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driver_nmea0183.c
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driver_nmea0183.c
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/*
* This file is Copyright (c) 2010 by the GPSD project
* SPDX-License-Identifier: BSD-2-clause
*/
/* for vsnprintf() FreeBSD wants __ISO_C_VISIBLE >= 1999 */
#define __ISO_C_VISIBLE 1999
#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <math.h>
#include <string.h>
#include <stdarg.h>
#include <time.h>
#include "gpsd.h"
#include "strfuncs.h"
#ifdef NMEA0183_ENABLE
/**************************************************************************
*
* Parser helpers begin here
*
**************************************************************************/
static void do_lat_lon(char *field[], struct gps_fix_t *out)
/* process a pair of latitude/longitude fields starting at field index BEGIN
* The input fields look like this:
* field[0]: 4404.1237962
* field[1]: N
* field[2]: 12118.8472460
* field[3]: W
* input format of lat/lon is NMEA style DDDMM.mmmmmmm
* yes, 7 digits of precision from survey grade GPS
*
*/
{
double d, m;
char str[20], *p;
if (*(p = field[0]) != '\0') {
double lat;
(void)strlcpy(str, p, sizeof(str));
lat = safe_atof(str);
m = 100.0 * modf(lat / 100.0, &d);
lat = d + m / 60.0;
p = field[1];
if (*p == 'S')
lat = -lat;
out->latitude = lat;
}
if (*(p = field[2]) != '\0') {
double lon;
(void)strlcpy(str, p, sizeof(str));
lon = safe_atof(str);
m = 100.0 * modf(lon / 100.0, &d);
lon = d + m / 60.0;
p = field[3];
if (*p == 'W')
lon = -lon;
out->longitude = lon;
}
}
/**************************************************************************
*
* Scary timestamp fudging begins here
*
* Four sentences, GGA and GLL and RMC and ZDA, contain timestamps.
* GGA/GLL/RMC timestamps look like hhmmss.ss, with the trailing .ss
* part optional. RMC has a date field, in the format ddmmyy. ZDA
* has separate fields for day/month/year, with a 4-digit year. This
* means that for RMC we must supply a century and for GGA and GLL we
* must supply a century, year, and day. We get the missing data from
* a previous RMC or ZDA; century in RMC is supplied from the daemon's
* context (initialized at startup time) if there has been no previous
* ZDA.
*
**************************************************************************/
#define DD(s) ((int)((s)[0]-'0')*10+(int)((s)[1]-'0'))
static void merge_ddmmyy(char *ddmmyy, struct gps_device_t *session)
/* sentence supplied ddmmyy, but no century part */
{
int yy = DD(ddmmyy + 4);
int mon = DD(ddmmyy + 2);
int mday = DD(ddmmyy);
int year;
/* check for century wrap */
if (session->nmea.date.tm_year % 100 == 99 && yy == 0)
gpsd_century_update(session, session->context->century + 100);
year = (session->context->century + yy);
if ( (1 > mon ) || (12 < mon ) ) {
gpsd_log(&session->context->errout, LOG_WARN,
"merge_ddmmyy(%s), malformed month\n", ddmmyy);
} else if ( (1 > mday ) || (31 < mday ) ) {
gpsd_log(&session->context->errout, LOG_WARN,
"merge_ddmmyy(%s), malformed day\n", ddmmyy);
} else {
gpsd_log(&session->context->errout, LOG_DATA,
"merge_ddmmyy(%s) sets year %d\n",
ddmmyy, year);
session->nmea.date.tm_year = year - 1900;
session->nmea.date.tm_mon = mon - 1;
session->nmea.date.tm_mday = mday;
}
}
static void merge_hhmmss(char *hhmmss, struct gps_device_t *session)
/* update from a UTC time */
{
int old_hour = session->nmea.date.tm_hour;
session->nmea.date.tm_hour = DD(hhmmss);
if (session->nmea.date.tm_hour < old_hour) /* midnight wrap */
session->nmea.date.tm_mday++;
session->nmea.date.tm_min = DD(hhmmss + 2);
session->nmea.date.tm_sec = DD(hhmmss + 4);
session->nmea.subseconds =
safe_atof(hhmmss + 4) - session->nmea.date.tm_sec;
}
static void register_fractional_time(const char *tag, const char *fld,
struct gps_device_t *session)
{
if (fld[0] != '\0') {
session->nmea.last_frac_time = session->nmea.this_frac_time;
session->nmea.this_frac_time = safe_atof(fld);
session->nmea.latch_frac_time = true;
gpsd_log(&session->context->errout, LOG_DATA,
"%s: registers fractional time %.2f\n",
tag, session->nmea.this_frac_time);
}
}
/**************************************************************************
*
* Compare GPS timestamps for equality. Depends on the fact that the
* timestamp granularity of GPS is 1/100th of a second. Use this to avoid
* naive float comparisons.
