On Thu, 17 Feb 2022 17:27:10 +0100 Andrea Merello <andrea.merello@xxxxxxxxx> wrote: Perhaps a comment on why it's worth having documentation for this device when we rarely bother? (complex device etc...) > Signed-off-by: Andrea Merello <andrea.merello@xxxxxx> > --- > Documentation/iio/bno055.rst | 53 ++++++++++++++++++++++++++++++++++++ Please add it to an appropriate index such as Docuemntation/iio/index.rst so that it actually gets linked to in the documentation built. One comment inline. > 1 file changed, 53 insertions(+) > create mode 100644 Documentation/iio/bno055.rst > > diff --git a/Documentation/iio/bno055.rst b/Documentation/iio/bno055.rst > new file mode 100644 > index 000000000000..4bb185075325 > --- /dev/null > +++ b/Documentation/iio/bno055.rst > @@ -0,0 +1,53 @@ > +.. SPDX-License-Identifier: GPL-2.0 > +============================== > +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). > + > +IIO attributes for unavailable measurements (e.g. Euler angles when fusion > +mode is disabled) just read zero. Hmm. Should probably return -EBUSY as 0 could be a valid value. > + > +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.
