File content as of revision 60:6b21ca38ee7c:

#include "bme680.h"

Bme680::Bme680(I2cCallbacks *callbacks) {
    _dev = new bme680_dev;
    _dev->dev_id = BME680_I2C_ADDR_PRIMARY<<1;
    _i2cCallbacks = callbacks;
}

int Bme680::init() {
    int rslt = soft_reset();
    
    if (rslt!=BME680_OK) return rslt;
    
    rslt = get_regs(BME680_CHIP_ID_ADDR, &(_dev->chip_id), 1);
    
    if (rslt!=BME680_OK) return rslt;
            
    if (_dev->chip_id == BME680_CHIP_ID) {
        rslt = get_calib_data();
    } else {
        rslt = BME680_E_DEV_NOT_FOUND;
    }
            
    return rslt;
}

int Bme680::measure(struct bme680_field_data* data, const int ambTemp, const uint16_t heatr_dur, const uint16_t heatr_temp){
    int rslt = null_ptr_check();
    if (rslt!=BME680_OK) return rslt;
    
    _dev->amb_temp = ambTemp;
    _dev->power_mode = BME680_FORCED_MODE;
    
    _dev->tph_sett.os_hum = BME680_OS_1X;
    _dev->tph_sett.os_pres = BME680_OS_16X;
    _dev->tph_sett.os_temp = BME680_OS_2X;
    
    _dev->gas_sett.run_gas = BME680_ENABLE_GAS_MEAS;
    _dev->gas_sett.heatr_dur = heatr_dur;
    _dev->gas_sett.heatr_temp = heatr_temp;
    
    uint16_t settings_sel = BME680_OST_SEL | BME680_OSP_SEL | BME680_OSH_SEL | BME680_GAS_SENSOR_SEL;

    uint16_t profile_dur = 0;
    get_profile_dur(&profile_dur);
    
    rslt = set_sensor_settings(settings_sel);
    
    if (rslt == BME680_OK) {
        rslt = set_sensor_mode();
        _i2cCallbacks->delay_ms_strict(profile_dur);
        if (rslt == BME680_OK) {
            rslt = get_sensor_data(data);
        }
        
        if (rslt == BME680_OK) {
            rslt = analyze_sensor_data(data);
        }
    }
        
    return rslt;
}

int Bme680::analyze_sensor_data(struct bme680_field_data *data)
{
    int rslt = BME680_OK;
    uint8_t self_test_failed = 0;

    const int16_t MIN_TEMPERATURE = INT16_C(0);      /* 0 degree Celsius */
    const int16_t MAX_TEMPERATURE = INT16_C(6000);   /* 60 degree Celsius */

    const uint32_t MIN_PRESSURE = UINT32_C(90000);    /* 900 hecto Pascals */
    const uint32_t MAX_PRESSURE = UINT32_C(110000);   /* 1100 hecto Pascals */

    const uint32_t MIN_HUMIDITY = UINT32_C(1000);    /* 20% relative humidity */
    const uint32_t MAX_HUMIDITY = UINT32_C(100000);    /* 80% relative humidity*/

    if ((data->temperature < MIN_TEMPERATURE) || (data->temperature > MAX_TEMPERATURE))
        self_test_failed++;

    if ((data->pressure < MIN_PRESSURE) || (data->pressure > MAX_PRESSURE))
        self_test_failed++;

    if ((data->humidity < MIN_HUMIDITY) || (data->humidity > MAX_HUMIDITY))
        self_test_failed++;

    if (!(data->status & BME680_GASM_VALID_MSK))
            self_test_failed++;

    if (self_test_failed)
        rslt = BME680_W_SELF_TEST_FAILED;

    return rslt;
}

int Bme680::soft_reset() {
    int rslt = null_ptr_check();
    if (rslt!=BME680_OK) return rslt;
    
    uint8_t reg_addr = BME680_SOFT_RESET_ADDR;
    uint8_t soft_rst_cmd = BME680_SOFT_RESET_CMD;    
    rslt = set_regs(&reg_addr, &soft_rst_cmd, 1);
    
    if (rslt==BME680_OK) {
        _i2cCallbacks->delay_ms_relaxed(BME680_RESET_PERIOD);
    }
    
    return rslt;
}

int Bme680::get_regs(uint8_t reg_addr, uint8_t *reg_data, uint16_t len)
{
    int rslt = null_ptr_check();
    if (rslt!=BME680_OK) return rslt;
    
