[PATCH v5 3/3] docs: iio: add documentation for adis16475 driver

From: Ramona Gradinariu
Date: Wed Feb 21 2024 - 03:59:50 EST

Add documentation for adis16475 driver which describes
the driver device files and shows how the user may use the
ABI for various scenarios (configuration, measurement, etc.).

Signed-off-by: Ramona Gradinariu <ramona.gradinariu@xxxxxxxxxx>
---
changes in v5:
- fixed various typos and inconsistencies
- used inline code format style where applicable
Documentation/iio/adis16475.rst | 406 ++++++++++++++++++++++++++++++++
Documentation/iio/index.rst | 1 +
2 files changed, 407 insertions(+)
create mode 100644 Documentation/iio/adis16475.rst

diff --git a/Documentation/iio/adis16475.rst b/Documentation/iio/adis16475.rst
new file mode 100644
index 000000000000..b4c0917eabc4
--- /dev/null
+++ b/Documentation/iio/adis16475.rst
@@ -0,0 +1,406 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+================
+ADIS16475 driver
+================
+
+This driver supports Analog Device's IMUs on SPI bus.
+
+1. Supported devices
+====================
+
+* `ADIS16465 <https://www.analog.com/ADIS16465>`_
+* `ADIS16467 <https://www.analog.com/ADIS16467>`_
+* `ADIS16470 <https://www.analog.com/ADIS16470>`_
+* `ADIS16475 <https://www.analog.com/ADIS16475>`_
+* `ADIS16477 <https://www.analog.com/ADIS16477>`_
+* `ADIS16500 <https://www.analog.com/ADIS16500>`_
+* `ADIS16505 <https://www.analog.com/ADIS16505>`_
+* `ADIS16507 <https://www.analog.com/ADIS16507>`_
+
+Each supported device is a precision, miniature microelectromechanical system
+(MEMS) inertial measurement unit (IMU) that includes a triaxial gyroscope and a
+triaxial accelerometer. Each inertial sensor in the IMU device combines with
+signal conditioning that optimizes dynamic performance. The factory calibration
+characterizes each sensor for sensitivity, bias, alignment, linear acceleration
+(gyroscope bias), and point of percussion (accelerometer location). As a result,
+each sensor has dynamic compensation formulas that provide accurate sensor
+measurements over a broad set of conditions.
+
+2. Device attributes
+====================
+
+Accelerometer, gyroscope measurements are always provided. Furthermore, the
+driver offers the capability to retrieve the delta angle and the delta velocity
+measurements computed by the device.
+
+The delta angle measurements represent a calculation of angular displacement
+between each sample update, while the delta velocity measurements represent a
+calculation of linear velocity change between each sample update.
+
+Finally, temperature data are provided which show a coarse measurement of
+the temperature inside of the IMU device. This data is most useful for
+monitoring relative changes in the thermal environment.
+
+The signal chain of each inertial sensor (accelerometers and gyroscopes)
+includes the application of unique correction formulas, which are derived from
+extensive characterization of bias, sensitivity, alignment, response to linear
+acceleration (gyroscopes), and point of percussion (accelerometer location)
+over a temperature range of −40°C to +85°C, for each ADIS device. These
+correction formulas are not accessible, but users do have the opportunity to
+adjust the bias for each sensor individually through the calibbias attribute.
+
+Each IIO device, has a device folder under ``/sys/bus/iio/devices/iio:deviceX``,
+where X is the IIO index of the device. Under these folders reside a set of
+device files, depending on the characteristics and features of the hardware
+device in questions. These files are consistently generalized and documented in
+the IIO ABI documentation.
+
+The following tables show the adis16475 related device files, found in the
+specific device folder path ``/sys/bus/iio/devices/iio:deviceX``.
