ardupilot/libraries/AP_Baro/AP_Baro.cpp

/*
   This program is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation, either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

/*
 *       APM_Baro.cpp - barometer driver
 *
 */
#include "AP_Baro.h"

#include <utility>
#include <stdio.h>

#include <GCS_MAVLink/GCS.h>
#include <AP_Common/AP_Common.h>
#include <AP_HAL/AP_HAL.h>
#include <AP_Math/AP_Math.h>
#include <AP_BoardConfig/AP_BoardConfig.h>
#include <AP_CANManager/AP_CANManager.h>
#include <AP_Vehicle/AP_Vehicle_Type.h>
#include <AP_HAL/I2CDevice.h>

#include "AP_Baro_SITL.h"
#include "AP_Baro_BMP085.h"
#include "AP_Baro_BMP280.h"
#include "AP_Baro_SPL06.h"
#include "AP_Baro_KellerLD.h"
#include "AP_Baro_MS5611.h"
#include "AP_Baro_ICM20789.h"
#include "AP_Baro_LPS2XH.h"
#include "AP_Baro_FBM320.h"
#include "AP_Baro_DPS280.h"
#include "AP_Baro_BMP388.h"
#include "AP_Baro_Dummy.h"
#include "AP_Baro_UAVCAN.h"
#include "AP_Baro_MSP.h"
#include "AP_Baro_ExternalAHRS.h"
#include "AP_Baro_ICP101XX.h"
#include "AP_Baro_ICP201XX.h"

#include <AP_Airspeed/AP_Airspeed.h>
#include <AP_AHRS/AP_AHRS.h>
#include <AP_Arming/AP_Arming.h>
#include <AP_Logger/AP_Logger.h>
#include <AP_GPS/AP_GPS.h>
#include <AP_Vehicle/AP_Vehicle.h>

#define INTERNAL_TEMPERATURE_CLAMP 35.0f

#ifndef HAL_BARO_FILTER_DEFAULT
 #define HAL_BARO_FILTER_DEFAULT 0 // turned off by default
#endif

#if !defined(HAL_PROBE_EXTERNAL_I2C_BAROS) && !HAL_MINIMIZE_FEATURES
#define HAL_PROBE_EXTERNAL_I2C_BAROS
#endif

#ifndef HAL_BARO_PROBE_EXT_DEFAULT
 #define HAL_BARO_PROBE_EXT_DEFAULT 0
#endif

#ifndef HAL_BARO_EXTERNAL_BUS_DEFAULT
 #define HAL_BARO_EXTERNAL_BUS_DEFAULT -1
#endif

#ifdef HAL_BUILD_AP_PERIPH
#define HAL_BARO_ALLOW_INIT_NO_BARO
#endif

extern const AP_HAL::HAL& hal;

// table of user settable parameters
const AP_Param::GroupInfo AP_Baro::var_info[] = {
    // NOTE: Index numbers 0 and 1 were for the old integer
    // ground temperature and pressure

#ifndef HAL_BUILD_AP_PERIPH
    // @Param: 1_GND_PRESS
    // @DisplayName: Ground Pressure
    // @Description: calibrated ground pressure in Pascals
    // @Units: Pa
    // @Increment: 1
    // @ReadOnly: True
    // @Volatile: True
    // @User: Advanced
    AP_GROUPINFO_FLAGS("1_GND_PRESS", 2, AP_Baro, sensors[0].ground_pressure, 0, AP_PARAM_FLAG_INTERNAL_USE_ONLY),

    // @Param: _GND_TEMP
    // @DisplayName: ground temperature
    // @Description: User provided ambient ground temperature in degrees Celsius. This is used to improve the calculation of the altitude the vehicle is at. This parameter is not persistent and will be reset to 0 every time the vehicle is rebooted. A value of 0 means use the internal measurement ambient temperature.
    // @Units: degC
    // @Increment: 1
    // @Volatile: True
    // @User: Advanced
    AP_GROUPINFO("_GND_TEMP", 3, AP_Baro, _user_ground_temperature, 0),

    // index 4 reserved for old AP_Int8 version in legacy FRAM
    //AP_GROUPINFO("ALT_OFFSET", 4, AP_Baro, _alt_offset, 0),

    // @Param: _ALT_OFFSET
    // @DisplayName: altitude offset
    // @Description: altitude offset in meters added to barometric altitude. This is used to allow for automatic adjustment of the base barometric altitude by a ground station equipped with a barometer. The value is added to the barometric altitude read by the aircraft. It is automatically reset to 0 when the barometer is calibrated on each reboot or when a preflight calibration is performed.
    // @Units: m
    // @Increment: 0.1
    // @User: Advanced
    AP_GROUPINFO("_ALT_OFFSET", 5, AP_Baro, _alt_offset, 0),

    // @Param: _PRIMARY
    // @DisplayName: Primary barometer
    // @Description: This selects which barometer will be the primary if multiple barometers are found
    // @Values: 0:FirstBaro,1:2ndBaro,2:3rdBaro
    // @User: Advanced
    AP_GROUPINFO("_PRIMARY", 6, AP_Baro, _primary_baro, 0),
#endif // HAL_BUILD_AP_PERIPH

    // @Param: _EXT_BUS
    // @DisplayName: External baro bus
    // @Description: This selects the bus number for looking for an I2C barometer. When set to -1 it will probe all external i2c buses based on the BARO_PROBE_EXT parameter.
    // @Values: -1:Disabled,0:Bus0,1:Bus1,6:Bus6
    // @User: Advanced
    AP_GROUPINFO("_EXT_BUS", 7, AP_Baro, _ext_bus, HAL_BARO_EXTERNAL_BUS_DEFAULT),

    // @Param{Sub}: _SPEC_GRAV
    // @DisplayName: Specific Gravity (For water depth measurement)
    // @Description: This sets the specific gravity of the fluid when flying an underwater ROV.
    // @Values: 1.0:Freshwater,1.024:Saltwater
    AP_GROUPINFO_FRAME("_SPEC_GRAV", 8, AP_Baro, _specific_gravity, 1.0, AP_PARAM_FRAME_SUB),

