/*
* This driver supports the Arbiter 1088A/B Satellite Controlled Clock.
* The claimed accuracy of this clock is 100 ns relative to the PPS
* output when receiving four or more satellites.
*
* The receiver should be configured before starting the NTP daemon, in
* order to establish reliable position and operating conditions. It
* does not initiate surveying or hold mode. For use with NTP, the
* daylight savings time feature should be disables (D0 command) and the
* broadcast mode set to operate in UTC (BU command).
*
* The timecode format supported by this driver is selected by the poll
* sequence "B5", which initiates a line in the following format to be
* repeated once per second until turned off by the "B0" poll sequence.
*
* Format B5 (24 ASCII printing characters):
*
* <cr><lf>i yy ddd hh:mm:ss.000bbb
*
* on-time = <cr>
* i = synchronization flag (' ' = locked, '?' = unlocked)
* yy = year of century
* ddd = day of year
* hh:mm:ss = hours, minutes, seconds
* .000 = fraction of second (not used)
* bbb = tailing spaces for fill
*
* The alarm condition is indicated by a '?' at i, which indicates the
* receiver is not synchronized. In normal operation, a line consisting
* of the timecode followed by the time quality character (TQ) followed
* by the receiver status string (SR) is written to the clockstats file.
* The time quality character is encoded in IEEE P1344 standard:
*
* Format TQ (IEEE P1344 estimated worst-case time quality)
*
* 0 clock locked, maximum accuracy
* F clock failure, time not reliable
* 4 clock unlocked, accuracy < 1 us
* 5 clock unlocked, accuracy < 10 us
* 6 clock unlocked, accuracy < 100 us
* 7 clock unlocked, accuracy < 1 ms
* 8 clock unlocked, accuracy < 10 ms
* 9 clock unlocked, accuracy < 100 ms
* A clock unlocked, accuracy < 1 s
* B clock unlocked, accuracy < 10 s
*
* The status string is encoded as follows:
*
* Format SR (25 ASCII printing characters)
*
* V=vv S=ss T=t P=pdop E=ee
*
* vv = satellites visible
* ss = relative signal strength
* t = satellites tracked
* pdop = position dilution of precision (meters)
* ee = hardware errors
*
* If flag4 is set, an additional line consisting of the receiver
* latitude (LA), longitude (LO), elevation (LH) (meters), and data
* buffer (DB) is written to this file. If channel B is enabled for
* deviation mode and connected to a 1-PPS signal, the last two numbers
* on the line are the deviation and standard deviation averaged over
* the last 15 seconds.
*
* PPS calibration fudge time1 .001240
*/
/*
* Interface definitions
*/
#define DEVICE "/dev/gps%d" /* device name and unit */
#define SPEED232 B9600 /* uart speed (9600 baud) */
#define PRECISION (-20) /* precision assumed (about 1 us) */
#define REFID "GPS " /* reference ID */
#define DESCRIPTION "Arbiter 1088A/B GPS Receiver" /* WRU */
#define LENARB 24 /* format B5 timecode length */
#define MAXSTA 40 /* max length of status string */
#define MAXPOS 80 /* max length of position string */
/*
* Transfer vector
*/
struct refclock refclock_arbiter = {
arb_start, /* start up driver */
arb_shutdown, /* shut down driver */
arb_poll, /* transmit poll message */
noentry, /* not used (old arb_control) */
noentry, /* initialize driver (not used) */
noentry, /* not used (old arb_buginfo) */
NOFLAGS /* not used */
};
/*
* arb_start - open the devices and initialize data for processing
*/
static int
arb_start(
int unit,
struct peer *peer
)
{
register struct arbunit *up;
struct refclockproc *pp;
int fd;
char device[20];
/*
* Open serial port. Use CLK line discipline, if available.
