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authorDavid Lechner <dlechner@baylibre.com>2024-04-25 16:10:00 +0200
committerJonathan Cameron <Jonathan.Cameron@huawei.com>2024-04-29 21:53:25 +0200
commit633e3015cae062a424a6dd5099710adfe83a5e14 (patch)
treeb3012679272ec529190f09cec48560959d737e3c /Documentation/iio
parentiio: adc: ad7944: add support for chain mode (diff)
downloadlinux-633e3015cae062a424a6dd5099710adfe83a5e14.tar.xz
linux-633e3015cae062a424a6dd5099710adfe83a5e14.zip
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>
Diffstat (limited to 'Documentation/iio')
-rw-r--r--Documentation/iio/ad7944.rst30
1 files changed, 28 insertions, 2 deletions
diff --git a/Documentation/iio/ad7944.rst b/Documentation/iio/ad7944.rst
index f418ab1288ae..0d26e56aba88 100644
--- a/Documentation/iio/ad7944.rst
+++ b/Documentation/iio/ad7944.rst
@@ -24,7 +24,7 @@ Supported features
SPI wiring modes
----------------
-The driver currently supports two of the many possible SPI wiring configurations.
+The driver currently supports three of the many possible SPI wiring configurations.
CS mode, 3-wire, without busy indicator
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -68,6 +68,27 @@ CS mode, 4-wire, without busy indicator
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
-----------------
@@ -86,7 +107,6 @@ Unimplemented features
- ``BUSY`` indication
- ``TURBO`` mode
-- Daisy chain mode
Device attributes
@@ -108,6 +128,9 @@ AD7944 and AD7985 are pseudo-differential ADCs and have the following attributes
| ``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
-----------------------
@@ -121,6 +144,9 @@ AD7986 is a fully-differential ADC and has the following attributes:
| ``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
==============