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    BMI270 - downsampling

    BMI270 - downsampling

    joma
    Established Member

    Hello,

    my BMI270 board is lying on the desk and I have following gyro values:

    Event: time 1159.868394, -------------- SYN_REPORT ------------
    Event: time 1159.878398, type 3 (EV_ABS), code 40 (ABS_MISC), value 113079
    Event: time 1159.878398, type 3 (EV_ABS), code 0 (ABS_X), value 0
    Event: time 1159.878398, type 3 (EV_ABS), code 1 (ABS_Y), value 2
    Event: time 1159.878398, type 3 (EV_ABS), code 2 (ABS_Z), value -2
    Event: time 1159.878398, -------------- SYN_REPORT ------------
    Event: time 1159.888399, type 3 (EV_ABS), code 40 (ABS_MISC), value 113080
    Event: time 1159.888399, type 3 (EV_ABS), code 2 (ABS_Z), value -3
    Event: time 1159.888399, -------------- SYN_REPORT ------------
    Event: time 1159.898404, type 3 (EV_ABS), code 40 (ABS_MISC), value 113081
    Event: time 1159.898404, type 3 (EV_ABS), code 0 (ABS_X), value 1
    Event: time 1159.898404, type 3 (EV_ABS), code 1 (ABS_Y), value 1
    Event: time 1159.898404, type 3 (EV_ABS), code 2 (ABS_Z), value -2
    Event: time 1159.898404, -------------- SYN_REPORT ------------
    Event: time 1159.908369, type 3 (EV_ABS), code 40 (ABS_MISC), value 113082
    Event: time 1159.908369, type 3 (EV_ABS), code 0 (ABS_X), value 0
    Event: time 1159.908369, type 3 (EV_ABS), code 1 (ABS_Y), value 2
    Event: time 1159.908369, type 3 (EV_ABS), code 2 (ABS_Z), value -3

    If I turn off downsampling (BMI2_FIFO_DOWNS_ADDR is set to 0x80) I'm getting following gyro values:

    Event: time 54.097798, -------------- SYN_REPORT ------------
    Event: time 54.097806, type 3 (EV_ABS), code 40 (ABS_MISC), value 5904
    Event: time 54.097806, type 3 (EV_ABS), code 0 (ABS_X), value -197
    Event: time 54.097806, type 3 (EV_ABS), code 1 (ABS_Y), value 183
    Event: time 54.097806, type 3 (EV_ABS), code 2 (ABS_Z), value 139
    Event: time 54.097806, -------------- SYN_REPORT ------------
    Event: time 54.097813, type 3 (EV_ABS), code 40 (ABS_MISC), value 5905
    Event: time 54.097813, type 3 (EV_ABS), code 0 (ABS_X), value 99
    Event: time 54.097813, type 3 (EV_ABS), code 1 (ABS_Y), value -59
    Event: time 54.097813, type 3 (EV_ABS), code 2 (ABS_Z), value 185
    Event: time 54.097813, -------------- SYN_REPORT ------------
    Event: time 54.097820, type 3 (EV_ABS), code 40 (ABS_MISC), value 5906
    Event: time 54.097820, type 3 (EV_ABS), code 0 (ABS_X), value 245
    Event: time 54.097820, type 3 (EV_ABS), code 1 (ABS_Y), value -93
    Event: time 54.097820, type 3 (EV_ABS), code 2 (ABS_Z), value -112

    Why are they about 100 times higher ? I would exept average values if filtering is on. Register (0x43) GYR_RANGE is 0 in both cases.

    When BMI2_FIFO_DOWNS_ADDR is set to 0x80 and ODR is set to 100 for gyro and accel, ODR for accel is fine, but gyro ODR reg is ignored and ODR is 6.4kHz. Why is this register ignored ?

    Thanks

    3 REPLIES 3

    BSTRobin
    Community Moderator
    Community Moderator

    Hello joma,

    It is not good way to disable gyr_fifo_filt_data bit in FIFO_DOWNS(0x45) register. This is not recommended.

    joma
    Established Member

    Thanks for the info. 

    Then how is it possible to sed 6.4 kHz ODR for gyro ?

    BSTRobin
    Community Moderator
    Community Moderator

    Hello joma,

    If you disable gyr_fifo_filt_data bit in FIFO_DOWNS(0x45) register, ODR was set to 6.4 kHz.

    BMI270 block diagram.png

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