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docs: iio: new docs for ad7380 driver
This adds a new page to document how to use the ad7380 ADC driver.
Credit: this docs is based on ad7944 docs.
Signed-off-by: Julien Stephan <jstephan@baylibre.com>
Link: https://patch.msgid.link/20240709-ad7380-add-docs-v1-1-458ced3dfcc5@baylibre.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
authored by
Julien Stephan
and committed by
Jonathan Cameron
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Documentation/iio/ad7380.rst
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Documentation/iio/ad7380.rst
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.. SPDX-License-Identifier: GPL-2.0-only
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=============
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AD7380 driver
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=============
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ADC driver for Analog Devices Inc. AD7380 and similar devices. The module name
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is ``ad7380``.
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Supported devices
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=================
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The following chips are supported by this driver:
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* `AD7380 <https://www.analog.com/en/products/ad7380.html>`_
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* `AD7381 <https://www.analog.com/en/products/ad7381.html>`_
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* `AD7383 <https://www.analog.com/en/products/ad7383.html>`_
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* `AD7384 <https://www.analog.com/en/products/ad7384.html>`_
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* `AD7380-4 <https://www.analog.com/en/products/ad7380-4.html>`_
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* `AD7381-4 <https://www.analog.com/en/products/ad7381-4.html>`_
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* `AD7383-4 <https://www.analog.com/en/products/ad7383-4.html>`_
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* `AD7384-4 <https://www.analog.com/en/products/ad7384-4.html>`_
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Supported features
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==================
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SPI wiring modes
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----------------
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ad738x ADCs can output data on several SDO lines (1/2/4). The driver currently
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supports only 1 SDO line.
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Reference voltage
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-----------------
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2 possible reference voltage sources are supported:
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- Internal reference (2.5V)
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- External reference (2.5V to 3.3V)
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The source is determined by the device tree. If ``refio-supply`` is present,
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then the external reference is used, else the internal reference is used.
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Oversampling and resolution boost
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---------------------------------
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This family supports 2 types of oversampling: normal average and rolling
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average. Only normal average is supported by the driver, as rolling average can
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be achieved by processing a captured data buffer. The following ratios are
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available: 1 (oversampling disabled)/2/4/8/16/32.
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When the on-chip oversampling function is enabled the performance of the ADC can
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exceed the default resolution. To accommodate the performance boost achievable,
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it is possible to enable an additional two bits of resolution. Because the
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resolution boost feature can only be enabled when oversampling is enabled and
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oversampling is not as useful without the resolution boost, the driver
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automatically enables the resolution boost if and only if oversampling is
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enabled.
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Since the resolution boost feature causes 16-bit chips to now have 18-bit data
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which means the storagebits has to change from 16 to 32 bits, we use the new
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ext_scan_type feature to allow changing the scan_type at runtime. Unfortunately
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libiio does not support it. So when enabling or disabling oversampling, user
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must restart iiod using the following command:
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.. code-block:: bash
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root:~# systemctl restart iiod
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Unimplemented features
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----------------------
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- 2/4 SDO lines
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- Rolling average oversampling
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- Power down mode
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- CRC indication
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- Alert
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Device buffers
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==============
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This driver supports IIO triggered buffers.
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See :doc:`iio_devbuf` for more information.
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Documentation/iio/index.rst
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Documentation/iio/index.rst
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MAINTAINERS
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MAINTAINERS
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W: https://wiki.analog.com/resources/tools-software/linux-drivers/iio-adc/ad738x
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W: https://ez.analog.com/linux-software-drivers
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F: Documentation/devicetree/bindings/iio/adc/adi,ad7380.yaml
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F: Documentation/iio/ad7380.rst
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F: drivers/iio/adc/ad7380.c
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AD7877 TOUCHSCREEN DRIVER