ardupilot/libraries/AP_Baro/AP_Baro.cpp

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/// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
/*
APM_Baro.cpp - barometer driver
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public License
as published by the Free Software Foundation; either version 2.1
of the License, or (at your option) any later version.
*/
#include <FastSerial.h>
#include <AP_Common.h>
#include <AP_Baro.h>
// table of user settable parameters
const AP_Param::GroupInfo AP_Baro::var_info[] PROGMEM = {
// @Param: ABS_PRESS
// @DisplayName: Absolute Pressure
// @Description: calibrated ground pressure
// @Increment: 1
AP_GROUPINFO("ABS_PRESS", 0, AP_Baro, _ground_pressure),
// @Param: ABS_PRESS
// @DisplayName: ground temperature
// @Description: calibrated ground temperature
// @Increment: 1
AP_GROUPINFO("TEMP", 1, AP_Baro, _ground_temperature),
AP_GROUPEND
};
// calibrate the barometer. This must be called at least once before
// the altitude() or climb_rate() interfaces can be used
void AP_Baro::calibrate(void (*callback)(unsigned long t))
{
int32_t ground_pressure = 0;
int16_t ground_temperature;
while (ground_pressure == 0 || !healthy) {
read(); // Get initial data from absolute pressure sensor
ground_pressure = get_pressure();
ground_temperature = get_temperature();
callback(20);
}
for (int i = 0; i < 30; i++) {
do {
read();
} while (!healthy);
ground_pressure = (ground_pressure * 9l + get_pressure()) / 10l;
ground_temperature = (ground_temperature * 9 + get_temperature()) / 10;
callback(20);
}
_ground_pressure.set_and_save(ground_pressure);
_ground_temperature.set_and_save(ground_temperature / 10.0f);
}
// return current altitude estimate relative to time that calibrate()
// was called. Returns altitude in meters
// note that this relies on read() being called regularly to get new data
float AP_Baro::get_altitude(void)
{
float scaling, temp;
if (_last_altitude_t == _last_update) {
// no new information
return _altitude;
}
// this has no filtering of the pressure values, use a separate
// filter if you want a smoothed value. The AHRS driver wants
// unsmoothed values
scaling = (float)_ground_pressure / (float)get_pressure();
temp = ((float)_ground_temperature) + 273.15f;
_altitude = log(scaling) * temp * 29.271267f;
_last_altitude_t = _last_update;
return _altitude;
}
// return current climb_rate estimeate relative to time that calibrate()
// was called. Returns climb rate in meters/s, positive means up
// note that this relies on read() being called regularly to get new data
float AP_Baro::get_climb_rate(void)
{
if (_last_climb_rate_t == _last_update) {
// no new information
return _climb_rate;
}
_last_climb_rate_t = _last_update;
// we use a 9 point derivative filter on the climb rate. This seems
// to produce somewhat reasonable results on real hardware
_climb_rate = _climb_rate_filter.apply(get_altitude(), _last_update) * 1.0e3;
return _climb_rate;
}