€•‡‘      Œsphinx.addnodes”Œdocument”“”)”}”(Œ	rawsource”Œ ”Œchildren”]”(Œtranslations”ŒLanguagesNode”“”)”}”(hhh]”(h Œpending_xref”“”)”}”(hhh]”Œdocutils.nodes”ŒText”“”ŒChinese (Simplified)”…””}”Œparent”hsbaŒ
attributes”}”(Œids”]”Œclasses”]”Œnames”]”Œdupnames”]”Œbackrefs”]”Œ	refdomain”Œstd”Œreftype”Œdoc”Œ	reftarget”Œ/translations/zh_CN/iio/iio_adc”Œmodname”NŒ	classname”NŒrefexplicit”ˆuŒtagname”hhhubh)”}”(hhh]”hŒChinese (Traditional)”…””}”hh2sbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ/translations/zh_TW/iio/iio_adc”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒItalian”…””}”hhFsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ/translations/it_IT/iio/iio_adc”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒJapanese”…””}”hhZsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ/translations/ja_JP/iio/iio_adc”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒKorean”…””}”hhnsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ/translations/ko_KR/iio/iio_adc”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒSpanish”…””}”hh‚sbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ/translations/sp_SP/iio/iio_adc”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubeh}”(h]”h ]”h"]”h$]”h&]”Œcurrent_language”ŒEnglish”uh1h
hhŒ	_document”hŒsource”NŒline”NubhŒcomment”“”)”}”(hŒ%SPDX-License-Identifier: GPL-2.0-only”h]”hŒ%SPDX-License-Identifier: GPL-2.0-only”…””}”hh£sbah}”(h]”h ]”h"]”h$]”h&]”Œ	xml:space”Œpreserve”uh1h¡hhhžhhŸŒ9/var/lib/git/docbuild/linux/Documentation/iio/iio_adc.rst”h KubhŒsection”“”)”}”(hhh]”(hŒtitle”“”)”}”(hŒIIO Abstractions for ADCs”h]”hŒIIO Abstractions for ADCs”…””}”(hh»hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¹hh¶hžhhŸh³h Kubhµ)”}”(hhh]”(hº)”}”(hŒ1. Overview”h]”hŒ1. Overview”…””}”(hhÌhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¹hhÉhžhhŸh³h KubhŒ	paragraph”“”)”}”(hX  The IIO subsystem supports many Analog to Digital Converters (ADCs). Some ADCs
have features and characteristics that are supported in specific ways by IIO
device drivers. This documentation describes common ADC features and explains
how they are supported by the IIO subsystem.”h]”hX  The IIO subsystem supports many Analog to Digital Converters (ADCs). Some ADCs
have features and characteristics that are supported in specific ways by IIO
device drivers. This documentation describes common ADC features and explains
how they are supported by the IIO subsystem.”…””}”(hhÜhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h K
hhÉhžhubeh}”(h]”Œoverview”ah ]”h"]”Œ1. overview”ah$]”h&]”uh1h´hh¶hžhhŸh³h Kubhµ)”}”(hhh]”(hº)”}”(hŒ1. ADC Channel Types”h]”hŒ1. ADC Channel Types”…””}”(hhõhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¹hhòhžhhŸh³h KubhÛ)”}”(hXä  ADCs can have distinct types of inputs, each of them measuring analog voltages
in a slightly different way. An ADC digitizes the analog input voltage over a
span that is often given by the provided voltage reference, the input type, and
the input polarity. The input range allowed to an ADC channel is needed to
determine the scale factor and offset needed to obtain the measured value in
real-world units (millivolts for voltage measurement, milliamps for current
measurement, etc.).”h]”hXä  ADCs can have distinct types of inputs, each of them measuring analog voltages
in a slightly different way. An ADC digitizes the analog input voltage over a
span that is often given by the provided voltage reference, the input type, and
the input polarity. The input range allowed to an ADC channel is needed to
determine the scale factor and offset needed to obtain the measured value in
real-world units (millivolts for voltage measurement, milliamps for current
measurement, etc.).”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h KhhòhžhubhÛ)”}”(hXT  Elaborate designs may have nonlinear characteristics or integrated components
(such as amplifiers and reference buffers) that might also have to be considered
to derive the allowed input range for an ADC. For clarity, the sections below
assume the input range only depends on the provided voltage references, input
type, and input polarity.”h]”hXT  Elaborate designs may have nonlinear characteristics or integrated components
(such as amplifiers and reference buffers) that might also have to be considered
to derive the allowed input range for an ADC. For clarity, the sections below
assume the input range only depends on the provided voltage references, input
type, and input polarity.”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h KhhòhžhubhÛ)”}”(hXï  There are three general types of ADC inputs (single-ended, differential,