#if BARO_MAX_INSTANCES > 1
    // @Param: 2_GND_PRESS
    // @DisplayName: Ground Pressure
    // @Description: calibrated ground pressure in Pascals
    // @Units: Pa
    // @Increment: 1
    // @ReadOnly: True
    // @Volatile: True
    // @User: Advanced
    AP_GROUPINFO_FLAGS("2_GND_PRESS", 9, AP_Baro, sensors[1].ground_pressure, 0, AP_PARAM_FLAG_INTERNAL_USE_ONLY),

    // Slot 10 used to be TEMP2
#endif

#if BARO_MAX_INSTANCES > 2
    // @Param: 3_GND_PRESS
    // @DisplayName: Absolute Pressure
    // @Description: calibrated ground pressure in Pascals
    // @Units: Pa
    // @Increment: 1
    // @ReadOnly: True
    // @Volatile: True
    // @User: Advanced
    AP_GROUPINFO_FLAGS("3_GND_PRESS", 11, AP_Baro, sensors[2].ground_pressure, 0, AP_PARAM_FLAG_INTERNAL_USE_ONLY),

    // Slot 12 used to be TEMP3
#endif

    // @Param: _FLTR_RNG
    // @DisplayName: Range in which sample is accepted
    // @Description: This sets the range around the average value that new samples must be within to be accepted. This can help reduce the impact of noise on sensors that are on long I2C cables. The value is a percentage from the average value. A value of zero disables this filter.
    // @Units: %
    // @Range: 0 100
    // @Increment: 1
    AP_GROUPINFO("_FLTR_RNG", 13, AP_Baro, _filter_range, HAL_BARO_FILTER_DEFAULT),

#if defined(HAL_PROBE_EXTERNAL_I2C_BAROS) || defined(AP_BARO_MSP_ENABLED)
    // @Param: _PROBE_EXT
    // @DisplayName: External barometers to probe
    // @Description: This sets which types of external i2c barometer to look for. It is a bitmask of barometer types. The I2C buses to probe is based on BARO_EXT_BUS. If BARO_EXT_BUS is -1 then it will probe all external buses, otherwise it will probe just the bus number given in BARO_EXT_BUS.
    // @Bitmask: 0:BMP085,1:BMP280,2:MS5611,3:MS5607,4:MS5637,5:FBM320,6:DPS280,7:LPS25H,8:Keller,9:MS5837,10:BMP388,11:SPL06,12:MSP
    // @User: Advanced
    AP_GROUPINFO("_PROBE_EXT", 14, AP_Baro, _baro_probe_ext, HAL_BARO_PROBE_EXT_DEFAULT),
#endif

    // @Param: 1_DEVID
    // @DisplayName: Baro ID
    // @Description: Barometer sensor ID, taking into account its type, bus and instance
    // @ReadOnly: True
    // @User: Advanced
    AP_GROUPINFO_FLAGS("1_DEVID", 15, AP_Baro, sensors[0].bus_id, 0, AP_PARAM_FLAG_INTERNAL_USE_ONLY),

#if BARO_MAX_INSTANCES > 1
    // @Param: 2_DEVID
    // @DisplayName: Baro ID2
    // @Description: Barometer2 sensor ID, taking into account its type, bus and instance
    // @ReadOnly: True
    // @User: Advanced
    AP_GROUPINFO_FLAGS("2_DEVID", 16, AP_Baro, sensors[1].bus_id, 0, AP_PARAM_FLAG_INTERNAL_USE_ONLY),
#endif

#if BARO_MAX_INSTANCES > 2
    // @Param: 3_DEVID
    // @DisplayName: Baro ID3
    // @Description: Barometer3 sensor ID, taking into account its type, bus and instance
    // @ReadOnly: True
    // @User: Advanced
    AP_GROUPINFO_FLAGS("3_DEVID", 17, AP_Baro, sensors[2].bus_id, 0, AP_PARAM_FLAG_INTERNAL_USE_ONLY),
#endif

#if HAL_BARO_WIND_COMP_ENABLED
    // @Group: 1_WCF_
    // @Path: AP_Baro_Wind.cpp
    AP_SUBGROUPINFO(sensors[0].wind_coeff, "1_WCF_", 18, AP_Baro, WindCoeff),

#if BARO_MAX_INSTANCES > 1
    // @Group: 2_WCF_
    // @Path: AP_Baro_Wind.cpp
    AP_SUBGROUPINFO(sensors[1].wind_coeff, "2_WCF_", 19, AP_Baro, WindCoeff),
#endif

#if BARO_MAX_INSTANCES > 2
    // @Group: 3_WCF_
    // @Path: AP_Baro_Wind.cpp
    AP_SUBGROUPINFO(sensors[2].wind_coeff, "3_WCF_", 20, AP_Baro, WindCoeff),
#endif
#ifndef HAL_BUILD_AP_PERIPH
    // @Param: _FIELD_ELV
    // @DisplayName: field elevation
    // @Description: User provided field elevation in meters. This is used to improve the calculation of the altitude the vehicle is at. This parameter is not persistent and will be reset to 0 every time the vehicle is rebooted. Changes to this parameter will only be used when disarmed. A value of 0 means the EKF origin height is used for takeoff height above sea level.
    // @Units: m
    // @Increment: 0.1
    // @Volatile: True
    // @User: Advanced
    AP_GROUPINFO("_FIELD_ELV", 22, AP_Baro, _field_elevation, 0),
#endif
#endif