*/
snprintf(device, sizeof(device), DEVICE, unit);
fd = refclock_open(&peer->srcadr, device, SPEED232, LDISC_CLK);
if (fd <= 0)
return (0);
/*
* Allocate and initialize unit structure
*/
up = emalloc_zero(sizeof(*up));
pp = peer->procptr;
pp->io.clock_recv = arb_receive;
pp->io.srcclock = peer;
pp->io.datalen = 0;
pp->io.fd = fd;
if (!io_addclock(&pp->io)) {
close(fd);
pp->io.fd = -1;
free(up);
return (0);
}
pp->unitptr = up;
/*
* arb_shutdown - shut down the clock
*/
static void
arb_shutdown(
int unit,
struct peer *peer
)
{
register struct arbunit *up;
struct refclockproc *pp;
pp = peer->procptr;
up = pp->unitptr;
if (-1 != pp->io.fd)
io_closeclock(&pp->io);
if (NULL != up)
free(up);
}
/*
* arb_receive - receive data from the serial interface
*/
static void
arb_receive(
struct recvbuf *rbufp
)
{
register struct arbunit *up;
struct refclockproc *pp;
struct peer *peer;
l_fp trtmp;
int temp;
u_char syncchar; /* synch indicator */
char tbuf[BMAX]; /* temp buffer */
/*
* Initialize pointers and read the timecode and timestamp
*/
peer = rbufp->recv_peer;
pp = peer->procptr;
up = pp->unitptr;
temp = refclock_gtlin(rbufp, tbuf, sizeof(tbuf), &trtmp);
/*
* Note we get a buffer and timestamp for both a <cr> and <lf>,
* but only the <cr> timestamp is retained. The program first
* sends a TQ and expects the echo followed by the time quality
* character. It then sends a B5 starting the timecode broadcast
* and expects the echo followed some time later by the on-time
* character <cr> and then the <lf> beginning the timecode
* itself. Finally, at the <cr> beginning the next timecode at
* the next second, the program sends a B0 shutting down the
* timecode broadcast.
*
* If flag4 is set, the program snatches the latitude, longitude
* and elevation and writes it to the clockstats file.
*/
if (temp == 0)
return;
/*
* Collect statistics. If nothing is recogized, just
* ignore; sometimes the clock doesn't stop spewing
* timecodes for awhile after the B0 command.
*
* If flag4 is not set, send TQ, SR, B5. If flag4 is
* sset, send TQ, SR, LA, LO, LH, DB, B5. When the
* median filter is full, send B0.
*/
if (!strncmp(tbuf, "TQ", 2)) {
up->qualchar = tbuf[2];
refclock_write(peer, "SR", 2, "SR");
return;
/*
* We get down to business, check the timecode format and decode
* its contents. If the timecode has valid length, but not in
* proper format, we declare bad format and exit. If the
* timecode has invalid length, which sometimes occurs when the
* B0 amputates the broadcast, we just quietly steal away. Note
* that the time quality character and receiver status string is
* tacked on the end for clockstats display.
*/
up->tcswitch++;
if (up->tcswitch <= 1 || temp < LENARB)
return;
/*
* Process the new sample in the median filter and determine the
* timecode timestamp.
*/
if (!refclock_process(pp))
refclock_report(peer, CEVNT_BADTIME);
else if (peer->disp > MAXDISTANCE)
refclock_receive(peer);
/*
* arb_poll - called by the transmit procedure
*/
static void
arb_poll(
int unit,
struct peer *peer
)
{
register struct arbunit *up;
struct refclockproc *pp;
/*
* Time to poll the clock. The Arbiter clock responds to a "B5"
* by returning a timecode in the format specified above.
* Transmission occurs once per second, unless turned off by a
* "B0". Note there is no checking on state, since this may not
* be the only customer reading the clock. Only one customer
* need poll the clock; all others just listen in.
*/
pp = peer->procptr;
up = pp->unitptr;
pp->polls++;
up->tcswitch = 0;
if (refclock_write(peer, "TQ", 2, "TQ") != 2)
refclock_report(peer, CEVNT_FAULT);
/*
* Process median filter samples. If none received, declare a
* timeout and keep going.
*/
if (pp->coderecv == pp->codeproc) {
refclock_report(peer, CEVNT_TIMEOUT);
return;
}
refclock_receive(peer);
record_clock_stats(&peer->srcadr, pp->a_lastcode);
#ifdef DEBUG
if (debug)
printf("arbiter: timecode %d %s\n",
pp->lencode, pp->a_lastcode);
#endif
}