pseudo-differential) and two possible polarities (unipolar, bipolar). The input
type (single-ended, differential, pseudo-differential) is one channel
characteristic, and is completely independent of the polarity (unipolar,
bipolar) aspect. A comprehensive article about ADC input types (on which this
doc is heavily based on) can be found at
https://www.analog.com/en/resources/technical-articles/sar-adc-input-types.html.”h]”(hXŸ  There are three general types of ADC inputs (single-ended, differential,
pseudo-differential) and two possible polarities (unipolar, bipolar). The input
type (single-ended, differential, pseudo-differential) is one channel
characteristic, and is completely independent of the polarity (unipolar,
bipolar) aspect. A comprehensive article about ADC input types (on which this
doc is heavily based on) can be found at
”…””}”(hj  hžhhŸNh NubhŒ	reference”“”)”}”(hŒOhttps://www.analog.com/en/resources/technical-articles/sar-adc-input-types.html”h]”hŒOhttps://www.analog.com/en/resources/technical-articles/sar-adc-input-types.html”…””}”(hj)  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”Œrefuri”j+  uh1j'  hj  ubhŒ.”…””}”(hj  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h K hhòhžhubhµ)”}”(hhh]”(hº)”}”(hŒ1.1 Single-ended channels”h]”hŒ1.1 Single-ended channels”…””}”(hjE  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¹hjB  hžhhŸh³h K)ubhÛ)”}”(hŒqSingle-ended channels digitize the analog input voltage relative to ground and
can be either unipolar or bipolar.”h]”hŒqSingle-ended channels digitize the analog input voltage relative to ground and
can be either unipolar or bipolar.”…””}”(hjS  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h K+hjB  hžhubhµ)”}”(hhh]”(hº)”}”(hŒ$1.1.1 Single-ended Unipolar Channels”h]”hŒ$1.1.1 Single-ended Unipolar Channels”…””}”(hjd  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¹hja  hžhhŸh³h K/ubhŒliteral_block”“”)”}”(hX  ---------- VREF -------------
    Â´ `           Â´ `                  _____________
  /     \       /     \               /             |
 /       \     /       \         --- <  IN    ADC   |
          \   /         \   /         \             |
           `-Â´           `-Â´           \       VREF |
-------- GND (0V) -----------           +-----------+
                                                ^
                                                |
                                           External VREF”h]”hX  ---------- VREF -------------
    Â´ `           Â´ `                  _____________
  /     \       /     \               /             |
 /       \     /       \         --- <  IN    ADC   |
          \   /         \   /         \             |
           `-Â´           `-Â´           \       VREF |
-------- GND (0V) -----------           +-----------+
                                                ^
                                                |
                                           External VREF”…””}”hjt  sbah}”(h]”h ]”h"]”h$]”h&]”h±h²uh1jr  hŸh³h K3hja  hžhubhÛ)”}”(hX‡  The input voltage to a **single-ended unipolar** channel is allowed to swing
from GND to VREF (where VREF is a voltage reference with electrical potential
higher than system ground). The maximum input voltage is also called VFS
(Voltage input Full-Scale), with VFS being determined by VREF. The voltage
reference may be provided from an external supply or derived from the chip power
source.”h]”(hŒThe input voltage to a ”…””}”(hj‚  hžhhŸNh NubhŒstrong”“”)”}”(hŒ**single-ended unipolar**”h]”hŒsingle-ended unipolar”…””}”(hjŒ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jŠ  hj‚  ubhXW   channel is allowed to swing
from GND to VREF (where VREF is a voltage reference with electrical potential
higher than system ground). The maximum input voltage is also called VFS
(Voltage input Full-Scale), with VFS being determined by VREF. The voltage
reference may be provided from an external supply or derived from the chip power
source.”…””}”(hj‚  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h K>hja  hžhubhÛ)”}”(hŒ^A single-ended unipolar channel could be described in device tree like the
following example::”h]”hŒ]A single-ended unipolar channel could be described in device tree like the
following example:”…””}”(hj¤  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h KEhja  hžhubjs  )”}”(hŒnadc@0 {
    ...
    #address-cells = <1>;
    #size-cells = <0>;

    channel@0 {
        reg = <0>;
    };
};”h]”hŒnadc@0 {
    ...
