path: root/src/driver/bme280.cc

/*
 *          /\
 *         /  \
 *        / !! \
 *       /______\
 *
 * In order to use the I2C interface, CSB needs to be pulled up before turning
 * on VDDIO (and after VDD). On most BME280 breakout boards sold on
 * AliExpress and similar sites, VDD and VDDIO are connected and there is only
 * one external VCC input, so following the power sequence outlined in the
 * datasheet is not possible. Additionally, the pull-up resistor connecting
 * CSB to VCC may delay logic high level on CSB long enough for the BM280
 * to start in SPI mode.
 *
 * In this case, you should connect (or power up, when using GPIO power)
 * breakout board pins in the following order:
 * * GND, SDA, SCLD
 * * CSB to 3V3
 * * VDD to 3V3
 */

/**\mainpage
 * Copyright (C) 2018 - 2019 Bosch Sensortec GmbH
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *
 * Redistributions in binary form must reproduce the above copyright
 * notice, this list of conditions and the following disclaimer in the
 * documentation and/or other materials provided with the distribution.
 *
 * Neither the name of the copyright holder nor the names of the
 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
 * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL COPYRIGHT HOLDER
 * OR CONTRIBUTORS BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
 * OR CONSEQUENTIAL DAMAGES(INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE
 *
 * The information provided is believed to be accurate and reliable.
 * The copyright holder assumes no responsibility
 * for the consequences of use
 * of such information nor for any infringement of patents or
 * other rights of third parties which may result from its use.
 * No license is granted by implication or otherwise under any patent or
 * patent rights of the copyright holder.
 *
 * File     bme280.c
 * Date     26 Aug 2019
 * Version  3.3.7
 *
 */

/*! @file bme280.c
 * @brief Sensor driver for BME280 sensor
 */
#include "driver/bme280.h"

/**\name Internal macros */
/* To identify osr settings selected by user */
#define OVERSAMPLING_SETTINGS   UINT8_C(0x07)

/* To identify filter and standby settings selected by user */
#define FILTER_STANDBY_SETTINGS UINT8_C(0x18)


/****************** Global Function Definitions *******************************/

/*!
 *  @brief This API is the entry point.
 *  It reads the chip-id and calibration data from the sensor.
 */
int8_t BME280::init()
{
    int8_t rslt;

    /* chip id read try count */
    uint8_t try_count = 5;
    uint8_t chip_id = 0;

    /* Check for null pointer in the device structure*/
    rslt = null_ptr_check();

    /* Proceed if null check is fine */
    if (rslt == BME280_OK)
    {
        while (try_count)
        {
            /* Read the chip-id of bme280 sensor */
            rslt = get_regs(BME280_CHIP_ID_ADDR, &chip_id, 1);

            /* Check for chip id validity */
            if ((rslt == BME280_OK) && (chip_id == BME280_CHIP_ID))
            {
                /* Reset the sensor */
                rslt = soft_reset();
                if (rslt == BME280_OK)
                {
                    /* Read the calibration data */
                    rslt = get_calib_data();
                }
                break;
            }

            /* Wait for 1 ms */
            delay_ms(1);
            --try_count;
        }

        /* Chip id check failed */
        if (!try_count)
        {
            rslt = BME280_E_DEV_NOT_FOUND;
        }
    }

    return rslt;
}

/*!
 * @brief This API reads the data from the given register address of the sensor.
 */
int8_t BME280::get_regs(uint8_t reg_addr, uint8_t *reg_data, uint16_t len)
{
    int8_t rslt;

    /* Check for null pointer in the device structure*/
    rslt = null_ptr_check();

    /* Proceed if null check is fine */
    if (rslt == BME280_OK)
    {
        /* If interface selected is SPI */
        if (intf != BME280_I2C_INTF)
        {
            reg_addr = reg_addr | 0x80;
        }

        /* Read the data  */
        rslt = read(dev_id, reg_addr, reg_data, len);

        /* Check for communication error */
        if (rslt != BME280_OK)
        {
            rslt = BME280_E_COMM_FAIL;
        }
    }

    return rslt;
}

/*!
 * @brief This API writes the given data to the register address
 * of the sensor.
 */
int8_t BME280::set_regs(uint8_t *reg_addr, const uint8_t *reg_data, uint8_t len)
{
    int8_t rslt;
    uint8_t temp_buff[20]; /* Typically not to write more than 10 registers */

    if (len > 10)
    {
        len = 10;
    }
    uint16_t temp_len;
    uint8_t reg_addr_cnt;

    /* Check for null pointer in the device structure*/
    rslt = null_ptr_check();

    /* Check for arguments validity */
    if ((rslt == BME280_OK) && (reg_addr != NULL) && (reg_data != NULL))
    {
        if (len != 0)
        {
            temp_buff[0] = reg_data[0];

