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|
/*
* refclock_chu - clock driver for Canadian radio CHU receivers
*/
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
#if defined(REFCLOCK) && defined(CLOCK_CHU)
/* #define AUDIO_CHUa */
#include <stdio.h>
#include <ctype.h>
#include <sys/time.h>
#include <time.h>
#include <math.h>
#ifdef AUDIO_CHU
#ifdef HAVE_SYS_AUDIOIO_H
#include <sys/audioio.h>
#endif /* HAVE_SYS_AUDIOIO_H */
#ifdef HAVE_SUN_AUDIOIO_H
#include <sun/audioio.h>
#endif /* HAVE_SUN_AUDIOIO_H */
#endif /* AUDIO_CHU */
#include "ntpd.h"
#include "ntp_io.h"
#include "ntp_refclock.h"
#include "ntp_calendar.h"
#include "ntp_stdlib.h"
/*
* Clock driver for Canadian radio CHU receivers
*
* This driver synchronizes the computer time using data encoded in
* radio transmissions from Canadian time/frequency station CHU in
* Ottawa, Ontario. Transmissions are made continuously on 3330 kHz,
* 7335 kHz and 14670 kHz in upper sideband, compatible AM mode. An
* ordinary shortwave receiver can be tuned manually to one of these
* frequencies or, in the case of ICOM receivers, the receiver can be
* tuned automatically using the minimuf and icom programs as
* propagation conditions change throughout the day and night.
*
* The driver can be compiled to use a Bell 103 compatible modem or
* modem chip to receive the radio signal and demodulate the data.
* Alternatively, the driver can be compiled to use the audio codec of
* the Sun workstation or another with compatible audio drivers. In the
* latter case, the driver implements the modem using DSP routines, so
* the radio can be connected directly to either the microphone on line
* input port. In either case, the driver decodes the data using a
* maximum likelihood technique which exploits the considerable degree
* of redundancy available to maximize accuracy and minimize errors.
*
* The CHU time broadcast includes an audio signal compatible with the
* Bell 103 modem standard (mark = 2225 Hz, space = 2025 Hz). It consist
* of nine, ten-character bursts transmitted at 300 bps and beginning
* each second from second 31 to second 39 of the minute. Each character
* consists of eight data bits plus one start bit and two stop bits to
* encode two hex digits. The burst data consist of five characters (ten
* hex digits) followed by a repeat of these characters. In format A,
* the characters are repeated in the same polarity; in format B, the
* characters are repeated in the opposite polarity.
*
* Format A bursts are sent at seconds 32 through 39 of the minute in
* hex digits
*
* 6dddhhmmss6dddhhmmss
*
* The first ten digits encode a frame marker (6) followed by the day
* (ddd), hour (hh in UTC), minute (mm) and the second (ss). Since
* format A bursts are sent during the third decade of seconds the tens
* digit of ss is always 3. The driver uses this to determine correct
* burst synchronization. These digits are then repeated with the same
* polarity.
*
* Format B bursts are sent at second 31 of the minute in hex digits
*
* xdyyyyttaaxdyyyyttaa
*
* The first ten digits encode a code (x described below) followed by
* the DUT1 (d in deciseconds), Gregorian year (yyyy), difference TAI -
* UTC (tt) and daylight time indicator (aa) peculiar to Canada. These
* digits are then repeated with inverted polarity.
*
* The x is coded
*
* 1 Sign of DUT (0 = +)
* 2 Leap second warning. One second will be added.
* 4 Leap second warning. One second will be subtracted.
* 8 Even parity bit for this nibble.
*
* By design, the last stop bit of the last character in the burst
* coincides with 0.5 second. Since characters have 11 bits and are
* transmitted at 300 bps, the last stop bit of the first character
* coincides with 0.5 - 10 * 11/300 = 0.133 second. Depending on the
* UART, character interrupts can vary somewhere between the beginning
* of bit 9 and end of bit 11. These eccentricities can be corrected
* along with the radio propagation delay using fudge time 1.
*
* Debugging aids
*
* The timecode format used for debugging and data recording includes
* data helpful in diagnosing problems with the radio signal and serial
* connections. With debugging enabled (-d -d -d on the ntpd command
* line), the driver produces one line for each burst in two formats
* corresponding to format A and B. Following is format A:
*
* n b f s m code
*
* where n is the number of characters in the burst (0-11), b the burst
* distance (0-40), f the field alignment (-1, 0, 1), s the
* synchronization distance (0-16), m the burst number (2-9) and code
* the burst characters as received. Note that the hex digits in each
* character are reversed, so the burst
*
* 10 38 0 16 9 06851292930685129293
*
* is interpreted as containing 11 characters with burst distance 38,
* field alignment 0, synchronization distance 16 and burst number 9.
* The nibble-swapped timecode shows day 58, hour 21, minute 29 and
* second 39.
*
* When the audio driver is compiled, format A is preceded by
* the current gain (0-255) and relative signal level (0-9999). The
* receiver folume control should be set so that the gain is somewhere
* near the middle of the range 0-255, which results in a signal level
* near 1000.
*
* Following is format B:
*
* n b s code
*
* where n is the number of characters in the burst (0-11), b the burst
* distance (0-40), s the synchronization distance (0-40) and code the
* burst characters as received. Note that the hex digits in each
* character are reversed and the last ten digits inverted, so the burst
*
* 11 40 1091891300ef6e76ecff
*
* is interpreted as containing 11 characters with burst distance 40.
* The nibble-swapped timecode shows DUT1 +0.1 second, year 1998 and TAI
* - UTC 31 seconds.
*
* In addition to the above, the reference timecode is updated and
* written to the clockstats file and debug score after the last burst
* received in the minute. The format is
*
* qq yyyy ddd hh:mm:ss nn dd tt
*
* where qq are the error flags, as described below, yyyy is the year,
* ddd the day, hh:mm:ss the time of day, nn the number of format A
* bursts received during the previous minute, dd the decoding distance
* and tt the number of timestamps. The error flags are cleared after
* every update.
