linux-kernel - [v3 13/13] docs: iio: add documentation for BNO055 driver

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Message-Id: <20220217162710.33615-14-andrea.merello@gmail.com>
Date:   Thu, 17 Feb 2022 17:27:10 +0100
From:   Andrea Merello <andrea.merello@...il.com>
To:     jic23@...nel.org, mchehab+huawei@...nel.org,
        linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org
Cc:     lars@...afoo.de, robh+dt@...nel.org, andy.shevchenko@...il.com,
        matt.ranostay@...sulko.com, ardeleanalex@...il.com,
        jacopo@...ndi.org, Andrea Merello <andrea.merello@...il.com>,
        Andrea Merello <andrea.merello@....it>
Subject: [v3 13/13] docs: iio: add documentation for BNO055 driver

Signed-off-by: Andrea Merello <andrea.merello@....it>
---
 Documentation/iio/bno055.rst | 53 ++++++++++++++++++++++++++++++++++++
 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.
+
+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.
-- 
2.17.1