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

============= AD7944 driver

ADC driver for Analog Devices Inc. AD7944 and similar devices. The module name is ad7944.

Supported devices

The following chips are supported by this driver:

AD7944 <https://www.analog.com/AD7944>_
AD7985 <https://www.analog.com/AD7985>_
AD7986 <https://www.analog.com/AD7986>_

Supported features

SPI wiring modes

The driver currently supports three of the many possible SPI wiring configurations.

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

.. code-block::

                                     +-------------+
                +--------------------| CS          |
                v                    |             |
VIO   +--------------------+         |     HOST    |
 |    |        CNV         |         |             |
 +--->| SDI   AD7944   SDO |-------->| SDI         |
      |        SCK         |         |             |
      +--------------------+         |             |
                ^                    |             |
                +--------------------| SCLK        |
                                     +-------------+

To select this mode in the device tree, set the adi,spi-mode property to "single" and omit the cnv-gpios property.

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

.. code-block::

                                     +-------------+
 +-----------------------------------| CS          |
 |                                   |             |
 |              +--------------------| GPIO        |
 |              v                    |             |
 |    +--------------------+         |     HOST    |
 |    |        CNV         |         |             |
 +--->| SDI   AD7944   SDO |-------->| SDI         |
      |        SCK         |         |             |
      +--------------------+         |             |
                ^                    |             |
                +--------------------| SCLK        |
                                     +-------------+

To select this mode in the device tree, omit the adi,spi-mode property and provide the cnv-gpios property.

Chain mode, without busy indicator ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

.. code-block::

                                                             +-------------+
              +-------------------------+--------------------| CS          |
              v                         v                    |             |
    +--------------------+    +--------------------+         |     HOST    |
    |        CNV         |    |        CNV         |         |             |

+--->| SDI AD7944 SDO |--->| SDI AD7944 SDO |-------->| SDI | | | SCK | | SCK | | | GND +--------------------+ +--------------------+ | | ^ ^ | | +-------------------------+--------------------| SCLK | +-------------+

To select this mode in the device tree, set the adi,spi-mode property to "chain", add the spi-cs-high flag, add the #daisy-chained-devices property, and omit the cnv-gpios property.

Reference voltage

All 3 possible reference voltage sources are supported:

Internal reference
External 1.2V reference and internal buffer
External reference

The source is determined by the device tree. If ref-supply is present, then the external reference is used. If refin-supply is present, then the internal buffer is used. If neither is present, then the internal reference is used.

Unimplemented features

BUSY indication
TURBO mode

Device attributes

There are two types of ADCs in this family, pseudo-differential and fully differential. The channel name is different depending on the type of ADC.

Pseudo-differential ADCs

AD7944 and AD7985 are pseudo-differential ADCs and have the following attributes:

+---------------------------------------+--------------------------------------------------------------+ | Attribute | Description | +=======================================+==============================================================+ | in_voltage0_raw | Raw ADC voltage value (IN+ referenced to ground sense). | +---------------------------------------+--------------------------------------------------------------+ | in_voltage0_scale | Scale factor to convert raw value to mV. | +---------------------------------------+--------------------------------------------------------------+

In "chain" mode, additional chips will appear as additional voltage input channels, e.g. in_voltage1_raw.

Fully-differential ADCs

AD7986 is a fully-differential ADC and has the following attributes:

+---------------------------------------+--------------------------------------------------------------+ | Attribute | Description | +=======================================+==============================================================+ | in_voltage0-voltage1_raw | Raw ADC voltage value (IN+ - IN-). | +---------------------------------------+--------------------------------------------------------------+ | in_voltage0-voltage1_scale | Scale factor to convert raw value to mV. | +---------------------------------------+--------------------------------------------------------------+

In "chain" mode, additional chips will appear as additional voltage input channels, e.g. in_voltage2-voltage3_raw.

Device buffers

This driver supports IIO triggered buffers.

See :doc:iio_devbuf for more information.