*
* Fudge factors
*
* For accuracies better than the low millisceconds, fudge time1 can be
* set to the radio propagation delay from CHU to the receiver. This can
* be done conviently using the minimuf program. When the modem driver
* is compiled, fudge flag3 enables the ppsclock line discipline. Fudge
* flag4 causes the dubugging output described above to be recorded in
* the clockstats file.
*
* When the audio driver is compiled, fudge flag2 selects the audio
* input port, where 0 is the mike port (default) and 1 is the line-in
* port. It does not seem useful to select the compact disc player port.
* Fudge flag3 enables audio monitoring of the input signal. For this
* purpose, the speaker volume must be set before the driver is started.
*/
/*
* Interface definitions
*/
#define SPEED232 B300 /* uart speed (300 baud) */
#define PRECISION (-10) /* precision assumed (about 1 ms) */
#define REFID "CHU" /* reference ID */
#ifdef AUDIO_CHU
#define DESCRIPTION "CHU Modem Receiver" /* WRU */
/*
* Audio demodulator definitions
*/
#define AUDIO_BUFSIZ 160 /* codec buffer size (Solaris only) */
#define SAMPLE 8000 /* nominal sample rate (Hz) */
#define BAUD 300 /* modulation rate (bps) */
#define OFFSET 128 /* companded sample offset */
#define SIZE 256 /* decompanding table size */
#define MAXSIG 6000. /* maximum signal level */
#define DRPOUT 100. /* dropout signal level */
#define LIMIT 1000. /* soft limiter threshold */
#define AGAIN 6. /* baseband gain */
#define LAG 10 /* discriminator lag */
#else
#define DEVICE "/dev/chu%d" /* device name and unit */
#define SPEED232 B300 /* UART speed (300 baud) */
#define DESCRIPTION "CHU Audio Receiver" /* WRU */
#endif /* AUDIO_CHU */
/*
* Decoder definitions
*/
#define CHAR (11. / 300.) /* character time (s) */
#define FUDGE .185 /* offset to first stop bit (s) */
#define BURST 11 /* max characters per burst */
#define MINCHAR 9 /* min characters per burst */
#define MINDIST 28 /* min burst distance (of 40) */
#define MINSYNC 8 /* min sync distance (of 16) */
#define MINDEC .5 /* decoder majority rule (of 1.) */
#define MINSTAMP 20 /* min timestamps (of 60) */
/*
* Hex extension codes (>= 16)
*/
#define HEX_MISS 16 /* miss */
#define HEX_SOFT 17 /* soft error */
#define HEX_HARD 18 /* hard error */
/*
* Error flags (up->errflg)
*/
#define CHU_ERR_RUNT 0x001 /* runt burst */
#define CHU_ERR_NOISE 0x002 /* noise burst */
#define CHU_ERR_BFRAME 0x004 /* invalid format B frame sync */
#define CHU_ERR_BFORMAT 0x008 /* invalid format B data */
#define CHU_ERR_AFRAME 0x010 /* invalid format A frame sync */
#define CHU_ERR_DECODE 0x020 /* invalid data decode */
#define CHU_ERR_STAMP 0x040 /* too few timestamps */
#define CHU_ERR_AFORMAT 0x080 /* invalid format A data */
#ifdef AUDIO_CHU
#define CHU_ERR_ERROR 0x100 /* codec error (overrun) */
#endif /* AUDIO_CHU */
#ifdef AUDIO_CHU
struct surv {
double shift[12]; /* mark register */
double max, min; /* max/min envelope signals */
double dist; /* sample distance */
int uart; /* decoded character */
};
#endif /* AUDIO_CHU */
/*
* CHU unit control structure
*/
struct chuunit {
u_char decode[20][16]; /* maximum likelihood decoding matrix */
l_fp cstamp[BURST]; /* character timestamps */
l_fp tstamp[MAXSTAGE]; /* timestamp samples */
l_fp timestamp; /* current buffer timestamp */
l_fp laststamp; /* last buffer timestamp */
l_fp charstamp; /* character time as a l_fp */
int errflg; /* error flags */
int bufptr; /* buffer index pointer */
int pollcnt; /* poll message counter */
/*
* Character burst variables
*/
int cbuf[BURST]; /* character buffer */
int ntstamp; /* number of timestamp samples */
int ndx; /* buffer start index */
int prevsec; /* previous burst second */
int burdist; /* burst distance */
int syndist; /* sync distance */
int burstcnt; /* format A bursts this minute */
#ifdef AUDIO_CHU
/*
* Audio codec variables
*/
double comp[SIZE]; /* decompanding table */
int port; /* codec port */
int gain; /* codec gain */
int bufcnt; /* samples in buffer */
int clipcnt; /* sample clip count */
int seccnt; /* second interval counter */
/*
* Modem variables
*/
l_fp tick; /* audio sample increment */
double bpf[9]; /* IIR bandpass filter */
double disc[LAG]; /* discriminator shift register */
double lpf[27]; /* FIR lowpass filter */
double monitor; /* audio monitor */
double maxsignal; /* signal level */
int discptr; /* discriminator pointer */
/*
* Maximum likelihood UART variables
*/
double baud; /* baud interval */
struct surv surv[8]; /* UART survivor structures */
int decptr; /* decode pointer */
int dbrk; /* holdoff counter */
#endif /* AUDIO_CHU */
};
/*
* Function prototypes