    _dev->com_rslt = _i2cCallbacks->read(_dev->dev_id, reg_addr, reg_data, len);
    if (_dev->com_rslt != 0)
        rslt = BME680_E_COM_FAIL;
    return rslt;
}


int Bme680::set_regs(const uint8_t *reg_addr, const uint8_t *reg_data, uint8_t len)
{
    int rslt = null_ptr_check();
    if (rslt!=BME680_OK) return rslt;
    
    /* Length of the temporary buffer is 2*(length of register)*/
    uint8_t tmp_buff[BME680_TMP_BUFFER_LENGTH] = { 0 };
    uint16_t index;
    
    if ((len > 0) && (len < BME680_TMP_BUFFER_LENGTH / 2)) {
        /* Interleave the 2 arrays */
        for (index = 0; index < len; index++) {
            tmp_buff[(2 * index)] = reg_addr[index];
            tmp_buff[(2 * index) + 1] = reg_data[index];
        }
        /* Write the interleaved array */
        _dev->com_rslt = _i2cCallbacks->write(_dev->dev_id, tmp_buff[0], &tmp_buff[1], (2 * len) - 1);
        if (_dev->com_rslt != 0) {
            rslt = BME680_E_COM_FAIL;
        }
    } else {
        rslt = BME680_E_INVALID_LENGTH;
    }
    
    return rslt;
}

int Bme680::null_ptr_check()
{
    if (_dev == NULL || _i2cCallbacks == NULL) {
        /* Device structure pointer is not valid */
        return BME680_E_NULL_PTR;
    } else {
        /* Device structure is fine */
        return BME680_OK;
    }
}

int Bme680::get_calib_data()
{
    int rslt;
    uint8_t coeff_array[BME680_COEFF_SIZE] = { 0 };
    uint8_t temp_var = 0; /* Temporary variable */

    /* Check for null pointer in the device structure*/
    rslt = null_ptr_check();
    if (rslt == BME680_OK) {
        rslt = get_regs(BME680_COEFF_ADDR1, coeff_array, BME680_COEFF_ADDR1_LEN);
        /* Append the second half in the same array */
        if (rslt == BME680_OK)
            rslt = get_regs(BME680_COEFF_ADDR2, &coeff_array[BME680_COEFF_ADDR1_LEN]
            , BME680_COEFF_ADDR2_LEN);

        /* Temperature related coefficients */
        _dev->calib.par_t1 = (uint16_t) (BME680_CONCAT_BYTES(coeff_array[BME680_T1_MSB_REG],
            coeff_array[BME680_T1_LSB_REG]));
        _dev->calib.par_t2 = (int16_t) (BME680_CONCAT_BYTES(coeff_array[BME680_T2_MSB_REG],
            coeff_array[BME680_T2_LSB_REG]));
        _dev->calib.par_t3 = (int8_t) (coeff_array[BME680_T3_REG]);

        /* Pressure related coefficients */
        _dev->calib.par_p1 = (uint16_t) (BME680_CONCAT_BYTES(coeff_array[BME680_P1_MSB_REG],
            coeff_array[BME680_P1_LSB_REG]));
        _dev->calib.par_p2 = (int16_t) (BME680_CONCAT_BYTES(coeff_array[BME680_P2_MSB_REG],
            coeff_array[BME680_P2_LSB_REG]));
        _dev->calib.par_p3 = (int8_t) coeff_array[BME680_P3_REG];
        _dev->calib.par_p4 = (int16_t) (BME680_CONCAT_BYTES(coeff_array[BME680_P4_MSB_REG],
            coeff_array[BME680_P4_LSB_REG]));
        _dev->calib.par_p5 = (int16_t) (BME680_CONCAT_BYTES(coeff_array[BME680_P5_MSB_REG],
            coeff_array[BME680_P5_LSB_REG]));
        _dev->calib.par_p6 = (int8_t) (coeff_array[BME680_P6_REG]);
        _dev->calib.par_p7 = (int8_t) (coeff_array[BME680_P7_REG]);
        _dev->calib.par_p8 = (int16_t) (BME680_CONCAT_BYTES(coeff_array[BME680_P8_MSB_REG],
            coeff_array[BME680_P8_LSB_REG]));
        _dev->calib.par_p9 = (int16_t) (BME680_CONCAT_BYTES(coeff_array[BME680_P9_MSB_REG],
            coeff_array[BME680_P9_LSB_REG]));
        _dev->calib.par_p10 = (uint8_t) (coeff_array[BME680_P10_REG]);

