/* * refclock_nmea.c - clock driver for an NMEA GPS CLOCK * Michael Petry Jun 20, 1994 * based on refclock_heathn.c * * Updated to add support for Accord GPS Clock * Venu Gopal Dec 05, 2007 * neo.venu@gmail.com, venugopal_d@pgad.gov.in * * Updated to process 'time1' fudge factor * Venu Gopal May 05, 2008 * * Converted to common PPSAPI code, separate PPS fudge time1 * from serial timecode fudge time2. * Dave Hart July 1, 2009 * hart@ntp.org, davehart@davehart.com */ #ifdef HAVE_CONFIG_H #include <config.h> #endif #include "ntp_types.h" #if defined(REFCLOCK) && defined(CLOCK_NMEA) #define NMEA_WRITE_SUPPORT 0 /* no write support at the moment */ #include <sys/stat.h> #include <stdio.h> #include <ctype.h> #ifdef HAVE_SYS_SOCKET_H #include <sys/socket.h> #endif #include "ntpd.h" #include "ntp_io.h" #include "ntp_unixtime.h" #include "ntp_refclock.h" #include "ntp_stdlib.h" #include "ntp_calendar.h" #include "timespecops.h" #ifdef HAVE_PPSAPI # include "ppsapi_timepps.h" # include "refclock_atom.h" #endif /* HAVE_PPSAPI */ /* * This driver supports NMEA-compatible GPS receivers * * Prototype was refclock_trak.c, Thanks a lot. * * The receiver used spits out the NMEA sentences for boat navigation. * And you thought it was an information superhighway. Try a raging river * filled with rapids and whirlpools that rip away your data and warp time. * * If HAVE_PPSAPI is defined code to use the PPSAPI will be compiled in. * On startup if initialization of the PPSAPI fails, it will fall back * to the "normal" timestamps. * * The PPSAPI part of the driver understands fudge flag2 and flag3. If * flag2 is set, it will use the clear edge of the pulse. If flag3 is * set, kernel hardpps is enabled. * * GPS sentences other than RMC (the default) may be enabled by setting * the relevent bits of 'mode' in the server configuration line * server 127.127.20.x mode X * * bit 0 - enables RMC (1) * bit 1 - enables GGA (2) * bit 2 - enables GLL (4) * bit 3 - enables ZDA (8) - Standard Time & Date * bit 3 - enables ZDG (8) - Accord GPS Clock's custom sentence with GPS time * very close to standard ZDA * * Multiple sentences may be selected except when ZDG/ZDA is selected. * * bit 4/5/6 - selects the baudrate for serial port : * 0 for 4800 (default) * 1 for 9600 * 2 for 19200 * 3 for 38400 * 4 for 57600 * 5 for 115200 */ #define NMEA_MESSAGE_MASK 0x0000FF0FU #define NMEA_BAUDRATE_MASK 0x00000070U #define NMEA_BAUDRATE_SHIFT 4 #define NMEA_DELAYMEAS_MASK 0x80 #define NMEA_EXTLOG_MASK 0x00010000U #define NMEA_DATETRUST_MASK 0x02000000U #define NMEA_PROTO_IDLEN 5 /* tag name must be at least 5 chars */ #define NMEA_PROTO_MINLEN 6 /* min chars in sentence, excluding CS */ #define NMEA_PROTO_MAXLEN 80 /* max chars in sentence, excluding CS */ #define NMEA_PROTO_FIELDS 32 /* not official; limit on fields per record */ /* * We check the timecode format and decode its contents. We only care * about a few of them, the most important being the $GPRMC format: * * $GPRMC,hhmmss,a,fddmm.xx,n,dddmmm.xx,w,zz.z,yyy.,ddmmyy,dd,v*CC * * mode (0,1,2,3) selects sentence ANY/ALL, RMC, GGA, GLL, ZDA * $GPGLL,3513.8385,S,14900.7851,E,232420.594,A*21 * $GPGGA,232420.59,3513.8385,S,14900.7851,E,1,05,3.4,00519,M,,,,*3F * $GPRMC,232418.19,A,3513.8386,S,14900.7853,E,00.0,000.0,121199,12.,E*77 * * Defining GPZDA to support Standard Time & Date * sentence. The sentence has the following format * * $--ZDA,HHMMSS.SS,DD,MM,YYYY,TH,TM,*CS<CR><LF> * * Apart from the familiar fields, * 'TH' Time zone Hours * 'TM' Time zone Minutes * * Defining GPZDG to support Accord GPS Clock's custom NMEA * sentence. The sentence has the following format * * $GPZDG,HHMMSS.S,DD,MM,YYYY,AA.BB,V*CS<CR><LF> * * It contains the GPS timestamp valid for next PPS pulse. * Apart from the familiar fields, * 'AA.BB' denotes the signal strength( should be < 05.00 ) * 'V' denotes the GPS sync status : * '0' indicates INVALID time, * '1' indicates accuracy of +/-20 ms * '2' indicates accuracy of +/-100 ns * * Defining PGRMF for Garmin GPS Fix Data * $PGRMF,WN,WS,DATE,TIME,LS,LAT,LAT_DIR,LON,LON_DIR,MODE,FIX,SPD,DIR,PDOP,TDOP * WN -- GPS week number (weeks since 1980-01-06, mod 1024) * WS -- GPS seconds in week * LS -- GPS leap seconds, accumulated ( UTC + LS == GPS ) * FIX -- Fix type: 0=nofix, 1=2D, 2=3D * DATE/TIME are standard date/time strings in UTC time scale * * The GPS time can be used to get the full century for the truncated * date spec. */ /* * Definitions */ #define DEVICE "/dev/gps%d" /* GPS serial device */ #define PPSDEV "/dev/gpspps%d" /* PPSAPI device override */ #define SPEED232 B4800 /* uart speed (4800 bps) */ #define PRECISION (-9) /* precision assumed (about 2 ms) */ #define PPS_PRECISION (-20) /* precision assumed (about 1 us) */ #define REFID "GPS\0" /* reference id */ #define DESCRIPTION "NMEA GPS Clock" /* who we are */ #ifndef O_NOCTTY #define M_NOCTTY 0 #else #define M_NOCTTY O_NOCTTY #endif #ifndef O_NONBLOCK #define M_NONBLOCK 0 #else #define M_NONBLOCK O_NONBLOCK #endif #define PPSOPENMODE (O_RDWR | M_NOCTTY | M_NONBLOCK) /* NMEA sentence array indexes for those we use */ #define NMEA_GPRMC 0 /* recommended min. nav. */ #define NMEA_GPGGA 1 /* fix and quality */ #define NMEA_GPGLL 2 /* geo. lat/long */ #define NMEA_GPZDA 3 /* date/time */ /* * $GPZDG is a proprietary sentence that violates the spec, by not * using $P and an assigned company identifier to prefix the sentence * identifier. When used with this driver, the system needs to be * isolated from other NTP networks, as it operates in GPS time, not * UTC as is much more common. GPS time is >15 seconds different from * UTC due to not respecting leap seconds since 1970 or so. Other * than the different timebase, $GPZDG is similar to $GPZDA. */ #define NMEA_GPZDG 4 #define NMEA_PGRMF 5 #define NMEA_ARRAY_SIZE (NMEA_PGRMF + 1) /* * Sentence selection mode bits */ #define USE_GPRMC 0x00000001u #define USE_GPGGA 0x00000002u #define USE_GPGLL 0x00000004u #define USE_GPZDA 0x00000008u #define USE_PGRMF 0x00000100u /* mapping from sentence index to controlling mode bit */ static const u_int32 sentence_mode[NMEA_ARRAY_SIZE] = { USE_GPRMC, USE_GPGGA, USE_GPGLL, USE_GPZDA, USE_GPZDA, USE_PGRMF }; /* date formats we support */ enum date_fmt { DATE_1_DDMMYY, /* use 1 field with 2-digit year */ DATE_3_DDMMYYYY /* use 3 fields with 4-digit year */ }; /* results for 'field_init()' * * Note: If a checksum is present, the checksum test must pass OK or the * sentence is tagged invalid. */ #define CHECK_EMPTY -1 /* no data */ #define CHECK_INVALID 0 /* not a valid NMEA sentence */ #define CHECK_VALID 1 /* valid but without checksum */ #define CHECK_CSVALID 2 /* valid with checksum OK */ /* * Unit control structure */ typedef struct { #ifdef HAVE_PPSAPI struct refclock_atom atom; /* PPSAPI structure */ int ppsapi_fd; /* fd used with PPSAPI */ u_char ppsapi_tried; /* attempt PPSAPI