*/
static int chu_start P((int, struct peer *));
static void chu_shutdown P((int, struct peer *));
static void chu_receive P((struct recvbuf *));
static void chu_poll P((int, struct peer *));
/*
* More function prototypes
*/
static void chu_decode P((struct peer *, int));
static void chu_burst P((struct peer *));
static void chu_clear P((struct peer *));
static void chu_update P((struct peer *, int));
static void chu_year P((struct peer *, int));
static int chu_dist P((int, int));
#ifdef AUDIO_CHU
static void chu_uart P((struct surv *, double));
static void chu_rf P((struct peer *, double));
static void chu_gain P((struct peer *));
static int chu_audio P((void));
static void chu_debug P((void));
#endif /* AUDIO_CHU */
/*
* Global variables
*/
static char hexchar[] = "0123456789abcdef_-=";
#ifdef AUDIO_CHU
#ifdef HAVE_SYS_AUDIOIO_H
struct audio_device device; /* audio device ident */
#endif /* HAVE_SYS_AUDIOIO_H */
static struct audio_info info; /* audio device info */
static int chu_ctl_fd; /* audio control file descriptor */
#endif /* AUDIO_CHU */
/*
* Transfer vector
*/
struct refclock refclock_chu = {
chu_start, /* start up driver */
chu_shutdown, /* shut down driver */
chu_poll, /* transmit poll message */
noentry, /* not used (old chu_control) */
noentry, /* initialize driver (not used) */
noentry, /* not used (old chu_buginfo) */
NOFLAGS /* not used */
};
/*
* chu_start - open the devices and initialize data for processing
*/
static int
chu_start(
int unit, /* instance number (not used) */
struct peer *peer /* peer structure pointer */
)
{
struct chuunit *up;
struct refclockproc *pp;
/*
* Local variables
*/
int fd; /* file descriptor */
#ifdef AUDIO_CHU
int i; /* index */
double step; /* codec adjustment */
/*
* Open audio device
*/
fd = open("/dev/audio", O_RDWR | O_NONBLOCK, 0777);
if (fd == -1) {
perror("chu: audio");
return (0);
}
#else
char device[20]; /* device name */
/*
* Open serial port. Use RAW line discipline (required).
*/
(void)sprintf(device, DEVICE, unit);
if (!(fd = refclock_open(device, SPEED232, LDISC_RAW))) {
return (0);
}
#endif /* AUDIO_CHU */
/*
* Allocate and initialize unit structure
*/
if (!(up = (struct chuunit *)
emalloc(sizeof(struct chuunit)))) {
(void) close(fd);
return (0);
}
memset((char *)up, 0, sizeof(struct chuunit));
pp = peer->procptr;
pp->unitptr = (caddr_t)up;
pp->io.clock_recv = chu_receive;
pp->io.srcclock = (caddr_t)peer;
pp->io.datalen = 0;
pp->io.fd = fd;
if (!io_addclock(&pp->io)) {
(void)close(fd);
free(up);
return (0);
}
/*
* Initialize miscellaneous variables
*/
peer->precision = PRECISION;
pp->clockdesc = DESCRIPTION;
memcpy((char *)&pp->refid, REFID, 4);
DTOLFP(CHAR, &up->charstamp);
up->pollcnt = 2;
#ifdef AUDIO_CHU
up->gain = (AUDIO_MAX_GAIN - AUDIO_MIN_GAIN) / 2;
if (chu_audio() < 0) {
io_closeclock(&pp->io);
free(up);
return (0);
}
/*
* The companded samples are encoded sign-magnitude. The table
* contains all the 256 values in the interest of speed.
*/
up->comp[0] = up->comp[OFFSET] = 0.;
up->comp[1] = 1; up->comp[OFFSET + 1] = -1.;
up->comp[2] = 3; up->comp[OFFSET + 2] = -3.;
step = 2.;
for (i = 3; i < OFFSET; i++) {
up->comp[i] = up->comp[i - 1] + step;
up->comp[OFFSET + i] = -up->comp[i];
if (i % 16 == 0)
step *= 2.;
}
DTOLFP(1. / SAMPLE, &up->tick);
#endif /* AUDIO_CHU */
return (1);
}
/*
* chu_shutdown - shut down the clock
*/
static void
chu_shutdown(
int unit, /* instance number (not used) */
struct peer *peer /* peer structure pointer */
)
{
struct chuunit *up;
struct refclockproc *pp;
pp = peer->procptr;
up = (struct chuunit *)pp->unitptr;
io_closeclock(&pp->io);
free(up);
}
#ifdef AUDIO_CHU
/*
* chu_receive - receive data from the audio device
*/
static void
chu_receive(
struct recvbuf *rbufp /* receive buffer structure pointer */
)
{
struct chuunit *up;
struct refclockproc *pp;
struct peer *peer;
/*
* Local variables
*/
double sample; /* codec sample */
u_char *dpt; /* buffer pointer */
l_fp ltemp; /* l_fp temp */
double dtemp; /* double temp */
int isneg; /* parity flag */
int i, j; /* index temps */
peer = (struct peer *)rbufp->recv_srcclock;
pp = peer->procptr;
up = (struct chuunit *)pp->unitptr;
/*
* Main loop - read until there ain't no more. Note codec
* samples are bit-inverted.
*/
up->timestamp = rbufp->recv_time;
up->bufcnt = rbufp->recv_length;
DTOLFP(up->bufcnt * 1. / SAMPLE, <emp);
L_SUB(&up->timestamp, <emp);
dpt = (u_char *)&rbufp->recv_space;
for (up->bufptr = 0; up->bufptr < up->bufcnt; up->bufptr++) {
sample = up->comp[~*dpt & 0xff];
/*
* Clip noise spikes greater than MAXSIG. If no clips,
* increase the gain a tad; if the clips are too high,
* decrease a tad.
