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Documentation: Add AD4000 documentation
Reviewed-by: David Lechner <dlechner@baylibre.com> Signed-off-by: Marcelo Schmitt <marcelo.schmitt@analog.com>
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‎Documentation/iio/ad4000.rst

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.. SPDX-License-Identifier: GPL-2.0-only
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=============
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AD4000 driver
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=============
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Device driver for Analog Devices Inc. AD4000 series of ADCs.
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Supported devices
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=================
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* `AD4000 <https://www.analog.com/AD4000>`_
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* `AD4001 <https://www.analog.com/AD4001>`_
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* `AD4002 <https://www.analog.com/AD4002>`_
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* `AD4003 <https://www.analog.com/AD4003>`_
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* `AD4004 <https://www.analog.com/AD4004>`_
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* `AD4005 <https://www.analog.com/AD4005>`_
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* `AD4006 <https://www.analog.com/AD4006>`_
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* `AD4007 <https://www.analog.com/AD4007>`_
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* `AD4008 <https://www.analog.com/AD4008>`_
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* `AD4010 <https://www.analog.com/AD4010>`_
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* `AD4011 <https://www.analog.com/AD4011>`_
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* `AD4020 <https://www.analog.com/AD4020>`_
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* `AD4021 <https://www.analog.com/AD4021>`_
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* `AD4022 <https://www.analog.com/AD4022>`_
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* `ADAQ4001 <https://www.analog.com/ADAQ4001>`_
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* `ADAQ4003 <https://www.analog.com/ADAQ4003>`_
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Wiring connections
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------------------
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Devices of the AD4000 series can be connected to the SPI host controller in a
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few different modes.
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CS mode, 3-wire turbo mode
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^^^^^^^^^^^^^^^^^^^^^^^^^^
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Datasheet "3-wire" mode is what most resembles standard SPI connection which,
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for these devices, comprises of connecting the controller CS line to device CNV
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pin and other SPI lines as usual. This configuration is (misleadingly) called
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"CS Mode, 3-Wire Turbo Mode" connection in datasheets.
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NOTE: The datasheet definition of 3-wire mode for the AD4000 series is NOT the
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same of standard spi-3wire mode.
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This is the only connection mode that allows configuration register access but
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it requires the SPI controller to support the ``SPI_MOSI_IDLE_HIGH`` feature.
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Omit the ``adi,sdi-pin`` property in device tree to select this mode.
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::
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+-------------+
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+ ----------------------------------| SDO |
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| | |
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| +-------------------| CS |
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| v | |
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| +--------------------+ | HOST |
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| | CNV | | |
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+--->| SDI AD4000 SDO |-------->| SDI |
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| SCK | | |
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+--------------------+ | |
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^ | |
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+--------------------| SCLK |
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+-------------+
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CS mode, 3-wire, without busy indicator
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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Another wiring configuration supported as "3-wire" mode has the SDI pin
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hard-wired to digital input/output interface supply (VIO). In this setup, the
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controller is not required to support ``SPI_MOSI_IDLE_HIGH`` but register access
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is not possible. This connection mode saves one wire and works with any SPI
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controller.
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Set the ``adi,sdi-pin`` device tree property to ``"high"`` to select this mode.
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::
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+-------------+
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+--------------------| CS |
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v | |
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VIO +--------------------+ | HOST |
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| | CNV | | |
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+--->| SDI AD4000 SDO |-------->| SDI |
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| SCK | | |
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+--------------------+ | |
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^ | |
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+--------------------| SCLK |
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+-------------+
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Alternatively, a GPIO may be connected to the device CNV pin. This is similar to
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the previous wiring configuration but saves the use of a CS line.
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::
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+-------------+
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+--------------------| GPIO |
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v | |
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VIO +--------------------+ | HOST |
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| | CNV | | |
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+--->| SDI AD4000 SDO |-------->| SDI |
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| SCK | | |
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+--------------------+ | |
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^ | |
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+--------------------| SCLK |
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+-------------+
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CS mode, 4-wire without busy indicator
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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In datasheet "4-wire" mode, the controller CS line is connected to the ADC SDI
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pin and a GPIO is connected to the ADC CNV pin. This connection mode may better
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suit scenarios where multiple ADCs can share one CNV trigger.
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Set ``adi,sdi-pin`` to ``"cs"`` to select this mode.
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::
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+-------------+
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+ ----------------------------------| CS |
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| | |
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| +-------------------| GPIO |
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| v | |
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| +--------------------+ | HOST |
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| | CNV | | |
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+--->| SDI AD4000 SDO |-------->| SDI |
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| SCK | | |
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+--------------------+ | |
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^ | |
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+--------------------| SCLK |
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+-------------+

‎Documentation/iio/index.rst

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.. toctree::
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:maxdepth: 1
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ad4000
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ad4695
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adis16475
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adis16480

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