            /* If interface selected is SPI */
            if (intf != BME280_I2C_INTF)
            {
                for (reg_addr_cnt = 0; reg_addr_cnt < len; reg_addr_cnt++)
                {
                    reg_addr[reg_addr_cnt] = reg_addr[reg_addr_cnt] & 0x7F;
                }
            }

            /* Burst write mode */
            if (len > 1)
            {
                /* Interleave register address w.r.t data for
                 * burst write
                 */
                interleave_reg_addr(reg_addr, temp_buff, reg_data, len);
                temp_len = ((len * 2) - 1);
            }
            else
            {
                temp_len = len;
            }
            rslt = write(dev_id, reg_addr[0], temp_buff, temp_len);

            /* Check for communication error */
            if (rslt != BME280_OK)
            {
                rslt = BME280_E_COMM_FAIL;
            }
        }
        else
        {
            rslt = BME280_E_INVALID_LEN;
        }
    }
    else
    {
        rslt = BME280_E_NULL_PTR;
    }

    return rslt;
}

/*!
 * @brief This API sets the oversampling, filter and standby duration
 * (normal mode) settings in the sensor.
 */
int8_t BME280::set_sensor_settings(uint8_t desired_settings)
{
    int8_t rslt;
    uint8_t sensor_mode;

    /* Check for null pointer in the device structure*/
    rslt = null_ptr_check();

    /* Proceed if null check is fine */
    if (rslt == BME280_OK)
    {
        rslt = get_sensor_mode(&sensor_mode);
        if ((rslt == BME280_OK) && (sensor_mode != BME280_SLEEP_MODE))
        {
            rslt = put_device_to_sleep();
        }
        if (rslt == BME280_OK)
        {
            /* Check if user wants to change oversampling
             * settings
             */
            if (are_settings_changed(OVERSAMPLING_SETTINGS, desired_settings))
            {
                rslt = set_osr_settings(desired_settings, &settings);
            }

            /* Check if user wants to change filter and/or
             * standby settings
             */
            if ((rslt == BME280_OK) && are_settings_changed(FILTER_STANDBY_SETTINGS, desired_settings))
            {
                rslt = set_filter_standby_settings(desired_settings, &settings);
            }
        }
    }

    return rslt;
}

/*!
 * @brief This API gets the oversampling, filter and standby duration
 * (normal mode) settings from the sensor.
 */
int8_t BME280::get_sensor_settings()
{
    int8_t rslt;
    uint8_t reg_data[4];

    /* Check for null pointer in the device structure*/
    rslt = null_ptr_check();

    /* Proceed if null check is fine */
    if (rslt == BME280_OK)
    {
        rslt = get_regs(BME280_CTRL_HUM_ADDR, reg_data, 4);
        if (rslt == BME280_OK)
        {
            parse_device_settings(reg_data, &settings);
        }
    }

    return rslt;
}

/*!
 * @brief This API sets the power mode of the sensor.
 */
int8_t BME280::set_sensor_mode(uint8_t sensor_mode)
{
    int8_t rslt;
    uint8_t last_set_mode;

    /* Check for null pointer in the device structure*/
    rslt = null_ptr_check();
    if (rslt == BME280_OK)
    {
        rslt = get_sensor_mode(&last_set_mode);

        /* If the sensor is not in sleep mode put the device to sleep
         * mode
         */
        if ((rslt == BME280_OK) && (last_set_mode != BME280_SLEEP_MODE))
        {
            rslt = put_device_to_sleep();
        }

        /* Set the power mode */
        if (rslt == BME280_OK)
        {
            rslt = write_power_mode(sensor_mode);
        }
    }

    return rslt;
}

/*!
 * @brief This API gets the power mode of the sensor.
 */
int8_t BME280::get_sensor_mode(uint8_t *sensor_mode)
{
    int8_t rslt;

    /* Check for null pointer in the device structure*/
    rslt = null_ptr_check();
    if (rslt == BME280_OK)
    {
        /* Read the power mode register */
        rslt = get_regs(BME280_PWR_CTRL_ADDR, sensor_mode, 1);

        /* Assign the power mode in the device structure */
        *sensor_mode = BME280_GET_BITS_POS_0(*sensor_mode, BME280_SENSOR_MODE);
    }

    return rslt;
}

/*!
 * @brief This API performs the soft reset of the sensor.
 */
int8_t BME280::soft_reset()
{
    int8_t rslt;
    uint8_t reg_addr = BME280_RESET_ADDR;
    uint8_t status_reg = 0;
    uint8_t try_run = 5;

    /* 0xB6 is the soft reset command */
    uint8_t soft_rst_cmd = BME280_SOFT_RESET_COMMAND;

    /* Check for null pointer in the device structure*/
    rslt = null_ptr_check();