#if APM_BUILD_COPTER_OR_HELI || APM_BUILD_TYPE(APM_BUILD_ArduPlane)
    // @Param: _ALTERR_MAX
    // @DisplayName: Altitude error maximum
    // @Description: This is the maximum acceptable altitude discrepancy between GPS altitude and barometric presssure altitude calculated against a standard atmosphere for arming checks to pass. If you are getting an arming error due to this parameter then you may have a faulty or substituted barometer. A common issue is vendors replacing a MS5611 in a "Pixhawk" with a MS5607. If you have that issue then please see BARO_OPTIONS parameter to force the MS5611 to be treated as a MS5607. This check is disabled if the value is zero.
    // @Units: m
    // @Increment: 1
    // @Range: 0 5000
    // @User: Advanced
    AP_GROUPINFO("_ALTERR_MAX", 23, AP_Baro, _alt_error_max, 2000),

    // @Param: _OPTIONS
    // @DisplayName: Barometer options
    // @Description: Barometer options
    // @Bitmask: 0:Treat MS5611 as MS5607
    // @User: Advanced
    AP_GROUPINFO("_OPTIONS", 24, AP_Baro, _options, 0),
#endif
    
    AP_GROUPEND
};

// singleton instance
AP_Baro *AP_Baro::_singleton;

#if HAL_GCS_ENABLED
#define BARO_SEND_TEXT(severity, format, args...) gcs().send_text(severity, format, ##args)
#else
#define BARO_SEND_TEXT(severity, format, args...)
#endif

/*
  AP_Baro constructor
 */
AP_Baro::AP_Baro()
{
    _singleton = this;

    AP_Param::setup_object_defaults(this, var_info);
    _field_elevation_active = _field_elevation;
}

// calibrate the barometer. This must be called at least once before
// the altitude() or climb_rate() interfaces can be used
void AP_Baro::calibrate(bool save)
{
    // start by assuming all sensors are calibrated (for healthy() test)
    for (uint8_t i=0; i<_num_sensors; i++) {
        sensors[i].calibrated = true;
        sensors[i].alt_ok = true;
    }

    if (hal.util->was_watchdog_reset()) {
        BARO_SEND_TEXT(MAV_SEVERITY_INFO, "Baro: skipping calibration after WDG reset");
        return;
    }

#if AP_SIM_BARO_ENABLED
    if (AP::sitl()->baro_count == 0) {
        return;
    }
#endif

    #ifdef HAL_BARO_ALLOW_INIT_NO_BARO
    if (_num_drivers == 0 || _num_sensors == 0 || drivers[0] == nullptr) {
            BARO_SEND_TEXT(MAV_SEVERITY_INFO, "Baro: no sensors found, skipping calibration");
            return;
    }
    #endif
    
    BARO_SEND_TEXT(MAV_SEVERITY_INFO, "Calibrating barometer");

    // reset the altitude offset when we calibrate. The altitude
    // offset is supposed to be for within a flight
    _alt_offset.set_and_save(0);

    // let the barometer settle for a full second after startup
    // the MS5611 reads quite a long way off for the first second,
    // leading to about 1m of error if we don't wait
    for (uint8_t i = 0; i < 10; i++) {
        uint32_t tstart = AP_HAL::millis();
        do {
            update();
            if (AP_HAL::millis() - tstart > 500) {
                AP_BoardConfig::config_error("Baro: unable to calibrate");
            }
            hal.scheduler->delay(10);
        } while (!healthy());
        hal.scheduler->delay(100);
    }

    // now average over 5 values for the ground pressure settings
    float sum_pressure[BARO_MAX_INSTANCES] = {0};
    uint8_t count[BARO_MAX_INSTANCES] = {0};
    const uint8_t num_samples = 5;

    for (uint8_t c = 0; c < num_samples; c++) {
        uint32_t tstart = AP_HAL::millis();
        do {
            update();
            if (AP_HAL::millis() - tstart > 500) {
                AP_BoardConfig::config_error("Baro: unable to calibrate");
            }
        } while (!healthy());
        for (uint8_t i=0; i<_num_sensors; i++) {
            if (healthy(i)) {
                sum_pressure[i] += sensors[i].pressure;
                count[i] += 1;
            }
        }
        hal.scheduler->delay(100);
    }
    for (uint8_t i=0; i<_num_sensors; i++) {
        if (count[i] == 0) {
            sensors[i].calibrated = false;
        } else {
            if (save) {
                float p0_sealevel = get_sealevel_pressure(sum_pressure[i] / count[i]);
                sensors[i].ground_pressure.set_and_save(p0_sealevel);
            }
        }
    }

    _guessed_ground_temperature = get_external_temperature();

    // panic if all sensors are not calibrated
    uint8_t num_calibrated = 0;
    for (uint8_t i=0; i<_num_sensors; i++) {
        if (sensors[i].calibrated) {
            BARO_SEND_TEXT(MAV_SEVERITY_INFO, "Barometer %u calibration complete", i+1);
            num_calibrated++;
        }
    }
    if (num_calibrated) {
        return;
    }
    AP_BoardConfig::config_error("Baro: all sensors uncalibrated");
}

/*
   update the barometer calibration
   this updates the baro ground calibration to the current values. It
   can be used before arming to keep the baro well calibrated
*/
void AP_Baro::update_calibration()
{
    const uint32_t now = AP_HAL::millis();
    const bool do_notify = now - _last_notify_ms > 10000;
    if (do_notify) {
        _last_notify_ms = now;
    }
    for (uint8_t i=0; i<_num_sensors; i++) {
        if (healthy(i)) {
            float corrected_pressure = get_sealevel_pressure(get_pressure(i) + sensors[i].p_correction);
            sensors[i].ground_pressure.set(corrected_pressure);
        }

        // don't notify the GCS too rapidly or we flood the link
        if (do_notify) {
            sensors[i].ground_pressure.notify();
        }
    }

    // always update the guessed ground temp
    _guessed_ground_temperature = get_external_temperature();

    // force EAS2TAS to recalculate
    _EAS2TAS = 0;
}

// return altitude difference in meters between current pressure and a
// given base_pressure in Pascal
float AP_Baro::get_altitude_difference(float base_pressure, float pressure) const
{
    float ret;
    float temp    = C_TO_KELVIN(get_ground_temperature());
    float scaling = pressure / base_pressure;