    #address-cells = <1>;
    #size-cells = <0>;

    channel@0 {
        reg = <0>;
    };
};”…””}”hj²  sbah}”(h]”h ]”h"]”h$]”h&]”h±h²uh1jr  hŸh³h KHhja  hžhubhÛ)”}”(hŒÊOne is always allowed to include ADC channel nodes in the device tree. Though,
if the device has a uniform set of inputs (e.g. all inputs are single-ended),
then declaring the channel nodes is optional.”h]”hŒÊOne is always allowed to include ADC channel nodes in the device tree. Though,
if the device has a uniform set of inputs (e.g. all inputs are single-ended),
then declaring the channel nodes is optional.”…””}”(hjÀ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h KRhja  hžhubhÛ)”}”(hŒóOne caveat for devices that support mixed single-ended and differential channels
is that single-ended channel nodes also need to provide a ``single-channel``
property when ``reg`` is an arbitrary number that doesn't match the input pin
number.”h]”(hŒ‹One caveat for devices that support mixed single-ended and differential channels
is that single-ended channel nodes also need to provide a ”…””}”(hjÎ  hžhhŸNh NubhŒliteral”“”)”}”(hŒ``single-channel``”h]”hŒsingle-channel”…””}”(hjØ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jÖ  hjÎ  ubhŒ
property when ”…””}”(hjÎ  hžhhŸNh Nubj×  )”}”(hŒ``reg``”h]”hŒreg”…””}”(hjê  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jÖ  hjÎ  ubhŒB is an arbitrary number that doesnâ€™t match the input pin
number.”…””}”(hjÎ  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h KVhja  hžhubhÛ)”}”(hŒSee ``Documentation/devicetree/bindings/iio/adc/adc.yaml`` for the complete
documentation of ADC specific device tree properties.”h]”(hŒSee ”…””}”(hj  hžhhŸNh Nubj×  )”}”(hŒ6``Documentation/devicetree/bindings/iio/adc/adc.yaml``”h]”hŒ2Documentation/devicetree/bindings/iio/adc/adc.yaml”…””}”(hj
  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jÖ  hj  ubhŒG for the complete
documentation of ADC specific device tree properties.”…””}”(hj  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h K[hja  hžhubeh}”(h]”Œsingle-ended-unipolar-channels”ah ]”h"]”Œ$1.1.1 single-ended unipolar channels”ah$]”h&]”uh1h´hjB  hžhhŸh³h K/ubhµ)”}”(hhh]”(hº)”}”(hŒ#1.1.2 Single-ended Bipolar Channels”h]”hŒ#1.1.2 Single-ended Bipolar Channels”…””}”(hj-  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¹hj*  hžhhŸh³h K`ubjs  )”}”(hXJ  ---------- +VREF ------------
    Â´ `           Â´ `                  _____________________
  /     \       /     \               /                     |
 /       \     /       \         --- <  IN          ADC     |
          \   /         \   /         \                     |
           `-Â´           `-Â´           \       +VREF  -VREF |
---------- -VREF ------------           +-------------------+
                                                ^       ^
                                                |       |
                           External +VREF ------+  External -VREF”h]”hXJ  ---------- +VREF ------------
    Â´ `           Â´ `                  _____________________
  /     \       /     \               /                     |
 /       \     /       \         --- <  IN          ADC     |
          \   /         \   /         \                     |
           `-Â´           `-Â´           \       +VREF  -VREF |
---------- -VREF ------------           +-------------------+
                                                ^       ^
                                                |       |
                           External +VREF ------+  External -VREF”…””}”hj;  sbah}”(h]”h ]”h"]”h$]”h&]”h±h²uh1jr  hŸh³h Kdhj*  hžhubhÛ)”}”(hXw  For a **single-ended bipolar** channel, the analog voltage input can go from
-VREF to +VREF (where -VREF is the voltage reference that has the lower
electrical potential while +VREF is the reference with the higher one). Some ADC
chips derive the lower reference from +VREF, others get it from a separate
input. Often, +VREF and -VREF are symmetric but they don't need to be so. When
-VREF is lower than system ground, these inputs are also called single-ended
true bipolar. Also, while there is a relevant difference between bipolar and
true bipolar from the electrical perspective, IIO makes no explicit distinction
between them.”h]”(hŒFor a ”…””}”(hjI  hžhhŸNh Nubj‹  )”}”(hŒ**single-ended bipolar**”h]”hŒsingle-ended bipolar”…””}”(hjQ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jŠ  hjI  ubhX[   channel, the analog voltage input can go from
-VREF to +VREF (where -VREF is the voltage reference that has the lower
electrical potential while +VREF is the reference with the higher one). Some ADC
chips derive the lower reference from +VREF, others get it from a separate
input. Often, +VREF and -VREF are symmetric but they donâ€™t need to be so. When
-VREF is lower than system ground, these inputs are also called single-ended
true bipolar. Also, while there is a relevant difference between bipolar and
true bipolar from the electrical perspective, IIO makes no explicit distinction
between them.”…””}”(hjI  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h Kohj*  hžhubhÛ)”}”(hŒMHere's an example device tree description of a single-ended bipolar channel::”h]”hŒNHereâ€™s an example device tree description of a single-ended bipolar channel:”…””}”(hji  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h Kyhj*  hžhubjs  )”}”(hŒadc@0 {
    ...
