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flightgear/src/Network/nmea.cxx

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// nmea.cxx -- NMEA protocal class
//
// Written by Curtis Olson, started November 1999.
//
// Copyright (C) 1999 Curtis L. Olson - http://www.flightgear.org/~curt
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License as
// published by the Free Software Foundation; either version 2 of the
// License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
// General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
//
// $Id$
#include <simgear/debug/logstream.hxx>
#include <simgear/math/sg_geodesy.hxx>
#include <simgear/io/iochannel.hxx>
#include <simgear/timing/sg_time.hxx>
#include <FDM/flight.hxx>
#include <Main/fg_props.hxx>
#include <Main/globals.hxx>
#include "nmea.hxx"
SG_USING_NAMESPACE(std);
FGNMEA::FGNMEA() {
}
FGNMEA::~FGNMEA() {
}
// calculate the nmea check sum
static char calc_nmea_cksum(char *sentence) {
unsigned char sum = 0;
int i, len;
// cout << sentence << endl;
len = strlen(sentence);
sum = sentence[0];
for ( i = 1; i < len; i++ ) {
// cout << sentence[i];
sum ^= sentence[i];
}
// cout << endl;
// printf("sum = %02x\n", sum);
return sum;
}
// generate NMEA message
bool FGNMEA::gen_message() {
// cout << "generating nmea message" << endl;
char rmc[256], gga[256], gsa[256];
char rmc_sum[10], gga_sum[10];
char dir;
int deg;
double min;
SGTime *t = globals->get_time_params();
char utc[10];
sprintf( utc, "%02d%02d%02d",
t->getGmt()->tm_hour, t->getGmt()->tm_min, t->getGmt()->tm_sec );
char gga_lat[20], rmc_lat[20];
double latd = cur_fdm_state->get_Latitude() * SGD_RADIANS_TO_DEGREES;
if ( latd < 0.0 ) {
latd = -latd;
dir = 'S';
} else {
dir = 'N';
}
deg = (int)(latd);
min = (latd - (double)deg) * 60.0;
sprintf( gga_lat, "%02d%07.4f,%c", abs(deg), min, dir);
sprintf( rmc_lat, "%02d%07.4f,%c", abs(deg), min, dir);
char gga_lon[20], rmc_lon[20];
double lond = cur_fdm_state->get_Longitude() * SGD_RADIANS_TO_DEGREES;
if ( lond < 0.0 ) {
lond = -lond;
dir = 'W';
} else {
dir = 'E';
}
deg = (int)(lond);
min = (lond - (double)deg) * 60.0;
sprintf( gga_lon, "%03d%07.4f,%c", abs(deg), min, dir);
sprintf( rmc_lon, "%03d%07.4f,%c", abs(deg), min, dir);
double vn = fgGetDouble( "/velocities/speed-north-fps" );
double ve = fgGetDouble( "/velocities/speed-east-fps" );
double fps = sqrt( vn*vn + ve*ve );
double mps = fps * SG_FEET_TO_METER;
double kts = mps * SG_METER_TO_NM * 3600;
char speed[10];
sprintf( speed, "%.1f", kts );
double hdg_true = atan2( ve, vn ) * SGD_RADIANS_TO_DEGREES;
if ( hdg_true < 0 ) {
hdg_true += 360.0;
}
char heading[10];
sprintf( heading, "%.1f", hdg_true );
char altitude_m[10];
sprintf( altitude_m, "%.1f",
cur_fdm_state->get_Altitude() * SG_FEET_TO_METER );
char date[10];
int year = t->getGmt()->tm_year;
while ( year >= 100 ) { year -= 100; }
sprintf( date, "%02d%02d%02d", t->getGmt()->tm_mday,
t->getGmt()->tm_mon+1, year );
char magvar[10];
float magdeg = fgGetDouble( "/environment/magnetic-variation-deg" );
if ( magdeg < 0.0 ) {
magdeg = -magdeg;
dir = 'W';
} else {
dir = 'E';
}
sprintf( magvar, "%.1f,%c", magdeg, dir );
// $GPRMC,HHMMSS,A,DDMM.MMMM,N,DDDMM.MMMM,W,XXX.X,XXX.X,DDMMYY,XXX.X,E,A*XX
sprintf( rmc, "GPRMC,%s,A,%s,%s,%s,%s,%s,%s,A",
utc, rmc_lat, rmc_lon, speed, heading, date, magvar );
sprintf( rmc_sum, "%02X", calc_nmea_cksum(rmc) );
// $GPGGA,HHMMSS,DDMM.MMMM,N,DDDMM.MMMM,W,1,NN,H.H,AAAA.A,M,GG.G,M,,*XX
sprintf( gga, "GPGGA,%s,%s,%s,1,08,0.9,%s,M,0.0,M,,",
utc, gga_lat, gga_lon, altitude_m );
sprintf( gga_sum, "%02X", calc_nmea_cksum(gga) );
sprintf( gsa, "%s",
"$GPGSA,A,3,01,02,03,,05,,07,,09,,11,12,0.9,0.9,2.0*38" );
SG_LOG( SG_IO, SG_DEBUG, rmc );
SG_LOG( SG_IO, SG_DEBUG, gga );
SG_LOG( SG_IO, SG_DEBUG, gsa );
string nmea_sentence;
// RMC sentence
nmea_sentence = "$";
nmea_sentence += rmc;
nmea_sentence += "*";
