mirror of https://github.com/ArduPilot/ardupilot
458 lines
13 KiB
C++
458 lines
13 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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/// @file AP_GPS_NMEA.cpp
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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.
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///
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#include <AP_Common/AP_Common.h>
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#include <ctype.h>
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#include <stdint.h>
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#include <stdlib.h>
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#include "AP_GPS_NMEA.h"
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extern const AP_HAL::HAL& hal;
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// optionally log all NMEA data for debug purposes
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// #define NMEA_LOG_PATH "nmea.log"
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#ifdef NMEA_LOG_PATH
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#include <stdio.h>
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#endif
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// Convenience macros //////////////////////////////////////////////////////////
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//
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#define DIGIT_TO_VAL(_x) (_x - '0')
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#define hexdigit(x) ((x)>9?'A'+((x)-10):'0'+(x))
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AP_GPS_NMEA::AP_GPS_NMEA(AP_GPS &_gps, AP_GPS::GPS_State &_state, AP_HAL::UARTDriver *_port) :
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AP_GPS_Backend(_gps, _state, _port)
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{
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// this guarantees that _term is always null terminated
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memset(_term, 0, sizeof(_term));
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}
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bool AP_GPS_NMEA::read(void)
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{
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int16_t numc;
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bool parsed = false;
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numc = port->available();
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while (numc--) {
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char c = port->read();
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#ifdef NMEA_LOG_PATH
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static FILE *logf = nullptr;
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if (logf == nullptr) {
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logf = fopen(NMEA_LOG_PATH, "wb");
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}
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if (logf != nullptr) {
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::fwrite(&c, 1, 1, logf);
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}
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#endif
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if (_decode(c)) {
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parsed = true;
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}
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}
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return parsed;
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}
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bool AP_GPS_NMEA::_decode(char c)
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{
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bool valid_sentence = false;
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_sentence_length++;
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switch (c) {
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case ',': // term terminators
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_parity ^= c;
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FALLTHROUGH;
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case '\r':
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case '\n':
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case '*':
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if (_term_offset < sizeof(_term)) {
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_term[_term_offset] = 0;
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valid_sentence = _term_complete();
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}
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++_term_number;
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_term_offset = 0;
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_is_checksum_term = c == '*';
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return valid_sentence;
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case '$': // sentence begin
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_term_number = _term_offset = 0;
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_parity = 0;
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_sentence_type = _GPS_SENTENCE_OTHER;
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_is_checksum_term = false;
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_gps_data_good = false;
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_sentence_length = 1;
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return valid_sentence;
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}
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// ordinary characters
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if (_term_offset < sizeof(_term) - 1)
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_term[_term_offset++] = c;
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if (!_is_checksum_term)
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_parity ^= c;
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return valid_sentence;
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}
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//
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// internal utilities
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//
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int16_t AP_GPS_NMEA::_from_hex(char a)
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{
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if (a >= 'A' && a <= 'F')
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return a - 'A' + 10;
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else if (a >= 'a' && a <= 'f')
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return a - 'a' + 10;
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else
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return a - '0';
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}
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int32_t AP_GPS_NMEA::_parse_decimal_100(const char *p)
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{
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char *endptr = nullptr;
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long ret = 100 * strtol(p, &endptr, 10);
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int sign = ret < 0 ? -1 : 1;
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if (ret >= (long)INT32_MAX) {
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return INT32_MAX;
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}
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if (ret <= (long)INT32_MIN) {
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return INT32_MIN;
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}
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if (endptr == nullptr || *endptr != '.') {
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return ret;
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}
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if (isdigit(endptr[1])) {
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ret += sign * 10 * DIGIT_TO_VAL(endptr[1]);
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if (isdigit(endptr[2])) {
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ret += sign * DIGIT_TO_VAL(endptr[2]);
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if (isdigit(endptr[3])) {
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ret += sign * (DIGIT_TO_VAL(endptr[3]) >= 5);
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}
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}
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}
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return ret;
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}
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/*
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parse a NMEA latitude/longitude degree value. The result is in degrees*1e7
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*/
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uint32_t AP_GPS_NMEA::_parse_degrees()
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{
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char *p, *q;
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uint8_t deg = 0, min = 0;
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float frac_min = 0;
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int32_t ret = 0;
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// scan for decimal point or end of field
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for (p = _term; *p && isdigit(*p); p++)
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;
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q = _term;
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// convert degrees
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while ((p - q) > 2 && *q) {
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if (deg)
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deg *= 10;
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deg += DIGIT_TO_VAL(*q++);
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}
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// convert minutes