+
++-------------------------------------------+----------------------------------------------------------+
+| 3-Axis Accelerometer related device files | Description |
++-------------------------------------------+----------------------------------------------------------+
+| in_accel_scale | Scale for the accelerometer channels. |
++-------------------------------------------+----------------------------------------------------------+
+| in_accel_x_calibbias | Calibration offset for the X-axis accelerometer channel. |
++-------------------------------------------+----------------------------------------------------------+
+| in_accel_calibbias_x | x-axis acceleration offset correction |
++-------------------------------------------+----------------------------------------------------------+
+| in_accel_x_raw | Raw X-axis accelerometer channel value. |
++-------------------------------------------+----------------------------------------------------------+
+| in_accel_calibbias_y | y-axis acceleration offset correction |
++-------------------------------------------+----------------------------------------------------------+
+| in_accel_y_raw | Raw Y-axis accelerometer channel value. |
++-------------------------------------------+----------------------------------------------------------+
+| in_accel_z_calibbias | Calibration offset for the Z-axis accelerometer channel. |
++-------------------------------------------+----------------------------------------------------------+
+| in_accel_z_raw | Raw Z-axis accelerometer channel value. |
++-------------------------------------------+----------------------------------------------------------+
+| in_deltavelocity_scale | Scale for delta velocity channels. |
++-------------------------------------------+----------------------------------------------------------+
+| in_deltavelocity_x_raw | Raw X-axis delta velocity channel value. |
++-------------------------------------------+----------------------------------------------------------+
+| in_deltavelocity_y_raw | Raw Y-axis delta velocity channel value. |
++-------------------------------------------+----------------------------------------------------------+
+| in_deltavelocity_z_raw | Raw Z-axis delta velocity channel value. |
++-------------------------------------------+----------------------------------------------------------+
+
++---------------------------------------+------------------------------------------------------+
+| 3-Axis Gyroscope related device files | Description |
++---------------------------------------+------------------------------------------------------+
+| in_anglvel_scale | Scale for the gyroscope channels. |
++---------------------------------------+------------------------------------------------------+
+| in_anglvel_x_calibbias | Calibration offset for the X-axis gyroscope channel. |
++---------------------------------------+------------------------------------------------------+
+| in_anglvel_calibbias_x | x-axis gyroscope offset correction |
++---------------------------------------+------------------------------------------------------+
+| in_anglvel_x_raw | Raw X-axis gyroscope channel value. |
++---------------------------------------+------------------------------------------------------+
+| in_anglvel_calibbias_y | y-axis gyroscope offset correction |
++---------------------------------------+------------------------------------------------------+
+| in_anglvel_y_raw | Raw Y-axis gyroscope channel value. |
++---------------------------------------+------------------------------------------------------+
+| in_anglvel_z_calibbias | Calibration offset for the Z-axis gyroscope channel. |
++---------------------------------------+------------------------------------------------------+
+| in_anglvel_z_raw | Raw Z-axis gyroscope channel value. |
++---------------------------------------+------------------------------------------------------+
+| in_deltaangl_scale | Scale for delta angle channels. |
++---------------------------------------+------------------------------------------------------+
+| in_deltaangl_x_raw | Raw X-axis delta angle channel value. |
++---------------------------------------+------------------------------------------------------+
+| in_deltaangl_y_raw | Raw Y-axis delta angle channel value. |
++---------------------------------------+------------------------------------------------------+
+| in_deltaangl_z_raw | Raw Z-axis delta angle channel value. |
++---------------------------------------+------------------------------------------------------+
+
++----------------------------------+-------------------------------------------+
+| Temperature sensor related files | Description |
++----------------------------------+-------------------------------------------+
+| in_temp0_raw | Raw temperature channel value. |
++----------------------------------+-------------------------------------------+
+| in_temp0_scale | Scale for the temperature sensor channel. |
++----------------------------------+-------------------------------------------+
+
++-------------------------------+---------------------------------------------------------+
+| Miscellaneous device files | Description |
++-------------------------------+---------------------------------------------------------+
+| name | Name of the IIO device. |
++-------------------------------+---------------------------------------------------------+
+| sampling_frequency | Currently selected sample rate. |
++-------------------------------+---------------------------------------------------------+
+| filter_low_pass_3db_frequency | Bandwidth for the accelerometer and gyroscope channels. |
++-------------------------------+---------------------------------------------------------+
+
+The following table shows the adis16475 related device debug files, found in the
+specific device debug folder path ``/sys/kernel/debug/iio/iio:deviceX``.
