1.. SPDX-License-Identifier: GPL-2.0 2 3============================== 4BNO055 driver 5============================== 6 71. Overview 8=========== 9 10This driver supports Bosch BNO055 IMUs (on both serial and I2C busses). 11 12Accelerometer, magnetometer and gyroscope measures are always provided. 13When "fusion_enable" sysfs attribute is set to 1, orientation (both Euler 14angles and quaternion), linear velocity and gravity vector are also 15provided, but some sensor settings (e.g. low pass filtering and range) 16became locked (the IMU firmware controls them). 17 18This driver supports also IIO buffers. 19 202. Calibration 21============== 22 23The IMU continuously performs an autocalibration procedure if (and only if) 24operating in fusion mode. The magnetometer autocalibration can however be 25disabled writing 0 in the sysfs in_magn_calibration_fast_enable attribute. 26 27The driver provides access to autocalibration flags (i.e. you can known if 28the IMU has successfully autocalibrated) and to the calibration data blob. 29 30The user can save this blob in a firmware file (i.e. in /lib/firmware) that 31the driver looks for at probe time. If found, then the IMU is initialized 32with this calibration data. This saves the user from performing the 33calibration procedure every time (which consist of moving the IMU in 34various way). 35 36The driver looks for calibration data file using two different names: first 37a file whose name is suffixed with the IMU unique ID (exposed in sysfs as 38serial_number) is searched for; this is useful when there is more than one 39IMU instance. If this file is not found, then a "generic" calibration file 40is searched for (which can be used when only one IMU is present, without 41struggling with fancy names, that change on each device). 42 43Valid calibration file names would be e.g. 44 bno055-caldata-0e7c26a33541515120204a35342b04ff.dat 45 bno055-caldata.dat 46 47In non-fusion mode the IIO 'offset' attributes provide access to the 48offsets from calibration data (if any), so that the user can apply them to 49the accel, angvel and magn IIO attributes. In fusion mode they are not 50needed (the IMU firmware internally applies those corrections) and they 51read as zero. 52