        /* Humidity related coefficients */
        _dev->calib.par_h1 = (uint16_t) (((uint16_t) coeff_array[BME680_H1_MSB_REG] << BME680_HUM_REG_SHIFT_VAL)
            | (coeff_array[BME680_H1_LSB_REG] & BME680_BIT_H1_DATA_MSK));
        _dev->calib.par_h2 = (uint16_t) (((uint16_t) coeff_array[BME680_H2_MSB_REG] << BME680_HUM_REG_SHIFT_VAL)
            | ((coeff_array[BME680_H2_LSB_REG]) >> BME680_HUM_REG_SHIFT_VAL));
        _dev->calib.par_h3 = (int8_t) coeff_array[BME680_H3_REG];
        _dev->calib.par_h4 = (int8_t) coeff_array[BME680_H4_REG];
        _dev->calib.par_h5 = (int8_t) coeff_array[BME680_H5_REG];
        _dev->calib.par_h6 = (uint8_t) coeff_array[BME680_H6_REG];
        _dev->calib.par_h7 = (int8_t) coeff_array[BME680_H7_REG];

        /* Gas heater related coefficients */
        _dev->calib.par_gh1 = (int8_t) coeff_array[BME680_GH1_REG];
        _dev->calib.par_gh2 = (int16_t) (BME680_CONCAT_BYTES(coeff_array[BME680_GH2_MSB_REG],
            coeff_array[BME680_GH2_LSB_REG]));
        _dev->calib.par_gh3 = (int8_t) coeff_array[BME680_GH3_REG];

        /* Other coefficients */
        if (rslt == BME680_OK) {
            rslt = get_regs(BME680_ADDR_RES_HEAT_RANGE_ADDR, &temp_var, 1);

            _dev->calib.res_heat_range = ((temp_var & BME680_RHRANGE_MSK) / 16);
            if (rslt == BME680_OK) {
                rslt = get_regs(BME680_ADDR_RES_HEAT_VAL_ADDR, &temp_var, 1);

                _dev->calib.res_heat_val = (int8_t) temp_var;
                if (rslt == BME680_OK)
                    rslt = get_regs(BME680_ADDR_RANGE_SW_ERR_ADDR, &temp_var, 1);
            }
        }
        _dev->calib.range_sw_err = ((int8_t) temp_var & (int8_t) BME680_RSERROR_MSK) / 16;
    }

    return rslt;
}

void Bme680::set_profile_dur(uint16_t duration)
{
    uint32_t tph_dur; /* Calculate in us */
    uint32_t meas_cycles;
    uint8_t os_to_meas_cycles[6] = {0, 1, 2, 4, 8, 16};

    meas_cycles = os_to_meas_cycles[_dev->tph_sett.os_temp];
    meas_cycles += os_to_meas_cycles[_dev->tph_sett.os_pres];
    meas_cycles += os_to_meas_cycles[_dev->tph_sett.os_hum];

    /* TPH measurement duration */
    tph_dur = meas_cycles * UINT32_C(1963);
    tph_dur += UINT32_C(477 * 4); /* TPH switching duration */
    tph_dur += UINT32_C(477 * 5); /* Gas measurement duration */
    tph_dur += UINT32_C(500); /* Get it to the closest whole number.*/
    tph_dur /= UINT32_C(1000); /* Convert to ms */

    tph_dur += UINT32_C(1); /* Wake up duration of 1ms */
    /* The remaining time should be used for heating */
    _dev->gas_sett.heatr_dur = duration - (uint16_t) tph_dur;
}

void Bme680::get_profile_dur(uint16_t *duration)
{
    uint32_t tph_dur; /* Calculate in us */
    uint32_t meas_cycles;
    uint8_t os_to_meas_cycles[6] = {0, 1, 2, 4, 8, 16};

    meas_cycles = os_to_meas_cycles[_dev->tph_sett.os_temp];
    meas_cycles += os_to_meas_cycles[_dev->tph_sett.os_pres];
    meas_cycles += os_to_meas_cycles[_dev->tph_sett.os_hum];

    /* TPH measurement duration */
    tph_dur = meas_cycles * UINT32_C(1963);
    tph_dur += UINT32_C(477 * 4); /* TPH switching duration */
    tph_dur += UINT32_C(477 * 5); /* Gas measurement duration */
    tph_dur += UINT32_C(500); /* Get it to the closest whole number.*/
    tph_dur /= UINT32_C(1000); /* Convert to ms */

    tph_dur += UINT32_C(1); /* Wake up duration of 1ms */

    *duration = (uint16_t) tph_dur;

