BNO055 Application Questions

[Lyndon]

Hi Everyone,

I will be having the following questions answered by Bosch shortly and will post the answers. If anyone already has the answers, it would be great if you could share! Thanks in advance.

Application:

• Is this a suitable chip for automotive applications? Asking because the gyroscope refused to calibrate when cold (~0C) and the engine was on
• SYS calibration status fluctuated wildly over a ~15 minute drive, with it being at 0 more than 50% of the time
• Our application is a J1939 digital compass, should we use NDOF mode or Compass mode?

Calibration:

• Is re-use of calibration values only valid right after ‘Power of Reset’ because it is always modifying the offset registers?
• Can it be turned off?
• What does SYS calibration mean, and why does it vary so much (with the vehicle in motion)?
• If the SYS calibration is 0, should fusion data be discarded?
• Can SYS calibration bit be < 3 if all other calibration status’ are =3?
• In modes other than NDOF, does SYS matter?
• How are all calibration status values calculated?
• If you manually load the offset and radius registers, (when) do the calibration status registers mean anything?
• What is meant by magnetometer and accelerometer radius?
• NDOF mode vs. NDOF_FMC_OFF mode – does this affect auto-calibration or only the initial calibration?
• Would the gyro or accelerometer ever need to be calibrated after end-of-line test at the factory?

Mode of Operation:

• What is the difference between Compass and NDOF mode?
• Is Compass mode tilt-compensated?
• How do we obtain accurate tilt compensated heading information if the gyro sensor is not used while the vehicle is in motion (as accelerometer data will be affected by vehicle acceleration)

Firmware:

• What is the newest revision?
• Are there any changes to (auto) calibration routines since 0.3.0.8?

[o_o]

Hi Lyndon,

That's a lot of questions, let me try my best to answer.

Application:

• Is this a suitable chip for automotive applications? Asking because the gyroscope refused to calibrate when cold (~0C) and the engine was on

The chip has an operating temperature of -40 to +85C. The gyroscope calibration require the device to be still, if the vibration from your engine exceeds a certain threshold, then it may never calibrate.

• SYS calibration status fluctuated wildly over a ~15 minute drive, with it being at 0 more than 50% of the time

This is a known issue in current firmware. See this thread.

• Our application is a J1939 digital compass, should we use NDOF mode or Compass mode?

Both would provide the same performance for this application

Calibration:

• Is re-use of calibration values only valid right after ‘Power of Reset’ because it is always modifying the offset registers?

The opposite would be true, your best estimate of the calibration is before powering off the device

• Can it be turned off?

no

• What does SYS calibration mean, and why does it vary so much (with the vehicle in motion)?

See above

• If the SYS calibration is 0, should fusion data be discarded?

Initially yes. Once it has become non-zero, data can be trusted from that point on.

• Can SYS calibration bit be < 3 if all other calibration status’ are =3?

In the built-in firmware yes, see above.

• In modes other than NDOF, does SYS matter?

The behavior is the same in all working modes

• How are all calibration status values calculated?

The calibration status is aligned to the Android definition of sensor status accuracy Unreliable to High.

• If you manually load the offset and radius registers, (when) do the calibration status registers mean anything?

If you manually load the calibration, you are responsible for its validity. The BNO055 will assume that it is good. If that is not the case, the performance will actually be worse until the sensor finds the correct values.

• What is meant by magnetometer and accelerometer radius?

The strength of the magnetic and gravitational fields. use to compensate for sensitivity error.

• NDOF mode vs. NDOF_FMC_OFF mode – does this affect auto-calibration or only the initial calibration?

FMC means "Fast Magnetometer Calibration". With this calibrator, the calibrated gyroscope data is compared with the magnetometer data to extrapolate the Earth's magnetic field 3D sphere.

• Would the gyro or accelerometer ever need to be calibrated after end-of-line test at the factory?

That depends on your accuracy requirements. Accelerometer calibration at the factory may be desired, but gyroscope calibration is better when done at every power-on (and very fast)

Mode of Operation:

• What is the difference between Compass and NDOF mode?

COMPASS = Android's Geomagnetic Rotation Vector.

NDOF = Andoid's Rotation Vector

• Is Compass mode tilt-compensated?

Yes

• How do we obtain accurate tilt compensated heading information if the gyro sensor is not used while the vehicle is in motion (as accelerometer data will be affected by vehicle acceleration)

The magnetometer is used in lieu of the gyroscope in M4G and Compass mode.

Firmware:

• What is the newest revision?

0.3.0.11

We are planning the release of a new firmware (hopefully soon) for customers to flash via the bootloader. Pre-programmed firmware will not change.

• Are there any changes to (auto) calibration routines since 0.3.0.8?

No

o_o

[Lyndon]

Hi o_o,

Thank you for your timely reply! Does FW ver: 0.3.0.11 address the calibration status issue? Is it possible to evaluate it now? Could we check out the changelog?

Thanks!

Lyndon

[o_o]

I'm surprised to hear that there are still devices with 0.3.0.8 in the field. The change was done a long time ago.

0.3.0.11 made some internal changes that do not impact any of the features or performance. Therefore, there is no changelog.

o_o

[Lyndon]

Would you be able to help me obtain the most recent firmware?

Thanks!

Lyndon