412 lines
8.5 KiB
C
412 lines
8.5 KiB
C
/*
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* refclock_nmea.c - clock driver for an NMEA GPS CLOCK
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* Michael Petry Jun 20, 1994
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* based on refclock_heathn.c
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*/
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#ifdef HAVE_CONFIG_H
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#include <config.h>
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#endif
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#if defined(REFCLOCK) && defined(CLOCK_NMEA)
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#include <stdio.h>
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#include <ctype.h>
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#include <sys/time.h>
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#include <time.h>
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#include "ntpd.h"
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#include "ntp_io.h"
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#include "ntp_refclock.h"
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#include "ntp_stdlib.h"
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/*
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* This driver supports the NMEA GPS Receiver with
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*
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* Protype was refclock_trak.c, Thanks a lot.
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*
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* The receiver used spits out the NMEA sentences for boat navigation.
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* And you thought it was an information superhighway. Try a raging river
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* filled with rapids and whirlpools that rip away your data and warp time.
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*/
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/*
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* Definitions
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*/
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#define DEVICE "/dev/gps%d" /* name of radio device */
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#define SPEED232 B4800 /* uart speed (4800 bps) */
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#define PRECISION (-9) /* precision assumed (about 2 ms) */
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#define DCD_PRECISION (-20) /* precision assumed (about 1 us) */
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#define REFID "GPS\0" /* reference id */
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#define DESCRIPTION "NMEA GPS Clock" /* who we are */
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#define LENNMEA 75 /* min timecode length */
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/*
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* Tables to compute the ddd of year form icky dd/mm timecode. Viva la
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* leap.
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*/
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static int day1tab[] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
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static int day2tab[] = {31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
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/*
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* Unit control structure
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*/
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struct nmeaunit {
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int pollcnt; /* poll message counter */
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int polled; /* Hand in a sample? */
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l_fp tstamp; /* timestamp of last poll */
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};
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/*
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* Function prototypes
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*/
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static int nmea_start P((int, struct peer *));
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static void nmea_shutdown P((int, struct peer *));
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static void nmea_receive P((struct recvbuf *));
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static void nmea_poll P((int, struct peer *));
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static void gps_send P((int, const char *, struct peer *));
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static char *field_parse P((char *, int));
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/*
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* Transfer vector
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*/
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struct refclock refclock_nmea = {
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nmea_start, /* start up driver */
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nmea_shutdown, /* shut down driver */
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nmea_poll, /* transmit poll message */
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noentry, /* handle control */
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noentry, /* initialize driver */
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noentry, /* buginfo */
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NOFLAGS /* not used */
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};
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/*
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* nmea_start - open the GPS devices and initialize data for processing
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*/
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static int
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nmea_start(
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int unit,
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struct peer *peer
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)
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{
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register struct nmeaunit *up;
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struct refclockproc *pp;
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int fd;
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char device[20];
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/*
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* Open serial port. Use CLK line discipline, if available.
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*/
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(void)sprintf(device, DEVICE, unit);
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if (!(fd = refclock_open(device, SPEED232, LDISC_CLK)))
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return (0);
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/*
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* Allocate and initialize unit structure
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*/
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if (!(up = (struct nmeaunit *)
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emalloc(sizeof(struct nmeaunit)))) {
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(void) close(fd);
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return (0);
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}
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memset((char *)up, 0, sizeof(struct nmeaunit));
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pp = peer->procptr;
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pp->io.clock_recv = nmea_receive;
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pp->io.srcclock = (caddr_t)peer;
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pp->io.datalen = 0;
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pp->io.fd = fd;
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if (!io_addclock(&pp->io)) {
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(void) close(fd);
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free(up);
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return (0);
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}
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pp->unitptr = (caddr_t)up;
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/*
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* Initialize miscellaneous variables
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*/
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peer->precision = DCD_PRECISION;
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pp->clockdesc = DESCRIPTION;
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memcpy((char *)&pp->refid, REFID, 4);
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up->pollcnt = 2;
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gps_send(pp->io.fd,"$PMOTG,RMC,0000*1D\r\n", peer);
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return (1);
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}
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/*
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* nmea_shutdown - shut down a GPS clock
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*/
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static void
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nmea_shutdown(
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int unit,
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struct peer *peer
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)
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{
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register struct nmeaunit *up;
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struct refclockproc *pp;
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pp = peer->procptr;
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up = (struct nmeaunit *)pp->unitptr;
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io_closeclock(&pp->io);
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free(up);
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}
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/*
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* nmea_receive - receive data from the serial interface
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*/
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static void
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nmea_receive(
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struct recvbuf *rbufp
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)
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{
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register struct nmeaunit *up;
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struct refclockproc *pp;
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struct peer *peer;
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l_fp trtmp;
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int month, day;
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int i;
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char *cp, *dp;
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int cmdtype;
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/*
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* Initialize pointers and read the timecode and timestamp
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*/
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peer = (struct peer *)rbufp->recv_srcclock;
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pp = peer->procptr;
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up = (struct nmeaunit *)pp->unitptr;
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pp->lencode = refclock_gtlin(rbufp, pp->a_lastcode, BMAX, &trtmp);
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/*
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* There is a case that a <CR><LF> gives back a "blank" line
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*/
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if (pp->lencode == 0)
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return;
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/*
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* We get a buffer and timestamp for each <cr>.
