, so this crudity works just fine. The input port is set and
projects / thirdparty / ntp.git / commitdiff