once */ u_char ppsapi_lit; /* time_pps_create() worked */ u_char ppsapi_gate; /* system is on PPS */ #endif /* HAVE_PPSAPI */ u_char gps_time; /* use GPS time, not UTC */ u_short century_cache; /* cached current century */ l_fp last_reftime; /* last processed reference stamp */ short epoch_warp; /* last epoch warp, for logging */ /* tally stats, reset each poll cycle */ struct { u_int total; u_int accepted; u_int rejected; /* GPS said not enough signal */ u_int malformed; /* Bad checksum, invalid date or time */ u_int filtered; /* mode bits, not GPZDG, same second */ u_int pps_used; } tally; /* per sentence checksum seen flag */ u_char cksum_type[NMEA_ARRAY_SIZE]; } nmea_unit; /* * helper for faster field access */ typedef struct { char *base; /* buffer base */ char *cptr; /* current field ptr */ int blen; /* buffer length */ int cidx; /* current field index */ } nmea_data; /* * NMEA gps week/time information * This record contains the number of weeks since 1980-01-06 modulo * 1024, the seconds elapsed since start of the week, and the number of * leap seconds that are the difference between GPS and UTC time scale. */ typedef struct { u_int32 wt_time; /* seconds since weekstart */ u_short wt_week; /* week number */ short wt_leap; /* leap seconds */ } gps_weektm; /* * The GPS week time scale starts on Sunday, 1980-01-06. We need the * rata die number of this day. */ #ifndef DAY_GPS_STARTS #define DAY_GPS_STARTS 722820 #endif /* * Function prototypes */ static void nmea_init (void); static int nmea_start (int, struct peer *); static void nmea_shutdown (int, struct peer *); static void nmea_receive (struct recvbuf *); static void nmea_poll (int, struct peer *); #ifdef HAVE_PPSAPI static void nmea_control (int, const struct refclockstat *, struct refclockstat *, struct peer *); #define NMEA_CONTROL nmea_control #else #define NMEA_CONTROL noentry #endif /* HAVE_PPSAPI */ static void nmea_timer (int, struct peer *); /* parsing helpers */ static int field_init (nmea_data * data, char * cp, int len); static char * field_parse (nmea_data * data, int fn); static void field_wipe (nmea_data * data, ...); static u_char parse_qual (nmea_data * data, int idx, char tag, int inv); static int parse_time (struct calendar * jd, long * nsec, nmea_data *, int idx); static int parse_date (struct calendar *jd, nmea_data*, int idx, enum date_fmt fmt); static int parse_weekdata (gps_weektm *, nmea_data *, int weekidx, int timeidx, int leapidx); /* calendar / date helpers */ static int unfold_day (struct calendar * jd, u_int32 rec_ui); static int unfold_century (struct calendar * jd, u_int32 rec_ui); static int gpsfix_century (struct calendar * jd, const gps_weektm * wd, u_short * ccentury); static l_fp eval_gps_time (struct peer * peer, const struct calendar * gpst, const struct timespec * gpso, const l_fp * xrecv); static int nmead_open (const char * device); static void save_ltc (struct refclockproc * const, const char * const, size_t); /* * If we want the driver to ouput sentences, too: re-enable the send * support functions by defining NMEA_WRITE_SUPPORT to non-zero... */ #if NMEA_WRITE_SUPPORT static void gps_send(int, const char *, struct peer *); # ifdef SYS_WINNT # undef write /* ports/winnt/include/config.h: #define write _write */ extern int async_write(int, const void *, unsigned int); # define write(fd, data, octets) async_write(fd, data, octets) # endif /* SYS_WINNT */ #endif /* NMEA_WRITE_SUPPORT */ static int32_t g_gpsMinBase; static int32_t g_gpsMinYear; /* * ------------------------------------------------------------------- * Transfer vector * ------------------------------------------------------------------- */ struct refclock refclock_nmea = { nmea_start, /* start up driver */ nmea_shutdown, /* shut down driver */ nmea_poll, /* transmit poll message */ NMEA_CONTROL, /* fudge control */ nmea_init, /* initialize driver */ noentry, /* buginfo */ nmea_timer /* called once per second */ }; /* * ------------------------------------------------------------------- * nmea_init - initialise data * * calculates a few runtime constants that cannot be made compile time * constants. * ------------------------------------------------------------------- */ static void nmea_init(void) { struct calendar date; /* - calculate min. base value for GPS epoch & century unfolding * This assumes that the build system was roughly in sync with * the world, and that really synchronising to a time before the * program was created would be unsafe or insane. If the build * date cannot be stablished, at least use the start of GPS * (1980-01-06) as minimum, because GPS can surely NOT * synchronise beyond it's own big bang. We add a little safety * margin for the fuzziness of the build date, which is in an * undefined time zone. */ if (ntpcal_get_build_date(&date)) g_gpsMinBase = ntpcal_date_to_rd(&date) - 2; else g_gpsMinBase = 0; if (g_gpsMinBase < DAY_GPS_STARTS) g_gpsMinBase = DAY_GPS_STARTS; ntpcal_rd_to_date(&date, g_gpsMinBase); g_gpsMinYear = date.year; g_gpsMinBase -= DAY_NTP_STARTS; } /* * ------------------------------------------------------------------- * nmea_start - open the GPS devices and initialize data for processing * * return 0 on error, 1 on success. Even on error the peer structures * must be in a state that permits 'nmea_shutdown()' to clean up all * resources, because it will be called immediately to do so. * ------------------------------------------------------------------- */ static int nmea_start( int unit, struct peer * peer ) { struct refclockproc * const pp = peer->procptr; nmea_unit * const up = emalloc_zero(sizeof(*up)); char device[20]; size_t devlen; u_int32 rate; int baudrate; const char * baudtext; /* Get baudrate choice from mode byte bits 4/5/6 */ rate = (peer->ttl & NMEA_BAUDRATE_MASK) >> NMEA_BAUDRATE_SHIFT; switch (rate) { case 0: baudrate = SPEED232; baudtext = "4800"; break; case 1: baudrate = B9600; baudtext = "9600"; break; case 2: baudrate = B19200; baudtext = "19200"; break; case 3: baudrate = B38400; baudtext = "38400"; break; #ifdef B57600 case 4: baudrate = B57600; baudtext = "57600"; break; #endif #ifdef B115200 case 5: baudrate = B115200; baudtext = "115200"; break; #endif default: baudrate = SPEED232; baudtext = "4800 (fallback)"; break; } /* Allocate and initialize unit structure */ pp->unitptr = (caddr_t)up; pp->io.fd = -1; pp->io.clock_recv = nmea_receive; pp->io.srcclock = peer; pp->io.datalen = 0; /* force change detection on first valid message */ memset(&up->last_reftime, 0xFF, sizeof(up->last_reftime)); /* force checksum on GPRMC, see below */ up->cksum_type[NMEA_GPRMC] = CHECK_CSVALID; #ifdef HAVE_PPSAPI up->ppsapi_fd = -1; #endif ZERO(up->tally); /* Initialize miscellaneous variables */ peer->precision = PRECISION; pp->clockdesc = DESCRIPTION; memcpy(&pp->refid, REFID, 4); /* Open serial port. Use CLK line discipline, if