*
**************************************************************************/
#define GPS_TIME_EQUAL(a, b) (fabs((a) - (b)) < 0.01)
/**************************************************************************
*
* NMEA sentence handling begins here
*
**************************************************************************/
static gps_mask_t processVTG(int count,
char *field[],
struct gps_device_t *session)
// $GPVTG,054.7,T,034.4,M,005.5,N,010.2,K
// $GPVTG,054.7,T,034.4,M,005.5,N,010.2,K,A
//
// where:
// 1,2 054.7,T True track made good (degrees)
// 3,4 034.4,M Magnetic track made good
// 5,6 005.5,N Ground speed, knots
// 7,8 010.2,K Ground speed, Kilometers per hour
// 9 A Mode Indicator (optional)
// A=autonomous, D=differential, E=Estimated,
// N=not valid, S=Simulator, M=Manual input mode
//
// see also:
// http://www.catb.org/gpsd/NMEA.html#_vtg_track_made_good_and_ground_speed
{
gps_mask_t mask = 0;
if( (field[1][0] == '\0') || (field[5][0] == '\0')){
return 0;
}
/* ignore empty/missing field, fix mode of last resort */
if ((count > 9) && ('\0' != field[9][0]) &&
(MODE_NOT_SEEN == session->newdata.mode)) {
switch (field[9][0]) {
case 'A':
/* Autonomous, 2D or 3D fix */
/* FALL THROUGH */
case 'D':
/* Differential, 2D or 3D fix */
session->newdata.mode = MODE_2D;
// MODE_SET here causes issues
// mask |= MODE_SET;
break;
case 'E':
/* Estimated, DR only */
/* FALL THROUGH */
case 'N':
/* Not Valid */
session->newdata.mode = MODE_NO_FIX;
// MODE_SET here causes issues
// mask |= MODE_SET;
// nothing to use here, leave
return 0;
default:
/* Huh? */
break;
}
}
// set true track
session->newdata.track = safe_atof(field[1]);
mask |= TRACK_SET;
// set magnetic variation
if (field[3][0] != '\0'){ // ignore empty fields
session->newdata.magnetic_track = safe_atof(field[3]);
mask |= MAGNETIC_TRACK_SET;
}
session->newdata.speed = safe_atof(field[5]) * KNOTS_TO_MPS;
mask |= SPEED_SET;
gpsd_log(&session->context->errout, LOG_DATA,
"VTG: course(T)=%.2f, course(M)=%.2f, speed=%.2f",
session->newdata.track, session->newdata.magnetic_track,
session->newdata.speed);
return mask;
}
static gps_mask_t processRMC(int count, char *field[],
struct gps_device_t *session)
/* Recommend Minimum Course Specific GPS/TRANSIT Data */
{
/*
* RMC,225446.33,A,4916.45,N,12311.12,W,000.5,054.7,191194,020.3,E,A*68
* 1 225446.33 Time of fix 22:54:46 UTC
* 2 A Status of Fix: A = Autonomous, valid;
* D = Differential, valid; V = invalid
* 3,4 4916.45,N Latitude 49 deg. 16.45 min North
* 5,6 12311.12,W Longitude 123 deg. 11.12 min West
* 7 000.5 Speed over ground, Knots
* 8 054.7 Course Made Good, True north
* 9 181194 Date of fix 18 November 1994
* 10,11 020.3,E Magnetic variation 20.3 deg East
* 12 A FAA mode indicator (NMEA 2.3 and later)
* A=autonomous, D=differential, E=Estimated,
* N=not valid, S=Simulator, M=Manual input mode
* *68 mandatory nmea_checksum
*
* * SiRF chipsets don't return either Mode Indicator or magnetic variation.
*/
gps_mask_t mask = 0;
if (strcmp(field[2], "V") == 0) {
/* copes with Magellan EC-10X, see below */
if (session->gpsdata.status != STATUS_NO_FIX) {
session->gpsdata.status = STATUS_NO_FIX;
mask |= STATUS_SET;
}
if (session->newdata.mode >= MODE_2D) {
session->newdata.mode = MODE_NO_FIX;
mask |= MODE_SET;
}
/* set something nz, so it won't look like an unknown sentence */
mask |= ONLINE_SET;
} else if (strcmp(field[2], "A") == 0) {
/*
* The MTK3301, Royaltek RGM-3800, and possibly other
* devices deliver bogus time values when the navigation
* warning bit is set.
*/
if (count > 9 && field[1][0] != '\0' && field[9][0] != '\0') {
merge_hhmmss(field[1], session);
merge_ddmmyy(field[9], session);
mask |= TIME_SET;
register_fractional_time(field[0], field[1], session);
}
do_lat_lon(&field[3], &session->newdata);
mask |= LATLON_SET;
session->newdata.speed = safe_atof(field[7]) * KNOTS_TO_MPS;
session->newdata.track = safe_atof(field[8]);
mask |= (TRACK_SET | SPEED_SET);
/*
* This copes with GPSes like the Magellan EC-10X that *only* emit
* GPRMC. In this case we set mode and status here so the client
* code that relies on them won't mistakenly believe it has never
* received a fix.