*/
if (sample > MAXSIG) {
sample = MAXSIG;
up->clipcnt++;
} else if (sample < -MAXSIG) {
sample = -MAXSIG;
up->clipcnt++;
}
up->seccnt = (up->seccnt + 1) % SAMPLE;
if (up->seccnt == 0) {
if (pp->sloppyclockflag & CLK_FLAG2)
up->port = AUDIO_LINE_IN;
else
up->port = AUDIO_MICROPHONE;
chu_gain(peer);
up->clipcnt = 0;
}
chu_rf(peer, sample);
/*
* During development, it is handy to have an audio
* monitor that can be switched to various signals. This
* code converts the linear signal left in up->monitor
* to codec format. If we can get the grass out of this
* thing and improve modem performance, this expensive
* code will be permanently nixed.
*/
isneg = 0;
dtemp = up->monitor;
if (sample < 0) {
isneg = 1;
dtemp-= dtemp;
}
i = 0;
j = OFFSET >> 1;
while (j != 0) {
if (dtemp > up->comp[i])
i += j;
else if (dtemp < up->comp[i])
i -= j;
else
break;
j >>= 1;
}
if (isneg)
*dpt = ~(i + OFFSET);
else
*dpt = ~i;
dpt++;
L_ADD(&up->timestamp, &up->tick);
}
/*
* Squawk to the monitor speaker if enabled.
*/
if (pp->sloppyclockflag & CLK_FLAG3)
if (write(pp->io.fd, (u_char *)&rbufp->recv_space,
(u_int)up->bufcnt) < 0)
perror("chu:");
}
/*
* chu_rf - filter and demodulate the FSK signal
*
* This routine implements a 300-baud Bell 103 modem with mark 2225 Hz
* and space 2025 Hz. It uses a bandpass filter followed by a soft
* limiter, FM discriminator and lowpass filter. A maximum likelihood
* decoder samples the baseband signal at eight times the baud rate and
* detects the start bit of each character.
*
* The filters are built for speed, which explains the rather clumsy
* code. Hopefully, the compiler will efficiently implement the move-
* and-muiltiply-and-add operations.
*/
void
chu_rf(
struct peer *peer, /* peer structure pointer */
double sample /* analog sample */
)
{
struct refclockproc *pp;
struct chuunit *up;
struct surv *sp;
/*
* Local variables
*/
double signal; /* bandpass signal */
double limit; /* limiter signal */
double disc; /* discriminator signal */
double lpf; /* lowpass signal */
double span; /* UART signal span */
double dist; /* UART signal distance */
int i, j; /* index temps */
pp = peer->procptr;
up = (struct chuunit *)pp->unitptr;
/*
* Bandpass filter. 4th-order elliptic, 500-Hz bandpass centered
* at 2125 Hz. Passband ripple 0.3 dB, stopband ripple 50 dB.
*/
signal = (up->bpf[8] = up->bpf[7]) * 5.844676e-01;
signal += (up->bpf[7] = up->bpf[6]) * 4.884860e-01;
signal += (up->bpf[6] = up->bpf[5]) * 2.704384e+00;
signal += (up->bpf[5] = up->bpf[4]) * 1.645032e+00;
signal += (up->bpf[4] = up->bpf[3]) * 4.644557e+00;
signal += (up->bpf[3] = up->bpf[2]) * 1.879165e+00;
signal += (up->bpf[2] = up->bpf[1]) * 3.522634e+00;
signal += (up->bpf[1] = up->bpf[0]) * 7.315738e-01;
up->bpf[0] = sample - signal;
signal = up->bpf[0] * 6.176213e-03
+ up->bpf[1] * 3.156599e-03
+ up->bpf[2] * 7.567487e-03
+ up->bpf[3] * 4.344580e-03
+ up->bpf[4] * 1.190128e-02
+ up->bpf[5] * 4.344580e-03
+ up->bpf[6] * 7.567487e-03
+ up->bpf[7] * 3.156599e-03
+ up->bpf[8] * 6.176213e-03;
up->monitor = signal / 4.; /* note monitor after filter */
/*
* Soft limiter/discriminator. The 11-sample discriminator lag
* interval corresponds to three cycles of 2125 Hz, which
* requires the sample frequency to be 2125 * 11 / 3 = 7791.7
* Hz. The discriminator output varies +-0.5 interval for input
* frequency 2025-2225 Hz. However, we don't get to sample at
* this frequency, so the discriminator output is biased. Life
* at 8000 Hz sucks.
*/
limit = signal;
if (limit > LIMIT)
limit = LIMIT;
else if (limit < -LIMIT)
limit = -LIMIT;
disc = up->disc[up->discptr] * -limit;
up->disc[up->discptr] = limit;
up->discptr = (up->discptr + 1 ) % LAG;
if (disc >= 0)
disc = sqrt(disc);
else
disc = -sqrt(-disc);
/*
* Lowpass filter. Raised cosine, Ts = 1 / 300, beta = 0.1.