    #address-cells = <1>;
    #size-cells = <0>;

    channel@0 {
        reg = <0>;
        bipolar;
    };
};”h]”hŒadc@0 {
    ...
    #address-cells = <1>;
    #size-cells = <0>;

    channel@0 {
        reg = <0>;
        bipolar;
    };
};”…””}”hjw  sbah}”(h]”h ]”h"]”h$]”h&]”h±h²uh1jr  hŸh³h K{hj*  hžhubeh}”(h]”Œsingle-ended-bipolar-channels”ah ]”h"]”Œ#1.1.2 single-ended bipolar channels”ah$]”h&]”uh1h´hjB  hžhhŸh³h K`ubeh}”(h]”Œsingle-ended-channels”ah ]”h"]”Œ1.1 single-ended channels”ah$]”h&]”uh1h´hhòhžhhŸh³h K)ubhµ)”}”(hhh]”(hº)”}”(hŒ1.2 Differential channels”h]”hŒ1.2 Differential channels”…””}”(hj˜  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¹hj•  hžhhŸh³h K‡ubhÛ)”}”(hX,  A differential voltage measurement digitizes the voltage level at the positive
input (IN+) relative to the negative input (IN-) over the -VREF to +VREF span.
In other words, a differential channel measures the potential difference between
IN+ and IN-, which is often denoted by the IN+ - IN- formula.”h]”hX,  A differential voltage measurement digitizes the voltage level at the positive
input (IN+) relative to the negative input (IN-) over the -VREF to +VREF span.
In other words, a differential channel measures the potential difference between
IN+ and IN-, which is often denoted by the IN+ - IN- formula.”…””}”(hj¦  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h K‰hj•  hžhubhµ)”}”(hhh]”(hº)”}”(hŒ#1.2.1 Differential Bipolar Channels”h]”hŒ#1.2.1 Differential Bipolar Channels”…””}”(hj·  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¹hj´  hžhhŸh³h Kubjs  )”}”(hXç  -------- +VREF ------         +-------------------+
  Â´ `       Â´ `              /                    |
/     \   /     \   /   --- <  IN+                |
       `-Â´       `-Â´         |                    |
-------- -VREF ------        |                    |
                             |            ADC     |
-------- +VREF ------        |                    |
      Â´ `       Â´ `          |                    |
\   /     \   /     \   --- <  IN-                |
 `-Â´       `-Â´               \       +VREF  -VREF |
-------- -VREF ------         +-------------------+
                                       ^       ^
                                       |       +---- External -VREF
                                External +VREF”h]”hXç  -------- +VREF ------         +-------------------+
  Â´ `       Â´ `              /                    |
/     \   /     \   /   --- <  IN+                |
       `-Â´       `-Â´         |                    |
-------- -VREF ------        |                    |
                             |            ADC     |
-------- +VREF ------        |                    |
      Â´ `       Â´ `          |                    |
\   /     \   /     \   --- <  IN-                |
 `-Â´       `-Â´               \       +VREF  -VREF |
-------- -VREF ------         +-------------------+
                                       ^       ^
                                       |       +---- External -VREF
                                External +VREF”…””}”hjÅ  sbah}”(h]”h ]”h"]”h$]”h&]”h±h²uh1jr  hŸh³h K“hj´  hžhubhÛ)”}”(hX1  The analog signals to **differential bipolar** inputs are also allowed to swing
from -VREF to +VREF. The bipolar part of the name means that the resulting value
of the difference (IN+ - IN-) can be positive or negative. If -VREF is below
system GND, these are also called differential true bipolar inputs.”h]”(hŒThe analog signals to ”…””}”(hjÓ  hžhhŸNh Nubj‹  )”}”(hŒ**differential bipolar**”h]”hŒdifferential bipolar”…””}”(hjÛ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jŠ  hjÓ  ubhX   inputs are also allowed to swing
from -VREF to +VREF. The bipolar part of the name means that the resulting value
of the difference (IN+ - IN-) can be positive or negative. If -VREF is below
system GND, these are also called differential true bipolar inputs.”…””}”(hjÓ  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h K¢hj´  hžhubhÛ)”}”(hŒ7Device tree example of a differential bipolar channel::”h]”hŒ6Device tree example of a differential bipolar channel:”…””}”(hjó  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h K§hj´  hžhubjs  )”}”(hŒžadc@0 {
    ...