+
++----------------------+-------------------------------------------------------------------------+
+| Debugfs device files | Description |
++----------------------+-------------------------------------------------------------------------+
+| serial_number | The serial number of the chip in hexadecimal format. |
++----------------------+-------------------------------------------------------------------------+
+| product_id | Chip specific product id (e.g. 16475, 16500, 16505, etc.). |
++----------------------+-------------------------------------------------------------------------+
+| flash_count | The number of flash writes performed on the device. |
++----------------------+-------------------------------------------------------------------------+
+| firmware_revision | String containing the firmware revision in the following format ##.##. |
++----------------------+-------------------------------------------------------------------------+
+| firmware_date | String containing the firmware date in the following format mm-dd-yyyy. |
++----------------------+-------------------------------------------------------------------------+
+
+Channels processed values
+-------------------------
+
+A channel value can be read from its _raw attribute. The value returned is the
+raw value as reported by the devices. To get the processed value of the channel,
+apply the following formula:
+
+.. code-block:: bash
+
+ processed value = (_raw + _offset) * _scale
+
+Where _offset and _scale are device attributes. If no _offset attribute is
+present, simply assume its value is 0.
+
+The adis16475 driver offers data for 5 types of channels, the table below shows
+the measurement units for the processed value, which are defined by the IIO
+framework:
+
++-------------------------------------+---------------------------+
+| Channel type | Measurement unit |
++-------------------------------------+---------------------------+
+| Acceleration on X, Y, and Z axis | Meters per Second squared |
++-------------------------------------+---------------------------+
+| Angular velocity on X, Y and Z axis | Radians per second |
++-------------------------------------+---------------------------+
+| Delta velocity on X. Y, and Z axis | Meters per Second |
++-------------------------------------+---------------------------+
+| Delta angle on X, Y, and Z axis | Radians |
++-------------------------------------+---------------------------+
+| Temperature | Millidegrees Celsius |
++-------------------------------------+---------------------------+
+
+Usage examples
+--------------
+
+Show device name:
+
+.. code-block:: bash
+
+ root:/sys/bus/iio/devices/iio:device0> cat name
+ adis16505-2
+
+Show accelerometer channels value:
+
+.. code-block:: bash
+
+ root:/sys/bus/iio/devices/iio:device0> cat in_accel_x_raw
+ -275924
+ root:/sys/bus/iio/devices/iio:device0> cat in_accel_y_raw
+ -30142222
+ root:/sys/bus/iio/devices/iio:device0> cat in_accel_z_raw
+ 261265769
+ root:/sys/bus/iio/devices/iio:device0> cat in_accel_scale
+ 0.000000037
+
