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 <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_Baro_BMP085.h"
#include "AP_Baro_HIL.h"
#include "AP_Baro_MS5611.h"
#include "AP_Baro_PX4.h"
#include "AP_Baro_qflight.h"
#include "AP_Baro_QURT.h"

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

    // @Param: ABS_PRESS
    // @DisplayName: Absolute Pressure
    // @Description: calibrated ground pressure in Pascals
    // @Units: pascals
    // @Increment: 1
    // @ReadOnly: True
    // @Volatile: True
    // @User: Advanced
    AP_GROUPINFO("ABS_PRESS", 2, AP_Baro, sensors[0].ground_pressure, 0),

    // @Param: TEMP
    // @DisplayName: ground temperature
    // @Description: calibrated ground temperature in degrees Celsius
    // @Units: degrees celsius
    // @Increment: 1
    // @ReadOnly: True
    // @Volatile: True
    // @User: Advanced
    AP_GROUPINFO("TEMP", 3, AP_Baro, sensors[0].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: meters
    // @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),

    // @Param: EXT_BUS
    // @DisplayName: External baro bus
    // @Description: This selects the bus number for looking for an I2C barometer
    // @Values: -1:Disabled,0:Bus0:1:Bus1
    // @User: Advanced
    AP_GROUPINFO("EXT_BUS", 7, AP_Baro, _ext_bus, -1),
    
    AP_GROUPEND
};

/*
  AP_Baro constructor
 */
AP_Baro::AP_Baro()
{
    AP_Param::setup_object_defaults(this, var_info);
}

// calibrate the barometer. This must be called at least once before
// the altitude() or climb_rate() interfaces can be used
void AP_Baro::calibrate()
{
    // reset the altitude offset when we calibrate. The altitude
    // offset is supposed to be for within a flight
    _alt_offset.set_and_save(0);

    // 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;
    }

    // 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_HAL::panic("PANIC: AP_Baro::read unsuccessful "
                        "for more than 500ms in AP_Baro::calibrate [2]\r\n");
            }
            hal.scheduler->delay(10);
        } while (!healthy());
        hal.scheduler->delay(100);
    }

    // now average over 5 values for the ground pressure and
    // temperature settings
    float sum_pressure[BARO_MAX_INSTANCES] = {0};
    float sum_temperature[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_HAL::panic("PANIC: AP_Baro::read unsuccessful "
                        "for more than 500ms in AP_Baro::calibrate [3]\r\n");
            }
        } while (!healthy());
        for (uint8_t i=0; i<_num_sensors; i++) {
            if (healthy(i)) {
                sum_pressure[i] += sensors[i].pressure;
                sum_temperature[i] += sensors[i].temperature;
                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 {
            sensors[i].ground_pressure.set_and_save(sum_pressure[i] / count[i]);
            sensors[i].ground_temperature.set_and_save(sum_temperature[i] / count[i]);
        }
    }

    // panic if all sensors are not calibrated
    for (uint8_t i=0; i<_num_sensors; i++) {
        if (sensors[i].calibrated) {
            return;
        }
    }
    AP_HAL::panic("AP_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()
{
    for (uint8_t i=0; i<_num_sensors; i++) {
        if (healthy(i)) {
            sensors[i].ground_pressure.set(get_pressure(i));
        }
        float last_temperature = sensors[i].ground_temperature;
        sensors[i].ground_temperature.set(get_calibration_temperature(i));

        // don't notify the GCS too rapidly or we flood the link
        uint32_t now = AP_HAL::millis();
        if (now - _last_notify_ms > 10000) {
            sensors[i].ground_pressure.notify();
            sensors[i].ground_temperature.notify();
            _last_notify_ms = now;
        }
        if (fabsf(last_temperature - sensors[i].ground_temperature) > 3) {
            // reset _EAS2TAS to force it to recalculate. This happens
            // when a digital airspeed sensor comes online
            _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    = get_ground_temperature() + 273.15f;
    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)));

    return ret;
}


// 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) < 100.0f) && !is_zero(_EAS2TAS)) {
        // not enough change to require re-calculating
        return _EAS2TAS;
    }

    float tempK = get_calibration_temperature() + 273.15f - 0.0065f * altitude;
    _EAS2TAS = safe_sqrt(1.225f / ((float)get_pressure() / (287.26f * tempK)));
    _last_altitude_EAS2TAS = altitude;
    return _EAS2TAS;
}

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

// 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 (_hil.have_alt) {
        return _hil.climb_rate;
    }
    // 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;
}


/*
  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_calibration_temperature(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;
    }
    // if we don't have an external temperature then use the minimum
    // of the barometer temperature and 25 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
    float ret = get_temperature(instance);
    if (ret > 25) {
        ret = 25;
    }
    return ret;
}


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;
}

/*
  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)
{
    if (_hil_mode) {
        drivers[0] = new AP_Baro_HIL(*this);
        _num_drivers = 1;
        return;
    }