    /* Proceed if null check is fine */
    if (rslt == BME280_OK)
    {
        /* Write the soft reset command in the sensor */
        rslt = set_regs(&reg_addr, &soft_rst_cmd, 1);

        if (rslt == BME280_OK)
        {
            /* If NVM not copied yet, Wait for NVM to copy */
            do
            {
                /* As per data sheet - Table 1, startup time is 2 ms. */
                delay_ms(2);
                rslt = get_regs(BME280_STATUS_REG_ADDR, &status_reg, 1);
            } while ((rslt == BME280_OK) && (try_run--) && (status_reg & BME280_STATUS_IM_UPDATE));

            if (status_reg & BME280_STATUS_IM_UPDATE)
            {
                rslt = BME280_E_NVM_COPY_FAILED;
            }

        }
    }

    return rslt;
}

/*!
 * @brief This API reads the pressure, temperature and humidity data from the
 * sensor, compensates the data and store it in the bme280_data structure
 * instance passed by the user.
 */
int8_t BME280::get_sensor_data(uint8_t sensor_comp, struct bme280_data *comp_data)
{
    int8_t rslt;

    /* Array to store the pressure, temperature and humidity data read from
     * the sensor
     */
    uint8_t reg_data[BME280_P_T_H_DATA_LEN] = { 0 };
    struct bme280_uncomp_data uncomp_data = { 0, 0, 0 };

    /* Check for null pointer in the device structure*/
    rslt = null_ptr_check();
    if ((rslt == BME280_OK) && (comp_data != NULL))
    {
        /* Read the pressure and temperature data from the sensor */
        rslt = get_regs(BME280_DATA_ADDR, reg_data, BME280_P_T_H_DATA_LEN);
        if (rslt == BME280_OK)
        {
            /* Parse the read data from the sensor */
            parse_sensor_data(reg_data, &uncomp_data);

            /* Compensate the pressure and/or temperature and/or
             * humidity data from the sensor
             */
            rslt = compensate_data(sensor_comp, &uncomp_data, comp_data, &calib_data);
        }
    }
    else
    {
        rslt = BME280_E_NULL_PTR;
    }

    return rslt;
}

/*!
 *  @brief This API is used to parse the pressure, temperature and
 *  humidity data and store it in the bme280_uncomp_data structure instance.
 */
void BME280::parse_sensor_data(const uint8_t *reg_data, struct bme280_uncomp_data *uncomp_data)
{
    /* Variables to store the sensor data */
    uint32_t data_xlsb;
    uint32_t data_lsb;
    uint32_t data_msb;

    /* Store the parsed register values for pressure data */
    data_msb = (uint32_t)reg_data[0] << 12;
    data_lsb = (uint32_t)reg_data[1] << 4;
    data_xlsb = (uint32_t)reg_data[2] >> 4;
    uncomp_data->pressure = data_msb | data_lsb | data_xlsb;

    /* Store the parsed register values for temperature data */
    data_msb = (uint32_t)reg_data[3] << 12;
    data_lsb = (uint32_t)reg_data[4] << 4;
    data_xlsb = (uint32_t)reg_data[5] >> 4;
    uncomp_data->temperature = data_msb | data_lsb | data_xlsb;

    /* Store the parsed register values for temperature data */
    data_lsb = (uint32_t)reg_data[6] << 8;
    data_msb = (uint32_t)reg_data[7];
    uncomp_data->humidity = data_msb | data_lsb;
}

/*!
 * @brief This API is used to compensate the pressure and/or
 * temperature and/or humidity data according to the component selected
 * by the user.
 */
int8_t BME280::compensate_data(uint8_t sensor_comp,
                              const struct bme280_uncomp_data *uncomp_data,
                              struct bme280_data *comp_data,
                              struct bme280_calib_data *calib_data)
{
    int8_t rslt = BME280_OK;

    if ((uncomp_data != NULL) && (comp_data != NULL) && (calib_data != NULL))
    {
        /* Initialize to zero */
        comp_data->temperature = 0;
        comp_data->pressure = 0;
        comp_data->humidity = 0;

        /* If pressure or temperature component is selected */
        if (sensor_comp & (BME280_PRESS | BME280_TEMP | BME280_HUM))
        {
            /* Compensate the temperature data */
            comp_data->temperature = compensate_temperature(uncomp_data, calib_data);
        }
        if (sensor_comp & BME280_PRESS)
        {
            /* Compensate the pressure data */
            comp_data->pressure = compensate_pressure(uncomp_data, calib_data);
        }
        if (sensor_comp & BME280_HUM)
        {
            /* Compensate the humidity data */
            comp_data->humidity = compensate_humidity(uncomp_data, calib_data);
        }
    }
    else
    {
        rslt = BME280_E_NULL_PTR;
    }

    return rslt;
}

/*!
 * @brief This internal API sets the oversampling settings for pressure,
 * temperature and humidity in the sensor.
 */
int8_t BME280::set_osr_settings(uint8_t desired_settings,
                               const struct bme280_settings *settings)
{
    int8_t rslt = BME280_W_INVALID_OSR_MACRO;

