mirror of https://github.com/ArduPilot/ardupilot
140 lines
3.7 KiB
C++
140 lines
3.7 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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#include "AP_GPS.h"
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#include "GPS_Backend.h"
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extern const AP_HAL::HAL& hal;
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AP_GPS_Backend::AP_GPS_Backend(AP_GPS &_gps, AP_GPS::GPS_State &_state, AP_HAL::UARTDriver *_port) :
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port(_port),
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gps(_gps),
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state(_state)
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{
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state.have_speed_accuracy = false;
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state.have_horizontal_accuracy = false;
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state.have_vertical_accuracy = false;
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}
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int32_t AP_GPS_Backend::swap_int32(int32_t v) const
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{
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const uint8_t *b = (const uint8_t *)&v;
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union {
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int32_t v;
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uint8_t b[4];
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} u;
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u.b[0] = b[3];
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u.b[1] = b[2];
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u.b[2] = b[1];
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u.b[3] = b[0];
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return u.v;
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}
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int16_t AP_GPS_Backend::swap_int16(int16_t v) const
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{
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const uint8_t *b = (const uint8_t *)&v;
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union {
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int16_t v;
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uint8_t b[2];
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} u;
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u.b[0] = b[1];
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u.b[1] = b[0];
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return u.v;
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}
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/**
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convert GPS week and milliseconds to unix epoch in milliseconds
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*/
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uint64_t AP_GPS::time_epoch_convert(uint16_t gps_week, uint32_t gps_ms)
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{
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const uint64_t ms_per_week = 7000ULL*86400ULL;
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const uint64_t unix_offset = 17000ULL*86400ULL + 52*10*7000ULL*86400ULL - GPS_LEAPSECONDS_MILLIS;
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uint64_t fix_time_ms = unix_offset + gps_week*ms_per_week + gps_ms;
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return fix_time_ms;
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}
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/**
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calculate current time since the unix epoch in microseconds
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*/
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uint64_t AP_GPS::time_epoch_usec(uint8_t instance)
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{
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const GPS_State &istate = state[instance];
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if (istate.last_gps_time_ms == 0) {
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return 0;
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}
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uint64_t fix_time_ms = time_epoch_convert(istate.time_week, istate.time_week_ms);
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// add in the milliseconds since the last fix
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return (fix_time_ms + (AP_HAL::millis() - istate.last_gps_time_ms)) * 1000ULL;
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}
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/**
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fill in time_week_ms and time_week from BCD date and time components
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assumes MTK19 millisecond form of bcd_time
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*/
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void AP_GPS_Backend::make_gps_time(uint32_t bcd_date, uint32_t bcd_milliseconds)
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{
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uint8_t year, mon, day, hour, min, sec;
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uint16_t msec;
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year = bcd_date % 100;
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mon = (bcd_date / 100) % 100;
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day = bcd_date / 10000;
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uint32_t v = bcd_milliseconds;
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msec = v % 1000; v /= 1000;
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sec = v % 100; v /= 100;
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min = v % 100; v /= 100;
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hour = v % 100; v /= 100;
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int8_t rmon = mon - 2;
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if (0 >= rmon) {
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rmon += 12;
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year -= 1;
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}
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// get time in seconds since unix epoch
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uint32_t ret = (year/4) - (GPS_LEAPSECONDS_MILLIS / 1000UL) + 367*rmon/12 + day;
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ret += year*365 + 10501;
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ret = ret*24 + hour;
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ret = ret*60 + min;
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ret = ret*60 + sec;
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// convert to time since GPS epoch
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ret -= 272764785UL;
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// get GPS week and time
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state.time_week = ret / (7*86400UL);
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state.time_week_ms = (ret % (7*86400UL)) * 1000;
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state.time_week_ms += msec;
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}
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/*
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fill in 3D velocity for a GPS that doesn't give vertical velocity numbers
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*/
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void AP_GPS_Backend::fill_3d_velocity(void)
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{
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float gps_heading = radians(state.ground_course);
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state.velocity.x = state.ground_speed * cosf(gps_heading);
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state.velocity.y = state.ground_speed * sinf(gps_heading);
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state.velocity.z = 0;
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state.have_vertical_velocity = false;
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}
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