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    BME688 not giving gas readings

    BME688 not giving gas readings

    boydy
    Member

    Hi

    I am developing a lightweight sensor board which contains the BME688.

    I am looking to implement the forced read mode, and have written code that I believe reflects the quick start.

    I am using the sensor with SPI and can communicate with the device, and am writing the code as a bare metal implementation in C.

    I am also able to read back any register value, and am getting values for temp, pressure and humidity - but nothing for gas resistance.

    The gas_r_lsb register is reporting 0x04, which suggests that the device has not achieved the heating current - yet no changes of times or target currents seem to change this.

    I have read back the registers in the device, and they all appear to be as expected. I have also observed that the current draw from the device does inrease if the heating time is increased, as I can see the linear device that powers it warm up by a few degrees with a thermal camera when the time is extended.

    As an experiment I also switched the device into paralell mode, but this made no difference to the output.

    What am I missing?

    Ta!

    9 REPLIES 9

    floitsch
    Occasional Visitor

    I have run into the same issue, and for me it was a confusion with the registers.

    Turns out that the BME680 and BME688 use different registers. Specifically, the Gas register is different. If you read the gas status on a BME688 using the BME680 registers you get 0x04, and it looks like the gas_valid_r bit is always 0.

    Does sound very similar. What register did you end up reading to get the correct result?

     

    BSTRobin
    Community Moderator
    Community Moderator

    Don't you use BME68x sensor API? https://github.com/BoschSensortec/BME68x-Sensor-API

    Unfortunately not - I was not able to port it to the processor that I am using in this application

    BSTRobin
    Community Moderator
    Community Moderator

    Hi boydy,

    There was example code  on STM32 for your  reference to migrate it to your platform.

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