*/
if (session->gpsdata.status == STATUS_NO_FIX) {
/* could be DGPS_FIX, we can't tell */
session->gpsdata.status = STATUS_FIX;
mask |= STATUS_SET;
}
if (session->newdata.mode < MODE_2D) {
session->newdata.mode = MODE_2D;
mask |= MODE_SET;
}
}
gpsd_log(&session->context->errout, LOG_DATA,
"RMC: ddmmyy=%s hhmmss=%s lat=%.2f lon=%.2f "
"speed=%.2f track=%.2f mode=%d status=%d\n",
field[9], field[1],
session->newdata.latitude,
session->newdata.longitude,
session->newdata.speed,
session->newdata.track,
session->newdata.mode,
session->gpsdata.status);
return mask;
}
static gps_mask_t processGLL(int count, char *field[],
struct gps_device_t *session)
/* Geographic position - Latitude, Longitude */
{
/* Introduced in NMEA 3.0.
*
* $GPGLL,4916.45,N,12311.12,W,225444,A,A*5C
*
* 1,2: 4916.46,N Latitude 49 deg. 16.45 min. North
* 3,4: 12311.12,W Longitude 123 deg. 11.12 min. West
* 5: 225444 Fix taken at 22:54:44 UTC
* 6: A Data valid
* 7: A Autonomous mode
* 8: *5C Mandatory NMEA checksum
*
* 1,2 Latitude, N (North) or S (South)
* 3,4 Longitude, E (East) or W (West)
* 5 UTC of position
* 6 A=Active, V=Void
* 7 Mode Indicator
* A = Autonomous mode
* D = Differential Mode
* E = Estimated (dead-reckoning) mode
* M = Manual Input Mode
* S = Simulated Mode
* N = Data Not Valid
*
* I found a note at <http://www.secoh.ru/windows/gps/nmfqexep.txt>
* indicating that the Garmin 65 does not return time and status.
* SiRF chipsets don't return the Mode Indicator.
* This code copes gracefully with both quirks.
*
* Unless you care about the FAA indicator, this sentence supplies nothing
* that GPRMC doesn't already. But at least one Garmin GPS -- the 48
* actually ships updates in GLL that aren't redundant.
*/
char *status = field[7];
gps_mask_t mask = 0;
if (field[5][0] != '\0') {
merge_hhmmss(field[5], session);
register_fractional_time(field[0], field[5], session);
if (session->nmea.date.tm_year == 0)
gpsd_log(&session->context->errout, LOG_WARN,
"can't use GLL time until after ZDA or RMC"
" has supplied a year.\n");
else {
mask = TIME_SET;
}
}
if (strcmp(field[6], "A") == 0 && (count < 8 || *status != 'N')) {
int newstatus;
do_lat_lon(&field[1], &session->newdata);
mask |= LATLON_SET;
newstatus = STATUS_FIX;
if (count >= 8 ) {
switch ( *status ) {
case 'D': /* differential */
case 'F': /* float RTK */
case 'R': /* integer RTK */
newstatus = STATUS_DGPS_FIX; /* differential */
break;
case 'S': /* simulator */
newstatus = STATUS_NO_FIX;
break;
case 'A':
default:
newstatus = STATUS_FIX;
break;
}
}
/*
* This is a bit dodgy. Technically we shouldn't set the mode
* bit until we see GSA. But it may be later in the cycle,
* some devices like the FV-18 don't send it by default, and
* elsewhere in the code we want to be able to test for the
* presence of a valid fix with mode > MODE_NO_FIX.
