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    BME688 Sequential Mode Timing

    BME688 Sequential Mode Timing

    amitr
    New Poster

    As already mentioned by my collegues, the BME688 Sequential mode is not detailed in the latest BME688 Datasheet (BME68X_ODR3_MSK/Apr2021)

    My first question would be -- is there a modified Datasheet that does describe this mode?

    Otherwise, I would like to understand the timing of this mode. After reverse engineering the Sequential mode demo code, I see that the mode field in reg Ctrl_meas gets the value 3 to select Sequential mode. Furthermore, there are 2 additional fields that specify a so-called "sleep duration during Sequential mode" -- which I don't fully understand. I see that this sleep-duration (saved as odr field in a memory structure) is saved in 2 bit fields (odr20 & odr3) in registers 0x75 and 0x71 respectuflly. The odr bit combinations map to delay times as follows:

    #define BME68X_ODR_0_59_MS                        UINT8_C(0)
    #define BME68X_ODR_62_5_MS                        UINT8_C(1)
    #define BME68X_ODR_125_MS                         UINT8_C(2)
    #define BME68X_ODR_250_MS                         UINT8_C(3)
    #define BME68X_ODR_500_MS                         UINT8_C(4)
    #define BME68X_ODR_1000_MS                        UINT8_C(5)
     
    The example SW calls this:
        uint16_t tempProf[10] = { 100, 200, 320 };
        uint16_t durProf[10] = { 150, 150, 150 };
        bme.setSeqSleep(BME68X_ODR_250_MS);
        bme.setHeaterProf(tempProf, durProf, 3);
        bme.setOpMode(BME68X_SEQUENTIAL_MODE);
     
    How does the timing chart in this mode work?
     
    From my tests, the only way I could find all 3 results in the FIELD buffers was to wait for  3*(150+250)mSec  before calling  bme.fetchData().
    This seems to point to the fact that there is a 250mSec sleep-lapse after every step of the 3 sequential mode steps.
    The comments in the code, rather, imply that there should be only one 250mSec lapse at the end ...
     
    Can someone from Bosch attach a timing chart, like the charts given for Forced and Parallel modes -- So it can be fully understood when each part of TPHG is being measured per each step in sequential mode and when the sensor is in a sleep-lapse?
     
    Thanks much in advance ...
    4 REPLIES 4

    BSTRobin
    Community Moderator
    Community Moderator

    Hi amitr,

    Currently, BME688 sequential mode timing was not open in document. We need to check whether we will open it in the future.

    BSTRobin
    Community Moderator
    Community Moderator

    Hi amitr,

    Could we know detailed information about your application?

    BSTRobin
    Community Moderator
    Community Moderator

    Hi amitr,

    Could you give feedback to us? Thanks.

    BSTRobin
    Community Moderator
    Community Moderator

    Since there was no feedback for a long time, we close this topic first. You could update feedback in the future if you have.

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