nmea_sentence += rmc_sum;
nmea_sentence += "\n";
// GGA sentence
nmea_sentence += "$";
nmea_sentence += gga;
nmea_sentence += "*";
nmea_sentence += gga_sum;
nmea_sentence += "\n";
// GSA sentence (totally faked)
nmea_sentence += gsa;
nmea_sentence += "\n";
// cout << nmea_sentence;
length = nmea_sentence.length();
strncpy( buf, nmea_sentence.c_str(), length );
return true;
}
// parse NMEA message. messages will look something like the
// following:
//
// $GPRMC,163227,A,3321.173,N,11039.855,W,000.1,270.0,171199,0.000,E*61
// $GPGGA,163227,3321.173,N,11039.855,W,1,,,3333,F,,,,*0F
bool FGNMEA::parse_message() {
SG_LOG( SG_IO, SG_INFO, "parse nmea message" );
string msg = buf;
msg = msg.substr( 0, length );
SG_LOG( SG_IO, SG_INFO, "entire message = " << msg );
string::size_type begin_line, end_line, begin, end;
begin_line = begin = 0;
// extract out each line
end_line = msg.find("\n", begin_line);
while ( end_line != string::npos ) {
string line = msg.substr(begin_line, end_line - begin_line);
begin_line = end_line + 1;
SG_LOG( SG_IO, SG_INFO, " input line = " << line );
// leading character
string start = msg.substr(begin, 1);
++begin;
SG_LOG( SG_IO, SG_INFO, " start = " << start );
// sentence
end = msg.find(",", begin);
if ( end == string::npos ) {
return false;
}
string sentence = msg.substr(begin, end - begin);
begin = end + 1;
SG_LOG( SG_IO, SG_INFO, " sentence = " << sentence );
double lon_deg, lon_min, lat_deg, lat_min;
double lon, lat, speed, heading, altitude;
if ( sentence == "GPRMC" ) {
// time
end = msg.find(",", begin);
if ( end == string::npos ) {
return false;
}
string utc = msg.substr(begin, end - begin);
begin = end + 1;
SG_LOG( SG_IO, SG_INFO, " utc = " << utc );
// junk
end = msg.find(",", begin);
if ( end == string::npos ) {
return false;
}
string junk = msg.substr(begin, end - begin);
begin = end + 1;
SG_LOG( SG_IO, SG_INFO, " junk = " << junk );
// lat val
end = msg.find(",", begin);
if ( end == string::npos ) {
return false;
}
string lat_str = msg.substr(begin, end - begin);
begin = end + 1;
lat_deg = atof( lat_str.substr(0, 2).c_str() );
lat_min = atof( lat_str.substr(2).c_str() );
// lat dir
end = msg.find(",", begin);
if ( end == string::npos ) {
return false;
}
string lat_dir = msg.substr(begin, end - begin);
begin = end + 1;
lat = lat_deg + ( lat_min / 60.0 );
if ( lat_dir == "S" ) {
lat *= -1;
}
cur_fdm_state->set_Latitude( lat * SGD_DEGREES_TO_RADIANS );
SG_LOG( SG_IO, SG_INFO, " lat = " << lat );
// lon val
end = msg.find(",", begin);
if ( end == string::npos ) {
return false;
}
string lon_str = msg.substr(begin, end - begin);
begin = end + 1;
lon_deg = atof( lon_str.substr(0, 3).c_str() );
lon_min = atof( lon_str.substr(3).c_str() );
// lon dir
end = msg.find(",", begin);
if ( end == string::npos ) {
return false;
}
string lon_dir = msg.substr(begin, end - begin);
begin = end + 1;
lon = lon_deg + ( lon_min / 60.0 );
if ( lon_dir == "W" ) {
lon *= -1;
}
cur_fdm_state->set_Longitude( lon * SGD_DEGREES_TO_RADIANS );
SG_LOG( SG_IO, SG_INFO, " lon = " << lon );
#if 0
double sl_radius, lat_geoc;
sgGeodToGeoc( cur_fdm_state->get_Latitude(),
cur_fdm_state->get_Altitude(),
&sl_radius, &lat_geoc );
cur_fdm_state->set_Geocentric_Position( lat_geoc,
cur_fdm_state->get_Longitude(),
sl_radius + cur_fdm_state->get_Altitude() );
#endif
// speed
end = msg.find(",", begin);
if ( end == string::npos ) {
return false;
}
string speed_str = msg.substr(begin, end - begin);
begin = end + 1;
speed = atof( speed_str.c_str() );
cur_fdm_state->set_V_calibrated_kts( speed );
// cur_fdm_state->set_V_ground_speed( speed );
SG_LOG( SG_IO, SG_INFO, " speed = " << speed );
// heading
end = msg.find(",", begin);
if ( end == string::npos ) {
return false;
}
string hdg_str = msg.substr(begin, end - begin);
begin = end + 1;
heading = atof( hdg_str.c_str() );
cur_fdm_state->set_Euler_Angles( cur_fdm_state->get_Phi(),