*/
if (session->newdata.mode < MODE_2D) {
session->newdata.mode = MODE_2D;
mask |= MODE_SET;
}
session->gpsdata.status = newstatus;
mask |= STATUS_SET;
}
gpsd_log(&session->context->errout, LOG_DATA,
"GLL: hhmmss=%s lat=%.2f lon=%.2f mode=%d status=%d\n",
field[5],
session->newdata.latitude,
session->newdata.longitude,
session->newdata.mode,
session->gpsdata.status);
return mask;
}
static gps_mask_t processGGA(int c UNUSED, char *field[],
struct gps_device_t *session)
/* Global Positioning System Fix Data */
{
/*
* GGA,123519,4807.038,N,01131.324,E,1,08,0.9,545.4,M,46.9,M, , *42
* 1 123519 Fix taken at 12:35:19 UTC
* 2,3 4807.038,N Latitude 48 deg 07.038' N
* 4,5 01131.324,E Longitude 11 deg 31.324' E
* 6 1 Fix quality: 0 = invalid, 1 = GPS, 2 = DGPS,
* 3=PPS (Precise Position Service),
* 4=RTK (Real Time Kinematic) with fixed integers,
* 5=Float RTK, 6=Estimated, 7=Manual, 8=Simulator
* 7 08 Number of satellites being tracked
* 8 0.9 Horizontal dilution of position
* 9,10 545.4,M Altitude, Metres above mean sea level
* 11,12 46.9,M Height of geoid (mean sea level) above WGS84
* ellipsoid, in Meters
* (empty field) time in seconds since last DGPS update
* (empty field) DGPS station ID number (0000-1023)
*/
gps_mask_t mask;
session->gpsdata.status = atoi(field[6]);
mask = STATUS_SET;
/*
* There are some receivers (the Trimble Placer 450 is an example) that
* don't ship a GSA with mode 1 when they lose satellite lock. Instead
* they just keep reporting GGA and GSA on subsequent cycles with the
* timestamp not advancing and a bogus mode. On the assumption that GGA
* is only issued once per cycle we can detect this here (it would be
* nicer to do it on GSA but GSA has no timestamp).
*/
session->nmea.latch_mode = strncmp(field[1],
session->nmea.last_gga_timestamp,
sizeof(session->nmea.last_gga_timestamp))==0;
if (session->nmea.latch_mode) {
session->gpsdata.status = STATUS_NO_FIX;
session->newdata.mode = MODE_NO_FIX;
} else
(void)strlcpy(session->nmea.last_gga_timestamp,
field[1],
sizeof(session->nmea.last_gga_timestamp));
/* if we have a fix and the mode latch is off, go... */
if (session->gpsdata.status > STATUS_NO_FIX) {
char *altitude;
merge_hhmmss(field[1], session);
register_fractional_time(field[0], field[1], session);
if (session->nmea.date.tm_year == 0)
gpsd_log(&session->context->errout, LOG_WARN,
"can't use GGA time until after ZDA or RMC"
" has supplied a year.\n");
else {
mask |= TIME_SET;
}
do_lat_lon(&field[2], &session->newdata);
mask |= LATLON_SET;
/* FIXME: satellites_visible is used as an accumulator in xxGSV
* so if we set it here we break xxGSV
* session->gpsdata.satellites_visible = atoi(field[7]);
*/
altitude = field[9];
/*
* SiRF chipsets up to version 2.2 report a null altitude field.
* See <http://www.sirf.com/Downloads/Technical/apnt0033.pdf>.
* If we see this, force mode to 2D at most.
*/
if (altitude[0] == '\0') {
if (session->newdata.mode > MODE_2D) {
session->newdata.mode = MODE_2D;
mask |= MODE_SET;
}
} else {
session->newdata.altitude = safe_atof(altitude);
mask |= ALTITUDE_SET;
/*
* This is a bit dodgy. Technically we shouldn't set the mode
* bit until we see GSA. But it may be later in the cycle,
* some devices like the FV-18 don't send it by default, and
* elsewhere in the code we want to be able to test for the
* presence of a valid fix with mode > MODE_NO_FIX.
*/
if (session->newdata.mode < MODE_3D) {
session->newdata.mode = MODE_3D;
mask |= MODE_SET;
}
}
if (strlen(field[11]) > 0) {
session->gpsdata.separation = safe_atof(field[11]);
} else {
session->gpsdata.separation =
wgs84_separation(session->newdata.latitude,
session->newdata.longitude);
}
}
gpsd_log(&session->context->errout, LOG_DATA,
"GGA: hhmmss=%s lat=%.2f lon=%.2f alt=%.2f mode=%d status=%d\n",
field[1],
session->newdata.latitude,
session->newdata.longitude,
session->newdata.altitude,
session->newdata.mode,
session->gpsdata.status);
return mask;
}
static gps_mask_t processGST(int count, char *field[],