    if (desired_settings & BME280_OSR_HUM_SEL)
    {
        rslt = set_osr_humidity_settings(settings);
    }
    if (desired_settings & (BME280_OSR_PRESS_SEL | BME280_OSR_TEMP_SEL))
    {
        rslt = set_osr_press_temp_settings(desired_settings, settings);
    }

    return rslt;
}

/*!
 * @brief This API sets the humidity oversampling settings of the sensor.
 */
int8_t BME280::set_osr_humidity_settings(const struct bme280_settings *settings)
{
    int8_t rslt;
    uint8_t ctrl_hum;
    uint8_t ctrl_meas;
    uint8_t reg_addr = BME280_CTRL_HUM_ADDR;

    ctrl_hum = settings->osr_h & BME280_CTRL_HUM_MSK;

    /* Write the humidity control value in the register */
    rslt = set_regs(&reg_addr, &ctrl_hum, 1);

    /* Humidity related changes will be only effective after a
     * write operation to ctrl_meas register
     */
    if (rslt == BME280_OK)
    {
        reg_addr = BME280_CTRL_MEAS_ADDR;
        rslt = get_regs(reg_addr, &ctrl_meas, 1);
        if (rslt == BME280_OK)
        {
            rslt = set_regs(&reg_addr, &ctrl_meas, 1);
        }
    }

    return rslt;
}

/*!
 * @brief This API sets the pressure and/or temperature oversampling settings
 * in the sensor according to the settings selected by the user.
 */
int8_t BME280::set_osr_press_temp_settings(uint8_t desired_settings,
                                          const struct bme280_settings *settings)
{
    int8_t rslt;
    uint8_t reg_addr = BME280_CTRL_MEAS_ADDR;
    uint8_t reg_data;

    rslt = BME280::get_regs(reg_addr, &reg_data, 1);
    if (rslt == BME280_OK)
    {
        if (desired_settings & BME280_OSR_PRESS_SEL)
        {
            fill_osr_press_settings(&reg_data, settings);
        }
        if (desired_settings & BME280_OSR_TEMP_SEL)
        {
            fill_osr_temp_settings(&reg_data, settings);
        }

        /* Write the oversampling settings in the register */
        rslt = BME280::set_regs(&reg_addr, &reg_data, 1);
    }

    return rslt;
}

/*!
 * @brief This internal API sets the filter and/or standby duration settings
 * in the sensor according to the settings selected by the user.
 */
int8_t BME280::set_filter_standby_settings(uint8_t desired_settings,
                                          const struct bme280_settings *settings)
{
    int8_t rslt;
    uint8_t reg_addr = BME280_CONFIG_ADDR;
    uint8_t reg_data;

    rslt = get_regs(reg_addr, &reg_data, 1);
    if (rslt == BME280_OK)
    {
        if (desired_settings & BME280_FILTER_SEL)
        {
            fill_filter_settings(&reg_data, settings);
        }
        if (desired_settings & BME280_STANDBY_SEL)
        {
            fill_standby_settings(&reg_data, settings);
        }

        /* Write the oversampling settings in the register */
        rslt = set_regs(&reg_addr, &reg_data, 1);
    }

    return rslt;
}

/*!
 * @brief This internal API fills the filter settings provided by the user
 * in the data buffer so as to write in the sensor.
 */
void BME280::fill_filter_settings(uint8_t *reg_data, const struct bme280_settings *settings)
{
    *reg_data = BME280_SET_BITS(*reg_data, BME280_FILTER, settings->filter);
}

/*!
 * @brief This internal API fills the standby duration settings provided by
 * the user in the data buffer so as to write in the sensor.
 */
void BME280::fill_standby_settings(uint8_t *reg_data, const struct bme280_settings *settings)
{
    *reg_data = BME280_SET_BITS(*reg_data, BME280_STANDBY, settings->standby_time);
}

/*!
 * @brief This internal API fills the pressure oversampling settings provided by
 * the user in the data buffer so as to write in the sensor.
 */
void BME280::fill_osr_press_settings(uint8_t *reg_data, const struct bme280_settings *settings)
{
    *reg_data = BME280_SET_BITS(*reg_data, BME280_CTRL_PRESS, settings->osr_p);
}

/*!
 * @brief This internal API fills the temperature oversampling settings
 * provided by the user in the data buffer so as to write in the sensor.
 */
void BME280::fill_osr_temp_settings(uint8_t *reg_data, const struct bme280_settings *settings)
{
    *reg_data = BME280_SET_BITS(*reg_data, BME280_CTRL_TEMP, settings->osr_t);
}