    #address-cells = <1>;
    #size-cells = <0>;

    channel@0 {
        reg = <0>;
        bipolar;
        diff-channels = <0 1>;
    };
};”h]”hŒžadc@0 {
    ...
    #address-cells = <1>;
    #size-cells = <0>;

    channel@0 {
        reg = <0>;
        bipolar;
        diff-channels = <0 1>;
    };
};”…””}”hj  sbah}”(h]”h ]”h"]”h$]”h&]”h±h²uh1jr  hŸh³h K©hj´  hžhubhÛ)”}”(hXV  In the ADC driver, ``differential = 1`` is set into ``struct iio_chan_spec`` for
the channel. Even though, there are three general input types, ``differential``
is only used to distinguish between differential and non-differential (either
single-ended or pseudo-differential) input types. See
``include/linux/iio/iio.h`` for more information.”h]”(hŒIn the ADC driver, ”…””}”(hj  hžhhŸNh Nubj×  )”}”(hŒ``differential = 1``”h]”hŒdifferential = 1”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jÖ  hj  ubhŒ is set into ”…””}”(hj  hžhhŸNh Nubj×  )”}”(hŒ``struct iio_chan_spec``”h]”hŒstruct iio_chan_spec”…””}”(hj)  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jÖ  hj  ubhŒD for
the channel. Even though, there are three general input types, ”…””}”(hj  hžhhŸNh Nubj×  )”}”(hŒ``differential``”h]”hŒdifferential”…””}”(hj;  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jÖ  hj  ubhŒ…
is only used to distinguish between differential and non-differential (either
single-ended or pseudo-differential) input types. See
”…””}”(hj  hžhhŸNh Nubj×  )”}”(hŒ``include/linux/iio/iio.h``”h]”hŒinclude/linux/iio/iio.h”…””}”(hjM  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jÖ  hj  ubhŒ for more information.”…””}”(hj  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h Kµhj´  hžhubeh}”(h]”Œdifferential-bipolar-channels”ah ]”h"]”Œ#1.2.1 differential bipolar channels”ah$]”h&]”uh1h´hj•  hžhhŸh³h Kubhµ)”}”(hhh]”(hº)”}”(hŒ$1.2.2 Differential Unipolar Channels”h]”hŒ$1.2.2 Differential Unipolar Channels”…””}”(hjp  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¹hjm  hžhhŸh³h K¼ubhÛ)”}”(hXË  For **differential unipolar** channels, the analog voltage at the positive input
must also be higher than the voltage at the negative input. Thus, the actual
input range allowed to a differential unipolar channel is IN- to +VREF. Because
IN+ is allowed to swing with the measured analog signal and the input setup must
guarantee IN+ will not go below IN- (nor IN- will raise above IN+), most
differential unipolar channel setups have IN- fixed to a known voltage that does
not fall within the voltage range expected for the measured signal. That leads
to a setup that is equivalent to a pseudo-differential channel. Thus,
differential unipolar setups can often be supported as pseudo-differential
unipolar channels.”h]”(hŒFor ”…””}”(hj~  hžhhŸNh Nubj‹  )”}”(hŒ**differential unipolar**”h]”hŒdifferential unipolar”…””}”(hj†  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jŠ  hj~  ubhX®   channels, the analog voltage at the positive input
must also be higher than the voltage at the negative input. Thus, the actual
input range allowed to a differential unipolar channel is IN- to +VREF. Because
IN+ is allowed to swing with the measured analog signal and the input setup must
guarantee IN+ will not go below IN- (nor IN- will raise above IN+), most
differential unipolar channel setups have IN- fixed to a known voltage that does
not fall within the voltage range expected for the measured signal. That leads
to a setup that is equivalent to a pseudo-differential channel. Thus,
differential unipolar setups can often be supported as pseudo-differential
unipolar channels.”…””}”(hj~  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h K¾hjm  hžhubeh}”(h]”Œdifferential-unipolar-channels”ah ]”h"]”Œ$1.2.2 differential unipolar channels”ah$]”h&]”uh1h´hj•  hžhhŸh³h K¼ubeh}”(h]”Œdifferential-channels”ah ]”h"]”Œ1.2 differential channels”ah$]”h&]”uh1h´hhòhžhhŸh³h K‡ubhµ)”}”(hhh]”(hº)”}”(hŒ 1.3 Pseudo-differential Channels”h]”hŒ 1.3 Pseudo-differential Channels”…””}”(hj±  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¹hj®  hžhhŸh³h KÊubhÛ)”}”(hXÆ  There is a third ADC input type which is called pseudo-differential or
single-ended to differential configuration. A pseudo-differential channel is
similar to a differential channel in that it also measures IN+ relative to IN-.