struct gps_device_t *session)
/* GST - GPS Pseudorange Noise Statistics */
{
/*
* GST,hhmmss.ss,x,x,x,x,x,x,x,*hh
* 1 UTC time of associated GGA fix
* 2 Total RMS standard deviation of ranges inputs to the nav solution
* 3 Standard deviation (meters) of semi-major axis of error ellipse
* 4 Standard deviation (meters) of semi-minor axis of error ellipse
* 5 Orientation of semi-major axis of error ellipse (true north degrees)
* 6 Standard deviation (meters) of latitude error
* 7 Standard deviation (meters) of longitude error
* 8 Standard deviation (meters) of altitude error
* 9 Checksum
*/
if (count < 8) {
return 0;
}
#define PARSE_FIELD(n) (*field[n]!='\0' ? safe_atof(field[n]) : NAN)
/* note this is not full UTC, just HHMMSS.ss */
/* this is not the current time,
* it references another GPA of the same stamp. So do not set
* any time stamps with it */
session->gpsdata.gst.utctime = PARSE_FIELD(1);
session->gpsdata.gst.rms_deviation = PARSE_FIELD(2);
session->gpsdata.gst.smajor_deviation = PARSE_FIELD(3);
session->gpsdata.gst.sminor_deviation = PARSE_FIELD(4);
session->gpsdata.gst.smajor_orientation = PARSE_FIELD(5);
session->gpsdata.gst.lat_err_deviation = PARSE_FIELD(6);
session->gpsdata.gst.lon_err_deviation = PARSE_FIELD(7);
session->gpsdata.gst.alt_err_deviation = PARSE_FIELD(8);
#undef PARSE_FIELD
/* add in the time of start of today */
/* since it is NOT current time, do not register_fractional_time() */
session->gpsdata.gst.utctime += mkgmtime(&session->nmea.date);
gpsd_log(&session->context->errout, LOG_DATA,
"GST: utc = %.3f, rms = %.2f, maj = %.2f, min = %.2f,"
" ori = %.2f, lat = %.2f, lon = %.2f, alt = %.2f\n",
session->gpsdata.gst.utctime,
session->gpsdata.gst.rms_deviation,
session->gpsdata.gst.smajor_deviation,
session->gpsdata.gst.sminor_deviation,
session->gpsdata.gst.smajor_orientation,
session->gpsdata.gst.lat_err_deviation,
session->gpsdata.gst.lon_err_deviation,
session->gpsdata.gst.alt_err_deviation);
return GST_SET | ONLINE_SET;
}
static int nmeaid_to_prn(char *talker, int satnum, unsigned char *gnssid,
unsigned char *svid)
/* deal with range-mapping attempts to use IDs 1-32 by Beidou, etc. */
{
/*
* According to https://github.com/mvglasow/satstat/wiki/NMEA-IDs
* and u-blox documentation.
* NMEA IDs can be roughly divided into the following ranges:
*
* 1..32: GPS
* 33..64: Various SBAS systems (EGNOS, WAAS, SDCM, GAGAN, MSAS)
* 65..96: GLONASS
* 152..158: Various SBAS systems (EGNOS, WAAS, SDCM, GAGAN, MSAS)
* 173..182: IMES
* 193..197: QZSS
* 201..235: Beidou (not NMEA, not u-blox?)
* 301..336: Galileo
* 401..437: Beidou
* null: GLONASS unused
*
* The issue is what to do when GPSes from these different systems
* fight for IDs in the 1-32 range, as in this pair of Beidou sentences
*
* $BDGSV,2,1,07,01,00,000,45,02,13,089,35,03,00,000,37,04,00,000,42*6E
* $BDGSV,2,2,07,05,27,090,,13,19,016,,11,07,147,*5E
*
* Because the PRNs are only used for generating a satellite
* chart, mistakes here aren't dangerous. The code will record
* and use multiple sats with the same ID in one skyview; in
* effect, they're recorded by the order in which they occur
* rather than by PRN.
*/
*gnssid = 0; /* default to gnssid is GPS */
*svid = 0; /* default to unnknown svid */
if (0 != satnum && 32 >= satnum) {
*svid = satnum;
if (talker[0] == 'B' && talker[1] == 'D') {
/* map Beidou IDs */
satnum += 200;
*gnssid = 3;
} else if (talker[0] == 'G' && talker[1] == 'B') {
/* map Beidou IDs */
*gnssid = 3;
satnum += 200;
} else if (talker[0] == 'G' && talker[1] == 'L') {
/* GLONASS GL doesn't seem to do this, better safe than sorry */
satnum += 64;
*gnssid = 6;
} else if (talker[0] == 'Q' && talker[1] == 'Z') {
/* QZSS */
satnum += 192;
*gnssid = 5;
} else if (talker[0] == 'G' && talker[1] == 'A') {
/* Galileo */
satnum += 300; /* Used by u-blox at least */
*gnssid = 2;
}
/* what about $GN? */
} else if ( 33 <= satnum && 64 >= satnum) {
// NMEA-ID (33..64) to SBAS PRN 120-151.