/*!
 * @brief This internal API parse the oversampling(pressure, temperature
 * and humidity), filter and standby duration settings and store in the
 * device structure.
 */
void BME280::parse_device_settings(const uint8_t *reg_data, struct bme280_settings *settings)
{
    settings->osr_h = BME280_GET_BITS_POS_0(reg_data[0], BME280_CTRL_HUM);
    settings->osr_p = BME280_GET_BITS(reg_data[2], BME280_CTRL_PRESS);
    settings->osr_t = BME280_GET_BITS(reg_data[2], BME280_CTRL_TEMP);
    settings->filter = BME280_GET_BITS(reg_data[3], BME280_FILTER);
    settings->standby_time = BME280_GET_BITS(reg_data[3], BME280_STANDBY);
}

/*!
 * @brief This internal API writes the power mode in the sensor.
 */
int8_t BME280::write_power_mode(uint8_t sensor_mode)
{
    int8_t rslt;
    uint8_t reg_addr = BME280_PWR_CTRL_ADDR;

    /* Variable to store the value read from power mode register */
    uint8_t sensor_mode_reg_val;

    /* Read the power mode register */
    rslt = get_regs(reg_addr, &sensor_mode_reg_val, 1);

    /* Set the power mode */
    if (rslt == BME280_OK)
    {
        sensor_mode_reg_val = BME280_SET_BITS_POS_0(sensor_mode_reg_val, BME280_SENSOR_MODE, sensor_mode);

        /* Write the power mode in the register */
        rslt = set_regs(&reg_addr, &sensor_mode_reg_val, 1);
    }

    return rslt;
}

/*!
 * @brief This internal API puts the device to sleep mode.
 */
int8_t BME280::put_device_to_sleep()
{
    int8_t rslt;
    uint8_t reg_data[4];
    struct bme280_settings settings;

    rslt = get_regs(BME280_CTRL_HUM_ADDR, reg_data, 4);
    if (rslt == BME280_OK)
    {
        parse_device_settings(reg_data, &settings);
        rslt = soft_reset();
        if (rslt == BME280_OK)
        {
            rslt = reload_device_settings(&settings);
        }
    }

    return rslt;
}

/*!
 * @brief This internal API reloads the already existing device settings in
 * the sensor after soft reset.
 */
int8_t BME280::reload_device_settings(const struct bme280_settings *settings)
{
    int8_t rslt;

    rslt = set_osr_settings(BME280_ALL_SETTINGS_SEL, settings);
    if (rslt == BME280_OK)
    {
        rslt = set_filter_standby_settings(BME280_ALL_SETTINGS_SEL, settings);
    }

    return rslt;
}

#ifdef BME280_FLOAT_ENABLE

/*!
 * @brief This internal API is used to compensate the raw temperature data and
 * return the compensated temperature data in double data type.
 */
double BME280::compensate_temperature(const struct bme280_uncomp_data *uncomp_data, struct bme280_calib_data *calib_data)
{
    double var1;
    double var2;
    double temperature;
    double temperature_min = -40;
    double temperature_max = 85;

    var1 = ((double)uncomp_data->temperature) / 16384.0 - ((double)calib_data->dig_T1) / 1024.0;
    var1 = var1 * ((double)calib_data->dig_T2);
    var2 = (((double)uncomp_data->temperature) / 131072.0 - ((double)calib_data->dig_T1) / 8192.0);
    var2 = (var2 * var2) * ((double)calib_data->dig_T3);
    calib_data->t_fine = (int32_t)(var1 + var2);
    temperature = (var1 + var2) / 5120.0;
    if (temperature < temperature_min)
    {
        temperature = temperature_min;
    }
    else if (temperature > temperature_max)
    {
        temperature = temperature_max;
    }

    return temperature;
}

/*!
 * @brief This internal API is used to compensate the raw pressure data and
 * return the compensated pressure data in double data type.
 */
double BME280::compensate_pressure(const struct bme280_uncomp_data *uncomp_data,
                                  const struct bme280_calib_data *calib_data)
{
    double var1;
    double var2;
    double var3;
    double pressure;
    double pressure_min = 30000.0;
    double pressure_max = 110000.0;

    var1 = ((double)calib_data->t_fine / 2.0) - 64000.0;
    var2 = var1 * var1 * ((double)calib_data->dig_P6) / 32768.0;
    var2 = var2 + var1 * ((double)calib_data->dig_P5) * 2.0;
    var2 = (var2 / 4.0) + (((double)calib_data->dig_P4) * 65536.0);
    var3 = ((double)calib_data->dig_P3) * var1 * var1 / 524288.0;
    var1 = (var3 + ((double)calib_data->dig_P2) * var1) / 524288.0;
    var1 = (1.0 + var1 / 32768.0) * ((double)calib_data->dig_P1);