    /* Get the gas duration only when the run gas is enabled */
    if (_dev->gas_sett.run_gas) {
        /* The remaining time should be used for heating */
        *duration += _dev->gas_sett.heatr_dur;
    }
}

int Bme680::get_sensor_data(struct bme680_field_data *data)
{
    int rslt = null_ptr_check();
    if (rslt!=BME680_OK) return rslt;
    
    /* Reading the sensor data in forced mode only */
    rslt = read_field_data(data);
    if (rslt == BME680_OK) {
        if (data->status & BME680_NEW_DATA_MSK)
            _dev->new_fields = 1;
        else
            _dev->new_fields = 0;
    }

    return rslt;
}

int Bme680::read_field_data(struct bme680_field_data *data){
    int rslt = null_ptr_check();
    if (rslt!=BME680_OK) return rslt;
    
    uint8_t buff[BME680_FIELD_LENGTH] = { 0 };
    uint8_t gas_range;
    uint32_t adc_temp;
    uint32_t adc_pres;
    uint16_t adc_hum;
    uint16_t adc_gas_res;
    uint8_t tries = 10;
    
    do {
        if (rslt == BME680_OK) {
            rslt = get_regs(((uint8_t) (BME680_FIELD0_ADDR)), buff, (uint16_t) BME680_FIELD_LENGTH);

            data->status = buff[0] & BME680_NEW_DATA_MSK;
            data->gas_index = buff[0] & BME680_GAS_INDEX_MSK;
            data->meas_index = buff[1];

            /* read the raw data from the sensor */
            adc_pres = (uint32_t) (((uint32_t) buff[2] * 4096) | ((uint32_t) buff[3] * 16)
                | ((uint32_t) buff[4] / 16));
            adc_temp = (uint32_t) (((uint32_t) buff[5] * 4096) | ((uint32_t) buff[6] * 16)
                | ((uint32_t) buff[7] / 16));
            adc_hum = (uint16_t) (((uint32_t) buff[8] * 256) | (uint32_t) buff[9]);
            adc_gas_res = (uint16_t) ((uint32_t) buff[13] * 4 | (((uint32_t) buff[14]) / 64));
            gas_range = buff[14] & BME680_GAS_RANGE_MSK;

            data->status |= buff[14] & BME680_GASM_VALID_MSK;
            data->status |= buff[14] & BME680_HEAT_STAB_MSK;

            if (data->status & BME680_NEW_DATA_MSK) {
                data->temperature = calc_temperature(adc_temp);
                data->pressure = calc_pressure(adc_pres);
                data->humidity = calc_humidity(adc_hum);
                data->gas_resistance = calc_gas_resistance(adc_gas_res, gas_range);
                break;
            }
            /* Delay to poll the data */
            _i2cCallbacks->delay_ms_relaxed(BME680_POLL_PERIOD_MS);
        }
        tries--;
    } while (tries);

    if (!tries){
        rslt = BME680_W_NO_NEW_DATA;
    }
    
    return rslt;
}

int Bme680::get_sensor_mode(struct bme680_dev *dev)
{
    int rslt = null_ptr_check();
    if (rslt!=BME680_OK) return rslt;
    
    uint8_t mode;

    rslt = get_regs(BME680_CONF_T_P_MODE_ADDR, &mode, 1);
    /* Masking the other register bit info*/
    _dev->power_mode = mode & BME680_MODE_MSK;

    return rslt;
}

int Bme680::set_sensor_mode()
{
    int rslt = null_ptr_check();
    if (rslt!=BME680_OK) return rslt;

    uint8_t tmp_pow_mode;
    uint8_t pow_mode = 0;
    uint8_t reg_addr = BME680_CONF_T_P_MODE_ADDR;

    /* Call repeatedly until in sleep */
    do {
        rslt = get_regs(BME680_CONF_T_P_MODE_ADDR, &tmp_pow_mode, 1);
        if (rslt == BME680_OK) {
            /* Put to sleep before changing mode */
            pow_mode = (tmp_pow_mode & BME680_MODE_MSK);

            if (pow_mode != BME680_SLEEP_MODE) {
                tmp_pow_mode = tmp_pow_mode & (~BME680_MODE_MSK); /* Set to sleep */
                rslt = set_regs(&reg_addr, &tmp_pow_mode, 1);
                _i2cCallbacks->delay_ms_relaxed(BME680_POLL_PERIOD_MS);
            }
        }
    } while (pow_mode != BME680_SLEEP_MODE);