    // This is an exact calculation that is within +-2.5m of the standard
    // atmosphere tables in the troposphere (up to 11,000 m amsl).
    ret = 153.8462f * temp * (1.0f - expf(0.190259f * logf(scaling)))-_field_elevation_active;

    return ret;
}

// return sea level pressure where in which the current measured pressure
// at field elevation returns the same altitude under the
// 1976 standard atmospheric model
float AP_Baro::get_sealevel_pressure(float pressure) const
{
    float temp    = C_TO_KELVIN(get_ground_temperature());
    float p0_sealevel;
    // This is an exact calculation that is within +-2.5m of the standard
    // atmosphere tables in the troposphere (up to 11,000 m amsl).
    p0_sealevel = 8.651154799255761e30f*pressure*powF((769231.0f-(5000.0f*_field_elevation_active)/temp),-5.255993146184937f);

    return p0_sealevel;
}


// return current scale factor that converts from equivalent to true airspeed
// valid for altitudes up to 10km AMSL
// assumes standard atmosphere lapse rate
float AP_Baro::get_EAS2TAS(void)
{
    float altitude = get_altitude();
    if ((fabsf(altitude - _last_altitude_EAS2TAS) < 25.0f) && !is_zero(_EAS2TAS)) {
        // not enough change to require re-calculating
        return _EAS2TAS;
    }

    float pressure = get_pressure();
    if (is_zero(pressure)) {
        return 1.0f;
    }

    // only estimate lapse rate for the difference from the ground location
    // provides a more consistent reading then trying to estimate a complete
    // ISA model atmosphere
    float tempK = C_TO_KELVIN(get_ground_temperature()) - ISA_LAPSE_RATE * altitude;
    const float eas2tas_squared = SSL_AIR_DENSITY / (pressure / (ISA_GAS_CONSTANT * tempK));
    if (!is_positive(eas2tas_squared)) {
        return 1.0f;
    }
    _EAS2TAS = sqrtf(eas2tas_squared);
    _last_altitude_EAS2TAS = altitude;
    return _EAS2TAS;
}

// return air density / sea level density - decreases as altitude climbs
float AP_Baro::get_air_density_ratio(void)
{
    const float eas2tas = get_EAS2TAS();
    if (eas2tas > 0.0f) {
        return 1.0f/(sq(eas2tas));
    } else {
        return 1.0f;
    }
}

// return current climb_rate estimate 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)
{
    // we use a 7 point derivative filter on the climb rate. This seems
    // to produce somewhat reasonable results on real hardware
    return _climb_rate_filter.slope() * 1.0e3f;
}

// returns the ground temperature in degrees C, selecting either a user
// provided one, or the internal estimate
float AP_Baro::get_ground_temperature(void) const
{
    if (is_zero(_user_ground_temperature)) {
        return _guessed_ground_temperature;
    } else {
        return _user_ground_temperature;
    }
}


/*
  set external temperature to be used for calibration (degrees C)
 */
void AP_Baro::set_external_temperature(float temperature)
{
    _external_temperature = temperature;
    _last_external_temperature_ms = AP_HAL::millis();
}

/*
  get the temperature in degrees C to be used for calibration purposes
 */
float AP_Baro::get_external_temperature(const uint8_t instance) const
{
    // if we have a recent external temperature then use it
    if (_last_external_temperature_ms != 0 && AP_HAL::millis() - _last_external_temperature_ms < 10000) {
        return _external_temperature;
    }
    
#ifndef HAL_BUILD_AP_PERIPH
#if AP_AIRSPEED_ENABLED
    // if we don't have an external temperature then try to use temperature
    // from the airspeed sensor
    AP_Airspeed *airspeed = AP_Airspeed::get_singleton();
    if (airspeed != nullptr) {
        float temperature;
        if (airspeed->healthy() && airspeed->get_temperature(temperature)) {
            return temperature;
        }
    }
#endif
#endif
    
    // if we don't have an external temperature and airspeed temperature
    // then use the minimum of the barometer temperature and 35 degrees C.
    // The reason for not just using the baro temperature is it tends to read high,
    // often 30 degrees above the actual temperature. That means the
    // EAS2TAS tends to be off by quite a large margin, as well as
    // the calculation of altitude difference betweeen two pressures
    // reporting a high temperature will cause the aircraft to
    // estimate itself as flying higher then it actually is.
    return MIN(get_temperature(instance), INTERNAL_TEMPERATURE_CLAMP);
}


bool AP_Baro::_add_backend(AP_Baro_Backend *backend)
{
    if (!backend) {
        return false;
    }
    if (_num_drivers >= BARO_MAX_DRIVERS) {
        AP_HAL::panic("Too many barometer drivers");
    }
    drivers[_num_drivers++] = backend;
    return true;
}

/*
  wrapper around hal.i2c_mgr->get_device() that prevents duplicate devices being opened
 */
bool AP_Baro::_have_i2c_driver(uint8_t bus, uint8_t address) const
{
    for (int i=0; i<_num_drivers; ++i) {
        if (AP_HAL::Device::make_bus_id(AP_HAL::Device::BUS_TYPE_I2C, bus, address, 0) ==
            AP_HAL::Device::change_bus_id(uint32_t(sensors[i].bus_id.get()), 0)) {
            // device already has been defined.
            return true;
        }
    }
    return false;
}

/*
  macro to add a backend with check for too many sensors
 We don't try to start more than the maximum allowed
 */
#define ADD_BACKEND(backend) \
    do { _add_backend(backend);     \
       if (_num_drivers == BARO_MAX_DRIVERS || \
          _num_sensors == BARO_MAX_INSTANCES) { \
          return; \
       } \
    } while (0)

/*
  initialise the barometer object, loading backend drivers
 */
void AP_Baro::init(void)
{
    init_done = true;

    // always set field elvation to zero on reboot in the case user
    // fails to update.  TBD automate sanity checking error bounds on
    // on previously saved value at new location etc.
    if (!is_zero(_field_elevation)) {
        _field_elevation.set_and_save(0.0f);
        _field_elevation.notify();
    }

