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docs: iio: ad7944: add documentation for chain mode
Add documentation for chain mode support that was recently added to the AD7944 ADC driver. Signed-off-by: David Lechner <dlechner@baylibre.com> Link: https://lore.kernel.org/r/20240425-iio-ad7944-chain-mode-v1-2-9d9220ff21e1@baylibre.com Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
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@ -24,7 +24,7 @@ Supported features
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SPI wiring modes
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SPI wiring modes
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----------------
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----------------
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The driver currently supports two of the many possible SPI wiring configurations.
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The driver currently supports three of the many possible SPI wiring configurations.
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CS mode, 3-wire, without busy indicator
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CS mode, 3-wire, without busy indicator
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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@ -68,6 +68,27 @@ CS mode, 4-wire, without busy indicator
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To select this mode in the device tree, omit the ``adi,spi-mode`` property and
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To select this mode in the device tree, omit the ``adi,spi-mode`` property and
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provide the ``cnv-gpios`` property.
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provide the ``cnv-gpios`` property.
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Chain mode, without busy indicator
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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.. code-block::
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+-------------+
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+-------------------------+--------------------| CS |
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v v | |
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+--------------------+ +--------------------+ | HOST |
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| CNV | | CNV | | |
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+--->| SDI AD7944 SDO |--->| SDI AD7944 SDO |-------->| SDI |
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| | SCK | | SCK | | |
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GND +--------------------+ +--------------------+ | |
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^ ^ | |
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+-------------------------+--------------------| SCLK |
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+-------------+
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To select this mode in the device tree, set the ``adi,spi-mode`` property to
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``"chain"``, add the ``spi-cs-high`` flag, add the ``#daisy-chained-devices``
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property, and omit the ``cnv-gpios`` property.
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Reference voltage
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Reference voltage
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-----------------
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-----------------
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@ -86,7 +107,6 @@ Unimplemented features
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- ``BUSY`` indication
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- ``BUSY`` indication
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- ``TURBO`` mode
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- ``TURBO`` mode
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- Daisy chain mode
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Device attributes
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Device attributes
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@ -108,6 +128,9 @@ AD7944 and AD7985 are pseudo-differential ADCs and have the following attributes
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| ``in_voltage0_scale`` | Scale factor to convert raw value to mV. |
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| ``in_voltage0_scale`` | Scale factor to convert raw value to mV. |
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+---------------------------------------+--------------------------------------------------------------+
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+---------------------------------------+--------------------------------------------------------------+
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In "chain" mode, additional chips will appear as additional voltage input
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channels, e.g. ``in_voltage1_raw``.
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Fully-differential ADCs
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Fully-differential ADCs
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-----------------------
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-----------------------
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@ -121,6 +144,9 @@ AD7986 is a fully-differential ADC and has the following attributes:
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| ``in_voltage0-voltage1_scale`` | Scale factor to convert raw value to mV. |
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| ``in_voltage0-voltage1_scale`` | Scale factor to convert raw value to mV. |
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+---------------------------------------+--------------------------------------------------------------+
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+---------------------------------------+--------------------------------------------------------------+
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In "chain" mode, additional chips will appear as additional voltage input
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channels, e.g. ``in_voltage2-voltage3_raw``.
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Device buffers
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Device buffers
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==============
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==============
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