available. */ devlen = snprintf(device, sizeof(device), DEVICE, unit); if (devlen >= sizeof(device)) { msyslog(LOG_ERR, "%s clock device name too long", refnumtoa(&peer->srcadr)); return FALSE; /* buffer overflow */ } pp->io.fd = refclock_open(device, baudrate, LDISC_CLK); if (0 >= pp->io.fd) { pp->io.fd = nmead_open(device); if (-1 == pp->io.fd) return FALSE; } LOGIF(CLOCKINFO, (LOG_NOTICE, "%s serial %s open at %s bps", refnumtoa(&peer->srcadr), device, baudtext)); /* succeed if this clock can be added */ return io_addclock(&pp->io) != 0; } /* * ------------------------------------------------------------------- * nmea_shutdown - shut down a GPS clock * * NOTE this routine is called after nmea_start() returns failure, * as well as during a normal shutdown due to ntpq :config unpeer. * ------------------------------------------------------------------- */ static void nmea_shutdown( int unit, struct peer * peer ) { struct refclockproc * const pp = peer->procptr; nmea_unit * const up = (nmea_unit *)pp->unitptr; UNUSED_ARG(unit); if (up != NULL) { #ifdef HAVE_PPSAPI if (up->ppsapi_lit) time_pps_destroy(up->atom.handle); if (up->ppsapi_tried && up->ppsapi_fd != pp->io.fd) close(up->ppsapi_fd); #endif free(up); } pp->unitptr = (caddr_t)NULL; if (-1 != pp->io.fd) io_closeclock(&pp->io); pp->io.fd = -1; } /* * ------------------------------------------------------------------- * nmea_control - configure fudge params * ------------------------------------------------------------------- */ #ifdef HAVE_PPSAPI static void nmea_control( int unit, const struct refclockstat * in_st, struct refclockstat * out_st, struct peer * peer ) { struct refclockproc * const pp = peer->procptr; nmea_unit * const up = (nmea_unit *)pp->unitptr; char device[32]; size_t devlen; UNUSED_ARG(in_st); UNUSED_ARG(out_st); /* * PPS control * * If /dev/gpspps$UNIT can be opened that will be used for * PPSAPI. Otherwise, the GPS serial device /dev/gps$UNIT * already opened is used for PPSAPI as well. (This might not * work, in which case the PPS API remains unavailable...) */ /* Light up the PPSAPI interface if not yet attempted. */ if ((CLK_FLAG1 & pp->sloppyclockflag) && !up->ppsapi_tried) { up->ppsapi_tried = TRUE; devlen = snprintf(device, sizeof(device), PPSDEV, unit); if (devlen < sizeof(device)) { up->ppsapi_fd = open(device, PPSOPENMODE, S_IRUSR | S_IWUSR); } else { up->ppsapi_fd = -1; msyslog(LOG_ERR, "%s PPS device name too long", refnumtoa(&peer->srcadr)); } if (-1 == up->ppsapi_fd) up->ppsapi_fd = pp->io.fd; if (refclock_ppsapi(up->ppsapi_fd, &up->atom)) { /* use the PPS API for our own purposes now. */ up->ppsapi_lit = refclock_params( pp->sloppyclockflag, &up->atom); if (!up->ppsapi_lit) { /* failed to configure, drop PPS unit */ time_pps_destroy(up->atom.handle); msyslog(LOG_WARNING, "%s set PPSAPI params fails", refnumtoa(&peer->srcadr)); } /* note: the PPS I/O handle remains valid until * flag1 is cleared or the clock is shut down. */ } else { msyslog(LOG_WARNING, "%s flag1 1 but PPSAPI fails", refnumtoa(&peer->srcadr)); } } /* shut down PPS API if activated */ if (!(CLK_FLAG1 & pp->sloppyclockflag) && up->ppsapi_tried) { /* shutdown PPS API */ if (up->ppsapi_lit) time_pps_destroy(up->atom.handle); up->atom.handle = 0; /* close/drop PPS fd */ if (up->ppsapi_fd != pp->io.fd) close(up->ppsapi_fd); up->ppsapi_fd = -1; /* clear markers and peer items */ up->ppsapi_gate = FALSE; up->ppsapi_lit = FALSE; up->ppsapi_tried = FALSE; peer->flags &= ~FLAG_PPS; peer->precision = PRECISION; } } #endif /* HAVE_PPSAPI */ /* * ------------------------------------------------------------------- * nmea_timer - called once per second * this only polls (older?) Oncore devices now * * Usually 'nmea_receive()' can get a timestamp every second, but at * least one Motorola unit needs prompting each time. Doing so in * 'nmea_poll()' gives only one sample per poll cycle, which actually * defeats the purpose of the median filter. Polling once per second * seems a much better idea. * ------------------------------------------------------------------- */ static void nmea_timer( int unit, struct peer * peer ) { #if NMEA_WRITE_SUPPORT struct refclockproc * const pp = peer->procptr; UNUSED_ARG(unit); if (-1 != pp->io.fd) /* any mode bits to evaluate here? */ gps_send(pp->io.fd, "$PMOTG,RMC,0000*1D\r\n", peer); #else UNUSED_ARG(unit); UNUSED_ARG(peer); #endif /* NMEA_WRITE_SUPPORT */ } #ifdef HAVE_PPSAPI /* * ------------------------------------------------------------------- * refclock_ppsrelate(...) -- correlate with PPS edge * * This function is used to correlate a receive time stamp and a * reference time with a PPS edge time stamp. It applies the necessary * fudges (fudge1 for PPS, fudge2 for receive time) and then tries to * move the receive time stamp to the corresponding edge. This can warp * into future, if a transmission delay of more than 500ms is not * compensated with a corresponding fudge time2 value, because then the * next PPS edge is nearer than the last. (Similiar to what the PPS ATOM * driver does, but we deal with full time stamps here, not just phase * shift information.) Likewise, a negative fudge time2 value must be * used if the reference time stamp correlates with the *following* PPS * pulse. * * Note that the receive time fudge value only needs to move the receive * stamp near a PPS edge but that close proximity is not required; * +/-100ms precision should be enough. But since the fudge value will * probably also be used to compensate the transmission delay when no * PPS edge can be related to the time stamp, it's best to get it as * close as possible. * * It should also be noted that the typical use case is matching to the * preceeding edge, as most units relate their sentences to the current * second. * * The function returns PPS_RELATE_NONE (0) if no PPS edge correlation * can be fixed; PPS_RELATE_EDGE (1) when a PPS edge could be fixed, but * the distance to the reference time stamp is too big (exceeds * +/-400ms) and the ATOM driver PLL cannot be used to fix the phase; * and PPS_RELATE_PHASE (2) when the ATOM driver PLL code can be used. * * On output, the receive time stamp is replaced with the corresponding * PPS edge time if a fix could be made; the PPS fudge is updated to * reflect the proper fudge time to apply. (This implies that * 'refclock_process_offset()' must be used!) * ------------------------------------------------------------------- */ #define PPS_RELATE_NONE 0 /* no pps correlation possible */ #define PPS_RELATE_EDGE 1 /* recv time fixed, no phase lock */ #define PPS_RELATE_PHASE 2 /* recv time fixed, phase lock ok */ static int refclock_ppsrelate( const struct refclockproc * pp , /* for sanity */ const struct refclock_atom * ap , /* for PPS io */ const l_fp * reftime , l_fp * rd_stamp, /* i/o read stamp */ double pp_fudge, /* pps fudge */ double * rd_fudge /* i/o read fudge */ ) { pps_info_t pps_info; struct timespec timeout; l_fp pp_stamp, pp_delta; double delta, idelta; if (pp->leap == LEAP_NOTINSYNC) return PPS_RELATE_NONE; /* clock is insane, no chance */ ZERO(timeout); ZERO(pps_info); if (time_pps_fetch(ap->handle, PPS_TSFMT_TSPEC, &pps_info, &timeout) < 0) return PPS_RELATE_NONE; /* can't get time stamps */ /* get last active PPS edge before receive */ if (ap->pps_params.mode & PPS_CAPTUREASSERT) timeout = pps_info.assert_timestamp; else if (ap->pps_params.mode & PPS_CAPTURECLEAR) timeout = pps_info.clear_timestamp; else return PPS_RELATE_NONE; /* WHICH edge, please?!? */ /* get delta between receive time and PPS time */ pp_stamp = tspec_stamp_to_lfp(timeout); pp_delta = *rd_stamp; L_SUB(&pp_delta, &pp_stamp); LFPTOD(&pp_delta, delta); delta += pp_fudge - *rd_fudge; if (fabs(delta) > 1.5) return PPS_RELATE_NONE; /* PPS timeout control */ /* eventually warp edges, check phase */ idelta = floor(delta + 0.5); pp_fudge -= idelta; delta -= idelta; if (fabs(delta) > 0.45) return PPS_RELATE_NONE; /* dead band control */ /* we actually have a PPS edge to relate with! */ *rd_stamp = pp_stamp; *rd_fudge = pp_fudge; /* if whole system out-of-sync, do not try to PLL */ if (sys_leap == LEAP_NOTINSYNC) return PPS_RELATE_EDGE; /* cannot PLL with atom code */ /* check against reftime if ATOM PLL can be used */ pp_delta = *reftime; L_SUB(&pp_delta, &pp_stamp); LFPTOD(&pp_delta, delta); delta += pp_fudge; if (fabs(delta) > 0.45) return PPS_RELATE_EDGE; /* cannot PLL with atom code */ /* all checks passed, gets an AAA rating here! */ return PPS_RELATE_PHASE; /* can PLL with atom code */ } #endif /* HAVE_PPSAPI */ /* * ------------------------------------------------------------------- * nmea_receive - receive data from the serial interface * * This is the workhorse for NMEA data evaluation: * * + it checks all NMEA data, and rejects sentences that are not valid * NMEA sentences * + it checks whether a sentence is known and to be used * + it parses the time and date data from the NMEA data string and * augments the missing bits. (century in dat, whole date, ...) * + it rejects data that is not from the first accepted sentence in a * burst * + it eventually replaces the receive time with the PPS edge time. * + it feeds the data to the internal processing stages. * ------------------------------------------------------------------- */ static void nmea_receive( struct recvbuf * rbufp ) { /* declare & init control structure ptrs */ struct peer * const peer = rbufp->recv_peer; struct refclockproc * const pp = peer->procptr; nmea_unit * const up = (nmea_unit*)pp->unitptr; /* Use these variables to hold data until we decide its worth keeping */ nmea_data rdata; char rd_lastcode[BMAX]; l_fp rd_timestamp, rd_reftime; int rd_lencode; double rd_fudge; /* working stuff */ struct calendar date; /* to keep & convert the time stamp */ struct timespec tofs; /* offset to full-second reftime */ gps_weektm gpsw; /* week time storage */ /* results of sentence/date/time parsing */ u_char sentence; /* sentence tag */ int checkres; char * cp; int rc_date; int rc_time; /* make sure data has defined pristine state */ ZERO(tofs); ZERO(date); ZERO(gpsw); /* * Read the timecode and timestamp, then initialise field * processing. The <CR><LF> at the NMEA line end is translated * to <LF><LF> by the terminal input routines on most systems, * and this gives us one spurious empty read per record which we * better ignore silently. */ rd_lencode = refclock_gtlin(rbufp, rd_lastcode, sizeof(rd_lastcode), &rd_timestamp); checkres = field_init(&rdata, rd_lastcode, rd_lencode); switch (checkres) { case CHECK_INVALID: DPRINTF(1, ("%s invalid data: '%s'\n", refnumtoa(&peer->srcadr), rd_lastcode)); refclock_report(peer, CEVNT_BADREPLY); return; case CHECK_EMPTY: return; default: DPRINTF(1, ("%s gpsread: %d '%s'\n", refnumtoa(&peer->srcadr), rd_lencode, rd_lastcode)); break; } up->tally.total++; /* * --> below this point we have a valid NMEA sentence <-- * * Check sentence name. Skip first 2 chars (talker ID) in most * cases, to allow for $GLGGA and $GPGGA etc. Since the name * field has at least 5 chars we can simply shift the field * start. */ cp = field_parse(&rdata, 0); if (strncmp(cp + 2, "RMC,", 4) == 0) sentence = NMEA_GPRMC; else if (strncmp(cp + 2, "GGA,", 4) == 0) sentence = NMEA_GPGGA; else if (strncmp(cp + 2, "GLL,", 4) == 0) sentence = NMEA_GPGLL; else if (strncmp(cp + 2, "ZDA,", 4) == 0) sentence = NMEA_GPZDA; else if (strncmp(cp + 2, "ZDG,", 4) == 0) sentence = NMEA_GPZDG; else if (strncmp(cp, "PGRMF,", 6) == 0) sentence = NMEA_PGRMF; else return; /* not something we know about */ /* Eventually output delay measurement now. */ if (peer->ttl & NMEA_DELAYMEAS_MASK) { mprintf_clock_stats(&peer->srcadr, "delay %0.6f %.*s", ldexp(rd_timestamp.l_uf, -32), (int)(strchr(rd_lastcode, ',') - rd_lastcode), rd_lastcode); } /* See if I want to process this message type */ if ((peer->ttl & NMEA_MESSAGE_MASK) && !(peer->ttl & sentence_mode[sentence])) { up->tally.filtered++; return; } /* * make sure it came in clean * * Apparently, older NMEA specifications (which are expensive) * did not require the checksum for all sentences. $GPMRC is * the only one so far identified which has always been required * to include a checksum. * * Today, most NMEA GPS receivers checksum every sentence. To * preserve its error-detection capabilities with modern GPSes * while allowing operation without checksums on all but $GPMRC, * we keep track of whether we've ever seen a valid checksum on * a given sentence, and if so, reject future instances without * checksum. ('up->cksum_type[NMEA_GPRMC]' is set in * 'nmea_start()' to enforce checksums for $GPRMC right from the * start.) */ if (up->cksum_type[sentence] <= (u_char)checkres) { up->cksum_type[sentence] = (u_char)checkres; } else { DPRINTF(1, ("%s checksum missing: '%s'\n", refnumtoa(&peer->srcadr), rd_lastcode)); refclock_report(peer, CEVNT_BADREPLY); up->tally.malformed++; return; } /* * $GPZDG provides GPS time not UTC, and the two mix poorly. * Once have processed a $GPZDG, do not process any further UTC * sentences (all but $GPZDG currently). */ if (up->gps_time && NMEA_GPZDG != sentence) { up->tally.filtered++; return; } DPRINTF(1, ("%s processing %d bytes, timecode '%s'\n", refnumtoa(&peer->srcadr), rd_lencode, rd_lastcode)); /* * Grab fields depending on clock string type and possibly wipe * sensitive data from the last timecode. */ switch (sentence) { case NMEA_GPRMC: /* Check quality byte, fetch data & time */ rc_time = parse_time(&date, &tofs.tv_nsec, &rdata, 1); pp->leap = parse_qual(&rdata, 2, 'A', 0); rc_date = parse_date(&date, &rdata, 9, DATE_1_DDMMYY) && unfold_century(&date, rd_timestamp.l_ui); if (CLK_FLAG4 & pp->sloppyclockflag) field_wipe(&rdata, 3, 4, 5, 6, -1); break; case NMEA_GPGGA: /* Check quality