    /* Already in sleep */
    if (_dev->power_mode != BME680_SLEEP_MODE) {
        tmp_pow_mode = (tmp_pow_mode & ~BME680_MODE_MSK) | (_dev->power_mode & BME680_MODE_MSK);
        if (rslt == BME680_OK) {
            rslt = set_regs(&reg_addr, &tmp_pow_mode, 1);
        }
    }
    
    return rslt;
}

int Bme680::set_gas_config()
{
    int rslt = null_ptr_check();
    if (rslt!=BME680_OK) return rslt;

    uint8_t reg_addr[2] = {0};
    uint8_t reg_data[2] = {0};

    if (_dev->power_mode == BME680_FORCED_MODE) {
        reg_addr[0] = BME680_RES_HEAT0_ADDR;
        reg_data[0] = calc_heater_res(_dev->gas_sett.heatr_temp);
        reg_addr[1] = BME680_GAS_WAIT0_ADDR;
        reg_data[1] = calc_heater_dur(_dev->gas_sett.heatr_dur);
        _dev->gas_sett.nb_conv = 0;
    } else {
        rslt = BME680_W_DEFINE_PWR_MODE;
    }
    
    if (rslt == BME680_OK) {
        rslt = set_regs(reg_addr, reg_data, 2);
    }
    
    return rslt;
}

uint8_t Bme680::calc_heater_dur(uint16_t dur)
{
    uint8_t factor = 0;
    uint8_t durval;

    if (dur >= 0xfc0) {
        durval = 0xff; /* Max duration*/
    } else {
        while (dur > 0x3F) {
            dur = dur / 4;
            factor += 1;
        }
        durval = (uint8_t) (dur + (factor * 64));
    }

    return durval;
}


uint8_t Bme680::calc_heater_res(uint16_t temp)
{
    uint8_t heatr_res;
    int32_t var1;
    int32_t var2;
    int32_t var3;
    int32_t var4;
    int32_t var5;
    int32_t heatr_res_x100;

    if (temp > 400) {
        temp = 400;
    }
    
    var1 = (((int32_t) _dev->amb_temp * _dev->calib.par_gh3) / 1000) * 256;
    var2 = (_dev->calib.par_gh1 + 784) * (((((_dev->calib.par_gh2 + 154009) * temp * 5) / 100) + 3276800) / 10);
    var3 = var1 + (var2 / 2);
    var4 = (var3 / (_dev->calib.res_heat_range + 4));
    var5 = (131 * _dev->calib.res_heat_val) + 65536;
    heatr_res_x100 = (int32_t) (((var4 / var5) - 250) * 34);
    heatr_res = (uint8_t) ((heatr_res_x100 + 50) / 100);

    return heatr_res;
}

int Bme680::boundary_check(uint8_t *value, uint8_t min, uint8_t max) {
    int rslt = BME680_OK;

    if (value != NULL) {
        // Check if value is below minimum value
        if (*value < min) {
            // Auto correct the invalid value to minimum value
            *value = min;
            _dev->info_msg |= BME680_I_MIN_CORRECTION;
        }
        // Check if value is above maximum value
        if (*value > max) {
            // Auto correct the invalid value to maximum value
            *value = max;
            _dev->info_msg |= BME680_I_MAX_CORRECTION;
        }
    } else {
        rslt = BME680_E_NULL_PTR;
    }

    return rslt;
}

int Bme680::set_sensor_settings(uint16_t desired_settings)
{
    int rslt = null_ptr_check();
    if (rslt!=BME680_OK) return rslt;
    
    uint8_t reg_addr;
    uint8_t data = 0;
    uint8_t count = 0;
    uint8_t reg_array[BME680_REG_BUFFER_LENGTH] = { 0 };
    uint8_t data_array[BME680_REG_BUFFER_LENGTH] = { 0 };
    uint8_t intended_power_mode = _dev->power_mode; // Save intended power mode

    // Check for null pointer in the device structure
    
    if (desired_settings & BME680_GAS_MEAS_SEL) {
        rslt = set_gas_config();
    }
    
    _dev->power_mode = BME680_SLEEP_MODE;
    if (rslt == BME680_OK) {
        rslt = set_sensor_mode();
    }
    
    // Selecting the filter
    if (desired_settings & BME680_FILTER_SEL) {
        rslt = boundary_check(&(_dev->tph_sett.filter), BME680_FILTER_SIZE_0, BME680_FILTER_SIZE_127);
        reg_addr = BME680_CONF_ODR_FILT_ADDR;

        if (rslt == BME680_OK) {
            rslt = get_regs(reg_addr, &data, 1);
        }
        
        if (desired_settings & BME680_FILTER_SEL) {
            data = BME680_SET_BITS(data, BME680_FILTER, _dev->tph_sett.filter);
        }
        
        reg_array[count] = reg_addr; // Append configuration
        data_array[count] = data;
        count++;
    }

