BMI088 accelerometer noise too high

[sebmadgwick]

I am migrating our design from the BMI090L to the BMI088. Both part datasheets state an accelerometer noise performance of 160 ug/sqrt(Hz) for X/Y, and 190 ug/sqrt(Hz) for Z. I am observing significantly higher accelerometer noise for the BMI088 as shown in the plots below.

The parts are mounted on identical host boards and use the same configuration: GYRO_RANGE_2000_DPS, ACCEL_RANGE_24G, and ACCEL_DATA_SYNC_MODE_400HZ. I am using the latest drivers for both parts.

If i remove the line bmi08a_load_config_file(&dev) from the BMI088 set up code then the accelerometer noise performance is improved significantly as shown in the plot below.

I suspect there is an issue with the BMI088 driver.

[sebmadgwick]

I can confirm that this change fixes the issue. Thank you.

My original code follows the example provided by Bosch. Anyone else following this example will have the same issue. I suggest that the example is updated.  There are other errors in the example code which are straightforward to fix.  Would you like to open a pull-request with the fixes?

[FAE_CA1]

Hi,

Thanks for the update.

The example code on the Github is ok without any issues. After soft-reset, the code brings BMI088 accel and gyro to normal mode. Then the code loads config file. After the config file is loaded successfully, the code starts to configure accel and gyro respectively. If loading the config file is at the end, then these accel and gyro configurations will be lost. Therefore, the example code is fine.

Thanks.

[sebmadgwick]

The example code does not run without issue. The example code results in poor accelerometer noise, and does not compile due to use of definitions (BMI08X_ACCEL_SYNC_DATA_RDY_INT and BMI08X_GYRO_DATA_RDY_INT) that have since been renamed in the API.  I am talking about this example code:

https://github.com/BoschSensortec/BMI08x-Sensor-API/blob/master/DataSync.md

The example code is in error according to your own statements:

1. "you should place "bmi08a_load_config_file(&bmi088);" right after the "bmi08a_soft_reset(&bmi088);"
2. "After soft-reset, the code brings BMI088 accel and gyro to normal mode. Then the code loads config file."

I do not require further support on this topic but I suggest the example code is fixed so that others do not have the same problem.  I am happy to create a pull request if that would be of use.

[FAE_CA1]

Hi,

Yes, please create a pull request. Thanks.