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    BME680/88 Reading Data Registers

    cweaver
    Member

    BME680/88 Reading Data Registers

    I'm having some issues reading both the MSB and LSB data registers from the BME688. I'm using two single-byte read I2C transactions to read first the MSB and then LSB registers. When I reset the sensor and read values, there are no issues, but after running the sensor, something is messed up. I currently don't have access to a logic analyzer but wanted to know is there a requirement to read both data registers in the same transaction?

     

    Thanks for any advice!

    Tags (3)
    2 REPLIES 2
    BSTRobin
    Community Moderator

    Re: BME680/88 Reading Data Registers

    Hello cweaver,

    You could read one or more sensor data. This is BME68X sensor API code, it demonstrated reading the raw data from the sensor.

    /* This internal API is used to read a single data of the sensor */
    static int8_t read_field_data(uint8_t index, struct bme68x_data *data, struct bme68x_dev *dev)
    {
    int8_t rslt = BME68X_OK;
    uint8_t buff[BME68X_LEN_FIELD] = { 0 };
    uint8_t gas_range_l, gas_range_h;
    uint32_t adc_temp;
    uint32_t adc_pres;
    uint16_t adc_hum;
    uint16_t adc_gas_res_low, adc_gas_res_high;
    uint8_t tries = 5;

    while ((tries) && (rslt == BME68X_OK))
    {
    rslt = bme68x_get_regs(((uint8_t)(BME68X_REG_FIELD0 + (index * BME68X_LEN_FIELD_OFFSET))),
    buff,
    (uint16_t)BME68X_LEN_FIELD,
    dev);
    if (!data)
    {
    rslt = BME68X_E_NULL_PTR;
    break;
    }

    data->status = buff[0] & BME68X_NEW_DATA_MSK;
    data->gas_index = buff[0] & BME68X_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_low = (uint16_t)((uint32_t)buff[13] * 4 | (((uint32_t)buff[14]) / 64));
    adc_gas_res_high = (uint16_t)((uint32_t)buff[15] * 4 | (((uint32_t)buff[16]) / 64));
    gas_range_l = buff[14] & BME68X_GAS_RANGE_MSK;
    gas_range_h = buff[16] & BME68X_GAS_RANGE_MSK;
    if (dev->variant_id == BME68X_VARIANT_GAS_HIGH)
    {
    data->status |= buff[16] & BME68X_GASM_VALID_MSK;
    data->status |= buff[16] & BME68X_HEAT_STAB_MSK;
    }
    else
    {
    data->status |= buff[14] & BME68X_GASM_VALID_MSK;
    data->status |= buff[14] & BME68X_HEAT_STAB_MSK;
    }

    if ((data->status & BME68X_NEW_DATA_MSK) && (rslt == BME68X_OK))
    {
    rslt = bme68x_get_regs(BME68X_REG_RES_HEAT0 + data->gas_index, &data->res_heat, 1, dev);
    if (rslt == BME68X_OK)
    {
    rslt = bme68x_get_regs(BME68X_REG_IDAC_HEAT0 + data->gas_index, &data->idac, 1, dev);
    }

    if (rslt == BME68X_OK)
    {
    rslt = bme68x_get_regs(BME68X_REG_GAS_WAIT0 + data->gas_index, &data->gas_wait, 1, dev);
    }

    if (rslt == BME68X_OK)
    {
    data->temperature = calc_temperature(adc_temp, dev);
    data->pressure = calc_pressure(adc_pres, dev);
    data->humidity = calc_humidity(adc_hum, dev);
    if (dev->variant_id == BME68X_VARIANT_GAS_HIGH)
    {
    data->gas_resistance = calc_gas_resistance_high(adc_gas_res_high, gas_range_h);
    }
    else
    {
    data->gas_resistance = calc_gas_resistance_low(adc_gas_res_low, gas_range_l, dev);
    }

    break;
    }
    }

    if (rslt == BME68X_OK)
    {
    dev->delay_us(BME68X_PERIOD_POLL, dev->intf_ptr);
    }

    tries--;
    }

    return rslt;
    }


    https://github.com/BoschSensortec/BME68x-Sensor-API/blob/master/bme68x.c

    cweaver
    Member

    Re: BME680/88 Reading Data Registers

    Thanks! I ultimately found a bug in my program outputting occasionally incorrect SPI transactions.

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