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while (p > q && *q) {
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if (min)
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min *= 10;
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min += DIGIT_TO_VAL(*q++);
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}
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// convert fractional minutes
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if (*p == '.') {
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q = p + 1;
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float frac_scale = 0.1f;
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while (*q && isdigit(*q)) {
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frac_min += DIGIT_TO_VAL(*q) * frac_scale;
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q++;
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frac_scale *= 0.1f;
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}
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}
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ret = (deg * (int32_t)10000000UL);
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ret += (min * (int32_t)10000000UL / 60);
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ret += (int32_t) (frac_min * (1.0e7f / 60.0f));
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return ret;
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}
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/*
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see if we have a new set of NMEA messages
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*/
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bool AP_GPS_NMEA::_have_new_message()
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{
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if (_last_RMC_ms == 0 ||
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_last_GGA_ms == 0) {
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return false;
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}
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uint32_t now = AP_HAL::millis();
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if (now - _last_RMC_ms > 150 ||
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now - _last_GGA_ms > 150) {
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return false;
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}
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if (_last_VTG_ms != 0 &&
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now - _last_VTG_ms > 150) {
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return false;
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}
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// prevent these messages being used again
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if (_last_VTG_ms != 0) {
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_last_VTG_ms = 1;
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}
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_last_GGA_ms = 1;
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_last_RMC_ms = 1;
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return true;
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}
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// Processes a just-completed term
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// Returns true if new sentence has just passed checksum test and is validated
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bool AP_GPS_NMEA::_term_complete()
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{
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// handle the last term in a message
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if (_is_checksum_term) {
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uint8_t checksum = 16 * _from_hex(_term[0]) + _from_hex(_term[1]);
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if (checksum == _parity) {
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if (_gps_data_good) {
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uint32_t now = AP_HAL::millis();
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switch (_sentence_type) {
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case _GPS_SENTENCE_RMC:
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_last_RMC_ms = now;
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//time = _new_time;
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//date = _new_date;
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state.location.lat = _new_latitude;
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state.location.lng = _new_longitude;
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state.ground_speed = _new_speed*0.01f;
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state.ground_course = wrap_360(_new_course*0.01f);
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make_gps_time(_new_date, _new_time * 10);
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set_uart_timestamp(_sentence_length);
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state.last_gps_time_ms = now;
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fill_3d_velocity();
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break;
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case _GPS_SENTENCE_GGA:
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_last_GGA_ms = now;
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state.location.alt = _new_altitude;
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state.location.lat = _new_latitude;
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state.location.lng = _new_longitude;
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state.num_sats = _new_satellite_count;
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state.hdop = _new_hdop;
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switch(_new_quality_indicator) {
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case 0: // Fix not available or invalid
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state.status = AP_GPS::NO_FIX;
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break;
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case 1: // GPS SPS Mode, fix valid
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state.status = AP_GPS::GPS_OK_FIX_3D;
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break;
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case 2: // Differential GPS, SPS Mode, fix valid
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state.status = AP_GPS::GPS_OK_FIX_3D_DGPS;
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break;
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case 3: // GPS PPS Mode, fix valid
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state.status = AP_GPS::GPS_OK_FIX_3D;
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break;
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case 4: // Real Time Kinematic. System used in RTK mode with fixed integers
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state.status = AP_GPS::GPS_OK_FIX_3D_RTK_FIXED;
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break;
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case 5: // Float RTK. Satellite system used in RTK mode, floating integers
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state.status = AP_GPS::GPS_OK_FIX_3D_RTK_FLOAT;
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break;
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case 6: // Estimated (dead reckoning) Mode
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state.status = AP_GPS::NO_FIX;
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break;
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default://to maintain compatibility with MAV_GPS_INPUT and others
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state.status = AP_GPS::GPS_OK_FIX_3D;
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break;
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}
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break;
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case _GPS_SENTENCE_VTG:
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_last_VTG_ms = now;
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state.ground_speed = _new_speed*0.01f;
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state.ground_course = wrap_360(_new_course*0.01f);
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fill_3d_velocity();
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// VTG has no fix indicator, can't change fix status
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break;
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}
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} else {
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switch (_sentence_type) {
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case _GPS_SENTENCE_RMC:
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case _GPS_SENTENCE_GGA:
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// Only these sentences give us information about
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// fix status.
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state.status = AP_GPS::NO_FIX;
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}
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}
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// see if we got a good message
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return _have_new_message();
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}
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// we got a bad message, ignore it
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return false;
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}
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// the first term determines the sentence type
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if (_term_number == 0) {
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/*
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The first two letters of the NMEA term are the talker
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ID. The most common is 'GP' but there are a bunch of others
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that are valid. We accept any two characters here.