byte, fetch time only */ rc_time = parse_time(&date, &tofs.tv_nsec, &rdata, 1); pp->leap = parse_qual(&rdata, 6, '0', 1); rc_date = unfold_day(&date, rd_timestamp.l_ui); if (CLK_FLAG4 & pp->sloppyclockflag) field_wipe(&rdata, 2, 4, -1); break; case NMEA_GPGLL: /* Check quality byte, fetch time only */ rc_time = parse_time(&date, &tofs.tv_nsec, &rdata, 5); pp->leap = parse_qual(&rdata, 6, 'A', 0); rc_date = unfold_day(&date, rd_timestamp.l_ui); if (CLK_FLAG4 & pp->sloppyclockflag) field_wipe(&rdata, 1, 3, -1); break; case NMEA_GPZDA: /* No quality. Assume best, fetch time & full date */ pp->leap = LEAP_NOWARNING; rc_time = parse_time(&date, &tofs.tv_nsec, &rdata, 1); rc_date = parse_date(&date, &rdata, 2, DATE_3_DDMMYYYY); break; case NMEA_GPZDG: /* Check quality byte, fetch time & full date */ rc_time = parse_time(&date, &tofs.tv_nsec, &rdata, 1); rc_date = parse_date(&date, &rdata, 2, DATE_3_DDMMYYYY); pp->leap = parse_qual(&rdata, 4, '0', 1); tofs.tv_sec = -1; /* GPZDG is following second */ break; case NMEA_PGRMF: /* get date, time, qualifier and GPS weektime. We need * date and time-of-day for the century fix, so we read * them first. */ rc_date = parse_weekdata(&gpsw, &rdata, 1, 2, 5) && parse_date(&date, &rdata, 3, DATE_1_DDMMYY); rc_time = parse_time(&date, &tofs.tv_nsec, &rdata, 4); pp->leap = parse_qual(&rdata, 11, '0', 1); rc_date = rc_date && gpsfix_century(&date, &gpsw, &up->century_cache); if (CLK_FLAG4 & pp->sloppyclockflag) field_wipe(&rdata, 6, 8, -1); break; default: INVARIANT(0); /* Coverity 97123 */ return; } /* Check sanity of time-of-day. */ if (rc_time == 0) { /* no time or conversion error? */ checkres = CEVNT_BADTIME; up->tally.malformed++; } /* Check sanity of date. */ else if (rc_date == 0) {/* no date or conversion error? */ checkres = CEVNT_BADDATE; up->tally.malformed++; } /* check clock sanity; [bug 2143] */ else if (pp->leap == LEAP_NOTINSYNC) { /* no good status? */ checkres = CEVNT_BADREPLY; up->tally.rejected++; } else checkres = -1; if (checkres != -1) { save_ltc(pp, rd_lastcode, rd_lencode); refclock_report(peer, checkres); return; } DPRINTF(1, ("%s effective timecode: %04u-%02u-%02u %02d:%02d:%02d\n", refnumtoa(&peer->srcadr), date.year, date.month, date.monthday, date.hour, date.minute, date.second)); /* Check if we must enter GPS time mode; log so if we do */ if (!up->gps_time && (sentence == NMEA_GPZDG)) { msyslog(LOG_INFO, "%s using GPS time as if it were UTC", refnumtoa(&peer->srcadr)); up->gps_time = 1; } /* * Get the reference time stamp from the calendar buffer. * Process the new sample in the median filter and determine the * timecode timestamp, but only if the PPS is not in control. * Discard sentence if reference time did not change. */ rd_reftime = eval_gps_time(peer, &date, &tofs, &rd_timestamp); if (L_ISEQU(&up->last_reftime, &rd_reftime)) { /* Do not touch pp->a_lastcode on purpose! */ up->tally.filtered++; return; } up->last_reftime = rd_reftime; rd_fudge = pp->fudgetime2; DPRINTF(1, ("%s using '%s'\n", refnumtoa(&peer->srcadr), rd_lastcode)); /* Data will be accepted. Update stats & log data. */ up->tally.accepted++; save_ltc(pp, rd_lastcode, rd_lencode); pp->lastrec = rd_timestamp; #ifdef HAVE_PPSAPI /* * If we have PPS running, we try to associate the sentence * with the last active edge of the PPS signal. */ if (up->ppsapi_lit) switch (refclock_ppsrelate( pp, &up->atom, &rd_reftime, &rd_timestamp, pp->fudgetime1, &rd_fudge)) { case PPS_RELATE_PHASE: up->ppsapi_gate = TRUE; peer->precision = PPS_PRECISION; peer->flags |= FLAG_PPS; DPRINTF(2, ("%s PPS_RELATE_PHASE\n", refnumtoa(&peer->srcadr))); up->tally.pps_used++; break; case PPS_RELATE_EDGE: up->ppsapi_gate = TRUE; peer->precision = PPS_PRECISION; DPRINTF(2, ("%s PPS_RELATE_EDGE\n", refnumtoa(&peer->srcadr))); break; case PPS_RELATE_NONE: default: /* * Resetting precision and PPS flag is done in * 'nmea_poll', since it might be a glitch. But * at the end of the poll cycle we know... */ DPRINTF(2, ("%s PPS_RELATE_NONE\n", refnumtoa(&peer->srcadr))); break; } #endif /* HAVE_PPSAPI */ refclock_process_offset(pp, rd_reftime, rd_timestamp, rd_fudge); } /* * ------------------------------------------------------------------- * nmea_poll - called by the transmit procedure * * Does the necessary bookkeeping stuff to keep the reported state of * the clock in sync with reality. * * We go to great pains to avoid changing state here, since there may * be more than one eavesdropper receiving the same timecode. * ------------------------------------------------------------------- */ static void nmea_poll( int unit, struct peer * peer ) { struct refclockproc * const pp = peer->procptr; nmea_unit * const up = (nmea_unit *)pp->unitptr; /* * Process median filter samples. If none received, declare a * timeout and keep going. */ #ifdef HAVE_PPSAPI /* * If we don't have PPS pulses and time stamps, turn PPS down * for now. */ if (!up->ppsapi_gate) { peer->flags &= ~FLAG_PPS; peer->precision = PRECISION; } else { up->ppsapi_gate = FALSE; } #endif /* HAVE_PPSAPI */ /* * If the median filter is empty, claim a timeout. Else process * the input data and keep the stats going. */ if (pp->coderecv == pp->codeproc) { refclock_report(peer, CEVNT_TIMEOUT); } else { pp->polls++; pp->lastref = pp->lastrec; refclock_receive(peer); } /* * If extended logging is required, write the tally stats to the * clockstats file; otherwise just do a normal clock stats * record. Clear the tally stats anyway. */ if (peer->ttl & NMEA_EXTLOG_MASK) { /* Log & reset counters with extended logging */ const char *nmea = pp->a_lastcode; if (*nmea == '\0') nmea = "(none)"; mprintf_clock_stats( &peer->srcadr, "%s %u %u %u %u %u %u", nmea, up->tally.total, up->tally.accepted, up->tally.rejected, up->tally.malformed, up->tally.filtered, up->tally.pps_used); } else { record_clock_stats(&peer->srcadr, pp->a_lastcode); } ZERO(up->tally); } /* * ------------------------------------------------------------------- * Save the last timecode string, making sure it's properly truncated * if necessary and NUL terminated in any case. */ static void save_ltc( struct refclockproc * const pp, const char * const tc, size_t len ) { if (len >= sizeof(pp->a_lastcode)) len = sizeof(pp->a_lastcode) - 1; pp->lencode = (u_short)len; memcpy(pp->a_lastcode, tc, len); pp->a_lastcode[len] = '\0'; } #if NMEA_WRITE_SUPPORT /* * ------------------------------------------------------------------- * gps_send(fd, cmd, peer) Sends a command to the GPS receiver. * as in gps_send(fd, "rqts,u", peer); * * If 'cmd' starts with a '$' it is assumed that this command is in raw * format, that is, starts with '$', ends with '<cr><lf>' and that any * checksum is correctly provided; the command will be send 'as is' in * that case. Otherwise the function will create the necessary frame * (start char, chksum, final CRLF) on the fly. * * We don't currently send any data, but would like to send RTCM SC104 * messages for differential positioning. It should also give us better * time. Without a PPS output, we're Just fooling ourselves because of * the serial code paths * ------------------------------------------------------------------- */ static void gps_send( int fd, const char * cmd, struct peer * peer ) { /* $...