234 lines
11 KiB
ReStructuredText
234 lines
11 KiB
ReStructuredText
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.. SPDX-License-Identifier: GPL-2.0
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===============
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ADXL380 driver
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===============
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This driver supports Analog Device's ADXL380/382 on SPI/I2C bus.
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1. Supported devices
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====================
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* `ADXL380 <https://www.analog.com/ADXL380>`_
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* `ADXL382 <https://www.analog.com/ADXL382>`_
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The ADXL380/ADXL382 is a low noise density, low power, 3-axis accelerometer with
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selectable measurement ranges. The ADXL380 supports the ±4 g, ±8 g, and ±16 g
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ranges, and the ADXL382 supports ±15 g, ±30 g, and ±60 g ranges.
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2. Device attributes
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====================
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Accelerometer measurements are always provided.
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Temperature data are also provided. This data can be used to monitor the
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internal system temperature or to improve the temperature stability of the
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device via calibration.
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Each IIO device, has a device folder under ``/sys/bus/iio/devices/iio:deviceX``,
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where X is the IIO index of the device. Under these folders reside a set of
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device files, depending on the characteristics and features of the hardware
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device in questions. These files are consistently generalized and documented in
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the IIO ABI documentation.
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The following tables show the adxl380 related device files, found in the
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specific device folder path ``/sys/bus/iio/devices/iio:deviceX``.
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+---------------------------------------------------+----------------------------------------------------------+
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| 3-Axis Accelerometer related device files | Description |
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+---------------------------------------------------+----------------------------------------------------------+
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| in_accel_scale | Scale for the accelerometer channels. |
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+---------------------------------------------------+----------------------------------------------------------+
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| in_accel_filter_high_pass_3db_frequency | Low pass filter bandwidth. |
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+---------------------------------------------------+----------------------------------------------------------+
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| in_accel_filter_high_pass_3db_frequency_available | Available low pass filter bandwidth configurations. |
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+---------------------------------------------------+----------------------------------------------------------+
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| in_accel_filter_low_pass_3db_frequency | High pass filter bandwidth. |
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+---------------------------------------------------+----------------------------------------------------------+
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| in_accel_filter_low_pass_3db_frequency_available | Available high pass filter bandwidth configurations. |
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+---------------------------------------------------+----------------------------------------------------------+
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| in_accel_x_calibbias | Calibration offset for the X-axis accelerometer channel. |
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+---------------------------------------------------+----------------------------------------------------------+
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| in_accel_x_raw | Raw X-axis accelerometer channel value. |
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+---------------------------------------------------+----------------------------------------------------------+
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| in_accel_y_calibbias | y-axis acceleration offset correction |
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+---------------------------------------------------+----------------------------------------------------------+
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| in_accel_y_raw | Raw Y-axis accelerometer channel value. |
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+---------------------------------------------------+----------------------------------------------------------+
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| in_accel_z_calibbias | Calibration offset for the Z-axis accelerometer channel. |
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+---------------------------------------------------+----------------------------------------------------------+
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| in_accel_z_raw | Raw Z-axis accelerometer channel value. |
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+---------------------------------------------------+----------------------------------------------------------+
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+----------------------------------+--------------------------------------------+
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| Temperature sensor related files | Description |
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+----------------------------------+--------------------------------------------+
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| in_temp_raw | Raw temperature channel value. |
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+----------------------------------+--------------------------------------------+
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| in_temp_offset | Offset for the temperature sensor channel. |
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+----------------------------------+--------------------------------------------+
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| in_temp_scale | Scale for the temperature sensor channel. |
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+----------------------------------+--------------------------------------------+
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+------------------------------+----------------------------------------------+
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| Miscellaneous device files | Description |
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+------------------------------+----------------------------------------------+
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| name | Name of the IIO device. |
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+------------------------------+----------------------------------------------+
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| sampling_frequency | Currently selected sample rate. |
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+------------------------------+----------------------------------------------+
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| sampling_frequency_available | Available sampling frequency configurations. |
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+------------------------------+----------------------------------------------+
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Channels processed values
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-------------------------
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A channel value can be read from its _raw attribute. The value returned is the
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raw value as reported by the devices. To get the processed value of the channel,
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apply the following formula:
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.. code-block:: bash
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processed value = (_raw + _offset) * _scale
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Where _offset and _scale are device attributes. If no _offset attribute is
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present, simply assume its value is 0.
