BNO055 driver

1. Overview

This driver supports Bosch BNO055 IMUs (on both serial and I2C busses).

Accelerometer, magnetometer and gyroscope measures are always provided. When “fusion_enable” sysfs attribute is set to 1, orientation (both Euler angles and quaternion), linear velocity and gravity vector are also provided, but some sensor settings (e.g. low pass filtering and range) became locked (the IMU firmware controls them).

This driver supports also IIO buffers.

2. Calibration

The IMU continuously performs an autocalibration procedure if (and only if) operating in fusion mode. The magnetometer autocalibration can however be disabled writing 0 in the sysfs in_magn_calibration_fast_enable attribute.

The driver provides access to autocalibration flags (i.e. you can known if the IMU has successfully autocalibrated) and to the calibration data blob.

The user can save this blob in a firmware file (i.e. in /lib/firmware) that the driver looks for at probe time. If found, then the IMU is initialized with this calibration data. This saves the user from performing the calibration procedure every time (which consist of moving the IMU in various way).

The driver looks for calibration data file using two different names: first a file whose name is suffixed with the IMU unique ID (exposed in sysfs as serial_number) is searched for; this is useful when there is more than one IMU instance. If this file is not found, then a “generic” calibration file is searched for (which can be used when only one IMU is present, without struggling with fancy names, that change on each device).

Valid calibration file names would be e.g.

bno055-caldata-0e7c26a33541515120204a35342b04ff.dat bno055-caldata.dat

In non-fusion mode the IIO ‘offset’ attributes provide access to the offsets from calibration data (if any), so that the user can apply them to the accel, angvel and magn IIO attributes. In fusion mode they are not needed (the IMU firmware internally applies those corrections) and they read as zero.