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Documentation: iio: ad4000: Add IIO Device characteristics section

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Complement ad4000 IIO driver documentation with considerations about
``_scale_available`` attribute and table of typical channel attributes.

Reviewed-by: David Lechner <dlechner@baylibre.com>
Signed-off-by: Marcelo Schmitt <marcelo.schmitt@analog.com>
Link: https://patch.msgid.link/6c8fe68d7d413ffdd33b154ba45600c7ce7013da.1743110188.git.marcelo.schmitt@analog.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
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Marcelo Schmitt 2025-03-27 18:25:12 -03:00 committed by Jonathan Cameron
parent 66ac231508
commit d66b2c84fb
1 changed files with 47 additions and 0 deletions
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Documentation/iio/ad4000.rst
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@ -144,3 +144,50 @@ Set ``adi,sdi-pin`` to ``"cs"`` to select this mode.
^ | | ^ | |
+--------------------| SCLK | +--------------------| SCLK |
+-------------+ +-------------+
IIO Device characteristics
==========================
The AD4000 series driver supports differential and pseudo-differential ADCs.
The span compression feature available in AD4000 series devices can be
enabled/disabled by changing the ``_scale_available`` attribute of the voltage
channel. Note that span compression configuration requires writing to AD4000
configuration register, which is only possible when the ADC is wired in 3-wire
turbo mode, and the SPI controller is ``SPI_MOSI_IDLE_HIGH`` capable. If those
conditions are not met, no ``_scale_available`` attribute is provided.
Besides that, differential and pseudo-differential voltage channels present
slightly different sysfs interfaces.
Pseudo-differential ADCs
------------------------
Typical voltage channel attributes of a pseudo-differential AD4000 series device:
+-------------------------------------------+------------------------------------------+
| Voltage Channel Attributes | Description |
+===========================================+==========================================+
| ``in_voltage0_raw`` | Raw ADC output code. |
+-------------------------------------------+------------------------------------------+
| ``in_voltage0_offset`` | Offset to convert raw value to mV. |
+-------------------------------------------+------------------------------------------+
| ``in_voltage0_scale`` | Scale factor to convert raw value to mV. |
+-------------------------------------------+------------------------------------------+
| ``in_voltage0_scale_available`` | Toggles input span compression |
+-------------------------------------------+------------------------------------------+
Differential ADCs
-----------------
Typical voltage channel attributes of a differential AD4000 series device:
+-------------------------------------------+------------------------------------------+
| Voltage Channel Attributes | Description |
+===========================================+==========================================+
| ``in_voltage0-voltage1_raw`` | Raw ADC output code. |
+-------------------------------------------+------------------------------------------+
| ``in_voltage0-voltage1_scale`` | Scale factor to convert raw value to mV. |
+-------------------------------------------+------------------------------------------+
| ``in_voltage0-voltage1_scale_available`` | Toggles input span compression |
+-------------------------------------------+------------------------------------------+