BHI260AB Calibration state after power cycle

[nameeri1]

Hello,

We are using a BHI260AB in our custom device. Currently, we calibrate the device according to the recommended process as described in the App Note and data sheet. We hold the device in different orientations until we reach a Calibration state of 3 for Acc, then move the device in figure eight pattern to calibrate the Mag to state 3, then place the device on a level surface to calibrate the Gyro to a state of 3. We then retreive the calibration data from the sensor (using bhy2_get_calibration_profile for each of the 3 sensors)and store that to a flash chip. We do this once at the factory.

Upon power up, after doing the initialization for the chip, we read the calibration data from flash and apply the calibration back to the chip (bhy2_set_calibration_profile for each of the sensors). We notice that the heading always returns 0 even though the calibration data was applied. Also, the sensors show that their calibration state is 0 again. Is there something that we are doing incorrectly? Please note that we are not putting the BHI260AB into a lower power state, we are removing power completely when the device is turned off. I have read on your forum the topic below which describes a very similar problem:

https://community.bosch-sensortec.com/t5/MEMS-sensors-forum/BNO055-unreliable-calibration-amp-headin...

Any help is greatly appreciated. Thanks

[BSTRobin]

Hi nameeri1,

Thanks for your inquiry.
What device is BHI260AB used on? What is the working environment around the device like?

[nameeri1]

Hi Robin,

We have a custom device. I assume you are asking about the metals surrounding the device. The bhi260ab is mounted within an aluminium enclosure. There are metal components housed within the aluminum structure as well. We have not performed a soft iron calibration. Do you think that would help with the compass reading after a power cycle?