    // zero bus IDs before probing
    for (uint8_t i = 0; i < BARO_MAX_INSTANCES; i++) {
        sensors[i].bus_id.set(0);
    }

#if AP_SIM_BARO_ENABLED
    SITL::SIM *sitl = AP::sitl();
    if (sitl == nullptr) {
        AP_HAL::panic("No SITL pointer");
    }
#if !AP_TEST_DRONECAN_DRIVERS
    // use dronecan instances instead of SITL instances
    for(uint8_t i = 0; i < sitl->baro_count; i++) {
        ADD_BACKEND(new AP_Baro_SITL(*this));
    }
#endif
#endif

#if AP_BARO_UAVCAN_ENABLED
    // Detect UAVCAN Modules, try as many times as there are driver slots
    for (uint8_t i = 0; i < BARO_MAX_DRIVERS; i++) {
        ADD_BACKEND(AP_Baro_UAVCAN::probe(*this));
    }
#endif

#if AP_BARO_EXTERNALAHRS_ENABLED
    const int8_t serial_port = AP::externalAHRS().get_port(AP_ExternalAHRS::AvailableSensor::BARO);
    if (serial_port >= 0) {
        ADD_BACKEND(new AP_Baro_ExternalAHRS(*this, serial_port));
    }
#endif

// macro for use by HAL_INS_PROBE_LIST
#define GET_I2C_DEVICE(bus, address) _have_i2c_driver(bus, address)?nullptr:hal.i2c_mgr->get_device(bus, address)

#if AP_SIM_BARO_ENABLED
#if CONFIG_HAL_BOARD == HAL_BOARD_SITL && AP_BARO_MS56XX_ENABLED
    ADD_BACKEND(AP_Baro_MS56XX::probe(*this,
                                      std::move(GET_I2C_DEVICE(_ext_bus, HAL_BARO_MS5611_I2C_ADDR))));
#endif
    // do not probe for other drivers when using simulation:
    return;
#endif

#if defined(HAL_BARO_PROBE_LIST)
    // probe list from BARO lines in hwdef.dat
    HAL_BARO_PROBE_LIST;
#elif AP_FEATURE_BOARD_DETECT
    switch (AP_BoardConfig::get_board_type()) {
    case AP_BoardConfig::PX4_BOARD_PX4V1:
#if AP_BARO_MS56XX_ENABLED && defined(HAL_BARO_MS5611_I2C_BUS)
        ADD_BACKEND(AP_Baro_MS56XX::probe(*this,
                                          std::move(GET_I2C_DEVICE(HAL_BARO_MS5611_I2C_BUS, HAL_BARO_MS5611_I2C_ADDR))));
#endif
        break;

    case AP_BoardConfig::PX4_BOARD_PIXHAWK:
    case AP_BoardConfig::PX4_BOARD_PHMINI:
    case AP_BoardConfig::PX4_BOARD_AUAV21:
    case AP_BoardConfig::PX4_BOARD_PH2SLIM:
    case AP_BoardConfig::PX4_BOARD_PIXHAWK_PRO:
#if AP_BARO_MS56XX_ENABLED
        ADD_BACKEND(AP_Baro_MS56XX::probe(*this,
                                          std::move(hal.spi->get_device(HAL_BARO_MS5611_NAME))));
#endif
        break;

    case AP_BoardConfig::PX4_BOARD_PIXHAWK2:
    case AP_BoardConfig::PX4_BOARD_SP01:
#if AP_BARO_MS56XX_ENABLED
        ADD_BACKEND(AP_Baro_MS56XX::probe(*this,
                                          std::move(hal.spi->get_device(HAL_BARO_MS5611_SPI_EXT_NAME))));
        ADD_BACKEND(AP_Baro_MS56XX::probe(*this,
                                          std::move(hal.spi->get_device(HAL_BARO_MS5611_NAME))));
#endif
        break;

    case AP_BoardConfig::PX4_BOARD_MINDPXV2:
#if AP_BARO_MS56XX_ENABLED
        ADD_BACKEND(AP_Baro_MS56XX::probe(*this,
                                          std::move(hal.spi->get_device(HAL_BARO_MS5611_NAME))));
#endif
        break;

    case AP_BoardConfig::PX4_BOARD_AEROFC:
#if AP_BARO_MS56XX_ENABLED
#ifdef HAL_BARO_MS5607_I2C_BUS
        ADD_BACKEND(AP_Baro_MS56XX::probe(*this,
                                          std::move(GET_I2C_DEVICE(HAL_BARO_MS5607_I2C_BUS, HAL_BARO_MS5607_I2C_ADDR)),
                                          AP_Baro_MS56XX::BARO_MS5607));
#endif
#endif  // AP_BARO_MS56XX_ENABLED
        break;

    case AP_BoardConfig::VRX_BOARD_BRAIN54:
#if AP_BARO_MS56XX_ENABLED
        ADD_BACKEND(AP_Baro_MS56XX::probe(*this,
                                          std::move(hal.spi->get_device(HAL_BARO_MS5611_NAME))));
        ADD_BACKEND(AP_Baro_MS56XX::probe(*this,
                                          std::move(hal.spi->get_device(HAL_BARO_MS5611_SPI_EXT_NAME))));
#ifdef HAL_BARO_MS5611_SPI_IMU_NAME
        ADD_BACKEND(AP_Baro_MS56XX::probe(*this,
                                          std::move(hal.spi->get_device(HAL_BARO_MS5611_SPI_IMU_NAME))));
#endif
#endif  // AP_BARO_MS56XX_ENABLED
        break;