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The adis16475 driver offers data for 2 types of channels, the table below shows
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the measurement units for the processed value, which are defined by the IIO
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framework:
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+-------------------------------------+---------------------------+
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| Channel type | Measurement unit |
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+-------------------------------------+---------------------------+
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| Acceleration on X, Y, and Z axis | Meters per Second squared |
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+-------------------------------------+---------------------------+
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| Temperature | Millidegrees Celsius |
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+-------------------------------------+---------------------------+
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Usage examples
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--------------
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Show device name:
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.. code-block:: bash
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root:/sys/bus/iio/devices/iio:device0> cat name
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adxl382
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Show accelerometer channels value:
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.. code-block:: bash
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root:/sys/bus/iio/devices/iio:device0> cat in_accel_x_raw
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-1771
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root:/sys/bus/iio/devices/iio:device0> cat in_accel_y_raw
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282
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root:/sys/bus/iio/devices/iio:device0> cat in_accel_z_raw
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-1523
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root:/sys/bus/iio/devices/iio:device0> cat in_accel_scale
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0.004903325
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- X-axis acceleration = in_accel_x_raw * in_accel_scale = −8.683788575 m/s^2
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- Y-axis acceleration = in_accel_y_raw * in_accel_scale = 1.38273765 m/s^2
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- Z-axis acceleration = in_accel_z_raw * in_accel_scale = -7.467763975 m/s^2
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Set calibration offset for accelerometer channels:
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.. code-block:: bash
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root:/sys/bus/iio/devices/iio:device0> cat in_accel_x_calibbias
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0
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root:/sys/bus/iio/devices/iio:device0> echo 50 > in_accel_x_calibbias
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root:/sys/bus/iio/devices/iio:device0> cat in_accel_x_calibbias
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50
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Set sampling frequency:
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.. code-block:: bash
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root:/sys/bus/iio/devices/iio:device0> cat sampling_frequency
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16000
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root:/sys/bus/iio/devices/iio:device0> cat sampling_frequency_available
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16000 32000 64000
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root:/sys/bus/iio/devices/iio:device0> echo 32000 > sampling_frequency
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root:/sys/bus/iio/devices/iio:device0> cat sampling_frequency
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32000
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Set low pass filter bandwidth for accelerometer channels:
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.. code-block:: bash
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root:/sys/bus/iio/devices/iio:device0> cat in_accel_filter_low_pass_3db_frequency
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32000
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root:/sys/bus/iio/devices/iio:device0> cat in_accel_filter_low_pass_3db_frequency_available
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32000 8000 4000 2000
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root:/sys/bus/iio/devices/iio:device0> echo 2000 > in_accel_filter_low_pass_3db_frequency
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root:/sys/bus/iio/devices/iio:device0> cat in_accel_filter_low_pass_3db_frequency
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2000
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3. Device buffers
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=================
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This driver supports IIO buffers.
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All devices support retrieving the raw acceleration and temperature measurements
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using buffers.
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Usage examples
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--------------
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Select channels for buffer read:
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.. code-block:: bash
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root:/sys/bus/iio/devices/iio:device0> echo 1 > scan_elements/in_accel_x_en
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root:/sys/bus/iio/devices/iio:device0> echo 1 > scan_elements/in_accel_y_en
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root:/sys/bus/iio/devices/iio:device0> echo 1 > scan_elements/in_accel_z_en
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root:/sys/bus/iio/devices/iio:device0> echo 1 > scan_elements/in_temp_en
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Set the number of samples to be stored in the buffer:
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.. code-block:: bash
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root:/sys/bus/iio/devices/iio:device0> echo 10 > buffer/length
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Enable buffer readings:
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.. code-block:: bash
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root:/sys/bus/iio/devices/iio:device0> echo 1 > buffer/enable
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Obtain buffered data:
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.. code-block:: bash
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root:/sys/bus/iio/devices/iio:device0> hexdump -C /dev/iio\:device0
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...
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002bc300 f7 e7 00 a8 fb c5 24 80 f7 e7 01 04 fb d6 24 80 |......$.......$.|
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002bc310 f7 f9 00 ab fb dc 24 80 f7 c3 00 b8 fb e2 24 80 |......$.......$.|
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002bc320 f7 fb 00 bb fb d1 24 80 f7 b1 00 5f fb d1 24 80 |......$...._..$.|
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002bc330 f7 c4 00 c6 fb a6 24 80 f7 a6 00 68 fb f1 24 80 |......$....h..$.|
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002bc340 f7 b8 00 a3 fb e7 24 80 f7 9a 00 b1 fb af 24 80 |......$.......$.|
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002bc350 f7 b1 00 67 fb ee 24 80 f7 96 00 be fb 92 24 80 |...g..$.......$.|
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002bc360 f7 ab 00 7a fc 1b 24 80 f7 b6 00 ae fb 76 24 80 |...z..$......v$.|
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002bc370 f7 ce 00 a3 fc 02 24 80 f7 c0 00 be fb 8b 24 80 |......$.......$.|
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002bc380 f7 c3 00 93 fb d0 24 80 f7 ce 00 d8 fb c8 24 80 |......$.......$.|
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002bc390 f7 bd 00 c0 fb 82 24 80 f8 00 00 e8 fb db 24 80 |......$.......$.|
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002bc3a0 f7 d8 00 d3 fb b4 24 80 f8 0b 00 e5 fb c3 24 80 |......$.......$.|
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002bc3b0 f7 eb 00 c8 fb 92 24 80 f7 e7 00 ea fb cb 24 80 |......$.......$.|
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002bc3c0 f7 fd 00 cb fb 94 24 80 f7 e3 00 f2 fb b8 24 80 |......$.......$.|
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...
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See ``Documentation/iio/iio_devbuf.rst`` for more information about how buffered
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data is structured.
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4. IIO Interfacing Tools
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========================
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See ``Documentation/iio/iio_tools.rst`` for the description of the available IIO
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interfacing tools.
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