    /* avoid exception caused by division by zero */
    if (var1)
    {
        pressure = 1048576.0 - (double) uncomp_data->pressure;
        pressure = (pressure - (var2 / 4096.0)) * 6250.0 / var1;
        var1 = ((double)calib_data->dig_P9) * pressure * pressure / 2147483648.0;
        var2 = pressure * ((double)calib_data->dig_P8) / 32768.0;
        pressure = pressure + (var1 + var2 + ((double)calib_data->dig_P7)) / 16.0;
        if (pressure < pressure_min)
        {
            pressure = pressure_min;
        }
        else if (pressure > pressure_max)
        {
            pressure = pressure_max;
        }
    }
    else /* Invalid case */
    {
        pressure = pressure_min;
    }

    return pressure;
}

/*!
 * @brief This internal API is used to compensate the raw humidity data and
 * return the compensated humidity data in double data type.
 */
double BME280::compensate_humidity(const struct bme280_uncomp_data *uncomp_data,
                                  const struct bme280_calib_data *calib_data)
{
    double humidity;
    double humidity_min = 0.0;
    double humidity_max = 100.0;
    double var1;
    double var2;
    double var3;
    double var4;
    double var5;
    double var6;

    var1 = ((double)calib_data->t_fine) - 76800.0;
    var2 = (((double)calib_data->dig_H4) * 64.0 + (((double)calib_data->dig_H5) / 16384.0) * var1);
    var3 = uncomp_data->humidity - var2;
    var4 = ((double)calib_data->dig_H2) / 65536.0;
    var5 = (1.0 + (((double)calib_data->dig_H3) / 67108864.0) * var1);
    var6 = 1.0 + (((double)calib_data->dig_H6) / 67108864.0) * var1 * var5;
    var6 = var3 * var4 * (var5 * var6);
    humidity = var6 * (1.0 - ((double)calib_data->dig_H1) * var6 / 524288.0);
    if (humidity > humidity_max)
    {
        humidity = humidity_max;
    }
    else if (humidity < humidity_min)
    {
        humidity = humidity_min;
    }

    return humidity;
}

#else

/*!
 * @brief This internal API is used to compensate the raw temperature data and
 * return the compensated temperature data in integer data type.
 */
int32_t BME280::compensate_temperature(const struct bme280_uncomp_data *uncomp_data,
                                      struct bme280_calib_data *calib_data)
{
    int32_t var1;
    int32_t var2;
    int32_t temperature;
    int32_t temperature_min = -4000;
    int32_t temperature_max = 8500;

    var1 = (int32_t)((uncomp_data->temperature / 8) - ((int32_t)calib_data->dig_T1 * 2));
    var1 = (var1 * ((int32_t)calib_data->dig_T2)) / 2048;
    var2 = (int32_t)((uncomp_data->temperature / 16) - ((int32_t)calib_data->dig_T1));
    var2 = (((var2 * var2) / 4096) * ((int32_t)calib_data->dig_T3)) / 16384;
    calib_data->t_fine = var1 + var2;
    temperature = (calib_data->t_fine * 5 + 128) / 256;
    if (temperature < temperature_min)
    {
        temperature = temperature_min;
    }
    else if (temperature > temperature_max)
    {
        temperature = temperature_max;
    }

    return temperature;
}
#ifdef BME280_64BIT_ENABLE

/*!
 * @brief This internal API is used to compensate the raw pressure data and
 * return the compensated pressure data in integer data type with higher
 * accuracy.
 */
uint32_t BME280::compensate_pressure(const struct bme280_uncomp_data *uncomp_data,
                                    const struct bme280_calib_data *calib_data)
{
    int64_t var1;
    int64_t var2;
    int64_t var3;
    int64_t var4;
    uint32_t pressure;
    uint32_t pressure_min = 3000000;
    uint32_t pressure_max = 11000000;

    var1 = ((int64_t)calib_data->t_fine) - 128000;
    var2 = var1 * var1 * (int64_t)calib_data->dig_P6;
    var2 = var2 + ((var1 * (int64_t)calib_data->dig_P5) * 131072);
    var2 = var2 + (((int64_t)calib_data->dig_P4) * 34359738368);
    var1 = ((var1 * var1 * (int64_t)calib_data->dig_P3) / 256) + ((var1 * ((int64_t)calib_data->dig_P2) * 4096));
    var3 = ((int64_t)1) * 140737488355328;
    var1 = (var3 + var1) * ((int64_t)calib_data->dig_P1) / 8589934592;

    /* To avoid divide by zero exception */
    if (var1 != 0)
    {
        var4 = 1048576 - uncomp_data->pressure;
        var4 = (((var4 * INT64_C(2147483648)) - var2) * 3125) / var1;
        var1 = (((int64_t)calib_data->dig_P9) * (var4 / 8192) * (var4 / 8192)) / 33554432;
        var2 = (((int64_t)calib_data->dig_P8) * var4) / 524288;
        var4 = ((var4 + var1 + var2) / 256) + (((int64_t)calib_data->dig_P7) * 16);
        pressure = (uint32_t)(((var4 / 2) * 100) / 128);
        if (pressure < pressure_min)
        {
            pressure = pressure_min;
        }
        else if (pressure > pressure_max)
        {
            pressure = pressure_max;
        }
    }
    else
    {
        pressure = pressure_min;
    }