/* SBAS */
satnum += 87;
*gnssid = 1;
*svid = satnum;
} else if (65 <= satnum && 96 >= satnum) {
/* GLONASS */
*gnssid = 6;
*svid = satnum - 65;
} else if (120 <= satnum && 158 >= satnum) {
/* SBAS */
*gnssid = 1;
*svid = satnum;
} else if (173 <= satnum && 182 >= satnum) {
/* IMES */
*gnssid = 4;
*svid = satnum - 172;
} else if (193 <= satnum && 197 >= satnum) {
/* QZSS */
*gnssid = 5;
*svid = satnum - 192;
} else if (301 <= satnum && 356 >= satnum) {
/* QZSS */
*gnssid = 2;
*svid = satnum - 300;
} else if (401 <= satnum && 437 >= satnum) {
/* BeiDou */
*gnssid = 3;
*svid = satnum - 400;
}
return satnum;
}
static gps_mask_t processGSA(int count, char *field[],
struct gps_device_t *session)
/* GPS DOP and Active Satellites */
{
#define GSA_TALKER field[0][1]
/*
* eg1. $GPGSA,A,3,,,,,,16,18,,22,24,,,3.6,2.1,2.2*3C
* eg2. $GPGSA,A,3,19,28,14,18,27,22,31,39,,,,,1.7,1.0,1.3*35
* 1 = Mode:
* M=Manual, forced to operate in 2D or 3D
* A=Automatic, 3D/2D
* 2 = Mode: 1=Fix not available, 2=2D, 3=3D
* 3-14 = PRNs of satellites used in position fix (null for unused fields)
* 15 = PDOP
* 16 = HDOP
* 17 = VDOP
*
* Not all documentation specifies the number of PRN fields, it
* may be variable. Most doc that specifies says 12 PRNs.
*
* the CH-4701 ourputs 24 PRNs!
*
* The Skytraq S2525F8-BD-RTK output both GPGSA and BDGSA in the
* same cycle:
* $GPGSA,A,3,23,31,22,16,03,07,,,,,,,1.8,1.1,1.4*3E
* $BDGSA,A,3,214,,,,,,,,,,,,1.8,1.1,1.4*18
* These need to be combined like GPGSV and BDGSV
*
* Some GPS emit GNGSA. So far we have not seen a GPS emit GNGSA
* and then another flavor of xxGSA
*
* Some Skytraq will emit all GPS in one GNGSA, Then follow with
* another GNGSA with the BeiDou birds.
*
* SEANEXX and others also do it:
* $GNGSA,A,3,31,26,21,,,,,,,,,,3.77,2.55,2.77*1A
* $GNGSA,A,3,75,86,87,,,,,,,,,,3.77,2.55,2.77*1C
* seems like the first is GNSS and the second GLONASS
*/
gps_mask_t mask;
char last_last_gsa_talker = session->nmea.last_gsa_talker;
/*
* One chipset called the i.Trek M3 issues GPGSA lines that look like
* this: "$GPGSA,A,1,,,,*32" when it has no fix. This is broken
* in at least two ways: it's got the wrong number of fields, and
* it claims to be a valid sentence (A flag) when it isn't.
* Alarmingly, it's possible this error may be generic to SiRFstarIII.
*/
if (count < 17) {
gpsd_log(&session->context->errout, LOG_DATA,
"xxGSA: malformed, setting ONLINE_SET only.\n");
mask = ONLINE_SET;
} else if (session->nmea.latch_mode) {
/* last GGA had a non-advancing timestamp; don't trust this GSA */
mask = ONLINE_SET;
} else {
int i;
session->newdata.mode = atoi(field[2]);
/*
* The first arm of this conditional ignores dead-reckoning
* fixes from an Antaris chipset. which returns E in field 2
* for a dead-reckoning estimate. Fix by Andreas Stricker.
*/
if (session->newdata.mode == 0 && field[2][0] == 'E')
mask = 0;
else
mask = MODE_SET;
gpsd_log(&session->context->errout, LOG_PROG,
"xxGSA sets mode %d\n", session->newdata.mode);
if (field[15][0] != '\0')
session->gpsdata.dop.pdop = safe_atof(field[15]);
if (field[16][0] != '\0')
session->gpsdata.dop.hdop = safe_atof(field[16]);
if (field[17][0] != '\0')
session->gpsdata.dop.vdop = safe_atof(field[17]);
/*
* might have gone from GPGSA to GLGSA/BDGSA
* or GNGSA to GNGSA
* in which case accumulate
*/
if ( '\0' == session->nmea.last_gsa_talker
|| (GSA_TALKER == session->nmea.last_gsa_talker
&& 'N' != GSA_TALKER) ) {
session->gpsdata.satellites_used = 0;
memset(session->nmea.sats_used, 0, sizeof(session->nmea.sats_used));
}
session->nmea.last_gsa_talker = GSA_TALKER;
if ((session->nmea.last_gsa_talker == 'D')
|| (session->nmea.last_gsa_talker == 'B'))
session->nmea.seen_bdgsa = true;
