From: Esteban Blanc Date: Fri, 14 Feb 2025 12:22:36 +0000 (+0100) Subject: docs: iio: ad4030: add documentation X-Git-Tag: v6.15-rc1~78^2~8^2~131 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=b29050e8b3b9ef771d66a70b32e48fa0e587c3ce;p=thirdparty%2Fkernel%2Flinux.git docs: iio: ad4030: add documentation This adds a new page to document how to use the ad4030 ADC driver Signed-off-by: Esteban Blanc Link: https://patch.msgid.link/20250214-eblanc-ad4630_v1-v4-6-135dd66cab6a@baylibre.com Signed-off-by: Jonathan Cameron --- diff --git a/Documentation/iio/ad4030.rst b/Documentation/iio/ad4030.rst new file mode 100644 index 0000000000000..b57424b650a8a --- /dev/null +++ b/Documentation/iio/ad4030.rst @@ -0,0 +1,180 @@ +.. SPDX-License-Identifier: GPL-2.0-only + +============= +AD4030 driver +============= + +ADC driver for Analog Devices Inc. AD4030 and similar devices. The module name +is ``ad4030``. + + +Supported devices +================= + +The following chips are supported by this driver: + +* `AD4030-24 `_ +* `AD4032-24 `_ +* `AD4630-16 `_ +* `AD4630-24 `_ +* `AD4632-16 `_ +* `AD4632-24 `_ + +IIO channels +============ + +Each "hardware" channel as described in the datasheet is split in 2 IIO +channels: + +- One channel for the differential data +- One channel for the common byte. + +The possible IIO channels depending on the numbers of "hardware" channel are: + ++------------------------------------+------------------------------------+ +| 1 channel ADC | 2 channels ADC | ++====================================+====================================+ +| - voltage0-voltage1 (differential) | - voltage0-voltage1 (differential) | +| - voltage2 (common-mode) | - voltage2-voltage3 (differential) | +| | - voltage4 (common-mode) | +| | - voltage5 (common-mode) | ++------------------------------------+------------------------------------+ + +Labels +------ + +For ease of use, the IIO channels provide a label. For a differential channel, +the label is ``differentialN`` where ``N`` is the "hardware" channel id. For a +common-mode channel, the label is ``common-modeN`` where ``N`` is the +"hardware" channel id. + +The possible labels are: + ++-----------------+-----------------+ +| 1 channel ADC | 2 channels ADC | ++=================+=================+ +| - differential0 | - differential0 | +| - common-mode0 | - differential1 | +| | - common-mode0 | +| | - common-mode1 | ++-----------------+-----------------+ + +Supported features +================== + +SPI wiring modes +---------------- + +The driver currently supports the following SPI wiring configurations: + +One lane mode +^^^^^^^^^^^^^ + +In this mode, each channel has its own SDO line to send the conversion results. +At the moment this mode can only be used on AD4030 which has one channel so only +one SDO line is used. + +.. code-block:: + + +-------------+ +-------------+ + | ADC | | HOST | + | | | | + | CNV |<--------| CNV | + | CS |<--------| CS | + | SDI |<--------| SDO | + | SDO0 |-------->| SDI | + | SCLK |<--------| SCLK | + +-------------+ +-------------+ + +Interleaved mode +^^^^^^^^^^^^^^^^ + +In this mode, both channels conversion results are bit interleaved one SDO line. +As such the wiring is the same as `One lane mode`_. + +SPI Clock mode +-------------- + +Only the SPI clocking mode is supported. + +Output modes +------------ + +There are more exposed IIO channels than channels as describe in the devices +datasheet. This is due to the `Differential data + common-mode`_ encoding +2 types of information in one conversion result. As such a "device" channel +provides 2 IIO channels, one for the differential data and one for the common +byte. + +Differential data +^^^^^^^^^^^^^^^^^ + +This mode is selected when: + +- Only differential channels are enabled in a buffered read +- Oversampling attribute is set to 1 + +Differential data + common-mode +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +This mode is selected when: + +- Differential and common-mode channels are enabled in a buffered read +- Oversampling attribute is set to 1 + +For the 24-bits chips, this mode is also available with 16-bits differential +data but is not selectable yet. + +Averaged differential data +^^^^^^^^^^^^^^^^^^^^^^^^^^ + +This mode is selected when: + +- Only differential channels are selected enabled in a buffered read +- Oversampling attribute is greater than 1 + +Digital Gain and Offset +----------------------- + +Each differential data channel has a 16-bits unsigned configurable hardware +gain applied to it. By default it's equal to 1. Note that applying gain can +cause numerical saturation. + +Each differential data channel has a signed configurable hardware offset. +For the ADCs ending in ``-24``, the gain is encoded on 24-bits. +Likewise, the ADCs ending in ``-16`` have a gain encoded on 16-bits. Note that +applying an offset can cause numerical saturation. + +The final differential data returned by the ADC is computed by first applying +the gain, then the offset. + +The gain is controlled by the ``calibscale`` IIO attribute while the offset is +controlled by the ``calibbias`` attribute. + +Reference voltage +----------------- + +The chip supports an external reference voltage via the ``REF`` input or an +internal buffered reference voltage via the ``REFIN`` input. The driver looks +at the device tree to determine which is being used. If ``ref-supply`` is +present, then the external reference voltage is used and the internal buffer is +disabled. If ``refin-supply`` is present, then the internal buffered reference +voltage is used. + +Reset +----- + +Both hardware and software reset are supported. The driver looks first at the +device tree to see if the ``reset-gpio`` is populated. +If not present, the driver will fallback to a software reset by wiring to the +device's registers. + +Unimplemented features +---------------------- + +- ``BUSY`` indication +- Additional wiring modes +- Additional clock modes +- Differential data 16-bits + common-mode for 24-bits chips +- Overrange events +- Test patterns diff --git a/Documentation/iio/index.rst b/Documentation/iio/index.rst index 5710f5b9e9582..2d334be2b7f29 100644 --- a/Documentation/iio/index.rst +++ b/Documentation/iio/index.rst @@ -19,6 +19,7 @@ Industrial I/O Kernel Drivers :maxdepth: 1 ad4000 + ad4030 ad4695 ad7380 ad7606 diff --git a/MAINTAINERS b/MAINTAINERS index 594ac38ad15d9..bd04375ab4a21 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -1314,6 +1314,7 @@ L: linux-iio@vger.kernel.org S: Supported W: https://ez.analog.com/linux-software-drivers F: Documentation/devicetree/bindings/iio/adc/adi,ad4030.yaml +F: Documentation/iio/ad4030.rst F: drivers/iio/adc/ad4030.c ANALOG DEVICES INC AD4130 DRIVER