*/
lpf = (up->lpf[26] = up->lpf[25]) * 2.538771e-02;
lpf += (up->lpf[25] = up->lpf[24]) * 1.084671e-01;
lpf += (up->lpf[24] = up->lpf[23]) * 2.003159e-01;
lpf += (up->lpf[23] = up->lpf[22]) * 2.985303e-01;
lpf += (up->lpf[22] = up->lpf[21]) * 4.003697e-01;
lpf += (up->lpf[21] = up->lpf[20]) * 5.028552e-01;
lpf += (up->lpf[20] = up->lpf[19]) * 6.028795e-01;
lpf += (up->lpf[19] = up->lpf[18]) * 6.973249e-01;
lpf += (up->lpf[18] = up->lpf[17]) * 7.831828e-01;
lpf += (up->lpf[17] = up->lpf[16]) * 8.576717e-01;
lpf += (up->lpf[16] = up->lpf[15]) * 9.183463e-01;
lpf += (up->lpf[15] = up->lpf[14]) * 9.631951e-01;
lpf += (up->lpf[14] = up->lpf[13]) * 9.907208e-01;
lpf += (up->lpf[13] = up->lpf[12]) * 1.000000e+00;
lpf += (up->lpf[12] = up->lpf[11]) * 9.907208e-01;
lpf += (up->lpf[11] = up->lpf[10]) * 9.631951e-01;
lpf += (up->lpf[10] = up->lpf[9]) * 9.183463e-01;
lpf += (up->lpf[9] = up->lpf[8]) * 8.576717e-01;
lpf += (up->lpf[8] = up->lpf[7]) * 7.831828e-01;
lpf += (up->lpf[7] = up->lpf[6]) * 6.973249e-01;
lpf += (up->lpf[6] = up->lpf[5]) * 6.028795e-01;
lpf += (up->lpf[5] = up->lpf[4]) * 5.028552e-01;
lpf += (up->lpf[4] = up->lpf[3]) * 4.003697e-01;
lpf += (up->lpf[3] = up->lpf[2]) * 2.985303e-01;
lpf += (up->lpf[2] = up->lpf[1]) * 2.003159e-01;
lpf += (up->lpf[1] = up->lpf[0]) * 1.084671e-01;
lpf += up->lpf[0] = disc * 2.538771e-02;
/*
printf("%8.3f %8.3f\n", disc, lpf);
return;
*/
/*
* Maximum likelihood decoder. The UART updates each of the
* eight survivors and determines the span, slice level and
* tentative decoded character. Valid 11-bit characters are
* framed so that bit 1 and bit 11 (stop bits) are mark and bit
* 2 (start bit) is space. When a valid character is found, the
* survivor with maximum distance determines the final decoded
* character.
*/
up->baud += 1. / SAMPLE;
if (up->baud > 1. / (BAUD * 8.)) {
up->baud -= 1. / (BAUD * 8.);
sp = &up->surv[up->decptr];
span = sp->max - sp->min;
up->maxsignal += (span - up->maxsignal) / 80.;
if (up->dbrk > 0) {
up->dbrk--;
} else if ((sp->uart & 0x403) == 0x401 && span > 1000.)
{
dist = 0;
j = 0;
for (i = 0; i < 8; i++) {
if (up->surv[i].dist > dist) {
dist = up->surv[i].dist;
j = i;
}
}
chu_decode(peer, (up->surv[j].uart >> 2) &
0xff);
up->dbrk = 80;
}
up->decptr = (up->decptr + 1) % 8;
chu_uart(sp, -lpf * AGAIN);
}
}
/*
* chu_uart - maximum likelihood UART
*
* This routine updates a shift register holding the last 11 envelope
* samples. It then computes the slice level and span over these samples
* and determines the tentative data bits and distance. The calling
* program selects over the last eight survivors the one with maximum
* distance to determine the decoded character.
*/
void
chu_uart(
struct surv *sp, /* survivor structure pointer */
double sample /* baseband signal */
)
{
/*
* Local variables
*/
double max, min; /* max/min envelope */
double slice; /* slice level */
double dist; /* distance */
double dtemp; /* double temp */
int i; /* index temp */
/*
* Save the sample and shift right. At the same time, measure
* the maximum and minimum over all eleven samples.
*/
max = -1e6;
min = 1e6;
sp->shift[0] = sample;
for (i = 11; i > 0; i--) {
sp->shift[i] = sp->shift[i - 1];
if (sp->shift[i] > max)
max = sp->shift[i];
if (sp->shift[i] < min)
min = sp->shift[i];
}
/*
* Determine the slice level midway beteen the maximum and
* minimum and the span as the maximum less the minimum. Compute
* the distance on the assumption the first and last bits must
* be mark, the second space and the rest either mark or space.
*/
slice = (max + min) / 2.;
dist = 0;
sp->uart = 0;
for (i = 1; i < 12; i++) {
sp->uart <<= 1;
dtemp = sp->shift[i];
if (dtemp > slice)
sp->uart |= 0x1;
if (i == 1 || i == 11) {
dist += dtemp - min;
} else if (i == 10) {
dist += max - dtemp;
} else {
if (dtemp > slice)
dist += dtemp - min;
else
dist += max - dtemp;
}
}
sp->max = max;
sp->min = min;
sp->dist = dist / (11 * (max - min));
}
#else /* AUDIO_CHU */
/*
* chu_receive - receive data from the serial interface
*/
static void
chu_receive(
struct recvbuf *rbufp /* receive buffer structure pointer */
)
{
struct chuunit *up;
struct refclockproc *pp;
struct peer *peer;
u_char *dpt; /* receive buffer pointer */
peer = (struct peer *)rbufp->recv_srcclock;
pp = peer->procptr;
up = (struct chuunit *)pp->unitptr;
/*
* Initialize pointers and read the timecode and timestamp.
*/
up->timestamp = rbufp->recv_time;
dpt = (u_char *)&rbufp->recv_space;
chu_decode(peer, *dpt);
}
#endif /* AUDIO_CHU */
/*
* chu_decode - decode the data
*/
static void
chu_decode(
struct peer *peer, /* peer structure pointer */
int hexhex /* data character */
)
{
struct refclockproc *pp;
struct chuunit *up;
/*
* Local variables
*/
l_fp tstmp; /* timestamp temp */
double dtemp; /* double temp */
pp = peer->procptr;
up = (struct chuunit *)pp->unitptr;
/*
* If the interval since the last character is greater than the
* longest burst, process the last burst and start a new one. If
* the interval is less than this but greater than two
* characters, consider this a noise burst and reject it.
