Signed-off-by: Andrea Merello <[email protected]>
---
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
On Thu, 17 Feb 2022 17:27:10 +0100
Andrea Merello <[email protected]> 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 <[email protected]>
> ---
> 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.
[...]
> > +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.
>
While it seems reasonable, that can be easily done while reading from
sysfs, but how do we handle this when reading from buffer?
Right now both sysfs and buffer read zero from unused chans, which it
is at least consistent..