    return pressure;
}
#else

/*!
 * @brief This internal API is used to compensate the raw pressure data and
 * return the compensated pressure data in integer data type.
 */
uint32_t BME280::compensate_pressure(const struct bme280_uncomp_data *uncomp_data,
                                    const struct bme280_calib_data *calib_data)
{
    int32_t var1;
    int32_t var2;
    int32_t var3;
    int32_t var4;
    uint32_t var5;
    uint32_t pressure;
    uint32_t pressure_min = 30000;
    uint32_t pressure_max = 110000;

    var1 = (((int32_t)calib_data->t_fine) / 2) - (int32_t)64000;
    var2 = (((var1 / 4) * (var1 / 4)) / 2048) * ((int32_t)calib_data->dig_P6);
    var2 = var2 + ((var1 * ((int32_t)calib_data->dig_P5)) * 2);
    var2 = (var2 / 4) + (((int32_t)calib_data->dig_P4) * 65536);
    var3 = (calib_data->dig_P3 * (((var1 / 4) * (var1 / 4)) / 8192)) / 8;
    var4 = (((int32_t)calib_data->dig_P2) * var1) / 2;
    var1 = (var3 + var4) / 262144;
    var1 = (((32768 + var1)) * ((int32_t)calib_data->dig_P1)) / 32768;

    /* avoid exception caused by division by zero */
    if (var1)
    {
        var5 = (uint32_t)((uint32_t)1048576) - uncomp_data->pressure;
        pressure = ((uint32_t)(var5 - (uint32_t)(var2 / 4096))) * 3125;
        if (pressure < 0x80000000)
        {
            pressure = (pressure << 1) / ((uint32_t)var1);
        }
        else
        {
            pressure = (pressure / (uint32_t)var1) * 2;
        }
        var1 = (((int32_t)calib_data->dig_P9) * ((int32_t)(((pressure / 8) * (pressure / 8)) / 8192))) / 4096;
        var2 = (((int32_t)(pressure / 4)) * ((int32_t)calib_data->dig_P8)) / 8192;
        pressure = (uint32_t)((int32_t)pressure + ((var1 + var2 + calib_data->dig_P7) / 16));
        if (pressure < pressure_min)
        {
            pressure = pressure_min;
        }
        else if (pressure > pressure_max)
        {
            pressure = pressure_max;
        }
    }
    else
    {
        pressure = pressure_min;
    }

    return pressure;
}
#endif

/*!
 * @brief This internal API is used to compensate the raw humidity data and
 * return the compensated humidity data in integer data type.
 */
uint32_t BME280::compensate_humidity(const struct bme280_uncomp_data *uncomp_data,
                                    const struct bme280_calib_data *calib_data)
{
    int32_t var1;
    int32_t var2;
    int32_t var3;
    int32_t var4;
    int32_t var5;
    uint32_t humidity;
    uint32_t humidity_max = 102400;

    var1 = calib_data->t_fine - ((int32_t)76800);
    var2 = (int32_t)(uncomp_data->humidity * 16384);
    var3 = (int32_t)(((int32_t)calib_data->dig_H4) * 1048576);
    var4 = ((int32_t)calib_data->dig_H5) * var1;
    var5 = (((var2 - var3) - var4) + (int32_t)16384) / 32768;
    var2 = (var1 * ((int32_t)calib_data->dig_H6)) / 1024;
    var3 = (var1 * ((int32_t)calib_data->dig_H3)) / 2048;
    var4 = ((var2 * (var3 + (int32_t)32768)) / 1024) + (int32_t)2097152;
    var2 = ((var4 * ((int32_t)calib_data->dig_H2)) + 8192) / 16384;
    var3 = var5 * var2;
    var4 = ((var3 / 32768) * (var3 / 32768)) / 128;
    var5 = var3 - ((var4 * ((int32_t)calib_data->dig_H1)) / 16);
    var5 = (var5 < 0 ? 0 : var5);
    var5 = (var5 > 419430400 ? 419430400 : var5);
    humidity = (uint32_t)(var5 / 4096);
    if (humidity > humidity_max)
    {
        humidity = humidity_max;
    }

    return humidity;
}
#endif

/*!
 * @brief This internal API reads the calibration data from the sensor, parse
 * it and store in the device structure.
 */
int8_t BME280::get_calib_data()
{
    int8_t rslt;
    uint8_t reg_addr = BME280_TEMP_PRESS_CALIB_DATA_ADDR;

    /* Array to store calibration data */
    uint8_t calib_data[BME280_TEMP_PRESS_CALIB_DATA_LEN] = { 0 };

    /* Read the calibration data from the sensor */
    rslt = get_regs(reg_addr, calib_data, BME280_TEMP_PRESS_CALIB_DATA_LEN);
    if (rslt == BME280_OK)
    {
        /* Parse temperature and pressure calibration data and store
         * it in device structure
         */
        parse_temp_press_calib_data(calib_data);
        reg_addr = BME280_HUMIDITY_CALIB_DATA_ADDR;