else if (session->nmea.last_gsa_talker == 'L')
session->nmea.seen_glgsa = true;
else if (session->nmea.last_gsa_talker == 'N')
session->nmea.seen_gngsa = true;
else if (session->nmea.last_gsa_talker == 'A')
session->nmea.seen_gagsa = true;
/* the magic 6 here counts the tag, two mode fields, and DOP fields */
for (i = 0; i < count - 6; i++) {
int prn;
unsigned char gnssid; /* UNUSED */
unsigned char svid; /* UNUSED */
/* skip empty fields, otherwise empty becomes prn=200 */
if ( '\0' == field[i + 3][0] ) {
continue;
}
prn = nmeaid_to_prn(field[0], atoi(field[i + 3]), &gnssid, &svid);
if (prn > 0) {
/* check first BEFORE over-writing memory */
if ( MAXCHANNELS <= session->gpsdata.satellites_used ) {
/* this should never happen as xxGSA is limited to 12 */
break;
}
session->nmea.sats_used[session->gpsdata.satellites_used++] =
(unsigned short)prn;
}
}
mask |= DOP_SET | USED_IS;
gpsd_log(&session->context->errout, LOG_DATA,
"xxGSA: mode=%d used=%d pdop=%.2f hdop=%.2f vdop=%.2f\n",
session->newdata.mode,
session->gpsdata.satellites_used,
session->gpsdata.dop.pdop,
session->gpsdata.dop.hdop,
session->gpsdata.dop.vdop);
}
/* assumes GLGSA or BDGSA, if present, is emitted directly
* after the GPGSA*/
if ((session->nmea.seen_glgsa || session->nmea.seen_bdgsa ||
session->nmea.seen_gagsa) && GSA_TALKER == 'P')
return ONLINE_SET;
/* first of two GNGSA */
/* if mode == 1 some GPS only output 1 GNGSA, so ship mode always */
if ( 'N' != last_last_gsa_talker && 'N' == GSA_TALKER)
return ONLINE_SET | MODE_SET;
return mask;
#undef GSA_TALKER
}
static gps_mask_t processGSV(int count, char *field[],
struct gps_device_t *session)
/* GPS Satellites in View */
{
#define GSV_TALKER field[0][1]
/*
* GSV,2,1,08,01,40,083,46,02,17,308,41,12,07,344,39,14,22,228,45*75
* 2 Number of sentences for full data
* 1 Sentence 1 of 2
* 08 Total number of satellites in view
* 01 Satellite PRN number
* 40 Elevation, degrees
* 083 Azimuth, degrees
* 46 Signal-to-noise ratio in decibels
* <repeat for up to 4 satellites per sentence>
*
* Can occur with talker IDs:
* BD (Beidou),
* GA (Galileo),
* GB (Beidou),
* GL (GLONASS),
* GN (GLONASS, any combination GNSS),
* GP (GPS, SBAS, QZSS),
* QZ (QZSS).
*
* GL may be (incorrectly) used when GSVs are mixed containing
* GLONASS, GN may be (incorrectly) used when GSVs contain GLONASS
* only. Usage is inconsistent.
*
* In the GLONASS version sat IDs run from 65-96 (NMEA0183
* standardizes this). At least two GPSes, the BU-353 GLONASS and
* the u-blox NEO-M8N, emit a GPGSV set followed by a GLGSV set.
* We have also seen two GPSes, the Skytraq S2525F8-BD-RTK and a
* SiRF-IV variant, that emit GPGSV followed by BDGSV. We need to
* combine these.
*
* The following shows how the Skytraq S2525F8-BD-RTK output both
* GPGSV and BDGSV in the same cycle:
* $GPGSV,4,1,13,23,66,310,29,03,65,186,33,26,43,081,27,16,41,124,38*78
* $GPGSV,4,2,13,51,37,160,38,04,37,066,25,09,34,291,07,22,26,156,37*77
* $GPGSV,4,3,13,06,19,301,,31,17,052,20,193,11,307,,07,11,232,27*4F
* $GPGSV,4,4,13,01,03,202,30*4A
* $BDGSV,1,1,02,214,55,153,40,208,01,299,*67
*
* The driver automatically adapts to either case, but it takes until the
* second cycle (usually 10 seconds from device connect) for it to
* learn to expect BSDGV or GLGSV.
*
* NMEA 4.1 adds a signal-ID field just before the checksum. First
* seen in May 2015 on a u-blox M8.
*/
int n, fldnum;
if (count <= 3) {
gpsd_log(&session->context->errout, LOG_WARN,
"malformed GPGSV - fieldcount %d <= 3\n",
count);
gpsd_zero_satellites(&session->gpsdata);
session->gpsdata.satellites_visible = 0;
return ONLINE_SET;
}
/*
* This check used to be !=0, but we have loosen it a little to let by
* NMEA 4.1 GSVs with an extra signal-ID field at the end.
