mirror of https://github.com/ArduPilot/ardupilot
191 lines
8.1 KiB
C++
191 lines
8.1 KiB
C++
/*
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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//
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// NMEA parser, adapted by Michael Smith from TinyGPS v9:
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//
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// TinyGPS - a small GPS library for Arduino providing basic NMEA parsing
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// Copyright (C) 2008-9 Mikal Hart
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// All rights reserved.
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//
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//
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/// @file AP_GPS_NMEA.h
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/// @brief NMEA protocol parser
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///
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/// This is a lightweight NMEA parser, derived originally from the
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/// TinyGPS parser by Mikal Hart. It is frugal in its use of memory
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/// and tries to avoid unnecessary arithmetic.
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///
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/// The parser handles GPGGA, GPRMC and GPVTG messages, and attempts to be
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/// robust in the face of occasional corruption in the input stream. It
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/// makes a basic effort to configure GPS' that are likely to be connected in
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/// NMEA mode (SiRF, MediaTek and ublox) to emit the correct message
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/// stream, but does not validate that the correct stream is being received.
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/// In particular, a unit emitting just GPRMC will show as having a fix
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/// even though no altitude data is being received.
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///
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/// GPVTG data is parsed, but as the message may not contain the the
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/// qualifier field (this is common with e.g. older SiRF units) it is
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/// not considered a source of fix-valid information.
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///
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#pragma once
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#include "AP_GPS.h"
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#include "GPS_Backend.h"
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/// NMEA parser
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///
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class AP_GPS_NMEA : public AP_GPS_Backend
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{
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friend class AP_GPS_NMEA_Test;
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public:
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using AP_GPS_Backend::AP_GPS_Backend;
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/// Checks the serial receive buffer for characters,
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/// attempts to parse NMEA data and updates internal state
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/// accordingly.
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bool read() override;
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static bool _detect(struct NMEA_detect_state &state, uint8_t data);
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const char *name() const override { return "NMEA"; }
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private:
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/// Coding for the GPS sentences that the parser handles
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enum _sentence_types : uint8_t { //there are some more than 10 fields in some sentences , thus we have to increase these value.
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_GPS_SENTENCE_RMC = 32,
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_GPS_SENTENCE_GGA = 64,
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_GPS_SENTENCE_VTG = 96,
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_GPS_SENTENCE_HDT = 128,
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_GPS_SENTENCE_PHD = 138, // extension for AllyStar GPS modules
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_GPS_SENTENCE_THS = 160, // True heading with quality indicator, available on Trimble MB-Two
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_GPS_SENTENCE_OTHER = 0
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};
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/// Update the decode state machine with a new character
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///
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/// @param c The next character in the NMEA input stream
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/// @returns True if processing the character has resulted in
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/// an update to the GPS state
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///
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bool _decode(char c);
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/// Parses the @p as a NMEA-style decimal number with
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/// up to 3 decimal digits.
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///
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/// @returns The value expressed by the string in @p,
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/// multiplied by 100.
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///
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static int32_t _parse_decimal_100(const char *p);
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/// Parses the current term as a NMEA-style degrees + minutes
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/// value with up to four decimal digits.
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///
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/// This gives a theoretical resolution limit of around 1cm.
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///
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/// @returns The value expressed by the string in _term,
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/// multiplied by 1e7.
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///
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uint32_t _parse_degrees();
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/// Processes the current term when it has been deemed to be
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/// complete.
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///
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/// Each GPS message is broken up into terms separated by commas.
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/// Each term is then processed by this function as it is received.
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///
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/// @returns True if completing the term has resulted in
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/// an update to the GPS state.
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bool _term_complete();
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/// return true if we have a new set of NMEA messages
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bool _have_new_message(void);
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uint8_t _parity; ///< NMEA message checksum accumulator
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bool _is_checksum_term; ///< current term is the checksum
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char _term[15]; ///< buffer for the current term within the current sentence
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uint8_t _sentence_type; ///< the sentence type currently being processed
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uint8_t _term_number; ///< term index within the current sentence
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uint8_t _term_offset; ///< character offset with the term being received
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uint16_t _sentence_length;
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bool _gps_data_good; ///< set when the sentence indicates data is good
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bool _sentence_done; ///< set when a sentence has been fully decoded
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// The result of parsing terms within a message is stored temporarily until
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// the message is completely processed and the checksum validated.
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// This avoids the need to buffer the entire message.
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int32_t _new_time; ///< time parsed from a term
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int32_t _new_date; ///< date parsed from a term
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int32_t _new_latitude; ///< latitude parsed from a term
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int32_t _new_longitude; ///< longitude parsed from a term
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int32_t _new_altitude; ///< altitude parsed from a term
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int32_t _new_speed; ///< speed parsed from a term
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int32_t _new_course; ///< course parsed from a term
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float _new_gps_yaw; ///< yaw parsed from a term
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uint16_t _new_hdop; ///< HDOP parsed from a term
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uint8_t _new_satellite_count; ///< satellite count parsed from a term
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uint8_t _new_quality_indicator; ///< GPS quality indicator parsed from a term
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uint32_t _last_RMC_ms;
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uint32_t _last_GGA_ms;
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uint32_t _last_VTG_ms;
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uint32_t _last_HDT_THS_ms;
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uint32_t _last_PHD_12_ms;
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uint32_t _last_PHD_26_ms;
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uint32_t _last_fix_ms;
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/// @name Init strings
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/// In ::init, an attempt is made to configure the GPS
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/// unit to send just the messages that we are interested
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/// in using these strings
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//@{
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static const char _SiRF_init_string[]; ///< init string for SiRF units
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static const char _MTK_init_string[]; ///< init string for MediaTek units
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static const char _ublox_init_string[]; ///< init string for ublox units
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//@}
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static const char _initialisation_blob[];
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/*
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the $PHD message is an extension from AllyStar that gives
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vertical velocity and more accuracy estimates. It is designed as
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a mapping from ublox UBX protocol messages to NMEA. So class 1,
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message 12 is a mapping to NMEA of the NAV-VELNED UBX message
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and contains the same fields. Class 1 message 26 is called
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"NAV-PVERR", but does not correspond to a UBX message
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example:
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$PHD,01,12,TIIITTITT,,245808000,0,0,0,0,0,10260304,0,0*27
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$PHD,01,26,TTTTTTT,,245808000,877,864,1451,11,11,17*17
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*/
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struct {
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uint8_t msg_class;
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uint8_t msg_id;
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uint32_t itow;
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int32_t fields[8];
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} _phd;
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};
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#define AP_GPS_NMEA_HEMISPHERE_INIT_STRING \
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"$JATT,NMEAHE,0\r\n" /* Prefix of GP on the HDT message */ \
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"$JASC,GPGGA,5\r\n" /* GGA at 5Hz */ \
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"$JASC,GPRMC,5\r\n" /* RMC at 5Hz */ \
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"$JASC,GPVTG,5\r\n" /* VTG at 5Hz */ \
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"$JASC,GPHDT,5\r\n" /* HDT at 5Hz */ \
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"$JMODE,SBASR,YES\r\n" /* Enable SBAS */
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