However, unlike bipolar differential channels, the negative input is limited to
a narrow voltage range (taken as a constant voltage) while only IN+ is allowed
to swing. A pseudo-differential channel can be made out from a differential pair
of inputs by restricting the negative input to a known voltage while allowing
only the positive input to swing. Sometimes, the input provided to IN- is called
common-mode voltage. Besides, some parts have a COM pin that allows single-ended
inputs to be referenced to a common-mode voltage, making them
pseudo-differential channels. Often, the common mode input voltage can be
described in the device tree as a voltage regulator (e.g. ``com-supply``) since
it is basically a constant voltage source.”h]”(hX†  There is a third ADC input type which is called pseudo-differential or
single-ended to differential configuration. A pseudo-differential channel is
similar to a differential channel in that it also measures IN+ relative to IN-.
However, unlike bipolar differential channels, the negative input is limited to
a narrow voltage range (taken as a constant voltage) while only IN+ is allowed
to swing. A pseudo-differential channel can be made out from a differential pair
of inputs by restricting the negative input to a known voltage while allowing
only the positive input to swing. Sometimes, the input provided to IN- is called
common-mode voltage. Besides, some parts have a COM pin that allows single-ended
inputs to be referenced to a common-mode voltage, making them
pseudo-differential channels. Often, the common mode input voltage can be
described in the device tree as a voltage regulator (e.g. ”…””}”(hj¿  hžhhŸNh Nubj×  )”}”(hŒ``com-supply``”h]”hŒ
com-supply”…””}”(hjÇ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jÖ  hj¿  ubhŒ2) since
it is basically a constant voltage source.”…””}”(hj¿  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h KÌhj®  hžhubhµ)”}”(hhh]”(hº)”}”(hŒ+1.3.1 Pseudo-differential Unipolar Channels”h]”hŒ+1.3.1 Pseudo-differential Unipolar Channels”…””}”(hjâ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¹hjß  hžhhŸh³h KÛubjs  )”}”(hX„  -------- +VREF ------          +-------------------+
  Â´ `       Â´ `               /                    |
/     \   /     \   /    --- <  IN+                |
       `-Â´       `-Â´          |                    |
--------- IN- -------         |            ADC     |
                              |                    |
Common-mode voltage -->  --- <  IN-                |
                              \       +VREF  -VREF |
                               +-------------------+
                                       ^       ^
                                       |       +---- External -VREF
                                External +VREF”h]”hX„  -------- +VREF ------          +-------------------+
  Â´ `       Â´ `               /                    |
/     \   /     \   /    --- <  IN+                |
       `-Â´       `-Â´          |                    |
--------- IN- -------         |            ADC     |
                              |                    |
Common-mode voltage -->  --- <  IN-                |
                              \       +VREF  -VREF |
                               +-------------------+
                                       ^       ^
                                       |       +---- External -VREF
                                External +VREF”…””}”hjð  sbah}”(h]”h ]”h"]”h$]”h&]”h±h²uh1jr  hŸh³h Kßhjß  hžhubhÛ)”}”(hXo  A **pseudo-differential unipolar** input has the limitations a differential
unipolar channel would have, meaning the analog voltage to the positive input
IN+ must stay within IN- to +VREF. The fixed voltage to IN- is often called
common-mode voltage and it must be within -VREF to +VREF as would be expected
from the signal to any differential channel negative input.”h]”(hŒA ”…””}”(hjþ  hžhhŸNh Nubj‹  )”}”(hŒ **pseudo-differential unipolar**”h]”hŒpseudo-differential unipolar”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jŠ  hjþ  ubhXM   input has the limitations a differential