    // Selecting heater control for the sensor
    if (desired_settings & BME680_HCNTRL_SEL) {
        rslt = boundary_check(&(_dev->gas_sett.heatr_ctrl), BME680_ENABLE_HEATER,
            BME680_DISABLE_HEATER);
        reg_addr = BME680_CONF_HEAT_CTRL_ADDR;

        if (rslt == BME680_OK){
            rslt = get_regs(reg_addr, &data, 1);
        }
        
        data = BME680_SET_BITS_POS_0(data, BME680_HCTRL, _dev->gas_sett.heatr_ctrl);

        reg_array[count] = reg_addr; // Append configuration
        data_array[count] = data;
        count++;
    }

    // Selecting heater T,P oversampling for the sensor
    if (desired_settings & (BME680_OST_SEL | BME680_OSP_SEL)) {
        rslt = boundary_check(&(_dev->tph_sett.os_temp), BME680_OS_NONE, BME680_OS_16X);
        reg_addr = BME680_CONF_T_P_MODE_ADDR;

        if (rslt == BME680_OK) {
            rslt = get_regs(reg_addr, &data, 1);
        }
        
        if (desired_settings & BME680_OST_SEL) {
            data = BME680_SET_BITS(data, BME680_OST, _dev->tph_sett.os_temp);
        }
        
        if (desired_settings & BME680_OSP_SEL) {
            data = BME680_SET_BITS(data, BME680_OSP, _dev->tph_sett.os_pres);
        }
        
        reg_array[count] = reg_addr;
        data_array[count] = data;
        count++;
    }

    // Selecting humidity oversampling for the sensor
    if (desired_settings & BME680_OSH_SEL) {
        rslt = boundary_check(&(_dev->tph_sett.os_hum), BME680_OS_NONE, BME680_OS_16X);
        reg_addr = BME680_CONF_OS_H_ADDR;

        if (rslt == BME680_OK) {
            rslt = get_regs(reg_addr, &data, 1);
        }
        
        data = BME680_SET_BITS_POS_0(data, BME680_OSH, _dev->tph_sett.os_hum);

        reg_array[count] = reg_addr; // Append configuration
        data_array[count] = data;
        count++;
    }

    // Selecting the runGas and NB conversion settings for the sensor
    if (desired_settings & (BME680_RUN_GAS_SEL | BME680_NBCONV_SEL)) {
        rslt = boundary_check(&(_dev->gas_sett.run_gas), BME680_RUN_GAS_DISABLE,
            BME680_RUN_GAS_ENABLE);
            
        if (rslt == BME680_OK) {
            // Validate boundary conditions
            rslt = boundary_check(&(_dev->gas_sett.nb_conv), BME680_NBCONV_MIN,
                BME680_NBCONV_MAX);
        }

        reg_addr = BME680_CONF_ODR_RUN_GAS_NBC_ADDR;

        if (rslt == BME680_OK)
            rslt = get_regs(reg_addr, &data, 1);

        if (desired_settings & BME680_RUN_GAS_SEL)
            data = BME680_SET_BITS(data, BME680_RUN_GAS, _dev->gas_sett.run_gas);

        if (desired_settings & BME680_NBCONV_SEL)
            data = BME680_SET_BITS_POS_0(data, BME680_NBCONV, _dev->gas_sett.nb_conv);

        reg_array[count] = reg_addr; // Append configuration
        data_array[count] = data;
        count++;
    }

    if (rslt == BME680_OK)
        rslt = set_regs(reg_array, data_array, count);

    // Restore previous intended power mode
    _dev->power_mode = intended_power_mode;

    return rslt;
}

int Bme680::get_sensor_settings(uint16_t desired_settings)
{
    int rslt = null_ptr_check();
    if (rslt!=BME680_OK) return rslt;
   
    /* starting address of the register array for burst read*/
    uint8_t reg_addr = BME680_CONF_HEAT_CTRL_ADDR;
    uint8_t data_array[BME680_REG_BUFFER_LENGTH] = { 0 };

    
    rslt = get_regs(reg_addr, data_array, BME680_REG_BUFFER_LENGTH);

    if (rslt == BME680_OK) {
        if (desired_settings & BME680_GAS_MEAS_SEL)
            rslt = get_gas_config();

