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    BME280 SPI maximum capacitive and inductive load

    honoju
    Member

    BME280 SPI maximum capacitive and inductive load

    Hello,

    Does anyone know if there is a maximum capacitive/inductive load for the BME280 SPI protocol?

    In the datasheet SPI timings table (capture in attachments), they mention 25pF as a usage condition for SDO but I am not sure if it is the maximum capacitive load for the BME280

    Thanks

    6 REPLIES 6
    Jet
    Occasional Contributor

    Re: BME280 SPI maximum capacitive and inductive load

    Hi Sir:

    Could you tell me why you want to know BME280 SPI maximum capacitive and inductive load ? Communication failed?

    25pF as a usage condition for SDO out delay is minimum condition, but  when we use SPI connection, atually we don't need to connect a 25pf capacity.

     

    honoju
    Member

    Re: BME280 SPI maximum capacitive and inductive load

    Hello,

    Thanks for your reply

    Well, I'm having trouble transmitting BME280 measurement data over 1m long cables and I suspect it is the capacitive and inductive loads the cables  present to the sensor that is problematic. The transmission works well when I use small jumper wires (few cm long).

    Depending on the distance between the cables (Vcc, GND, SDI, SCK, CS and SDO), I am sometimes getting only temperature and pressure data but not the humidity data and other times I am getting none of the three measurements.

     

    Jet
    Occasional Contributor

    Re: BME280 SPI maximum capacitive and inductive load

    Hi Sir:

    I think it is too long distance between sensor and host by using over 1m long cables to transmit and receive data, it is easy to be interfered and lead to the signal quality unstable.

    Maybe you need to shorten this distance.

    Or you might try to add a resistance close to host between them to form impedance matching circuit and then observe the results.

     

    honoju
    Member

    Re: BME280 SPI maximum capacitive and inductive load

    Hello Jet,

    I am going to try impedance matching

    Thanks for your reply

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