unipolar channel would have, meaning the analog voltage to the positive input
IN+ must stay within IN- to +VREF. The fixed voltage to IN- is often called
common-mode voltage and it must be within -VREF to +VREF as would be expected
from the signal to any differential channel negative input.”…””}”(hjþ  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h Kìhjß  hžhubhÛ)”}”(hXð  The voltage measured from IN+ is relative to IN- but, unlike differential
channels, pseudo-differential setups are intended to gauge single-ended input
signals. To enable applications to calculate IN+ voltage with respect to system
ground, the IIO channel may provide an ``_offset`` sysfs attribute to be added
to ADC output when converting raw data to voltage units. In many setups, the
common-mode voltage input is at GND level and the ``_offset`` attribute is
omitted due to being always zero.”h]”(hX  The voltage measured from IN+ is relative to IN- but, unlike differential
channels, pseudo-differential setups are intended to gauge single-ended input
signals. To enable applications to calculate IN+ voltage with respect to system
ground, the IIO channel may provide an ”…””}”(hj  hžhhŸNh Nubj×  )”}”(hŒ``_offset``”h]”hŒ_offset”…””}”(hj&  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jÖ  hj  ubhŒœ sysfs attribute to be added
to ADC output when converting raw data to voltage units. In many setups, the
common-mode voltage input is at GND level and the ”…””}”(hj  hžhhŸNh Nubj×  )”}”(hŒ``_offset``”h]”hŒ_offset”…””}”(hj8  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jÖ  hj  ubhŒ/ attribute is
omitted due to being always zero.”…””}”(hj  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h Kòhjß  hžhubhÛ)”}”(hŒ>Device tree example for pseudo-differential unipolar channel::”h]”hŒ=Device tree example for pseudo-differential unipolar channel:”…””}”(hjP  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h Kúhjß  hžhubjs  )”}”(hŒ¯adc@0 {
    ...
    #address-cells = <1>;
    #size-cells = <0>;

    channel@0 {
        reg = <0>;
        single-channel = <0>;
        common-mode-channel = <1>;
    };
};”h]”hŒ¯adc@0 {
    ...
    #address-cells = <1>;
    #size-cells = <0>;

    channel@0 {
        reg = <0>;
        single-channel = <0>;
        common-mode-channel = <1>;
    };
};”…””}”hj^  sbah}”(h]”h ]”h"]”h$]”h&]”h±h²uh1jr  hŸh³h Kühjß  hžhubhÛ)”}”(hŒdDo not set ``differential`` in the channel ``iio_chan_spec`` struct of
pseudo-differential channels.”h]”(hŒDo not set ”…””}”(hjl  hžhhŸNh Nubj×  )”}”(hŒ``differential``”h]”hŒdifferential”…””}”(hjt  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jÖ  hjl  ubhŒ in the channel ”…””}”(hjl  hžhhŸNh Nubj×  )”}”(hŒ``iio_chan_spec``”h]”hŒiio_chan_spec”…””}”(hj†  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jÖ  hjl  ubhŒ( struct of
pseudo-differential channels.”…””}”(hjl  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h Mhjß  hžhubeh}”(h]”Œ%pseudo-differential-unipolar-channels”ah ]”h"]”Œ+1.3.1 pseudo-differential unipolar channels”ah$]”h&]”uh1h´hj®  hžhhŸh³h KÛubhµ)”}”(hhh]”(hº)”}”(hŒ*1.3.2 Pseudo-differential Bipolar Channels”h]”hŒ*1.3.2 Pseudo-differential Bipolar Channels”…””}”(hj©  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¹hj¦  hžhhŸh³h Mubjs  )”}”(hX‡  -------- +VREF ------          +-------------------+
  Â´ `       Â´ `               /                    |
/     \   /     \   /    --- <  IN+                |
       `-Â´       `-Â´          |                    |
-------- -VREF ------         |            ADC     |
                              |                    |
Common-mode voltage -->  --- <  IN-                |
                              \       +VREF  -VREF |
                               +-------------------+
                                        ^       ^
                                        |       +---- External -VREF
                                 External +VREF”h]”hX‡  -------- +VREF ------          +-------------------+