        /* get the T,P,H ,Filter,ODR settings here */
        if (desired_settings & BME680_FILTER_SEL)
            _dev->tph_sett.filter = BME680_GET_BITS(data_array[BME680_REG_FILTER_INDEX],
                BME680_FILTER);

        if (desired_settings & (BME680_OST_SEL | BME680_OSP_SEL)) {
            _dev->tph_sett.os_temp = BME680_GET_BITS(data_array[BME680_REG_TEMP_INDEX], BME680_OST);
            _dev->tph_sett.os_pres = BME680_GET_BITS(data_array[BME680_REG_PRES_INDEX], BME680_OSP);
        }

        if (desired_settings & BME680_OSH_SEL)
            _dev->tph_sett.os_hum = BME680_GET_BITS_POS_0(data_array[BME680_REG_HUM_INDEX],
                BME680_OSH);

        /* get the gas related settings */
        if (desired_settings & BME680_HCNTRL_SEL)
            _dev->gas_sett.heatr_ctrl = BME680_GET_BITS_POS_0(data_array[BME680_REG_HCTRL_INDEX],
                BME680_HCTRL);

        if (desired_settings & (BME680_RUN_GAS_SEL | BME680_NBCONV_SEL)) {
            _dev->gas_sett.nb_conv = BME680_GET_BITS_POS_0(data_array[BME680_REG_NBCONV_INDEX],
                BME680_NBCONV);
            _dev->gas_sett.run_gas = BME680_GET_BITS(data_array[BME680_REG_RUN_GAS_INDEX],
                BME680_RUN_GAS);
        }
    }

    return rslt;
}

int Bme680::get_gas_config()
{
    int rslt = null_ptr_check();
    if (rslt!=BME680_OK) return rslt;
    
    /* starting address of the register array for burst read*/
    uint8_t reg_addr1 = BME680_ADDR_SENS_CONF_START;
    uint8_t reg_addr2 = BME680_ADDR_GAS_CONF_START;
    uint8_t reg_data = 0;

    if (rslt == BME680_OK) {
        rslt = get_regs(reg_addr1, &reg_data, 1);
        if (rslt == BME680_OK) {
            _dev->gas_sett.heatr_temp = reg_data;
            rslt = get_regs(reg_addr2, &reg_data, 1);
            if (rslt == BME680_OK) {
                /* Heating duration register value */
                _dev->gas_sett.heatr_dur = reg_data;
            }
        }
    }
    
    return rslt;
}

int16_t Bme680::calc_temperature(uint32_t temp_adc)
{
    int64_t var1;
    int64_t var2;
    int64_t var3;
    int16_t calc_temp;

    var1 = ((int32_t) temp_adc >> 3) - ((int32_t) _dev->calib.par_t1 << 1);
    var2 = (var1 * (int32_t) _dev->calib.par_t2) >> 11;
    var3 = ((var1 >> 1) * (var1 >> 1)) >> 12;
    var3 = ((var3) * ((int32_t) _dev->calib.par_t3 << 4)) >> 14;
    _dev->calib.t_fine = (int32_t) (var2 + var3);
    calc_temp = (int16_t) (((_dev->calib.t_fine * 5) + 128) >> 8);

    return calc_temp;
}

uint32_t Bme680::calc_pressure(uint32_t pres_adc)
{
    int32_t var1 = 0;
    int32_t var2 = 0;
    int32_t var3 = 0;
    int32_t pressure_comp = 0;

    var1 = (((int32_t)_dev->calib.t_fine) >> 1) - 64000;
    var2 = ((((var1 >> 2) * (var1 >> 2)) >> 11) *
        (int32_t)_dev->calib.par_p6) >> 2;
    var2 = var2 + ((var1 * (int32_t)_dev->calib.par_p5) << 1);
    var2 = (var2 >> 2) + ((int32_t)_dev->calib.par_p4 << 16);
    var1 = (((((var1 >> 2) * (var1 >> 2)) >> 13) *
        ((int32_t)_dev->calib.par_p3 << 5)) >> 3) +
        (((int32_t)_dev->calib.par_p2 * var1) >> 1);
    var1 = var1 >> 18;
    var1 = ((32768 + var1) * (int32_t)_dev->calib.par_p1) >> 15;
    pressure_comp = 1048576 - pres_adc;
    pressure_comp = (int32_t)((pressure_comp - (var2 >> 12)) * ((uint32_t)3125));
    if (pressure_comp >= BME680_MAX_OVERFLOW_VAL)
        pressure_comp = ((pressure_comp / (uint32_t)var1) << 1);
    else
        pressure_comp = ((pressure_comp << 1) / (uint32_t)var1);
    var1 = ((int32_t)_dev->calib.par_p9 * (int32_t)(((pressure_comp >> 3) *
        (pressure_comp >> 3)) >> 13)) >> 12;
    var2 = ((int32_t)(pressure_comp >> 2) *
        (int32_t)_dev->calib.par_p8) >> 13;
    var3 = ((int32_t)(pressure_comp >> 8) * (int32_t)(pressure_comp >> 8) *
        (int32_t)(pressure_comp >> 8) *
        (int32_t)_dev->calib.par_p10) >> 17;