    case AP_BoardConfig::VRX_BOARD_BRAIN51:
    case AP_BoardConfig::VRX_BOARD_BRAIN52:
    case AP_BoardConfig::VRX_BOARD_BRAIN52E:
    case AP_BoardConfig::VRX_BOARD_CORE10:
    case AP_BoardConfig::VRX_BOARD_UBRAIN51:
    case AP_BoardConfig::VRX_BOARD_UBRAIN52:
#if AP_BARO_MS56XX_ENABLED
        ADD_BACKEND(AP_Baro_MS56XX::probe(*this,
                                          std::move(hal.spi->get_device(HAL_BARO_MS5611_NAME))));
#endif  // AP_BARO_MS56XX_ENABLED
        break;

    case AP_BoardConfig::PX4_BOARD_PCNC1:
#if AP_BARO_ICM20789_ENABLED
        ADD_BACKEND(AP_Baro_ICM20789::probe(*this,
                                            std::move(GET_I2C_DEVICE(1, 0x63)),
                                            std::move(hal.spi->get_device(HAL_INS_MPU60x0_NAME))));
#endif
        break;

    case AP_BoardConfig::PX4_BOARD_FMUV5:
    case AP_BoardConfig::PX4_BOARD_FMUV6:
#if AP_BARO_MS56XX_ENABLED
        ADD_BACKEND(AP_Baro_MS56XX::probe(*this,
                                          std::move(hal.spi->get_device(HAL_BARO_MS5611_NAME))));
#endif
        break;

    default:
        break;
    }
#elif HAL_BARO_DEFAULT == HAL_BARO_LPS25H_IMU_I2C
	ADD_BACKEND(AP_Baro_LPS2XH::probe_InvensenseIMU(*this,
                                                    std::move(GET_I2C_DEVICE(HAL_BARO_LPS25H_I2C_BUS, HAL_BARO_LPS25H_I2C_ADDR)),
                                                    HAL_BARO_LPS25H_I2C_IMU_ADDR));
#elif HAL_BARO_DEFAULT == HAL_BARO_20789_I2C_I2C
    ADD_BACKEND(AP_Baro_ICM20789::probe(*this,
                                        std::move(GET_I2C_DEVICE(HAL_BARO_20789_I2C_BUS, HAL_BARO_20789_I2C_ADDR_PRESS)),
                                        std::move(GET_I2C_DEVICE(HAL_BARO_20789_I2C_BUS, HAL_BARO_20789_I2C_ADDR_ICM))));
#elif HAL_BARO_DEFAULT == HAL_BARO_20789_I2C_SPI
    ADD_BACKEND(AP_Baro_ICM20789::probe(*this,
                                        std::move(GET_I2C_DEVICE(HAL_BARO_20789_I2C_BUS, HAL_BARO_20789_I2C_ADDR_PRESS)),
                                        std::move(hal.spi->get_device("icm20789"))));
#endif

    // can optionally have baro on I2C too
    if (_ext_bus >= 0) {
#if APM_BUILD_TYPE(APM_BUILD_ArduSub)
#if AP_BARO_MS56XX_ENABLED
        ADD_BACKEND(AP_Baro_MS56XX::probe(*this,
                                          std::move(GET_I2C_DEVICE(_ext_bus, HAL_BARO_MS5837_I2C_ADDR)), AP_Baro_MS56XX::BARO_MS5837));
#endif
#if AP_BARO_KELLERLD_ENABLED
        ADD_BACKEND(AP_Baro_KellerLD::probe(*this,
                                          std::move(GET_I2C_DEVICE(_ext_bus, HAL_BARO_KELLERLD_I2C_ADDR))));
#endif
#else
#if AP_BARO_MS56XX_ENABLED
        ADD_BACKEND(AP_Baro_MS56XX::probe(*this,
                                          std::move(GET_I2C_DEVICE(_ext_bus, HAL_BARO_MS5611_I2C_ADDR))));
#endif
#endif
    }

#ifdef HAL_PROBE_EXTERNAL_I2C_BAROS
    _probe_i2c_barometers();
#endif

#if AP_BARO_MSP_ENABLED
    if ((_baro_probe_ext.get() & PROBE_MSP) && msp_instance_mask == 0) {
        // allow for late addition of MSP sensor
        msp_instance_mask |= 1;
    }
    for (uint8_t i=0; i<8; i++) {
        if (msp_instance_mask & (1U<<i)) {
            ADD_BACKEND(new AP_Baro_MSP(*this, i));
        }
    }
#endif

#if !defined(HAL_BARO_ALLOW_INIT_NO_BARO) // most boards requires external baro
#if AP_SIM_BARO_ENABLED
    if (sitl->baro_count == 0) {
        return;
    }
#endif
    if (_num_drivers == 0 || _num_sensors == 0 || drivers[0] == nullptr) {
        AP_BoardConfig::config_error("Baro: unable to initialise driver");
    }
#endif
#ifdef HAL_BUILD_AP_PERIPH
    // AP_Periph always is set calibrated. We only want the pressure,
    // so ground calibration is unnecessary
    for (uint8_t i=0; i<_num_sensors; i++) {
        sensors[i].calibrated = true;
        sensors[i].alt_ok = true;
    }
#endif
}

/*
  probe all the i2c barometers enabled with BARO_PROBE_EXT. This is
  used on boards without a builtin barometer
 */
void AP_Baro::_probe_i2c_barometers(void)
{
    uint32_t probe = _baro_probe_ext.get();
    (void)probe;  // may be unused if most baros compiled out
    uint32_t mask = hal.i2c_mgr->get_bus_mask_external();
    if (AP_BoardConfig::get_board_type() == AP_BoardConfig::PX4_BOARD_PIXHAWK2) {
        // for the purpose of baro probing, treat CubeBlack internal i2c as external. It has
        // no internal i2c baros, so this is safe
        mask |= hal.i2c_mgr->get_bus_mask_internal();
    }
    // if the user has set BARO_EXT_BUS then probe the bus given by that parameter
    int8_t ext_bus = _ext_bus;
    if (ext_bus >= 0) {
        mask = 1U << (uint8_t)ext_bus;
    }