        /* Read the humidity calibration data from the sensor */
        rslt = get_regs(reg_addr, calib_data, BME280_HUMIDITY_CALIB_DATA_LEN);
        if (rslt == BME280_OK)
        {
            /* Parse humidity calibration data and store it in
             * device structure
             */
            parse_humidity_calib_data(calib_data);
        }
    }

    return rslt;
}

/*!
 * @brief This internal API interleaves the register address between the
 * register data buffer for burst write operation.
 */
void BME280::interleave_reg_addr(const uint8_t *reg_addr, uint8_t *temp_buff, const uint8_t *reg_data, uint8_t len)
{
    uint8_t index;

    for (index = 1; index < len; index++)
    {
        temp_buff[(index * 2) - 1] = reg_addr[index];
        temp_buff[index * 2] = reg_data[index];
    }
}

/*!
 *  @brief This internal API is used to parse the temperature and
 *  pressure calibration data and store it in device structure.
 */
void BME280::parse_temp_press_calib_data(const uint8_t *reg_data)
{
    calib_data.dig_T1 = BME280_CONCAT_BYTES(reg_data[1], reg_data[0]);
    calib_data.dig_T2 = (int16_t)BME280_CONCAT_BYTES(reg_data[3], reg_data[2]);
    calib_data.dig_T3 = (int16_t)BME280_CONCAT_BYTES(reg_data[5], reg_data[4]);
    calib_data.dig_P1 = BME280_CONCAT_BYTES(reg_data[7], reg_data[6]);
    calib_data.dig_P2 = (int16_t)BME280_CONCAT_BYTES(reg_data[9], reg_data[8]);
    calib_data.dig_P3 = (int16_t)BME280_CONCAT_BYTES(reg_data[11], reg_data[10]);
    calib_data.dig_P4 = (int16_t)BME280_CONCAT_BYTES(reg_data[13], reg_data[12]);
    calib_data.dig_P5 = (int16_t)BME280_CONCAT_BYTES(reg_data[15], reg_data[14]);
    calib_data.dig_P6 = (int16_t)BME280_CONCAT_BYTES(reg_data[17], reg_data[16]);
    calib_data.dig_P7 = (int16_t)BME280_CONCAT_BYTES(reg_data[19], reg_data[18]);
    calib_data.dig_P8 = (int16_t)BME280_CONCAT_BYTES(reg_data[21], reg_data[20]);
    calib_data.dig_P9 = (int16_t)BME280_CONCAT_BYTES(reg_data[23], reg_data[22]);
    calib_data.dig_H1 = reg_data[25];
}

/*!
 *  @brief This internal API is used to parse the humidity calibration data
 *  and store it in device structure.
 */
void BME280::parse_humidity_calib_data(const uint8_t *reg_data)
{
    int16_t dig_H4_lsb;
    int16_t dig_H4_msb;
    int16_t dig_H5_lsb;
    int16_t dig_H5_msb;

    calib_data.dig_H2 = (int16_t)BME280_CONCAT_BYTES(reg_data[1], reg_data[0]);
    calib_data.dig_H3 = reg_data[2];
    dig_H4_msb = (int16_t)(int8_t)reg_data[3] * 16;
    dig_H4_lsb = (int16_t)(reg_data[4] & 0x0F);
    calib_data.dig_H4 = dig_H4_msb | dig_H4_lsb;
    dig_H5_msb = (int16_t)(int8_t)reg_data[5] * 16;
    dig_H5_lsb = (int16_t)(reg_data[4] >> 4);
    calib_data.dig_H5 = dig_H5_msb | dig_H5_lsb;
    calib_data.dig_H6 = (int8_t)reg_data[6];
}

/*!
 * @brief This internal API is used to identify the settings which the user
 * wants to modify in the sensor.
 */
uint8_t BME280::are_settings_changed(uint8_t sub_settings, uint8_t desired_settings)
{
    uint8_t settings_changed = FALSE;

    if (sub_settings & desired_settings)
    {
        /* User wants to modify this particular settings */
        settings_changed = TRUE;
    }
    else
    {
        /* User don't want to modify this particular settings */
        settings_changed = FALSE;
    }

    return settings_changed;
}

/*!
 * @brief This internal API is used to validate the device structure pointer for
 * null conditions.
 */
int8_t BME280::null_ptr_check()
{
    int8_t rslt;

    if ((read == NULL) || (write == NULL) || (delay_ms == NULL))
    {
        /* Device structure pointer is not valid */
        rslt = BME280_E_NULL_PTR;
    }
    else
    {
        /* Device structure is fine */
        rslt = BME280_OK;
    }

    return rslt;
}

BME280 bme280(BME280_I2C_ADDR_PRIM);