ardupilot/libraries/AP_Baro/AP_Baro_BMP280.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/>.
 */
#include "AP_Baro_BMP280.h"

#include <utility>

extern const AP_HAL::HAL &hal;

#define BMP280_MODE_SLEEP  0
#define BMP280_MODE_FORCED 1
#define BMP280_MODE_NORMAL 3
#define BMP280_MODE BMP280_MODE_NORMAL

#define BMP280_OVERSAMPLING_1  1
#define BMP280_OVERSAMPLING_2  2
#define BMP280_OVERSAMPLING_4  3
#define BMP280_OVERSAMPLING_8  4
#define BMP280_OVERSAMPLING_16 5
#define BMP280_OVERSAMPLING_P BMP280_OVERSAMPLING_16
#define BMP280_OVERSAMPLING_T BMP280_OVERSAMPLING_2

#define BMP280_FILTER_COEFFICIENT 2

#define BMP280_ID            0x58

#define BMP280_REG_CALIB     0x88
#define BMP280_REG_ID        0xD0
#define BMP280_REG_RESET     0xE0
#define BMP280_REG_STATUS    0xF3
#define BMP280_REG_CTRL_MEAS 0xF4
#define BMP280_REG_CONFIG    0xF5
#define BMP280_REG_DATA      0xF7

AP_Baro_BMP280::AP_Baro_BMP280(AP_Baro &baro, AP_HAL::OwnPtr<AP_HAL::Device> dev)
    : AP_Baro_Backend(baro)
    , _dev(std::move(dev))
{
}

AP_Baro_Backend *AP_Baro_BMP280::probe(AP_Baro &baro,
                                       AP_HAL::OwnPtr<AP_HAL::Device> dev)
{
    if (!dev) {
        return nullptr;
    }

    AP_Baro_BMP280 *sensor = new AP_Baro_BMP280(baro, std::move(dev));
    if (!sensor || !sensor->_init()) {
        delete sensor;
        return nullptr;
    }
    return sensor;
}

bool AP_Baro_BMP280::_init()
{
    if (!_dev | !_dev->get_semaphore()->take(HAL_SEMAPHORE_BLOCK_FOREVER)) {
        return false;
    }

    _has_sample = false;

    _dev->set_speed(AP_HAL::Device::SPEED_HIGH);

    uint8_t whoami;
    if (!_dev->read_registers(BMP280_REG_ID, &whoami, 1)  ||
        whoami != BMP280_ID) {
        // not a BMP280
        _dev->get_semaphore()->give();
        return false;
    }

    // read the calibration data
    uint8_t buf[24];
    _dev->read_registers(BMP280_REG_CALIB, buf, sizeof(buf));

    _t1 = ((int16_t)buf[1] << 8) | buf[0];
    _t2 = ((int16_t)buf[3] << 8) | buf[2];
    _t3 = ((int16_t)buf[5] << 8) | buf[4];
    _p1 = ((int16_t)buf[7] << 8) | buf[6];
    _p2 = ((int16_t)buf[9] << 8) | buf[8];
    _p3 = ((int16_t)buf[11] << 8) | buf[10];
    _p4 = ((int16_t)buf[13] << 8) | buf[12];
    _p5 = ((int16_t)buf[15] << 8) | buf[14];
    _p6 = ((int16_t)buf[17] << 8) | buf[16];
    _p7 = ((int16_t)buf[19] << 8) | buf[18];
    _p8 = ((int16_t)buf[21] << 8) | buf[20];
    _p9 = ((int16_t)buf[23] << 8) | buf[22];

    // SPI write needs bit mask
    uint8_t mask = 0xFF;
    if (_dev->bus_type() == AP_HAL::Device::BUS_TYPE_SPI) {
        mask = 0x7F;
    }

    _dev->write_register((BMP280_REG_CTRL_MEAS & mask), (BMP280_OVERSAMPLING_T << 5) |
                         (BMP280_OVERSAMPLING_P << 2) | BMP280_MODE);

    _dev->write_register((BMP280_REG_CONFIG & mask), BMP280_FILTER_COEFFICIENT << 2);

    _instance = _frontend.register_sensor();

    _dev->get_semaphore()->give();

    // request 50Hz update
    _dev->register_periodic_callback(20 * AP_USEC_PER_MSEC, FUNCTOR_BIND_MEMBER(&AP_Baro_BMP280::_timer, void));

    return true;
}



//  acumulate a new sensor reading
void AP_Baro_BMP280::_timer(void)
{
    uint8_t buf[6];

    _dev->read_registers(BMP280_REG_DATA, buf, sizeof(buf));

    _update_temperature((buf[3] << 12) | (buf[4] << 4) | (buf[5] >> 4));
    _update_pressure((buf[0] << 12) | (buf[1] << 4) | (buf[2] >> 4));
}

// transfer data to the frontend
void AP_Baro_BMP280::update(void)
{
    if (_sem->take_nonblocking()) {
        if (!_has_sample) {
            _sem->give();
            return;
        }

        _copy_to_frontend(_instance, _pressure, _temperature);
        _has_sample = false;
        _sem->give();
    }
}

// calculate temperature
void AP_Baro_BMP280::_update_temperature(int32_t temp_raw)
{
    int32_t var1, var2, t;

    // according to datasheet page 22
    var1 = ((((temp_raw >> 3) - ((int32_t)_t1 << 1))) * ((int32_t)_t2)) >> 11;
    var2 = (((((temp_raw >> 4) - ((int32_t)_t1)) * ((temp_raw >> 4) - ((int32_t)_t1))) >> 12) * ((int32_t)_t3)) >> 14;
    _t_fine = var1 + var2;
    t = (_t_fine * 5 + 128) >> 8;
    if (_sem->take(HAL_SEMAPHORE_BLOCK_FOREVER)) {
        _temperature = ((float)t) / 100;
        _sem->give();
    }
}

// calculate pressure
void AP_Baro_BMP280::_update_pressure(int32_t press_raw)
{
    int64_t var1, var2, p;

    // according to datasheet page 22
    var1 = ((int64_t)_t_fine) - 128000;
    var2 = var1 * var1 * (int64_t)_p6;
    var2 = var2 + ((var1 * (int64_t)_p5) << 17);
    var2 = var2 + (((int64_t)_p4) << 35);
    var1 = ((var1 * var1 * (int64_t)_p3) >> 8) + ((var1 * (int64_t)_p2) << 12);
    var1 = (((((int64_t)1) << 47) + var1)) * ((int64_t)_p1) >> 33;

    if (var1 == 0) {
        return;
    }

    p = 1048576 - press_raw;
    p = (((p << 31) - var2) * 3125) / var1;
    var1 = (((int64_t)_p9) * (p >> 13) * (p >> 13)) >> 25;
    var2 = (((int64_t)_p8) * p) >> 19;
    p = ((p + var1 + var2) >> 8) + (((int64_t)_p7) << 4);

    if (_sem->take(HAL_SEMAPHORE_BLOCK_FOREVER)) {
        _pressure = (float)p / 25600;
        _has_sample = true;
        _sem->give();
    }
}