    static const struct BaroProbeSpec {
        uint32_t bit;
        AP_Baro_Backend* (*probefn)(AP_Baro&, AP_HAL::OwnPtr<AP_HAL::Device>);
        uint8_t addr;
    } baroprobespec[] {
#if AP_BARO_BMP085_ENABLED
        { PROBE_BMP085, AP_Baro_BMP085::probe, HAL_BARO_BMP085_I2C_ADDR },
#endif
#if AP_BARO_BMP280_ENABLED
        { PROBE_BMP280, AP_Baro_BMP280::probe, HAL_BARO_BMP280_I2C_ADDR },
        { PROBE_BMP280, AP_Baro_BMP280::probe, HAL_BARO_BMP280_I2C_ADDR2 },
#endif
#if AP_BARO_SPL06_ENABLED
        { PROBE_SPL06, AP_Baro_SPL06::probe, HAL_BARO_SPL06_I2C_ADDR },
        { PROBE_SPL06, AP_Baro_SPL06::probe, HAL_BARO_SPL06_I2C_ADDR2 },
#endif
#if AP_BARO_BMP388_ENABLED
        { PROBE_BMP388, AP_Baro_BMP388::probe, HAL_BARO_BMP388_I2C_ADDR },
        { PROBE_BMP388, AP_Baro_BMP388::probe, HAL_BARO_BMP388_I2C_ADDR2 },
#endif
#if AP_BARO_MS56XX_ENABLED
        { PROBE_MS5611, AP_Baro_MS56XX::probe_5611, HAL_BARO_MS5611_I2C_ADDR },
        { PROBE_MS5611, AP_Baro_MS56XX::probe_5611, HAL_BARO_MS5611_I2C_ADDR2 },
        { PROBE_MS5607, AP_Baro_MS56XX::probe_5607, HAL_BARO_MS5607_I2C_ADDR },
        { PROBE_MS5637, AP_Baro_MS56XX::probe_5637, HAL_BARO_MS5637_I2C_ADDR },
#endif
#if AP_BARO_FBM320_ENABLED
        { PROBE_FBM320, AP_Baro_FBM320::probe, HAL_BARO_FBM320_I2C_ADDR },
        { PROBE_FBM320, AP_Baro_FBM320::probe, HAL_BARO_FBM320_I2C_ADDR2 },
#endif
#if AP_BARO_DPS280_ENABLED
        { PROBE_DPS280, AP_Baro_DPS280::probe_280, HAL_BARO_DPS280_I2C_ADDR },
        { PROBE_DPS280, AP_Baro_DPS280::probe_280, HAL_BARO_DPS280_I2C_ADDR2 },
#endif
#if AP_BARO_LPS2XH_ENABLED
        { PROBE_LPS25H, AP_Baro_LPS2XH::probe, HAL_BARO_LPS25H_I2C_ADDR },
#endif

#if APM_BUILD_TYPE(APM_BUILD_ArduSub)
#if AP_BARO_KELLERLD_ENABLED
        { PROBE_KELLER, AP_Baro_KellerLD::probe, HAL_BARO_KELLERLD_I2C_ADDR },
#endif
#if AP_BARO_MS56XX_ENABLED
        { PROBE_MS5837, AP_Baro_MS56XX::probe_5837, HAL_BARO_MS5837_I2C_ADDR },
#endif
#endif  // APM_BUILD_TYPE(APM_BUILD_ArduSub)
    };

    for (const auto &spec : baroprobespec) {
        if (!(probe & spec.bit)) {
            // not in mask to be probed for
            continue;
        }
        FOREACH_I2C_MASK(i, mask) {
            ADD_BACKEND(spec.probefn(*this, std::move(GET_I2C_DEVICE(i, spec.addr))));
        }
    }
}

bool AP_Baro::should_log() const
{
    AP_Logger *logger = AP_Logger::get_singleton();
    if (logger == nullptr) {
        return false;
    }
    if (_log_baro_bit == (uint32_t)-1) {
        return false;
    }
    if (!logger->should_log(_log_baro_bit)) {
        return false;
    }
    return true;
}

/*
  call update on all drivers
 */
void AP_Baro::update(void)
{
    WITH_SEMAPHORE(_rsem);

    if (fabsf(_alt_offset - _alt_offset_active) > 0.01f) {
        // If there's more than 1cm difference then slowly slew to it via LPF.
        // The EKF does not like step inputs so this keeps it happy.
        _alt_offset_active = (0.95f*_alt_offset_active) + (0.05f*_alt_offset);
    } else {
        _alt_offset_active = _alt_offset;
    }

#if HAL_LOGGING_ENABLED
    bool old_primary_healthy = sensors[_primary].healthy;
#endif

    for (uint8_t i=0; i<_num_drivers; i++) {
        drivers[i]->backend_update(i);
    }

    for (uint8_t i=0; i<_num_sensors; i++) {
        if (sensors[i].healthy) {
            // update altitude calculation
            float ground_pressure = sensors[i].ground_pressure;
            if (!is_positive(ground_pressure) || isnan(ground_pressure) || isinf(ground_pressure)) {
                sensors[i].ground_pressure.set(sensors[i].pressure);
            }
            float altitude = sensors[i].altitude;
            float corrected_pressure = sensors[i].pressure + sensors[i].p_correction;
            if (sensors[i].type == BARO_TYPE_AIR) {
#if HAL_BARO_WIND_COMP_ENABLED
                corrected_pressure -= wind_pressure_correction(i);
#endif
                altitude = get_altitude_difference(sensors[i].ground_pressure, corrected_pressure);
            } else if (sensors[i].type == BARO_TYPE_WATER) {
                //101325Pa is sea level air pressure, 9800 Pascal/ m depth in water.
                //No temperature or depth compensation for density of water.
                altitude = (sensors[i].ground_pressure - corrected_pressure) / 9800.0f / _specific_gravity;
            }
            // sanity check altitude
            sensors[i].alt_ok = !(isnan(altitude) || isinf(altitude));
            if (sensors[i].alt_ok) {
                sensors[i].altitude = altitude + _alt_offset_active;
            }
        }
    }