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*/
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if (_term[0] < 'A' || _term[0] > 'Z' ||
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_term[1] < 'A' || _term[1] > 'Z') {
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_sentence_type = _GPS_SENTENCE_OTHER;
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return false;
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}
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const char *term_type = &_term[2];
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if (strcmp(term_type, "RMC") == 0) {
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_sentence_type = _GPS_SENTENCE_RMC;
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} else if (strcmp(term_type, "GGA") == 0) {
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_sentence_type = _GPS_SENTENCE_GGA;
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} else if (strcmp(term_type, "VTG") == 0) {
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_sentence_type = _GPS_SENTENCE_VTG;
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// VTG may not contain a data qualifier, presume the solution is good
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// unless it tells us otherwise.
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_gps_data_good = true;
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} else {
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_sentence_type = _GPS_SENTENCE_OTHER;
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}
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return false;
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}
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// 32 = RMC, 64 = GGA, 96 = VTG
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if (_sentence_type != _GPS_SENTENCE_OTHER && _term[0]) {
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switch (_sentence_type + _term_number) {
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// operational status
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//
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case _GPS_SENTENCE_RMC + 2: // validity (RMC)
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_gps_data_good = _term[0] == 'A';
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break;
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case _GPS_SENTENCE_GGA + 6: // Fix data (GGA)
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_gps_data_good = _term[0] > '0';
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_new_quality_indicator = _term[0] - '0';
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break;
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case _GPS_SENTENCE_VTG + 9: // validity (VTG) (we may not see this field)
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_gps_data_good = _term[0] != 'N';
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break;
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case _GPS_SENTENCE_GGA + 7: // satellite count (GGA)
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_new_satellite_count = atol(_term);
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break;
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case _GPS_SENTENCE_GGA + 8: // HDOP (GGA)
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_new_hdop = (uint16_t)_parse_decimal_100(_term);
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break;
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// time and date
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//
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case _GPS_SENTENCE_RMC + 1: // Time (RMC)
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case _GPS_SENTENCE_GGA + 1: // Time (GGA)
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_new_time = _parse_decimal_100(_term);
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break;
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case _GPS_SENTENCE_RMC + 9: // Date (GPRMC)
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_new_date = atol(_term);
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break;
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// location
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//
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case _GPS_SENTENCE_RMC + 3: // Latitude
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case _GPS_SENTENCE_GGA + 2:
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_new_latitude = _parse_degrees();
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break;
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case _GPS_SENTENCE_RMC + 4: // N/S
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case _GPS_SENTENCE_GGA + 3:
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if (_term[0] == 'S')
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_new_latitude = -_new_latitude;
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break;
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case _GPS_SENTENCE_RMC + 5: // Longitude
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case _GPS_SENTENCE_GGA + 4:
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_new_longitude = _parse_degrees();
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break;
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case _GPS_SENTENCE_RMC + 6: // E/W
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case _GPS_SENTENCE_GGA + 5:
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if (_term[0] == 'W')
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_new_longitude = -_new_longitude;
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break;
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case _GPS_SENTENCE_GGA + 9: // Altitude (GPGGA)
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_new_altitude = _parse_decimal_100(_term);
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break;
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// course and speed
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//
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case _GPS_SENTENCE_RMC + 7: // Speed (GPRMC)
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case _GPS_SENTENCE_VTG + 5: // Speed (VTG)
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_new_speed = (_parse_decimal_100(_term) * 514) / 1000; // knots-> m/sec, approximiates * 0.514
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break;
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case _GPS_SENTENCE_RMC + 8: // Course (GPRMC)
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case _GPS_SENTENCE_VTG + 1: // Course (VTG)
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_new_course = _parse_decimal_100(_term);
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break;
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}
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}
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return false;
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}
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/*
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detect a NMEA GPS. Adds one byte, and returns true if the stream
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matches a NMEA string
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*/
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bool
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AP_GPS_NMEA::_detect(struct NMEA_detect_state &state, uint8_t data)
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{
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switch (state.step) {
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case 0:
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state.ck = 0;
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if ('$' == data) {
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state.step++;
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}
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break;
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case 1:
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if ('*' == data) {
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state.step++;
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} else {
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state.ck ^= data;
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}
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break;
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case 2:
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if (hexdigit(state.ck>>4) == data) {
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state.step++;
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} else {
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state.step = 0;
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}
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break;
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case 3:
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if (hexdigit(state.ck&0xF) == data) {
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state.step = 0;
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return true;
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}
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state.step = 0;
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break;
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}
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return false;
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}
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