#if HAL_BARO_DEFAULT == HAL_BARO_PX4 || HAL_BARO_DEFAULT == HAL_BARO_VRBRAIN
    switch (AP_BoardConfig::get_board_type()) {
    case AP_BoardConfig::PX4_BOARD_PX4V1:
#ifdef HAL_BARO_MS5611_I2C_BUS
        ADD_BACKEND(AP_Baro_MS56XX::probe(*this,
                                          std::move(hal.i2c_mgr->get_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_PH2SLIM:
        ADD_BACKEND(AP_Baro_MS56XX::probe(*this,
                                          std::move(hal.spi->get_device(HAL_BARO_MS5611_NAME))));
        break;

    case AP_BoardConfig::PX4_BOARD_PIXHAWK2:
        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))));
        break;

    case AP_BoardConfig::PX4_BOARD_PIXRACER:
        ADD_BACKEND(AP_Baro_MS56XX::probe(*this,
                                          std::move(hal.spi->get_device(HAL_BARO_MS5611_SPI_INT_NAME))));
        break;

    default:
        drivers[0] = new AP_Baro_PX4(*this);
        _num_drivers = 1;
        break;
    }
#elif HAL_BARO_DEFAULT == HAL_BARO_HIL
    drivers[0] = new AP_Baro_HIL(*this);
    _num_drivers = 1;
#elif HAL_BARO_DEFAULT == HAL_BARO_BMP085
    drivers[0] = new AP_Baro_BMP085(*this,
        std::move(hal.i2c_mgr->get_device(HAL_BARO_BMP085_BUS, HAL_BARO_BMP085_I2C_ADDR)));
    _num_drivers = 1;
#elif HAL_BARO_DEFAULT == HAL_BARO_MS5611_I2C
    ADD_BACKEND(AP_Baro_MS56XX::probe(*this,
                                      std::move(hal.i2c_mgr->get_device(HAL_BARO_MS5611_I2C_BUS, HAL_BARO_MS5611_I2C_ADDR))));
#elif HAL_BARO_DEFAULT == HAL_BARO_MS5611_SPI
    ADD_BACKEND(AP_Baro_MS56XX::probe(*this,
                                      std::move(hal.spi->get_device(HAL_BARO_MS5611_NAME))));
#elif HAL_BARO_DEFAULT == HAL_BARO_MS5607_I2C
    ADD_BACKEND(AP_Baro_MS56XX::probe(*this,
                                      std::move(hal.i2c_mgr->get_device(HAL_BARO_MS5607_I2C_BUS, HAL_BARO_MS5607_I2C_ADDR)),
                                      AP_Baro_MS56XX::BARO_MS5607));
#elif HAL_BARO_DEFAULT == HAL_BARO_MS5637_I2C
    ADD_BACKEND(AP_Baro_MS56XX::probe(*this,
                                      std::move(hal.i2c_mgr->get_device(HAL_BARO_MS5637_I2C_BUS, HAL_BARO_MS5637_I2C_ADDR)),
                                      AP_Baro_MS56XX::BARO_MS5637));
#elif HAL_BARO_DEFAULT == HAL_BARO_QFLIGHT
    drivers[0] = new AP_Baro_QFLIGHT(*this);
    _num_drivers = 1;
#elif HAL_BARO_DEFAULT == HAL_BARO_QURT
    drivers[0] = new AP_Baro_QURT(*this);
    _num_drivers = 1;
#endif

    // can optionally have baro on I2C too
    if (_ext_bus >= 0) {
        ADD_BACKEND(AP_Baro_MS56XX::probe(*this,
                                          std::move(hal.i2c_mgr->get_device(_ext_bus, HAL_BARO_MS5611_I2C_ADDR))));
    }
    
    if (_num_drivers == 0 || _num_sensors == 0 || drivers[0] == nullptr) {
        AP_HAL::panic("Baro: unable to initialise driver");
    }
}


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

    // consider a sensor as healthy if it has had an update in the
    // last 0.5 seconds
    uint32_t now = AP_HAL::millis();
    for (uint8_t i=0; i<_num_sensors; i++) {
        sensors[i].healthy = (now - sensors[i].last_update_ms < 500) && !is_zero(sensors[i].pressure);
    }

    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_zero(ground_pressure) || isnan(ground_pressure) || isinf(ground_pressure)) {
                sensors[i].ground_pressure = sensors[i].pressure;
            }
            float altitude = get_altitude_difference(sensors[i].ground_pressure, sensors[i].pressure);
            // sanity check altitude
            sensors[i].alt_ok = !(isnan(altitude) || isinf(altitude));
            if (sensors[i].alt_ok) {
                sensors[i].altitude = altitude + _alt_offset_active;
            }
        }
        if (_hil.have_alt) {
            sensors[0].altitude = _hil.altitude;
        }
        if (_hil.have_last_update) {
            sensors[0].last_update_ms = _hil.last_update_ms;
        }
    }

    // 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;
            }
        }
    }
}

/*
  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;
}