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*/
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pp->lastrec = up->tstamp = trtmp;
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up->pollcnt = 2;
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#ifdef DEBUG
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if (debug)
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printf("nmea: timecode %d %s\n", pp->lencode,
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pp->a_lastcode);
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#endif
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/*
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* We check the timecode format and decode its contents. The
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* we only care about a few of them. The most important being
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* the $GPRMC format
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* $GPRMC,hhmmss,a,fddmm.xx,n,dddmmm.xx,w,zz.z,yyy.,ddmmyy,dd,v*CC
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* $GPGGA,162617.0,4548.339,N,00837.719,E,1,07,0.97,00262,M,048,M,,*5D
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*/
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#define GPRMC 0
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#define GPXXX 1
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#define GPGCA 2
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cp = pp->a_lastcode;
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cmdtype=0;
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if(strncmp(cp,"$GPRMC",6)==0) {
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cmdtype=GPRMC;
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}
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else if(strncmp(cp,"$GPGGA",6)==0) {
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cmdtype=GPGCA;
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}
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else if(strncmp(cp,"$GPXXX",6)==0) {
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cmdtype=GPXXX;
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}
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else
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return;
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switch( cmdtype ) {
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case GPRMC:
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case GPGCA:
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/*
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* Check time code format of NMEA
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*/
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dp = field_parse(cp,1);
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if( !isdigit((int)dp[0]) ||
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!isdigit((int)dp[1]) ||
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!isdigit((int)dp[2]) ||
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!isdigit((int)dp[3]) ||
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!isdigit((int)dp[4]) ||
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!isdigit((int)dp[5])
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) {
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refclock_report(peer, CEVNT_BADREPLY);
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return;
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}
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/*
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* Test for synchronization. Check for quality byte.
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*/
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dp = field_parse(cp,2);
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if( dp[0] != 'A') {
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refclock_report(peer, CEVNT_BADREPLY);
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return;
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}
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break;
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case GPXXX:
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return;
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default:
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return;
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}
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if (cmdtype ==GPGCA) {
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/* only time */
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time_t tt = time(NULL);
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struct tm * t = gmtime(&tt);
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day = t->tm_mday;
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month = t->tm_mon + 1;
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pp->year= t->tm_year;
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} else {
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dp = field_parse(cp,9);
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/*
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* Convert date and check values.
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*/
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day = dp[0] - '0';
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day = (day * 10) + dp[1] - '0';
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month = dp[2] - '0';
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month = (month * 10) + dp[3] - '0';
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pp->year = dp[4] - '0';
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pp->year = (pp->year * 10) + dp[5] - '0';
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}
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if (month < 1 || month > 12 || day < 1) {
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refclock_report(peer, CEVNT_BADTIME);
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return;
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}
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if (pp->year % 4) {
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if (day > day1tab[month - 1]) {
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refclock_report(peer, CEVNT_BADTIME);
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return;
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}
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for (i = 0; i < month - 1; i++)
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day += day1tab[i];
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} else {
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if (day > day2tab[month - 1]) {
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refclock_report(peer, CEVNT_BADTIME);
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return;
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}
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for (i = 0; i < month - 1; i++)
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day += day2tab[i];
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}
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pp->day = day;
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dp = field_parse(cp,1);
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/*
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* Convert time and check values.
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*/
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pp->hour = ((dp[0] - '0') * 10) + dp[1] - '0';
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pp->minute = ((dp[2] - '0') * 10) + dp[3] - '0';
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pp->second = ((dp[4] - '0') * 10) + dp[5] - '0';
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pp->msec = 0;
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if (pp->hour > 23 || pp->minute > 59 || pp->second > 59) {
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refclock_report(peer, CEVNT_BADTIME);
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return;
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}
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/*
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* Process the new sample in the median filter and determine the
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* reference clock offset and dispersion. We use lastrec as both
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* the reference time and receive time, in order to avoid being
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* cute, like setting the reference time later than the receive
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* time, which may cause a paranoid protocol module to chuck out
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* the data.
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*/
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if (!refclock_process(pp)) {
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refclock_report(peer, CEVNT_BADTIME);
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return;
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}
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/*
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* Only go on if we had been polled.
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*/
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if (!up->polled)
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return;
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up->polled = 0;
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refclock_receive(peer);
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record_clock_stats(&peer->srcadr, pp->a_lastcode);
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}
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/*
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* nmea_poll - called by the transmit procedure
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*
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* We go to great pains to avoid changing state here, since there may be
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* more than one eavesdropper receiving the same timecode.
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*/
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static void
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nmea_poll(
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int unit,
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struct peer *peer
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)
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{
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register struct nmeaunit *up;
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struct refclockproc *pp;
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pp = peer->procptr;
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up = (struct nmeaunit *)pp->unitptr;
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if (up->pollcnt == 0)
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refclock_report(peer, CEVNT_TIMEOUT);
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else
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up->pollcnt--;
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pp->polls++;
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up->polled = 1;
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/*
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* usually nmea_receive can get a timestamp every second
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*/
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gps_send(pp->io.fd,"$PMOTG,RMC,0000*1D\r\n", peer);
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}
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/*
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*
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* gps_send(fd,cmd, peer) Sends a command to the GPS receiver.
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* as gps_send(fd,"rqts,u\r", peer);
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*
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* We don't currently send any data, but would like to send
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* RTCM SC104 messages for differential positioning. It should
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* also give us better time. Without a PPS output, we're
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* Just fooling ourselves because of the serial code paths
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*
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*/
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static void
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gps_send(
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int fd,
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const char *cmd,
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struct peer *peer
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)
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{
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if (write(fd, cmd, strlen(cmd)) == -1) {
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refclock_report(peer, CEVNT_FAULT);
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}
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}
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static char *
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field_parse(
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char *cp,
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int fn
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)
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{
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char *tp;
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int i = fn;
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for (tp = cp; *tp != '\0'; tp++) {
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if (*tp == ',')
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i--;
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if (i == 0)
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break;
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}
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return (++tp);
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}
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#else
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int refclock_nmea_bs;
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#endif /* REFCLOCK */
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