*xy<CR><LF><NUL> add 7 */ char buf[NMEA_PROTO_MAXLEN + 7]; int len; u_char dcs; const u_char *beg, *end; if (*cmd != '$') { /* get checksum and length */ beg = end = (const u_char*)cmd; dcs = 0; while (*end >= ' ' && *end != '*') dcs ^= *end++; len = end - beg; /* format into output buffer with overflow check */ len = snprintf(buf, sizeof(buf), "$%.*s*%02X\r\n", len, beg, dcs); if ((size_t)len >= sizeof(buf)) { DPRINTF(1, ("%s gps_send: buffer overflow for command '%s'\n", refnumtoa(&peer->srcadr), cmd)); return; /* game over player 1 */ } cmd = buf; } else { len = strlen(cmd); } DPRINTF(1, ("%s gps_send: '%.*s'\n", refnumtoa(&peer->srcadr), len - 2, cmd)); /* send out the whole stuff */ if (write(fd, cmd, len) == -1) refclock_report(peer, CEVNT_FAULT); } #endif /* NMEA_WRITE_SUPPORT */ /* * ------------------------------------------------------------------- * helpers for faster field splitting * ------------------------------------------------------------------- * * set up a field record, check syntax and verify checksum * * format is $XXXXX,1,2,3,4*ML * * 8-bit XOR of characters between $ and * noninclusive is transmitted * in last two chars M and L holding most and least significant nibbles * in hex representation such as: * * $GPGLL,5057.970,N,00146.110,E,142451,A*27 * $GPVTG,089.0,T,,,15.2,N,,*7F * * Some other constraints: * + The field name must at least 5 upcase characters or digits and must * start with a character. * + The checksum (if present) must be uppercase hex digits. * + The length of a sentence is limited to 80 characters (not including * the final CR/LF nor the checksum, but including the leading '$') * * Return values: * + CHECK_INVALID * The data does not form a valid NMEA sentence or a checksum error * occurred. * + CHECK_VALID * The data is a valid NMEA sentence but contains no checksum. * + CHECK_CSVALID * The data is a valid NMEA sentence and passed the checksum test. * ------------------------------------------------------------------- */ static int field_init( nmea_data * data, /* context structure */ char * cptr, /* start of raw data */ int dlen /* data len, not counting trailing NUL */ ) { u_char cs_l; /* checksum local computed */ u_char cs_r; /* checksum remote given */ char * eptr; /* buffer end end pointer */ char tmp; /* char buffer */ cs_l = 0; cs_r = 0; /* some basic input constraints */ if (dlen < 0) dlen = 0; eptr = cptr + dlen; *eptr = '\0'; /* load data context */ data->base = cptr; data->cptr = cptr; data->cidx = 0; data->blen = dlen; /* syntax check follows here. check allowed character * sequences, updating the local computed checksum as we go. * * regex equiv: '^\$[A-Z][A-Z0-9]{4,}[^*]*(\*[0-9A-F]{2})?$' */ /* -*- start character: '^\$' */ if (*cptr == '\0') return CHECK_EMPTY; if (*cptr++ != '$') return CHECK_INVALID; /* -*- advance context beyond start character */ data->base++; data->cptr++; data->blen--; /* -*- field name: '[A-Z][A-Z0-9]{4,},' */ if (*cptr < 'A' || *cptr > 'Z') return CHECK_INVALID; cs_l ^= *cptr++; while ((*cptr >= 'A' && *cptr <= 'Z') || (*cptr >= '0' && *cptr <= '9') ) cs_l ^= *cptr++; if (*cptr != ',' || (cptr - data->base) < NMEA_PROTO_IDLEN) return CHECK_INVALID; cs_l ^= *cptr++; /* -*- data: '[^*]*' */ while (*cptr && *cptr != '*') cs_l ^= *cptr++; /* -*- checksum field: (\*[0-9A-F]{2})?$ */ if (*cptr == '\0') return CHECK_VALID; if (*cptr != '*' || cptr != eptr - 3 || (cptr - data->base) >= NMEA_PROTO_MAXLEN) return CHECK_INVALID; for (cptr++; (tmp = *cptr) != '\0'; cptr++) { if (tmp >= '0' && tmp <= '9') cs_r = (cs_r << 4) + (tmp - '0'); else if (tmp >= 'A' && tmp <= 'F') cs_r = (cs_r << 4) + (tmp - 'A' + 10); else break; } /* -*- make sure we are at end of string and csum matches */ if (cptr != eptr || cs_l != cs_r) return CHECK_INVALID; return CHECK_CSVALID; } /* * ------------------------------------------------------------------- * fetch a data field by index, zero being the name field. If this * function is called repeatedly with increasing indices, the total load * is O(n), n being the length of the string; if it is called with * decreasing indices, the total load is O(n^2). Try not to go backwards * too often. * ------------------------------------------------------------------- */ static char * field_parse( nmea_data * data, int fn ) { char tmp; if (fn < data->cidx) { data->cidx = 0; data->cptr = data->base; } while ((fn > data->cidx) && (tmp = *data->cptr) != '\0') { data->cidx += (tmp == ','); data->cptr++; } return data->cptr; } /* * ------------------------------------------------------------------- * Wipe (that is, overwrite with '_') data fields and the checksum in * the last timecode. The list of field indices is given as integers * in a varargs list, preferrably in ascending order, in any case * terminated by a negative field index. * * A maximum number of 8 fields can be overwritten at once to guard * against runaway (that is, unterminated) argument lists. * * This function affects what a remote user can see with * * ntpq -c clockvar <server> * * Note that this also removes the wiped fields from any clockstats * log. Some NTP operators monitor their NMEA GPS using the change in * location in clockstats over time as as a proxy for the quality of * GPS reception and thereby time reported. * ------------------------------------------------------------------- */ static void field_wipe( nmea_data * data, ... ) { va_list va; /* vararg index list */ int fcnt; /* safeguard against runaway arglist */ int fidx; /* field to nuke, or -1 for checksum */ char * cp; /* overwrite destination */ fcnt = 8; cp = NULL; va_start(va, data); do { fidx = va_arg(va, int); if (fidx >= 0 && fidx <= NMEA_PROTO_FIELDS) { cp = field_parse(data, fidx); } else { cp = data->base + data->blen; if (data->blen >= 3 && cp[-3] == '*') cp -= 2; } for ( ; '\0' != *cp && '*' != *cp && ',' != *cp; cp++) if ('.' != *cp) *cp = '_'; } while (fcnt-- && fidx >= 0); va_end(va); } /* * ------------------------------------------------------------------- * PARSING HELPERS * ------------------------------------------------------------------- * * Check sync status * * If the character at the data field start matches the tag value, * return LEAP_NOWARNING and LEAP_NOTINSYNC otherwise. If the 'inverted' * flag is given, just the opposite value is returned. If there is no * data field (*cp points to the NUL byte) the result is LEAP_NOTINSYNC. * ------------------------------------------------------------------- */ static u_char parse_qual( nmea_data * rd, int idx, char tag, int inv ) { static const u_char table[2] = { LEAP_NOTINSYNC, LEAP_NOWARNING }; char * dp; dp = field_parse(rd, idx); return table[ *dp && ((*dp == tag) == !inv) ]; } /* * ------------------------------------------------------------------- * Parse a time stamp in HHMMSS[.sss] format with error checking. * * returns 1 on success, 0 on failure * ------------------------------------------------------------------- */ static int parse_time( struct calendar * jd, /* result calendar pointer */ long * ns, /* storage for nsec fraction */ nmea_data * rd, int idx ) { static const unsigned long weight[4] = { 0, 100000000, 10000000, 1000000 }; int rc; u_int h; u_int m; u_int s; int p1; int p2; u_long f; char * dp; dp = field_parse(rd, idx); rc = sscanf(dp, "%2u%2u%2u%n.