*/
tstmp = up->timestamp;
if (L_ISZERO(&up->laststamp))
up->laststamp = up->timestamp;
L_SUB(&tstmp, &up->laststamp);
up->laststamp = up->timestamp;
LFPTOD(&tstmp, dtemp);
if (dtemp > BURST * CHAR) {
chu_burst(peer);
up->ndx = 0;
} else if (dtemp > 2.5 * CHAR) {
up->ndx = 0;
}
/*
* Append the character to the current burst and append the
* timestamp to the timestamp list.
*/
if (up->ndx < BURST) {
up->cbuf[up->ndx] = hexhex & 0xff;
up->cstamp[up->ndx] = up->timestamp;
up->ndx++;
}
}
/*
* chu_burst - search for valid burst format
*/
static void
chu_burst(
struct peer *peer
)
{
struct chuunit *up;
struct refclockproc *pp;
/*
* Local variables
*/
int i; /* index temp */
pp = peer->procptr;
up = (struct chuunit *)pp->unitptr;
/*
* Correlate a block of five characters with the next block of
* five characters. The burst distance is defined as the number
* of bits that match in the two blocks for format A and that
* match the inverse for format B.
*/
if (up->ndx < MINCHAR) {
up->errflg |= CHU_ERR_RUNT;
return;
}
up->burdist = 0;
for (i = 0; i < 5 && i < up->ndx - 5; i++)
up->burdist += chu_dist(up->cbuf[i], up->cbuf[i + 5]);
/*
* If the burst distance is at least MINDIST, this must be a
* format A burst; if the value is not greater than -MINDIST, it
* must be a format B burst; otherwise, it is a noise burst and
* of no use to anybody.
*/
if (up->burdist >= MINDIST) {
chu_update(peer, up->ndx);
} else if (up->burdist <= -MINDIST) {
chu_year(peer, up->ndx);
} else {
up->errflg |= CHU_ERR_NOISE;
return;
}
/*
* If this is a valid burst, wait a guard time of ten seconds to
* allow for more bursts, then arm the poll update routine to
* process the minute. Don't do this if this is called from the
* timer interrupt routine.
*/
if (peer->outdate == current_time)
up->pollcnt = 2;
else
peer->nextdate = current_time + 10;
}
/*
* chu_year - decode format B burst
*/
static void
chu_year(
struct peer *peer,
int nchar
)
{
struct refclockproc *pp;
struct chuunit *up;
/*
* Local variables
*/
u_char code[11]; /* decoded timecode */
l_fp offset; /* timestamp offset */
int leap; /* leap/dut code */
int dut; /* UTC1 correction */
int tai; /* TAI - UTC correction */
int dst; /* Canadian DST code */
int i; /* index temp */
pp = peer->procptr;
up = (struct chuunit *)pp->unitptr;
/*
* In a format B burst, a character is considered valid only if
* the first occurrence matches the last occurrence. The burst
* is considered valid only if all characters are valid; that
* is, only if the distance is 40.
*/
sprintf(pp->a_lastcode, "%2d %2d ", nchar, -up->burdist);
for (i = 0; i < nchar; i++)
sprintf(&pp->a_lastcode[strlen(pp->a_lastcode)], "%02x",
up->cbuf[i]);
pp->lencode = strlen(pp->a_lastcode);
if (pp->sloppyclockflag & CLK_FLAG4)
record_clock_stats(&peer->srcadr, pp->a_lastcode);
#ifdef DEBUG
if (debug > 2)
printf("chu: %s\n", pp->a_lastcode);
#endif
if (-up->burdist < 40) {
up->errflg |= CHU_ERR_BFRAME;
return;
}
/*
* Convert the burst data to internal format. If this succeeds,
* save the timestamps for later. The leap, dut, tai and dst are
* presently unused.
*/
for (i = 0; i < 5; i++) {
code[2 * i] = hexchar[up->cbuf[i] & 0xf];
code[2 * i + 1] = hexchar[(up->cbuf[i] >>
4) & 0xf];
}
if (sscanf((char *)code, "%1x%1d%4d%2d%2x", &leap, &dut,
&pp->year, &tai, &dst) != 5) {
up->errflg |= CHU_ERR_BFORMAT;
return;
}
offset.l_ui = 31;
offset.l_f = 0;
for (i = 0; i < nchar && i < 10; i++) {
up->tstamp[up->ntstamp] = up->cstamp[i];
L_SUB(&up->tstamp[up->ntstamp], &offset);
L_ADD(&offset, &up->charstamp);
if (up->ntstamp < MAXSTAGE)
up->ntstamp++;
}
}
/*
* chu_update - decode format A burst
*/
static void
chu_update(
struct peer *peer,
int nchar
)
{
struct refclockproc *pp;
struct chuunit *up;
/*
* Local variables
*/
l_fp offset; /* timestamp offset */
int val; /* distance */
int temp; /* common temp */
int i, j, k; /* index temps */
pp = peer->procptr;
up = (struct chuunit *)pp->unitptr;
/*
* Determine correct burst phase. There are three cases
* corresponding to in-phase, one character early or one
* character late. These cases are distinguished by the position
* of the framing digits x6 at positions 0 and 5 and x3 at
* positions 4 and 9. The correct phase is when the distance
* relative to the framing digits is maximum. The burst is valid
* only if the maximum distance is at least MINSYNC.
