ark1668ed-bsp/linux/Documentation/iio/ad4000.rst

.. SPDX-License-Identifier: GPL-2.0-only

=============
AD4000 driver
=============

Device driver for Analog Devices Inc. AD4000 series of ADCs.

Supported devices
=================

* `AD4000 <https://www.analog.com/AD4000>`_
* `AD4001 <https://www.analog.com/AD4001>`_
* `AD4002 <https://www.analog.com/AD4002>`_
* `AD4003 <https://www.analog.com/AD4003>`_
* `AD4004 <https://www.analog.com/AD4004>`_
* `AD4005 <https://www.analog.com/AD4005>`_
* `AD4006 <https://www.analog.com/AD4006>`_
* `AD4007 <https://www.analog.com/AD4007>`_
* `AD4008 <https://www.analog.com/AD4008>`_
* `AD4010 <https://www.analog.com/AD4010>`_
* `AD4011 <https://www.analog.com/AD4011>`_
* `AD4020 <https://www.analog.com/AD4020>`_
* `AD4021 <https://www.analog.com/AD4021>`_
* `AD4022 <https://www.analog.com/AD4022>`_
* `ADAQ4001 <https://www.analog.com/ADAQ4001>`_
* `ADAQ4003 <https://www.analog.com/ADAQ4003>`_

Wiring connections
------------------

Devices of the AD4000 series can be connected to the SPI host controller in a
few different modes.

CS mode, 3-wire turbo mode
^^^^^^^^^^^^^^^^^^^^^^^^^^

Datasheet "3-wire" mode is what most resembles standard SPI connection which,
for these devices, comprises of connecting the controller CS line to device CNV
pin and other SPI lines as usual. This configuration is (misleadingly) called
"CS Mode, 3-Wire Turbo Mode" connection in datasheets.
NOTE: The datasheet definition of 3-wire mode for the AD4000 series is NOT the
same of standard spi-3wire mode.
This is the only connection mode that allows configuration register access but
it requires the SPI controller to support the ``SPI_MOSI_IDLE_HIGH`` feature.

Omit the ``adi,sdi-pin`` property in device tree to select this mode.

::

                                         +-------------+
     + ----------------------------------| SDO         |
     |                                   |             |
     |               +-------------------| CS          |
     |               v                   |             |
     |    +--------------------+         |     HOST    |
     |    |        CNV         |         |             |
     +--->| SDI   AD4000   SDO |-------->| SDI         |
          |        SCK         |         |             |
          +--------------------+         |             |
                    ^                    |             |
                    +--------------------| SCLK        |
                                         +-------------+

CS mode, 3-wire, without busy indicator
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Another wiring configuration supported as "3-wire" mode has the SDI pin
hard-wired to digital input/output interface supply (VIO). In this setup, the
controller is not required to support ``SPI_MOSI_IDLE_HIGH`` but register access
is not possible. This connection mode saves one wire and works with any SPI
controller.

Set the ``adi,sdi-pin`` device tree property to ``"high"`` to select this mode.

::

                                         +-------------+
                    +--------------------| CS          |
                    v                    |             |
    VIO   +--------------------+         |     HOST    |
     |    |        CNV         |         |             |
     +--->| SDI   AD4000   SDO |-------->| SDI         |
          |        SCK         |         |             |
          +--------------------+         |             |
                    ^                    |             |
                    +--------------------| SCLK        |
                                         +-------------+

Alternatively, a GPIO may be connected to the device CNV pin. This is similar to
the previous wiring configuration but saves the use of a CS line.

::

                                         +-------------+
                    +--------------------| GPIO        |
                    v                    |             |
    VIO   +--------------------+         |     HOST    |
     |    |        CNV         |         |             |
     +--->| SDI   AD4000   SDO |-------->| SDI         |
          |        SCK         |         |             |
          +--------------------+         |             |
                    ^                    |             |
                    +--------------------| SCLK        |
                                         +-------------+

CS mode, 4-wire without busy indicator
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

In datasheet "4-wire" mode, the controller CS line is connected to the ADC SDI
pin and a GPIO is connected to the ADC CNV pin. This connection mode may better
suit scenarios where multiple ADCs can share one CNV trigger.

Set ``adi,sdi-pin`` to ``"cs"`` to select this mode.


::

                                         +-------------+
     + ----------------------------------| CS          |
     |                                   |             |
     |               +-------------------| GPIO        |
     |               v                   |             |
     |    +--------------------+         |     HOST    |
     |    |        CNV         |         |             |
     +--->| SDI   AD4000   SDO |-------->| SDI         |
          |        SCK         |         |             |
          +--------------------+         |             |
                    ^                    |             |
                    +--------------------| SCLK        |
                                         +-------------+