%3lu%n", &h, &m, &s, &p1, &f, &p2); if (rc < 3 || p1 != 6) { DPRINTF(1, ("nmea: invalid time code: '%.6s'\n", dp)); return FALSE; } /* value sanity check */ if (h > 23 || m > 59 || s > 60) { DPRINTF(1, ("nmea: invalid time spec %02u:%02u:%02u\n", h, m, s)); return FALSE; } jd->hour = (u_char)h; jd->minute = (u_char)m; jd->second = (u_char)s; /* if we have a fraction, scale it up to nanoseconds. */ if (rc == 4) *ns = f * weight[p2 - p1 - 1]; else *ns = 0; return TRUE; } /* * ------------------------------------------------------------------- * Parse a date string from an NMEA sentence. This could either be a * partial date in DDMMYY format in one field, or DD,MM,YYYY full date * spec spanning three fields. This function does some extensive error * checking to make sure the date string was consistent. * * returns 1 on success, 0 on failure * ------------------------------------------------------------------- */ static int parse_date( struct calendar * jd, /* result pointer */ nmea_data * rd, int idx, enum date_fmt fmt ) { int rc; u_int y; u_int m; u_int d; int p; char * dp; dp = field_parse(rd, idx); switch (fmt) { case DATE_1_DDMMYY: rc = sscanf(dp, "%2u%2u%2u%n", &d, &m, &y, &p); if (rc != 3 || p != 6) { DPRINTF(1, ("nmea: invalid date code: '%.6s'\n", dp)); return FALSE; } break; case DATE_3_DDMMYYYY: rc = sscanf(dp, "%2u,%2u,%4u%n", &d, &m, &y, &p); if (rc != 3 || p != 10) { DPRINTF(1, ("nmea: invalid date code: '%.10s'\n", dp)); return FALSE; } break; default: DPRINTF(1, ("nmea: invalid parse format: %d\n", fmt)); return FALSE; } /* value sanity check */ if (d < 1 || d > 31 || m < 1 || m > 12) { DPRINTF(1, ("nmea: invalid date spec (YMD) %04u:%02u:%02u\n", y, m, d)); return FALSE; } /* store results */ jd->monthday = (u_char)d; jd->month = (u_char)m; jd->year = (u_short)y; return TRUE; } /* * ------------------------------------------------------------------- * Parse GPS week time info from an NMEA sentence. This info contains * the GPS week number, the GPS time-of-week and the leap seconds GPS * to UTC. * * returns 1 on success, 0 on failure * ------------------------------------------------------------------- */ static int parse_weekdata( gps_weektm * wd, nmea_data * rd, int weekidx, int timeidx, int leapidx ) { u_long secs; int fcnt; /* parse fields and count success */ fcnt = sscanf(field_parse(rd, weekidx), "%hu", &wd->wt_week); fcnt += sscanf(field_parse(rd, timeidx), "%lu", &secs); fcnt += sscanf(field_parse(rd, leapidx), "%hd", &wd->wt_leap); if (fcnt != 3 || wd->wt_week >= 1024 || secs >= 7*SECSPERDAY) { DPRINTF(1, ("nmea: parse_weekdata: invalid weektime spec\n")); return FALSE; } wd->wt_time = (u_int32)secs; return TRUE; } /* * ------------------------------------------------------------------- * funny calendar-oriented stuff -- perhaps a bit hard to grok. * ------------------------------------------------------------------- * * Unfold a time-of-day (seconds since midnight) around the current * system time in a manner that guarantees an absolute difference of * less than 12hrs. * * This function is used for NMEA sentences that contain no date * information. This requires the system clock to be in +/-12hrs * around the true time, or the clock will synchronize the system 1day * off if not augmented with a time sources that also provide the * necessary date information. * * The function updates the calendar structure it also uses as * input to fetch the time from. * * returns 1 on success, 0 on failure * ------------------------------------------------------------------- */ static int unfold_day( struct calendar * jd, u_int32 rec_ui ) { vint64 rec_qw; ntpcal_split rec_ds; /* * basically this is the peridiodic extension of the receive * time - 12hrs to the time-of-day with a period of 1 day. * But we would have to execute this in 64bit arithmetic, and we * cannot assume we can do this; therefore this is done * in split representation. */ rec_qw = ntpcal_ntp_to_ntp(rec_ui - SECSPERDAY/2, NULL); rec_ds = ntpcal_daysplit(&rec_qw); rec_ds.lo = ntpcal_periodic_extend(rec_ds.lo, ntpcal_date_to_daysec(jd), SECSPERDAY); rec_ds.hi += ntpcal_daysec_to_date(jd, rec_ds.lo); return (ntpcal_rd_to_date(jd, rec_ds.hi + DAY_NTP_STARTS) >= 0); } /* * ------------------------------------------------------------------- * A 2-digit year is expanded into full year spec around the year found * in 'jd->year'. This should be in +79/-19 years around the system time, * or the result will be off by 100 years. The assymetric behaviour was * chosen to enable inital sync for systems that do not have a * battery-backup clock and start with a date that is typically years in * the past. * * Since the GPS epoch starts at 1980-01-06, the resulting year will be * not be before 1980 in any case. * * returns 1 on success, 0 on failure * ------------------------------------------------------------------- */ static int unfold_century( struct calendar * jd, u_int32 rec_ui ) { struct calendar rec; int32 baseyear; ntpcal_ntp_to_date(&rec, rec_ui, NULL); baseyear = rec.year - 20; if (baseyear < g_gpsMinYear) baseyear = g_gpsMinYear; jd->year = (u_short)ntpcal_periodic_extend(baseyear, jd->year, 100); return ((baseyear <= jd->year) && (baseyear + 100 > jd->year)); } /* * ------------------------------------------------------------------- * A 2-digit year is expanded into a full year spec by correlation with * a GPS week number and the current leap second count. * * The GPS week time scale counts weeks since Sunday, 1980-01-06, modulo * 1024 and seconds since start of the week. The GPS time scale is based * on international atomic time (TAI), so the leap second difference to * UTC is also needed for a proper conversion. * * A brute-force analysis (that is, test for every date) shows that a * wrong assignment of the century can not happen between the years 1900 * to 2399 when comparing the week signatures for different * centuries. (I *think* that will not happen for 400*1024 years, but I * have no valid proof. -*-perlinger@ntp.org-*-) * * This function is bound to to work between years 1980 and 2399 * (inclusive), which should suffice for now ;-) * * Note: This function needs a full date&time spec on input due to the * necessary leap second corrections! * * returns 1 on success, 0 on failure * ------------------------------------------------------------------- */ static int gpsfix_century( struct calendar * jd, const gps_weektm * wd, u_short * century ) { int32 days; int32 doff; u_short week; u_short year; int loop; /* Get day offset. Assumes that the input time is in range and * that the leap seconds do not shift more than +/-1 day. */ doff = ntpcal_date_to_daysec(jd) + wd->wt_leap; doff = (doff >= SECSPERDAY) - (doff < 0); /* * Loop over centuries to get a match, starting with the last * successful one. (Or with the 19th century if the cached value * is out of range...) */ year = jd->year % 100; for (loop = 5; loop > 0; loop--,(*century)++) { if (*century < 19 || *century >= 24) *century = 19; /* Get days and week in GPS epoch */ jd->year = year + *century * 100; days = ntpcal_date_to_rd(jd) - DAY_GPS_STARTS + doff; week = (days / 7) % 1024; if (days >= 0 && wd->wt_week == week) return TRUE; /* matched... */ } jd->year = year; return FALSE; /* match failed... */ } /* * ------------------------------------------------------------------- * And now the final execise: Considering the fact that many (most?) * GPS receivers cannot handle a GPS epoch wrap well, we try to * compensate for that problem by unwrapping a GPS epoch around the * receive stamp. Another execise in periodic unfolding, of course, * but with enough points to take care of. * * Note: The integral part of 'tofs' is intended to handle small(!) * systematic offsets, as -1 for handling $GPZDG, which gives the * following second. (sigh...) The absolute value shall be less than a * day (86400 seconds). * ------------------------------------------------------------------- */ static l_fp eval_gps_time( struct peer * peer, /* for logging etc */ const struct calendar * gpst, /* GPS time stamp */ const struct timespec * tofs, /* GPS frac second & offset */ const l_fp * xrecv /* receive time stamp */ ) { struct refclockproc * const pp = peer->procptr; nmea_unit * const up = (nmea_unit *)pp->unitptr; l_fp retv; /* components of calculation */ int32_t rcv_sec, rcv_day; /* receive ToD and day */ int32_t gps_sec, gps_day; /* GPS ToD and day in NTP epoch */ int32_t adj_day, weeks; /* adjusted GPS day and week shift */ /* some temporaries to shuffle data */ vint64 vi64; ntpcal_split rs64; /* evaluate time stamp from receiver. */ gps_sec = ntpcal_date_to_daysec(gpst); gps_day = ntpcal_date_to_rd(gpst) - DAY_NTP_STARTS; /* merge in fractional offset */ retv = tspec_intv_to_lfp(*tofs); gps_sec += retv.l_i; /* If we fully trust the GPS receiver, just combine days and * seconds and be done. */ if (peer->ttl & NMEA_DATETRUST_MASK) { retv.l_ui = ntpcal_dayjoin(gps_day, gps_sec).D_s.lo; return retv; } /* So we do not trust the GPS receiver to deliver a correct date * due to the GPS epoch changes. We map the date from the * receiver into the +/-512 week interval around the receive * time in that case. This would be a tad easier with 64bit * calculations, but again, we restrict the code to 32bit ops * when possible. */ /* - make sure the GPS fractional day is normalised * Applying the offset value might have put us slightly over the * edge of the allowed range for seconds-of-day. Doing a full * division with floor correction is overkill here; a simple * addition or subtraction step is sufficient. Using WHILE loops * gives the right result even if the offset exceeds one day, * which is NOT what it's intented for! */ while (gps_sec >= SECSPERDAY) { gps_sec -= SECSPERDAY; gps_day += 1; } while (gps_sec < 0) { gps_sec += SECSPERDAY; gps_day -= 1; } /* - get unfold base: day of full recv time - 512 weeks */ vi64 = ntpcal_ntp_to_ntp(xrecv->l_ui, NULL); rs64 = ntpcal_daysplit(&vi64); rcv_sec = rs64.lo; rcv_day = rs64.hi - 512 * 7; /* - take the fractional days into account * If the fractional day of the GPS time is smaller than the * fractional day of the receive time, we shift the base day for * the unfold by 1. */ if ( gps_sec < rcv_sec || (gps_sec == rcv_sec && retv.l_uf < xrecv->l_uf)) rcv_day += 1; /* - don't warp ahead of GPS invention! */ if (rcv_day < g_gpsMinBase) rcv_day = g_gpsMinBase; /* - let the magic happen: */ adj_day = ntpcal_periodic_extend(rcv_day, gps_day, 1024*7); /* - check if we should log a GPS epoch warp */ weeks = (adj_day - gps_day) / 7; if (weeks != up->epoch_warp) { up->epoch_warp = weeks; LOGIF(CLOCKINFO, (LOG_INFO, "%s Changed GPS epoch warp to %d weeks", refnumtoa(&peer->srcadr), weeks)); } /* - build result and be done */ retv.l_ui = ntpcal_dayjoin(adj_day, gps_sec).D_s.lo; return retv; } /* * =================================================================== * * NMEAD support * * original nmead support added by Jon Miner (cp_n18@yahoo.com) * * See http://home.hiwaay.net/~taylorc/gps/nmea-server/ * for information about nmead * * To use this, you need to create a link from /dev/gpsX to * the server:port where nmead is running. Something like this: * * ln -s server:port /dev/gps1 * * Split into separate function by Juergen Perlinger * (perlinger-at-ntp-dot-org) * * =================================================================== */ static int nmead_open( const char * device ) { int fd = -1; /* result file descriptor */ #ifdef HAVE_READLINK char host[80]; /* link target buffer */ char * port; /* port name or number */ int rc; /* result code (several)*/ int sh; /* socket handle */ struct addrinfo ai_hint; /* resolution hint */ struct addrinfo *ai_list; /* resolution result */ struct addrinfo *ai; /* result scan ptr */ fd = -1; /* try to read as link, make sure no overflow occurs */ rc = readlink(device, host, sizeof(host)); if ((size_t)rc >= sizeof(host)) return fd; /* error / overflow / truncation */ host[rc] = '\0'; /* readlink does not place NUL */ /* get port */ port = strchr(host, ':'); if (!port) return fd; /* not 'host:port' syntax ? */ *port++ = '\0'; /* put in separator */ /* get address infos and try to open socket * * This getaddrinfo() is naughty in ntpd's nonblocking main * thread, but you have to go out of your wary to use this code * and typically the blocking is at startup where its impact is * reduced. The same holds for the 'connect()', as it is * blocking, too... */ ZERO(ai_hint); ai_hint.ai_protocol = IPPROTO_TCP; ai_hint.ai_socktype = SOCK_STREAM; if (getaddrinfo(host, port, &ai_hint, &ai_list)) return fd; for (ai = ai_list; ai && (fd == -1); ai = ai->ai_next) { sh = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol); if (INVALID_SOCKET == sh) continue; rc = connect(sh, ai->ai_addr, ai->ai_addrlen); if (-1 != rc) fd = sh; else close(sh); } freeaddrinfo(ai_list); #else fd = -1; #endif return fd; } #else NONEMPTY_TRANSLATION_UNIT #endif /* REFCLOCK && CLOCK_NMEA */