firmware/src/gps/NMEAGPS.cpp
2021-10-24 12:38:35 +00:00

231 lines
6.8 KiB
C++

#include "configuration.h"
#include "NMEAGPS.h"
#include "RTC.h"
#include <TinyGPS++.h>
// GPS solutions older than this will be rejected - see TinyGPSDatum::age()
#define GPS_SOL_EXPIRY_MS 300 // in millis
#define NMEA_MSG_GXGSA "GNGSA" // GSA message (GPGSA, GNGSA etc)
static int32_t toDegInt(RawDegrees d)
{
int32_t degMult = 10000000; // 1e7
int32_t r = d.deg * degMult + d.billionths / 100;
if (d.negative)
r *= -1;
return r;
}
bool NMEAGPS::setupGPS()
{
GPS::setupGPS();
#ifdef PIN_GPS_PPS
// pulse per second
// FIXME - move into shared GPS code
pinMode(PIN_GPS_PPS, INPUT);
#endif
// Currently disabled per issue #525 (TinyGPS++ crash bug)
// when fixed upstream, can be un-disabled to enable 3D FixType and PDOP
#ifndef TINYGPS_OPTION_NO_CUSTOM_FIELDS
// see NMEAGPS.h
gsafixtype.begin(reader, NMEA_MSG_GXGSA, 2);
gsapdop.begin(reader, NMEA_MSG_GXGSA, 15);
DEBUG_MSG("Using " NMEA_MSG_GXGSA " for 3DFIX and PDOP\n");
#else
DEBUG_MSG("GxGSA NOT available\n");
#endif
return true;
}
/**
* Perform any processing that should be done only while the GPS is awake and looking for a fix.
* Override this method to check for new locations
*
* @return true if we've acquired a new location
*/
bool NMEAGPS::lookForTime()
{
auto ti = reader.time;
auto d = reader.date;
if (ti.isValid() && d.isValid()) { // Note: we don't check for updated, because we'll only be called if needed
/* Convert to unix time
The Unix epoch (or Unix time or POSIX time or Unix timestamp) is the number of seconds that have elapsed since January 1, 1970
(midnight UTC/GMT), not counting leap seconds (in ISO 8601: 1970-01-01T00:00:00Z).
*/
struct tm t;
t.tm_sec = ti.second();
t.tm_min = ti.minute();
t.tm_hour = ti.hour();
t.tm_mday = d.day();
t.tm_mon = d.month() - 1;
t.tm_year = d.year() - 1900;
t.tm_isdst = false;
DEBUG_MSG("NMEA GPS time %d\n", t.tm_sec);
perhapsSetRTC(RTCQualityGPS, t);
return true;
} else
return false;
}
/**
* Perform any processing that should be done only while the GPS is awake and looking for a fix.
* Override this method to check for new locations
*
* @return true if we've acquired a new location
*/
bool NMEAGPS::lookForLocation()
{
// By default, TinyGPS++ does not parse GPGSA lines, which give us
// the 2D/3D fixType (see NMEAGPS.h)
// At a minimum, use the fixQuality indicator in GPGGA (FIXME?)
fixQual = reader.fixQuality();
#ifndef TINYGPS_OPTION_NO_CUSTOM_FIELDS
fixType = atoi(gsafixtype.value()); // will set to zero if no data
DEBUG_MSG("FIX QUAL=%d, TYPE=%d\n", fixQual, fixType);
#endif
// check if GPS has an acceptable lock
if (! hasLock())
return false;
#ifdef GPS_EXTRAVERBOSE
DEBUG_MSG("AGE: LOC=%d FIX=%d DATE=%d TIME=%d\n",
reader.location.age(),
#ifndef TINYGPS_OPTION_NO_CUSTOM_FIELDS
gsafixtype.age(),
#else
0,
#endif
reader.date.age(), reader.time.age());
#endif // GPS_EXTRAVERBOSE
// check if a complete GPS solution set is available for reading
// tinyGPSDatum::age() also includes isValid() test
// FIXME
if (! ((reader.location.age() < GPS_SOL_EXPIRY_MS) &&
#ifndef TINYGPS_OPTION_NO_CUSTOM_FIELDS
(gsafixtype.age() < GPS_SOL_EXPIRY_MS) &&
#endif
(reader.time.age() < GPS_SOL_EXPIRY_MS) &&
(reader.date.age() < GPS_SOL_EXPIRY_MS)))
{
DEBUG_MSG("SOME data is TOO OLD\n");
return false;
}
// Is this a new point or are we re-reading the previous one?
