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    BMI160 watermark interrupt FIFO data being repeated

    BMI160 watermark interrupt FIFO data being repeated

    michiels
    Member

    Hi,


    We are using the watermark interrupt to read 64 gyroscope and accelerometer samples at a time. This works fine when the device is laying still on a desk but when we repeat the test with the device being moved around we seem to get the same values being read from the FIFO at some instances.
    We have checked with the bmi160_get_int_status function to see if maybe any other inter-rupts are being triggered but that does not seem to be the case.


    Any thoughts?

    Thanks and best regards,

    Michiel

    8 REPLIES 8

    Hi,

    I have found that this issue happened always when I got a certain pattern (0x80 0x00) in my data which let me to this part in the driver code:

     

    * @brief This API checks the presence of non-valid frames in the read fifo data.
    */
    static void check_frame_validity(uint16_t *data_index, const struct bmi160_dev *dev)
    {
    if ((*data_index + 2) < dev->fifo->length)
    {
    /* Check if FIFO is empty */
    if ((dev->fifo->data[*data_index] == FIFO_CONFIG_MSB_CHECK) &&
    (dev->fifo->data[*data_index + 1] == FIFO_CONFIG_LSB_CHECK))
    {
    /*Update the data index as complete*/
    *data_index = dev->fifo->length;
    }
    }

    }

    Is this a bug in the driver or is this intentional behavior?

    Best regards,

    Michiel

    BSTRobin
    Community Moderator
    Community Moderator

    Hello michiels,

    It is recommended that you refer to the example code and check whether the FIFO reading data is normal according to your ODR and FIFO watermark settings. For example, if you set 100 Hz ODR, enable accel, gyro and FIFO header, and set FIFO watermark to 78(means 78*4 bytes FIFO data), then after receiving FIFO watermark interrupt, you will read 24 frames of accel and gyro data, with a time interval of about 240ms.

    First confirm that the FIFO reading is normal, and then check whether the data is correct.

    Hi BSTRobin,

    Before I do the read operation I check the available data as is done in the example application (rslt = get_fifo_byte_counter(&bytes_to_read, dev);). This reads consistently 768. When I toggle a GPIO pin of my microcontroller outside to check the interrupt timings it is also consistent. Also if the PCB is laying still on the desk this issue does not appear to happen. It consistently happens when the desribed pattern appears in the data and it does not happen when I turn of the check for the data. When I for example plot the data it looks correct when I ignore this 0x80 0x00.

    Thanks and best regards,

    Michiel

    BSTRobin
    Community Moderator
    Community Moderator

    Hello michiels,

    Did you run reference code?

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