+- X-axis acceleration = in_accel_x_raw * in_accel_scale = −0.010209188 m/s^2
+- Y-axis acceleration = in_accel_y_raw * in_accel_scale = −1.115262214 m/s^2
+- Z-axis acceleration = in_accel_z_raw * in_accel_scale = 9.666833453 m/s^2
+
+Show gyroscope channels value:
+
+.. code-block:: bash
+
+ root:/sys/bus/iio/devices/iio:device0> cat in_anglvel_x_raw
+ -3324626
+ root:/sys/bus/iio/devices/iio:device0> cat in_anglvel_y_raw
+ 1336980
+ root:/sys/bus/iio/devices/iio:device0> cat in_anglvel_z_raw
+ -602983
+ root:/sys/bus/iio/devices/iio:device0> cat in_anglvel_scale
+ 0.000000006
+
+- X-axis angular velocity = in_anglvel_x_raw * in_anglvel_scale = −0.019947756 rad/s
+- Y-axis angular velocity = in_anglvel_y_raw * in_anglvel_scale = 0.00802188 rad/s
+- Z-axis angular velocity = in_anglvel_z_raw * in_anglvel_scale = −0.003617898 rad/s
+
+Set calibration offset for accelerometer channels:
+
+.. code-block:: bash
+
+ root:/sys/bus/iio/devices/iio:device0> cat in_accel_x_calibbias
+ 0
+
+ root:/sys/bus/iio/devices/iio:device0> echo 5000 > in_accel_x_calibbias
+ root:/sys/bus/iio/devices/iio:device0> cat in_accel_x_calibbias
+ 5000
+
+Set calibration offset for gyroscope channels:
+
+.. code-block:: bash
+
+ root:/sys/bus/iio/devices/iio:device0> cat in_anglvel_y_calibbias
+ 0
+
+ root:/sys/bus/iio/devices/iio:device0> echo -5000 > in_anglvel_y_calibbias
+ root:/sys/bus/iio/devices/iio:device0> cat in_anglvel_y_calibbias
+ -5000
+
+Set sampling frequency:
+
+.. code-block:: bash
+
+ root:/sys/bus/iio/devices/iio:device0> cat sampling_frequency
+ 2000.000000
+
+ root:/sys/bus/iio/devices/iio:device0> echo 1000 > sampling_frequency
+ 1000.000000
+
+Set bandwidth for accelerometer and gyroscope:
+
+.. code-block:: bash
+
+ root:/sys/bus/iio/devices/iio:device0> cat filter_low_pass_3db_frequency
+ 720
+
+ root:/sys/bus/iio/devices/iio:device0> echo 360 > filter_low_pass_3db_frequency
+ root:/sys/bus/iio/devices/iio:device0> cat filter_low_pass_3db_frequency
+ 360
+
+Show serial number:
+
+.. code-block:: bash
+
+ root:/sys/kernel/debug/iio/iio:device0> cat serial_number
+ 0x04f9
+
+Show product id:
+
+.. code-block:: bash
+
+ root:/sys/kernel/debug/iio/iio:device0> cat product_id
+ 16505
+
+Show flash count:
+
+.. code-block:: bash
+
+ root:/sys/kernel/debug/iio/iio:device0> cat flash_count
+ 150
+
+Show firmware revision:
+
+.. code-block:: bash
+
+ root:/sys/kernel/debug/iio/iio:device0> cat firmware_revision
+ 1.6
+
+Show firmware date:
+
+.. code-block:: bash
+
+ root:/sys/kernel/debug/iio/iio:device0> cat firmware_date
+ 06-27-2019
+
+3. Device buffers
+=================
+
+This driver supports IIO buffers.
+
+All devices support retrieving the raw acceleration, gyroscope and temperature
+measurements using buffers.
+
+The following device families also support retrieving the delta velocity, delta
+angle and temperature measurements using buffers:
+ - ADIS16477
+ - ADIS16500
+ - ADIS16505
+ - ADIS16507
+
+However, when retrieving acceleration or gyroscope data using buffers, delta
+readings will not be available and vice versa.