if (! reader.location.isUpdated())
return false;
// We know the solution is fresh and valid, so just read the data
auto loc = reader.location.value();
// Some GPSes (Air530) seem to send a zero longitude when the current fix is bogus
// Bail out EARLY to avoid overwriting previous good data (like #857)
if(toDegInt(loc.lat) == 0) {
DEBUG_MSG("Ignoring bogus NMEA position\n");
return false;
}
p.location_source = Position_LocSource_LOCSRC_GPS_INTERNAL;
// Dilution of precision (an accuracy metric) is reported in 10^2 units, so we need to scale down when we use it
#ifndef TINYGPS_OPTION_NO_CUSTOM_FIELDS
p.HDOP = reader.hdop.value();
p.PDOP = TinyGPSPlus::parseDecimal(gsapdop.value());
DEBUG_MSG("PDOP=%d, HDOP=%d\n", dop, reader.hdop.value());
#else
// FIXME! naive PDOP emulation (assumes VDOP==HDOP)
// correct formula is PDOP = SQRT(HDOP^2 + VDOP^2)
p.HDOP = reader.hdop.value();
p.PDOP = 1.41 * reader.hdop.value();
#endif
// Discard incomplete or erroneous readings
if (reader.hdop.value() == 0)
return false;
p.latitude_i = toDegInt(loc.lat);
p.longitude_i = toDegInt(loc.lng);
p.alt_geoid_sep = reader.geoidHeight.meters();
p.altitude_hae = reader.altitude.meters() + p.alt_geoid_sep;
p.altitude = reader.altitude.meters();
p.fix_quality = fixQual;
#ifndef TINYGPS_OPTION_NO_CUSTOM_FIELDS
p.fix_type = fixType;
#endif
// positional timestamp
struct tm t;
t.tm_sec = reader.time.second();
t.tm_min = reader.time.minute();
t.tm_hour = reader.time.hour();
t.tm_mday = reader.date.day();
t.tm_mon = reader.date.month() - 1;
t.tm_year = reader.date.year() - 1900;
t.tm_isdst = false;
p.pos_timestamp = mktime(&t);
// Nice to have, if available
if (reader.satellites.isUpdated()) {
p.sats_in_view = reader.satellites.value();
}
if (reader.course.isUpdated() && reader.course.isValid()) {
if (reader.course.value() < 36000) { // sanity check
p.ground_track = reader.course.value() * 1e3; // Scale the heading (in degrees * 10^-2) to match the expected degrees * 10^-5
} else {
DEBUG_MSG("BOGUS course.value() REJECTED: %d\n",
reader.course.value());
}
}
/*
// REDUNDANT?
// expect gps pos lat=37.520825, lon=-122.309162, alt=158
DEBUG_MSG("new NMEA GPS pos lat=%f, lon=%f, alt=%d, dop=%g, heading=%f\n",
latitude * 1e-7, longitude * 1e-7, altitude, dop * 1e-2,
heading * 1e-5);
*/
return true;
}
bool NMEAGPS::hasLock()
{
// Using GPGGA fix quality indicator
if (fixQual >= 1 && fixQual <= 5) {
#ifndef TINYGPS_OPTION_NO_CUSTOM_FIELDS
// Use GPGSA fix type 2D/3D (better) if available
if (fixType == 3 || fixType == 0) // zero means "no data received"
#endif
return true;
}
return false;
}
bool NMEAGPS::whileIdle()
{
bool isValid = false;
// First consume any chars that have piled up at the receiver
while (_serial_gps->available() > 0) {
int c = _serial_gps->read();
// DEBUG_MSG("%c", c);
isValid |= reader.encode(c);
}
return isValid;
}