cur_fdm_state->get_Theta(),
heading * SGD_DEGREES_TO_RADIANS );
SG_LOG( SG_IO, SG_INFO, " heading = " << heading );
} else if ( sentence == "GPGGA" ) {
// time
end = msg.find(",", begin);
if ( end == string::npos ) {
return false;
}
string utc = msg.substr(begin, end - begin);
begin = end + 1;
SG_LOG( SG_IO, SG_INFO, " utc = " << utc );
// lat val
end = msg.find(",", begin);
if ( end == string::npos ) {
return false;
}
string lat_str = msg.substr(begin, end - begin);
begin = end + 1;
lat_deg = atof( lat_str.substr(0, 2).c_str() );
lat_min = atof( lat_str.substr(2).c_str() );
// lat dir
end = msg.find(",", begin);
if ( end == string::npos ) {
return false;
}
string lat_dir = msg.substr(begin, end - begin);
begin = end + 1;
lat = lat_deg + ( lat_min / 60.0 );
if ( lat_dir == "S" ) {
lat *= -1;
}
// cur_fdm_state->set_Latitude( lat * SGD_DEGREES_TO_RADIANS );
SG_LOG( SG_IO, SG_INFO, " lat = " << lat );
// lon val
end = msg.find(",", begin);
if ( end == string::npos ) {
return false;
}
string lon_str = msg.substr(begin, end - begin);
begin = end + 1;
lon_deg = atof( lon_str.substr(0, 3).c_str() );
lon_min = atof( lon_str.substr(3).c_str() );
// lon dir
end = msg.find(",", begin);
if ( end == string::npos ) {
return false;
}
string lon_dir = msg.substr(begin, end - begin);
begin = end + 1;
lon = lon_deg + ( lon_min / 60.0 );
if ( lon_dir == "W" ) {
lon *= -1;
}
// cur_fdm_state->set_Longitude( lon * SGD_DEGREES_TO_RADIANS );
SG_LOG( SG_IO, SG_INFO, " lon = " << lon );
// junk
end = msg.find(",", begin);
if ( end == string::npos ) {
return false;
}
string junk = msg.substr(begin, end - begin);
begin = end + 1;
SG_LOG( SG_IO, SG_INFO, " junk = " << junk );
// junk
end = msg.find(",", begin);
if ( end == string::npos ) {
return false;
}
junk = msg.substr(begin, end - begin);
begin = end + 1;
SG_LOG( SG_IO, SG_INFO, " junk = " << junk );
// junk
end = msg.find(",", begin);
if ( end == string::npos ) {
return false;
}
junk = msg.substr(begin, end - begin);
begin = end + 1;
SG_LOG( SG_IO, SG_INFO, " junk = " << junk );
// altitude
end = msg.find(",", begin);
if ( end == string::npos ) {
return false;
}
string alt_str = msg.substr(begin, end - begin);
altitude = atof( alt_str.c_str() );
begin = end + 1;
// altitude units
end = msg.find(",", begin);
if ( end == string::npos ) {
return false;
}
string alt_units = msg.substr(begin, end - begin);
begin = end + 1;
if ( alt_units != "F" ) {
altitude *= SG_METER_TO_FEET;
}
cur_fdm_state->set_Altitude( altitude );
SG_LOG( SG_IO, SG_INFO, " altitude = " << altitude );
}
// printf("%.8f %.8f\n", lon, lat);
begin = begin_line;
end_line = msg.find("\n", begin_line);
}
return true;
}
// open hailing frequencies
bool FGNMEA::open() {
if ( is_enabled() ) {
SG_LOG( SG_IO, SG_ALERT, "This shouldn't happen, but the channel "
<< "is already in use, ignoring" );
return false;
}
SGIOChannel *io = get_io_channel();
if ( ! io->open( get_direction() ) ) {
SG_LOG( SG_IO, SG_ALERT, "Error opening channel communication layer." );
return false;
}
set_enabled( true );
return true;
}
// process work for this port
bool FGNMEA::process() {
SGIOChannel *io = get_io_channel();
if ( get_direction() == SG_IO_OUT ) {
gen_message();
if ( ! io->write( buf, length ) ) {
SG_LOG( SG_IO, SG_WARN, "Error writing data." );
return false;
}
} else if ( get_direction() == SG_IO_IN ) {
if ( (length = io->readline( buf, FG_MAX_MSG_SIZE )) > 0 ) {
parse_message();
} else {
SG_LOG( SG_IO, SG_WARN, "Error reading data." );
return false;
}
if ( (length = io->readline( buf, FG_MAX_MSG_SIZE )) > 0 ) {
parse_message();
} else {
SG_LOG( SG_IO, SG_WARN, "Error reading data." );
return false;
}
}
return true;
}
// close the channel
bool FGNMEA::close() {
SGIOChannel *io = get_io_channel();
set_enabled( false );
if ( ! io->close() ) {
return false;
}
return true;
}
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