    // ensure the climb rate filter is updated
    if (healthy()) {
        _climb_rate_filter.update(get_altitude(), get_last_update());
    }

    // choose primary sensor
    if (_primary_baro >= 0 && _primary_baro < _num_sensors && healthy(_primary_baro)) {
        _primary = _primary_baro;
    } else {
        _primary = 0;
        for (uint8_t i=0; i<_num_sensors; i++) {
            if (healthy(i)) {
                _primary = i;
                break;
            }
        }
    }
#ifndef HAL_BUILD_AP_PERIPH
    update_field_elevation();
#endif

    // logging
#if HAL_LOGGING_ENABLED
    if (should_log()) {
        Write_Baro();
    }

#define MASK_LOG_ANY                    0xFFFF

    // log sensor healthy state change:
    if (sensors[_primary].healthy != old_primary_healthy) {
        if (AP::logger().should_log(MASK_LOG_ANY)) {
            const LogErrorCode code = sensors[_primary].healthy ? LogErrorCode::ERROR_RESOLVED : LogErrorCode::UNHEALTHY;
            AP::logger().Write_Error(LogErrorSubsystem::BARO, code);
        }
    }
#endif
}

/*
  update field elevation value
 */
void AP_Baro::update_field_elevation(void)
{
    const uint32_t now_ms = AP_HAL::millis();
    bool new_field_elev = false;
    const bool armed = hal.util->get_soft_armed();
    if (now_ms - _field_elevation_last_ms >= 1000) {
        if (is_zero(_field_elevation_active) &&
            is_zero(_field_elevation)) {
            // auto-set based on origin
            Location origin;
            if (!armed && AP::ahrs().get_origin(origin)) {
                _field_elevation_active = origin.alt * 0.01;
                new_field_elev = true;
            }
        } else if (fabsf(_field_elevation_active-_field_elevation) > 1.0 &&
                   !is_zero(_field_elevation)) {
            // user has set field elevation
            if (!armed) {
                _field_elevation_active = _field_elevation;
                new_field_elev = true;
            } else {
                _field_elevation.set(_field_elevation_active);
                _field_elevation.notify();
                BARO_SEND_TEXT(MAV_SEVERITY_ALERT, "Failed to Set Field Elevation: Armed");
            }
        }
    }
    if (new_field_elev && !armed) {
        _field_elevation_last_ms = now_ms;
        AP::ahrs().resetHeightDatum();
        update_calibration();
        BARO_SEND_TEXT(MAV_SEVERITY_INFO, "Field Elevation Set: %.0fm", _field_elevation_active);
    }
}

/*
  call accumulate on all drivers
 */
void AP_Baro::accumulate(void)
{
    for (uint8_t i=0; i<_num_drivers; i++) {
        drivers[i]->accumulate();
    }
}


/* register a new sensor, claiming a sensor slot. If we are out of
   slots it will panic
*/
uint8_t AP_Baro::register_sensor(void)
{
    if (_num_sensors >= BARO_MAX_INSTANCES) {
        AP_HAL::panic("Too many barometers");
    }
    return _num_sensors++;
}


/*
  check if all barometers are healthy
 */
bool AP_Baro::all_healthy(void) const
{
     for (uint8_t i=0; i<_num_sensors; i++) {
         if (!healthy(i)) {
             return false;
         }
     }
     return _num_sensors > 0;
}

// set a pressure correction from AP_TempCalibration
void AP_Baro::set_pressure_correction(uint8_t instance, float p_correction)
{
    if (instance < _num_sensors) {
        sensors[instance].p_correction = p_correction;
    }
}

#if AP_BARO_MSP_ENABLED
/*
  handle MSP barometer data
 */
void AP_Baro::handle_msp(const MSP::msp_baro_data_message_t &pkt)
{
    if (pkt.instance > 7) {
        return;
    }
    if (!init_done) {
        msp_instance_mask |= 1U<<pkt.instance;
    } else if (msp_instance_mask != 0) {
        for (uint8_t i=0; i<_num_drivers; i++) {
            drivers[i]->handle_msp(pkt);
        }
    }
}
#endif

#if AP_BARO_EXTERNALAHRS_ENABLED
/*
  handle ExternalAHRS barometer data
 */
void AP_Baro::handle_external(const AP_ExternalAHRS::baro_data_message_t &pkt)
{
    for (uint8_t i=0; i<_num_drivers; i++) {
        drivers[i]->handle_external(pkt);
    }
}
#endif  // AP_BARO_EXTERNALAHRS_ENABLED

// returns false if we fail arming checks, in which case the buffer will be populated with a failure message
bool AP_Baro::arming_checks(size_t buflen, char *buffer) const
{
    if (!all_healthy()) {
        hal.util->snprintf(buffer, buflen, "not healthy");
        return false;
    }

#if APM_BUILD_COPTER_OR_HELI || APM_BUILD_TYPE(APM_BUILD_ArduPlane)
    /*
      check for a pressure altitude discrepancy between GPS alt and
      baro alt this catches bad barometers, such as when a MS5607 has
      been substituted for a MS5611
     */
    const auto &gps = AP::gps();
    if (_alt_error_max > 0 && gps.status() >= AP_GPS::GPS_Status::GPS_OK_FIX_3D) {
        const float alt_amsl = gps.location().alt*0.01;
        // note the addition of _field_elevation_active as this is subtracted in get_altitude_difference()
        const float alt_pressure = get_altitude_difference(SSL_AIR_PRESSURE, get_pressure()) + _field_elevation_active;
        const float error = fabsf(alt_amsl - alt_pressure);
        if (error > _alt_error_max) {
            hal.util->snprintf(buffer, buflen, "GPS alt error %.0fm (see BARO_ALTERR_MAX)", error);
            return false;
        }
    }
#endif
    return true;
}

namespace AP {

AP_Baro &baro()
{
    return *AP_Baro::get_singleton();
}

};