*/
up->syndist = k = 0;
val = -16;
for (i = -1; i < 2; i++) {
temp = up->cbuf[i + 4] & 0xf;
if (i >= 0)
temp |= (up->cbuf[i] & 0xf) << 4;
val = chu_dist(temp, 0x63);
temp = (up->cbuf[i + 5] & 0xf) << 4;
if (i + 9 < nchar)
temp |= up->cbuf[i + 9] & 0xf;
val += chu_dist(temp, 0x63);
if (val > up->syndist) {
up->syndist = val;
k = i;
}
}
temp = (up->cbuf[k + 4] >> 4) & 0xf;
if (temp > 9 || k + 9 >= nchar || temp != ((up->cbuf[k + 9] >>
4) & 0xf))
temp = 0;
#ifdef AUDIO_CHU
sprintf(pp->a_lastcode, "%3d %4.0f %2d %2d %2d %2d %1d ",
up->gain, up->maxsignal, nchar, up->burdist, k, up->syndist,
temp);
#else
sprintf(pp->a_lastcode, "%2d %2d %2d %2d %1d ", nchar,
up->burdist, k, up->syndist, temp);
#endif /* AUDIO_CHU */
for (i = 0; i < nchar; i++)
sprintf(&pp->a_lastcode[strlen(pp->a_lastcode)], "%02x",
up->cbuf[i]);
pp->lencode = strlen(pp->a_lastcode);
if (pp->sloppyclockflag & CLK_FLAG4)
record_clock_stats(&peer->srcadr, pp->a_lastcode);
#ifdef DEBUG
if (debug > 2)
printf("chu: %s\n", pp->a_lastcode);
#endif
if (up->syndist < MINSYNC) {
up->errflg |= CHU_ERR_AFRAME;
return;
}
/*
* A valid burst requires the first seconds number to match the
* last seconds number. If so, the burst timestamps are
* corrected to the current minute and saved for later
* processing. In addition, the seconds decode is advanced from
* the previous burst to the current one.
*/
if (temp != 0) {
offset.l_ui = 30 + temp;
offset.l_f = 0;
i = 0;
if (k < 0)
offset = up->charstamp;
else if (k > 0)
i = 1;
for (; i < nchar && i < k + 10; i++) {
up->tstamp[up->ntstamp] = up->cstamp[i];
L_SUB(&up->tstamp[up->ntstamp], &offset);
L_ADD(&offset, &up->charstamp);
if (up->ntstamp < MAXSTAGE)
up->ntstamp++;
}
while (temp > up->prevsec) {
for (j = 15; j > 0; j--) {
up->decode[9][j] = up->decode[9][j - 1];
up->decode[19][j] =
up->decode[19][j - 1];
}
up->decode[9][j] = up->decode[19][j] = 0;
up->prevsec++;
}
}
i = -(2 * k);
for (j = 0; j < nchar; j++) {
if (i < 0 || i > 19) {
i += 2;
continue;
}
up->decode[i++][up->cbuf[j] & 0xf]++;
up->decode[i++][(up->cbuf[j] >> 4) & 0xf]++;
}
up->burstcnt++;
}
/*
* chu_poll - called by the transmit procedure
*/
static void
chu_poll(
int unit,
struct peer *peer
)
{
struct refclockproc *pp;
struct chuunit *up;
/*
* Local variables
*/
u_char code[11]; /* decoded timecode */
l_fp toffset, offset; /* l_fp temps */
int mindist; /* minimum distance */
int val1, val2; /* maximum distance */
int synchar; /* should be a 6 in traffic */
double dtemp; /* double temp */
int temp; /* common temp */
int i, j, k; /* index temps */
pp = peer->procptr;
up = (struct chuunit *)pp->unitptr;
/*
* Process the last burst, if still in the burst buffer.
* Don't mess with anything if nothing has been heard.
*/
chu_burst(peer);
if (up->pollcnt == 0)
refclock_report(peer, CEVNT_TIMEOUT);
else
up->pollcnt--;
if (up->burstcnt == 0) {
chu_clear(peer);
return;
}
/*
* Majority decoder. Select the character with the most
* occurrences for each burst position. The distance for the
* character is this number of occurrences. If no occurrences
* are found, assume a miss '_'; if only a single occurrence is
* found, assume a soft error '-'; if two different characters
* with the same distance are found, assume a hard error '='.
* The decoding distance is defined as the minimum of the
* character distances.
*/
mindist = 16;
for (i = 0; i < 10; i++) {
val1 = val2 = 0;
k = 0;
for (j = 0; j < 16; j++) {
temp = up->decode[i][j] + up->decode[i + 10][j];
if (temp > val1) {
val2 = val1;
val1 = temp;
k = j;
}
}
if (val1 > 0 && val1 == val2)
code[i] = HEX_HARD;
else if (val1 < 2)
code[i] = HEX_SOFT;
else
code[i] = k;
if (val1 < mindist)
mindist = val1;
code[i] = hexchar[code[i]];
}
code[i] = 0;
if (mindist < up->burstcnt * 2 * MINDEC)
up->errflg |= CHU_ERR_DECODE;
if (up->ntstamp < MINSTAMP)
up->errflg |= CHU_ERR_STAMP;
/*
* Compute the timecode timestamp from the days, hours and
* minutes of the timecode. Use clocktime() for the aggregate
* minutes and the minute offset computed from the burst
* seconds. Note that this code relies on the filesystem time
* for the years and does not use the years of the timecode.