    pressure_comp = (int32_t)(pressure_comp) + ((var1 + var2 + var3 +
        ((int32_t)_dev->calib.par_p7 << 7)) >> 4);

    return (uint32_t)pressure_comp;

}

uint32_t Bme680::calc_humidity(uint16_t hum_adc)
{
    int32_t var1;
    int32_t var2;
    int32_t var3;
    int32_t var4;
    int32_t var5;
    int32_t var6;
    int32_t temp_scaled;
    int32_t calc_hum;

    temp_scaled = (((int32_t) _dev->calib.t_fine * 5) + 128) >> 8;
    var1 = (int32_t) (hum_adc - ((int32_t) ((int32_t) _dev->calib.par_h1 * 16)))
        - (((temp_scaled * (int32_t) _dev->calib.par_h3) / ((int32_t) 100)) >> 1);
    var2 = ((int32_t) _dev->calib.par_h2
        * (((temp_scaled * (int32_t) _dev->calib.par_h4) / ((int32_t) 100))
            + (((temp_scaled * ((temp_scaled * (int32_t) _dev->calib.par_h5) / ((int32_t) 100))) >> 6)
                / ((int32_t) 100)) + (int32_t) (1 << 14))) >> 10;
    var3 = var1 * var2;
    var4 = (int32_t) _dev->calib.par_h6 << 7;
    var4 = ((var4) + ((temp_scaled * (int32_t) _dev->calib.par_h7) / ((int32_t) 100))) >> 4;
    var5 = ((var3 >> 14) * (var3 >> 14)) >> 10;
    var6 = (var4 * var5) >> 1;
    calc_hum = (((var3 + var6) >> 10) * ((int32_t) 1000)) >> 12;

    if (calc_hum > 100000) /* Cap at 100%rH */
        calc_hum = 100000;
    else if (calc_hum < 0)
        calc_hum = 0;

    return (uint32_t) calc_hum;
}

uint32_t Bme680::calc_gas_resistance(uint16_t gas_res_adc, uint8_t gas_range)
{
    int64_t var1;
    uint64_t var2;
    int64_t var3;
    uint32_t calc_gas_res;
    /**Look up table 1 for the possible gas range values */
    uint32_t lookupTable1[16] = { UINT32_C(2147483647), UINT32_C(2147483647), UINT32_C(2147483647), UINT32_C(2147483647),
        UINT32_C(2147483647), UINT32_C(2126008810), UINT32_C(2147483647), UINT32_C(2130303777),
        UINT32_C(2147483647), UINT32_C(2147483647), UINT32_C(2143188679), UINT32_C(2136746228),
        UINT32_C(2147483647), UINT32_C(2126008810), UINT32_C(2147483647), UINT32_C(2147483647) };
    /**Look up table 2 for the possible gas range values */
    uint32_t lookupTable2[16] = { UINT32_C(4096000000), UINT32_C(2048000000), UINT32_C(1024000000), UINT32_C(512000000),
        UINT32_C(255744255), UINT32_C(127110228), UINT32_C(64000000), UINT32_C(32258064), UINT32_C(16016016),
        UINT32_C(8000000), UINT32_C(4000000), UINT32_C(2000000), UINT32_C(1000000), UINT32_C(500000),
        UINT32_C(250000), UINT32_C(125000) };

    var1 = (int64_t) ((1340 + (5 * (int64_t) _dev->calib.range_sw_err)) *
        ((int64_t) lookupTable1[gas_range])) >> 16;
    var2 = (((int64_t) ((int64_t) gas_res_adc << 15) - (int64_t) (16777216)) + var1);
    var3 = (((int64_t) lookupTable2[gas_range] * (int64_t) var1) >> 9);
    calc_gas_res = (uint32_t) ((var3 + ((int64_t) var2 >> 1)) / (int64_t) var2);

    return calc_gas_res;
}