+
+Usage examples
+--------------
+
+Set device trigger in current_trigger, if not already set:
+
+.. code-block:: bash
+
+ root:/sys/bus/iio/devices/iio:device0> cat trigger/current_trigger
+
+ root:/sys/bus/iio/devices/iio:device0> echo adis16505-2-dev0 > trigger/current_trigger
+ root:/sys/bus/iio/devices/iio:device0> cat trigger/current_trigger
+ adis16505-2-dev0
+
+Select channels for buffer read:
+
+.. code-block:: bash
+
+ root:/sys/bus/iio/devices/iio:device0> echo 1 > scan_elements/in_deltavelocity_x_en
+ root:/sys/bus/iio/devices/iio:device0> echo 1 > scan_elements/in_deltavelocity_y_en
+ root:/sys/bus/iio/devices/iio:device0> echo 1 > scan_elements/in_deltavelocity_z_en
+ root:/sys/bus/iio/devices/iio:device0> echo 1 > scan_elements/in_temp0_en
+
+Set the number of samples to be stored in the buffer:
+
+.. code-block:: bash
+
+ root:/sys/bus/iio/devices/iio:device0> echo 10 > buffer/length
+
+Enable buffer readings:
+
+.. code-block:: bash
+
+ root:/sys/bus/iio/devices/iio:device0> echo 1 > buffer/enable
+
+Obtain buffered data:
+
+.. code-block:: bash
+
+ root:/sys/bus/iio/devices/iio:device0> hexdump -C /dev/iio\:device0
+ ...
+ 00001680 01 1f 00 00 ff ff fe ef 00 00 47 bf 00 03 35 55 |..........G...5U|
+ 00001690 01 1f 00 00 ff ff ff d9 00 00 46 f1 00 03 35 35 |..........F...55|
+ 000016a0 01 1f 00 00 ff ff fe fc 00 00 46 cb 00 03 35 7b |..........F...5{|
+ 000016b0 01 1f 00 00 ff ff fe 41 00 00 47 0d 00 03 35 8b |.......A..G...5.|
+ 000016c0 01 1f 00 00 ff ff fe 37 00 00 46 b4 00 03 35 90 |.......7..F...5.|
+ 000016d0 01 1d 00 00 ff ff fe 5a 00 00 45 d7 00 03 36 08 |.......Z..E...6.|
+ 000016e0 01 1b 00 00 ff ff fe fb 00 00 45 e7 00 03 36 60 |..........E...6`|
+ 000016f0 01 1a 00 00 ff ff ff 17 00 00 46 bc 00 03 36 de |..........F...6.|
+ 00001700 01 1a 00 00 ff ff fe 59 00 00 46 d7 00 03 37 b8 |.......Y..F...7.|
+ 00001710 01 1a 00 00 ff ff fe ae 00 00 46 95 00 03 37 ba |..........F...7.|
+ 00001720 01 1a 00 00 ff ff fe c5 00 00 46 63 00 03 37 9f |..........Fc..7.|
+ 00001730 01 1a 00 00 ff ff fe 55 00 00 46 89 00 03 37 c1 |.......U..F...7.|
+ 00001740 01 1a 00 00 ff ff fe 31 00 00 46 aa 00 03 37 f7 |.......1..F...7.|
+ ...
+
+See ``Documentation/iio/iio_devbuf.rst`` for more information about how buffered
+data is structured.
+
+4. IIO Interfacing Tools
+========================
+
+Linux Kernel Tools
+------------------
+
+Linux Kernel provides some userspace tools that can be used to retrieve data
+from IIO sysfs:
+
+* lsiio: example application that provides a list of IIO devices and triggers
+* iio_event_monitor: example application that reads events from an IIO device
+ and prints them
+* iio_generic_buffer: example application that reads data from buffer
+* iio_utils: set of APIs, typically used to access sysfs files.
+
+LibIIO
+------
+
+LibIIO is a C/C++ library that provides generic access to IIO devices. The
+library abstracts the low-level details of the hardware, and provides a simple
+yet complete programming interface that can be used for advanced projects.
+
+For more information about LibIIO, please see:
+https://github.com/analogdevicesinc/libiio
diff --git a/Documentation/iio/index.rst b/Documentation/iio/index.rst
index 206a0aff5ca1..30b09eefe75e 100644
--- a/Documentation/iio/index.rst
+++ b/Documentation/iio/index.rst
@@ -16,5 +16,6 @@ Industrial I/O Kernel Drivers
.. toctree::
:maxdepth: 1

+ adis16475
bno055
ep93xx_adc
--
2.34.1