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    BME688 gas resistance reading stuck, but only with bsec

    Remyhx
    New Poster

    BME688 gas resistance reading stuck, but only with bsec

    Hi,

    I use BSEC 1.6.1480 with Arduino 1.8.16 on an esp32 board / BME688 SDO tied to GND. I am interested in the IAQ index, seems to work. But strange thing: if i use the basic example, unchanged, the gas resistance reading seems not ok (stuck at 12917167 ohm). For example:

    4170038, 23.09, 99831.00, 48.16, 12917167.00, 81.06, 1, 23.03, 48.33, 49.49, 597.95, 0.72
    4173039, 23.10, 99833.00, 48.13, 12917167.00, 81.09, 1, 23.04, 48.28, 49.50, 598.00, 0.72
    4176038, 23.08, 99831.00, 48.13, 12917167.00, 81.16, 1, 23.02, 48.34, 49.53, 598.13, 0.72
    4179039, 23.09, 99831.00, 48.16, 12917167.00, 81.19, 1, 23.03, 48.33, 49.55, 598.18, 0.72
    4182038, 23.09, 99833.00, 48.17, 12917167.00, 81.20, 1, 23.03, 48.36, 49.55, 598.20, 0.72
    4185039, 23.09, 99831.00, 48.11, 12917167.00, 81.27, 1, 23.03, 48.29, 49.58, 598.32, 0.72
    4188038, 23.08, 99831.00, 48.13, 12917167.00, 81.33, 1, 23.02, 48.34, 49.61, 598.43, 0.73
    4191039, 23.09, 99833.00, 48.15, 12917167.00, 81.36, 1, 23.03, 48.32, 49.62, 598.48, 0.73
    4194038, 23.09, 99831.00, 48.13, 12917167.00, 81.40, 1, 23.03, 48.31, 49.64, 598.55, 0.73
    4197038, 23.09, 99829.00, 48.17, 12917167.00, 81.41, 1, 23.03, 48.35, 49.64, 598.56, 0.73
    4200038, 23.10, 99831.00, 48.14, 12917167.00, 81.42, 1, 23.04, 48.30, 49.64, 598.58, 0.73
    4203039, 23.09, 99833.00, 48.13, 12917167.00, 81.45, 1, 23.03, 48.32, 49.66, 598.64, 0.73
    4206038, 23.09, 99833.00, 48.11, 12917167.00, 81.51, 1, 23.03, 48.30, 49.68, 598.73, 0.73
    4209039, 23.09, 99831.00, 48.12, 12917167.00, 81.55, 1, 23.03, 48.31, 49.70, 598.81, 0.73
    4212038, 23.10, 99829.00, 48.13, 12917167.00, 81.56, 1, 23.04, 48.29, 49.71, 598.83, 0.73
    4215039, 23.10, 99833.00, 48.12, 12917167.00, 81.58, 1, 23.04, 48.29, 49.71, 598.86, 0.73
    4218038, 23.11, 99829.00, 48.13, 12917167.00, 81.56, 1, 23.05, 48.28, 49.71, 598.83, 0.73
    4221039, 23.11, 99833.00, 48.13, 12917167.00, 81.55, 1, 23.05, 48.29, 49.70, 598.81, 0.73
    4224038, 23.10, 99831.00, 48.08, 12917167.00, 81.59, 1, 23.04, 48.27, 49.72, 598.89, 0.73
    4227039, 23.10, 99831.00, 48.02, 12917167.00, 81.69, 1, 23.04, 48.21, 49.76, 599.05, 0.73
    4230038, 23.10, 99831.00, 48.02, 12917167.00, 81.78, 1, 23.04, 48.21, 49.80, 599.21, 0.73

    Strange thing is, if i use the Adafruit library gas resistance reading appears to be normal, at least dynamic. But no IAQ reading.

    I could only use the IAQ reading and ignore gas resistance, but i worrie about a faulty IAQ reading. Compared to the Sensirion vocindex buildup a fake index could be appearing. When i test with alcohol spray (not directly applied of course) in the room, the voc index drops by 5, instead of climbing...

    Do you have a suggestion?

     

    NB: Adafruit BME680 version 2.0.1(!) / look at the ohm change...

    Temperature = 23.41 *C
    Pressure = 998.68 hPa
    Humidity = 48.96 %
    Gas = 23.78 KOhms
    Approx. Altitude = 122.02 m

    Gas kOhms changes, with alcoholspray aerosol drops.

    Zanshin library for BME680:

    Loop Temp°C Humid% Press hPa Alt m Air mΩ
    ==== ====== ====== ========= ======= ======
    1 23.51 51.088 998.52 123.48-1901.67
    2 23.74 51.132 998.52 123.48-1901.67
    3 23.52 51.074 998.56 123.14-1901.67
    4 23.36 51.199 998.54 123.31-1901.67

    Gas resistance seems faulty too. Strange!

     

    5 REPLIES 5
    Minhwan
    Community Moderator

    Re: BME688 gas resistance reading stuck, but only with bsec

    Hello, 

     

    Our latest BSEC 1 library is v.1.4.8.0. Could you download and try it? 

    https://www.bosch-sensortec.com/software-tools/software/bsec/

    And, if you are using BME688, you can also use BSEC 2 and it's nice opportuinity since BSEC 2 can implement our AI studio feature as well. 

    https://www.bosch-sensortec.com/software-tools/software/bme688-software/

    Please let me know if you have still issues after applying latest library. 

    Thanks, 

    Remyhx
    New Poster

    Re: BME688 gas resistance reading stuck, but only with bsec

    Thanks for the reply! I already use this version (1.4.8.0).

    It’s strange the Adafruit lib works (except for the iaq index), bsec doesn’t. Please also consider the dropping iaq index by applying an ethanol aerosol in the room, where it should rise! Maybe i should therefore consider bsec 2.

    Only it’s unclear for me after downloading the v2 how to install in Arduino. Should i just replace the precompiled lib with the 1.4.8.0 one? The zip file seems to not be importable into Arduino, I didn’t found clear instructions how to import, maybe missed it. (Only reference to the old library instructions)

    Edit/Update -> After downloading the version 2 BSEC i unzipped everything and put the examples\bsec2 contents in the erased 'old' 1.4.8.0 directory. It works now!

    Remyhx
    New Poster

    Re: BME688 gas resistance reading stuck, but only with bsec

    Unfortunately it seemed to work at first, but after changing the sample rate (of the example file) from High Performance to ULP the gas resistance seems to be fixed again.

    Only things i changed:

    - sample rate to BSEC_SAMPLE_RATE_ULP

    - deleted BSEC_OUTPUT_RAW_GAS_INDEX, BSEC_OUTPUT_GAS_ESTIMATE_1, BSEC_OUTPUT_GAS_ESTIMATE_2, BSEC_OUTPUT_GAS_ESTIMATE_3, BSEC_OUTPUT_GAS_ESTIMATE_4 from the sensor list, because I don't need it for my project.

    Now Gas Resistance gets stuck at around 5000 ohms.

     

    Using direct readout (not by BSEC) is fine. Or using the high performance, but not suitable for the battery operated device.

    It's really a pity Bosch seems to not be fine with some lite version of an algoritm like Sensirion shares with its vocindex. Sensirion is not usable for the project because of the 1Hz recommendation.

    Minhwan
    Community Moderator

    Re: BME688 gas resistance reading stuck, but only with bsec

    Hello, 

     

    Currently, we don't provide mode switch feature. Therefore, when you enable sensor, please set ULP. 

    If our example doesn't work, please let me know about example. 

    Thanks, 

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