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Diffstat (limited to 'contrib/ntp/ntpd/refclock_chu.c')
| -rw-r--r-- | contrib/ntp/ntpd/refclock_chu.c | 1464 |
1 files changed, 1464 insertions, 0 deletions
diff --git a/contrib/ntp/ntpd/refclock_chu.c b/contrib/ntp/ntpd/refclock_chu.c new file mode 100644 index 0000000..0b2ae78 --- /dev/null +++ b/contrib/ntp/ntpd/refclock_chu.c @@ -0,0 +1,1464 @@ +/* + * 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 */ |