*/
if (sscanf((char *)code, "%1x%3d%2d%2d", &synchar, &pp->day, &pp->hour,
&pp->minute) != 4)
up->errflg |= CHU_ERR_AFORMAT;
sprintf(pp->a_lastcode,
"%02x %4d %3d %02d:%02d:%02d %2d %2d %2d",
up->errflg, pp->year, pp->day, pp->hour, pp->minute,
pp->second, up->burstcnt, mindist, up->ntstamp);
pp->lencode = strlen(pp->a_lastcode);
record_clock_stats(&peer->srcadr, pp->a_lastcode);
#ifdef DEBUG
if (debug > 2)
printf("chu: %s\n", pp->a_lastcode);
#endif
if (up->errflg & (CHU_ERR_DECODE | CHU_ERR_STAMP |
CHU_ERR_AFORMAT)) {
refclock_report(peer, CEVNT_BADREPLY);
chu_clear(peer);
return;
}
L_CLR(&offset);
if (!clocktime(pp->day, pp->hour, pp->minute, 0, GMT,
up->tstamp[0].l_ui, &pp->yearstart, &offset.l_ui)) {
refclock_report(peer, CEVNT_BADTIME);
chu_clear(peer);
return;
}
pp->polls++;
pp->leap = LEAP_NOWARNING;
pp->lastref = offset;
pp->variance = 0;
for (i = 0; i < up->ntstamp; i++) {
toffset = offset;
L_SUB(&toffset, &up->tstamp[i]);
LFPTOD(&toffset, dtemp);
SAMPLE(dtemp + FUDGE + pp->fudgetime1);
}
if (i > 0)
refclock_receive(peer);
chu_clear(peer);
}
/*
* chu_clear - clear decoding matrix
*/
static void
chu_clear(
struct peer *peer
)
{
struct refclockproc *pp;
struct chuunit *up;
/*
* Local variables
*/
int i, j; /* index temps */
pp = peer->procptr;
up = (struct chuunit *)pp->unitptr;
/*
* Clear stuff for following minute.
*/
up->ndx = up->ntstamp = up->prevsec = 0;
up->errflg = 0;
up->burstcnt = 0;
for (i = 0; i < 20; i++) {
for (j = 0; j < 16; j++)
up->decode[i][j] = 0;
}
}
/*
* chu_dist - determine the distance of two octet arguments
*/
static int
chu_dist(
int x, /* an octet of bits */
int y /* another octet of bits */
)
{
/*
* Local variables
*/
int val; /* bit count */
int temp; /* misc temporary */
int i; /* index temporary */
/*
* The distance is determined as the weight of the exclusive OR
* of the two arguments. The weight is determined by the number
* of one bits in the result. Each one bit increases the weight,
* while each zero bit decreases it.
*/
temp = x ^ y;
val = 0;
for (i = 0; i < 8; i++) {
if ((temp & 0x1) == 0)
val++;
else
val--;
temp >>= 1;
}
return (val);
}
#ifdef AUDIO_CHU
/*
* chu_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
chu_gain(
struct peer *peer /* peer structure pointer */
)
{
struct refclockproc *pp;
struct chuunit *up;
pp = peer->procptr;
up = (struct chuunit *)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. Set the new bits in the structure
* and call AUDIO_SETINFO. Upon return, the old bits are in the
* structure.
*/
if (up->clipcnt == 0) {
up->gain += 4;
if (up->gain > AUDIO_MAX_GAIN)
up->gain = AUDIO_MAX_GAIN;
} else if (up->clipcnt > SAMPLE / 100) {
up->gain -= 4;
if (up->gain < AUDIO_MIN_GAIN)
up->gain = AUDIO_MIN_GAIN;
}
AUDIO_INITINFO(&info);
info.record.port = up->port;
info.record.gain = up->gain;
info.record.error = 0;
ioctl(chu_ctl_fd, (int)AUDIO_SETINFO, &info);
if (info.record.error)
up->errflg |= CHU_ERR_ERROR;
}
/*
* chu_audio - initialize audio device
*
* This code works with SunOS 4.1.3 and Solaris 2.6; however, it is
* believed generic and applicable to other systems with a minor twid
* or two. All it does is open the device, set the buffer size (Solaris
* only), preset the gain and set the input port. It assumes that the
* codec sample rate (8000 Hz), precision (8 bits), number of channels
* (1) and encoding (ITU-T G.711 mu-law companded) have been set by
* default.
*/
static int
chu_audio(
)
{
/*
* Open audio control device
*/
if ((chu_ctl_fd = open("/dev/audioctl", O_RDWR)) < 0) {
perror("audioctl");
return(-1);
}
#ifdef HAVE_SYS_AUDIOIO_H
/*
* Set audio device parameters.
*/
AUDIO_INITINFO(&info);
info.record.buffer_size = AUDIO_BUFSIZ;
if (ioctl(chu_ctl_fd, (int)AUDIO_SETINFO, &info) < 0) {
perror("AUDIO_SETINFO");
close(chu_ctl_fd);
return(-1);
}
#endif /* HAVE_SYS_AUDIOIO_H */
#ifdef DEBUG
chu_debug();
#endif /* DEBUG */
return(0);
}
#ifdef DEBUG
/*
* chu_debug - display audio parameters
*
* This code doesn't really do anything, except satisfy curiousity and
* verify the ioctl's work.
*/
static void
chu_debug(
)
{
if (debug == 0)
return;
#ifdef HAVE_SYS_AUDIOIO_H
ioctl(chu_ctl_fd, (int)AUDIO_GETDEV, &device);
printf("chu: name %s, version %s, config %s\n",
device.name, device.version, device.config);
#endif /* HAVE_SYS_AUDIOIO_H */
ioctl(chu_ctl_fd, (int)AUDIO_GETINFO, &info);
printf(
"chu: samples %d, channels %d, precision %d, encoding %d\n",
info.record.sample_rate, info.record.channels,
info.record.precision, info.record.encoding);
#ifdef HAVE_SYS_AUDIOIO_H
printf("chu: gain %d, port %d, buffer %d\n",
info.record.gain, info.record.port,
info.record.buffer_size);
#else /* HAVE_SYS_AUDIOIO_H */
printf("chu: gain %d, port %d\n",
info.record.gain, info.record.port);
#endif /* HAVE_SYS_AUDIOIO_H */
printf(
"chu: samples %d, eof %d, pause %d, error %d, waiting %d, balance %d\n",
info.record.samples, info.record.eof,
info.record.pause, info.record.error,
info.record.waiting, info.record.balance);
printf("chu: monitor %d, muted %d\n",
info.monitor_gain, info.output_muted);
}
#endif /* DEBUG */
#endif /* AUDIO_CHU */
#else
int refclock_chu_bs;
#endif /* REFCLOCK */
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