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

=============
AD7191 driver
=============

Device driver for Analog Devices AD7191 ADC.

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

* `AD7191 <https://www.analog.com/AD7191>`_

The AD7191 is a high precision, low noise, 24-bit Σ-Δ ADC with integrated PGA.
It features two differential input channels, an internal temperature sensor, and
configurable sampling rates.

Devicetree
==========

Pin Configuration
-----------------

The driver supports both pin-strapped and GPIO-controlled configurations for ODR
(Output Data Rate) and PGA (Programmable Gain Amplifier) settings. These
configurations are mutually exclusive - you must use either pin-strapped or GPIO
control for each setting, not both.

ODR Configuration
^^^^^^^^^^^^^^^^^

The ODR can be configured either through GPIO control or pin-strapping:

- When using GPIO control, specify the "odr-gpios" property in the device tree
- For pin-strapped configuration, specify the "adi,odr-value" property in the
  device tree

Available ODR settings:

  - 120 Hz (ODR1=0, ODR2=0)
  - 60 Hz (ODR1=0, ODR2=1)
  - 50 Hz (ODR1=1, ODR2=0)
  - 10 Hz (ODR1=1, ODR2=1)

PGA Configuration
^^^^^^^^^^^^^^^^^

The PGA can be configured either through GPIO control or pin-strapping:

- When using GPIO control, specify the "pga-gpios" property in the device tree
- For pin-strapped configuration, specify the "adi,pga-value" property in the
  device tree

Available PGA gain settings:

  - 1x (PGA1=0, PGA2=0)
  - 8x (PGA1=0, PGA2=1)
  - 64x (PGA1=1, PGA2=0)
  - 128x (PGA1=1, PGA2=1)

Clock Configuration
-------------------

The AD7191 supports both internal and external clock sources:

- When CLKSEL pin is tied LOW: Uses internal 4.92MHz clock (no clock property
  needed)
- When CLKSEL pin is tied HIGH: Requires external clock source
  - Can be a crystal between MCLK1 and MCLK2 pins
  - Or a CMOS-compatible clock driving MCLK2 pin
  - Must specify the "clocks" property in device tree when using external clock

SPI Interface Requirements
--------------------------

The AD7191 has specific SPI interface requirements:

- The DOUT/RDY output is dual-purpose and requires SPI bus locking
- DOUT/RDY must be connected to an interrupt-capable GPIO
- The SPI controller's chip select must be connected to the PDOWN pin of the ADC
- When CS (PDOWN) is high, the device powers down and resets internal circuitry
- SPI mode 3 operation (CPOL=1, CPHA=1) is required

Power Supply Requirements
-------------------------

The device requires the following power supplies:

- AVdd: Analog power supply
- DVdd: Digital power supply
- Vref: Reference voltage supply (external)

All power supplies must be specified in the device tree.

Channel Configuration
=====================

The device provides three channels:

1. Temperature Sensor
   - 24-bit unsigned
   - Internal temperature measurement
   - Temperature in millidegrees Celsius

2. Differential Input (AIN1-AIN2)
   - 24-bit unsigned
   - Differential voltage measurement
   - Configurable gain via PGA

3. Differential Input (AIN3-AIN4)
   - 24-bit unsigned
   - Differential voltage measurement
   - Configurable gain via PGA

Buffer Support
==============

This driver supports IIO triggered buffers. See Documentation/iio/iio_devbuf.rst
for more information about IIO triggered buffers.