BNO055 no motion duration [acc_nm_set 0x16]

[Hubanl]

I am having trouble understanding the equations used to set the duration of the no motion trigger of the bno055 sensor.

According to the datasheet the slo_no_mot_dur <5:0>  is configured using bit6 - bit1.

For example if i have the following bits: 0 010000 1

I would take the equation in the middle, which computes down to: 0*4 + 20 = 20s

However, in practice this is around 36s, far from the computed 20s. Is the formula incorrect? Or am i missing something else?

Thanks in advance!

[FAE_CA1 · Accepted solution]

Hi,

Thanks for your inquiry.

If you read BNO055 register 0x01 at page 0, you will get value of 0xFB for accel chip ID. This means that BMA280 is inside BNO055 because BMA280 chip ID is 0xFB. If you look at page 42 of BMA280 datasheet at https://www.bosch-sensortec.com/media/boschsensortec/downloads/datasheets/bst-bma280-ds000.pdf, you will find that when slo_no_mot_dur <5:0>  = 0b010000 = 16, the duration = 40s which is close to 36s that you got. So the formula should be,

        slo_no_mot_dur <5:4> = '0b01' --> [slo_no_mot_dur <3:0> * 8 + 40] second

Sorry for the typo in BNO055 datasheet. We will fix it in the new version later.

Thanks.