Add documentation for chain mode support that was recently added to the AD7944 ADC driver. Signed-off-by: David Lechner <dlechner@xxxxxxxxxxxx> --- Documentation/iio/ad7944.rst | 30 ++++++++++++++++++++++++++++-- 1 file 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 ============== -- 2.43.2