*/
if (count % 4 > 1) {
gpsd_log(&session->context->errout, LOG_WARN,
"malformed GPGSV - fieldcount %d %% 4 != 0\n",
count);
gpsd_zero_satellites(&session->gpsdata);
session->gpsdata.satellites_visible = 0;
return ONLINE_SET;
}
session->nmea.await = atoi(field[1]);
if ((session->nmea.part = atoi(field[2])) < 1) {
gpsd_log(&session->context->errout, LOG_WARN,
"malformed GPGSV - bad part\n");
gpsd_zero_satellites(&session->gpsdata);
return ONLINE_SET;
} else if (session->nmea.part == 1) {
/*
* might have gone from GPGSV to GLGSV/BDGSV/QZGSV,
* in which case accumulate
*/
if (session->nmea.last_gsv_talker == '\0'
|| GSV_TALKER == session->nmea.last_gsv_talker) {
gpsd_zero_satellites(&session->gpsdata);
}
session->nmea.last_gsv_talker = GSV_TALKER;
if (session->nmea.last_gsv_talker == 'L')
session->nmea.seen_glgsv = true;
if (session->nmea.last_gsv_talker == 'D' || session->nmea.last_gsv_talker == 'B')
session->nmea.seen_bdgsv = true;
if (session->nmea.last_gsv_talker == 'Z')
session->nmea.seen_qzss = true;
if (session->nmea.last_gsv_talker == 'A')
session->nmea.seen_gagsv = true;
}
for (fldnum = 4; fldnum < count / 4 * 4;) {
struct satellite_t *sp;
int svid;
if (session->gpsdata.satellites_visible >= MAXCHANNELS) {
gpsd_log(&session->context->errout, LOG_ERROR,
"internal error - too many satellites [%d]!\n",
session->gpsdata.satellites_visible);
gpsd_zero_satellites(&session->gpsdata);
break;
}
sp = &session->gpsdata.skyview[session->gpsdata.satellites_visible];
svid = atoi(field[fldnum++]);
sp->PRN = (short)nmeaid_to_prn(field[0], svid, &sp->gnssid, &sp->svid);
sp->elevation = (short)atoi(field[fldnum++]);
sp->azimuth = (short)atoi(field[fldnum++]);
sp->ss = (float)atoi(field[fldnum++]);
sp->used = false;
if (sp->PRN > 0)
for (n = 0; n < MAXCHANNELS; n++)
if (session->nmea.sats_used[n] == (unsigned short)sp->PRN) {
sp->used = true;
break;
}
/*
* Incrementing this unconditionally falls afoul of chipsets like
* the Motorola Oncore GT+ that emit empty fields at the end of the
* last sentence in a GPGSV set if the number of satellites is not
* a multiple of 4.
*/
if (sp->PRN != 0)
session->gpsdata.satellites_visible++;
}
/*
* Alas, we can't sanity check field counts when there are multiple sat
* pictures, because the visible member counts *all* satellites - you
* get a bad result on the second and later SV spans. Note, this code
* assumes that if any of the special sat pics occur they come right
* after a stock GPGSV one.
*
* FIXME: Add per-talker totals so we can do this check properly.
*/
if (!(session->nmea.seen_glgsv || session->nmea.seen_bdgsv
|| session->nmea.seen_qzss || session->nmea.seen_gagsv))
if (session->nmea.part == session->nmea.await
&& atoi(field[3]) != session->gpsdata.satellites_visible)
gpsd_log(&session->context->errout, LOG_WARN,
"GPGSV field 3 value of %d != actual count %d\n",
atoi(field[3]), session->gpsdata.satellites_visible);
/* not valid data until we've seen a complete set of parts */
if (session->nmea.part < session->nmea.await) {
gpsd_log(&session->context->errout, LOG_PROG,
"Partial satellite data (%d of %d).\n",
session->nmea.part, session->nmea.await);
return ONLINE_SET;
}
/*
* This sanity check catches an odd behavior of SiRFstarII receivers.
* When they can't see any satellites at all (like, inside a
* building) they sometimes cough up a hairball in the form of a
* GSV packet with all the azimuth entries 0 (but nonzero
* elevations). This behavior was observed under SiRF firmware
* revision 231.000.000_A2.
*/
for (n = 0; n < session->gpsdata.satellites_visible; n++)
if (session->gpsdata.skyview[n].azimuth != 0)
goto sane;
gpsd_log(&session->context->errout, LOG_WARN,
"Satellite data no good (%d of %d).\n",
session->nmea.part, session->nmea.await);
gpsd_zero_satellites(&session->gpsdata);
return ONLINE_SET;
sane:
session->gpsdata.skyview_time = NAN;
gpsd_log(&session->context->errout, LOG_DATA,
"GSV: Satellite data OK (%d of %d).\n",
session->nmea.part, session->nmea.await);
/* assumes GLGSV or BDGSV group, if present, is emitted after the GPGSV */
if ((session->nmea.seen_glgsv || session->nmea.seen_bdgsv
|| session->nmea.seen_qzss || session->nmea.seen_gagsv)
&& GSV_TALKER == 'P')
return ONLINE_SET;
/* clear computed DOPs so they get recomputed. */
session->gpsdata.dop.xdop = NAN;
session->gpsdata.dop.ydop = NAN;
session->gpsdata.dop.tdop = NAN;
session->gpsdata.dop.gdop = NAN;
return SATELLITE_SET;