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    BME280 Humidity Compensation Example

    JESE
    New Poster

    BME280 Humidity Compensation Example

    Hi Guys

    So, I've had a sensor in production for the last 3 years, to report Temperature & RH, using the BME280.
    Recently, I've noted that at higher Humidity conditions and Lower Temperatures, the compensated RH result jumps from say 70% at 12°C to 100%.

    Revisiting the latest data sheet (R1.9), Section 8.1 documents example C code to resolve RH.
    Trying to turn the following in to intelligable format to impliment for integer process, I've hit several ambiguities...

    double bme280_compensate_H_double(BME280_S32_t adc_H); {    ... Unexpected semi-colon

    then this superlative line of code:
    var_H = (adc_H – (((double)dig_H4) * 64.0 + ((double)dig_H5) / 16384.0 * var_H)) * (((double)dig_H2) / 65536.0 * (1.0 + ((double)dig_H6) / 67108864.0 * var_H * (1.0 + ((double)dig_H3) / 67108864.0 * var_H)));

    Any one any suggestion as to the order of preference that should be applied withing parenthasis? I was taught BODMAS, Brackets of, Division, Multiplication, then Addition and Substarction. IMO, the above line of code could do with a make over. I'd then be happy to share an integer math equivalent for
    any one else implimenting on an 8 or 16 bit micro...

     

    1 REPLY 1
    FAE_CA1
    Community Moderator

    Re: BME280 Humidity Compensation Example

    Hi,

    Thanks for your inquiry.

    Please see the attached "sample_calculation_BME280.xlsx" for more information. Of cause, you can use integers operation in 8 bit or 16 bit MCUs.

    Thanks.

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