  Â´ `       Â´ `               /                    |
/     \   /     \   /    --- <  IN+                |
       `-Â´       `-Â´          |                    |
-------- -VREF ------         |            ADC     |
                              |                    |
Common-mode voltage -->  --- <  IN-                |
                              \       +VREF  -VREF |
                               +-------------------+
                                        ^       ^
                                        |       +---- External -VREF
                                 External +VREF”…””}”hj·  sbah}”(h]”h ]”h"]”h$]”h&]”h±h²uh1jr  hŸh³h Mhj¦  hžhubhÛ)”}”(hX³  A **pseudo-differential bipolar** input is not limited by the level at IN- but
it will be limited to -VREF or to GND on the lower end of the input range
depending on the particular ADC. Similar to their unipolar counter parts,
pseudo-differential bipolar channels ought to declare an ``_offset`` attribute
to enable the conversion of raw ADC data to voltage units. For the setup with
IN- connected to GND, ``_offset`` is often omitted.”h]”(hŒA ”…””}”(hjÅ  hžhhŸNh Nubj‹  )”}”(hŒ**pseudo-differential bipolar**”h]”hŒpseudo-differential bipolar”…””}”(hjÍ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jŠ  hjÅ  ubhŒû input is not limited by the level at IN- but
it will be limited to -VREF or to GND on the lower end of the input range
depending on the particular ADC. Similar to their unipolar counter parts,
pseudo-differential bipolar channels ought to declare an ”…””}”(hjÅ  hžhhŸNh Nubj×  )”}”(hŒ``_offset``”h]”hŒ_offset”…””}”(hjß  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jÖ  hjÅ  ubhŒo attribute
to enable the conversion of raw ADC data to voltage units. For the setup with
IN- connected to GND, ”…””}”(hjÅ  hžhhŸNh Nubj×  )”}”(hŒ``_offset``”h]”hŒ_offset”…””}”(hjñ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jÖ  hjÅ  ubhŒ is often omitted.”…””}”(hjÅ  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h Mhj¦  hžhubhÛ)”}”(hŒ=Device tree example for pseudo-differential bipolar channel::”h]”hŒ<Device tree example for pseudo-differential bipolar channel:”…””}”(hj	  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÚhŸh³h M$hj¦  hžhubjs  )”}”(hŒÀadc@0 {
    ...
    #address-cells = <1>;
    #size-cells = <0>;

    channel@0 {
        reg = <0>;
        bipolar;
        single-channel = <0>;
        common-mode-channel = <1>;
    };
};”h]”hŒÀadc@0 {
    ...
    #address-cells = <1>;
    #size-cells = <0>;

    channel@0 {
        reg = <0>;
        bipolar;
        single-channel = <0>;
        common-mode-channel = <1>;
    };
};”…””}”hj  sbah}”(h]”h ]”h"]”h$]”h&]”h±h²uh1jr  hŸh³h M&hj¦  hžhubeh}”(h]”Œ$pseudo-differential-bipolar-channels”ah ]”h"]”Œ*1.3.2 pseudo-differential bipolar channels”ah$]”h&]”uh1h´hj®  hžhhŸh³h Mubeh}”(h]”Œpseudo-differential-channels”ah ]”h"]”Œ 1.3 pseudo-differential channels”ah$]”h&]”uh1h´hhòhžhhŸh³h KÊubeh}”(h]”Œadc-channel-types”ah ]”h"]”Œ1. adc channel types”ah$]”h&]”uh1h´hh¶hžhhŸh³h Kubeh}”(h]”Œiio-abstractions-for-adcs”ah ]”h"]”Œiio abstractions for adcs”ah$]”h&]”uh1h´hhhžhhŸh³h Kubeh}”(h]”h ]”h"]”h$]”h&]”Œsource”h³uh1hŒcurrent_source”NŒcurrent_line”NŒsettings”Œdocutils.frontend”ŒValues”“”)”}”(h¹NŒ	generator”NŒ	datestamp”NŒsource_link”NŒ
source_url”NŒtoc_backlinks”Œentry”Œfootnote_backlinks”KŒsectnum_xform”KŒstrip_comments”NŒstrip_elements_with_classes”NŒstrip_classes”NŒreport_level”KŒ
halt_level”KŒexit_status_level”KŒdebug”NŒwarning_stream”NŒ	traceback”ˆŒinput_encoding”Œ	utf-8-sig”Œinput_encoding_error_handler”Œstrict”Œoutput_encoding”Œutf-8”Œoutput_encoding_error_handler”jh  Œerror_encoding”Œutf-8”Œerror_encoding_error_handler”Œbackslashreplace”Œlanguage_code”Œen”Œrecord_dependencies”NŒconfig”NŒ	id_prefix”hŒauto_id_prefix”Œid”Œdump_settings”NŒdump_internals”NŒdump_transforms”NŒdump_pseudo_xml”NŒexpose_internals”NŒstrict_visitor”NŒ_disable_config”NŒ_source”h³Œ_destination”NŒ_config_files”]”Œ7/var/lib/git/docbuild/linux/Documentation/docutils.conf”aŒfile_insertion_enabled”ˆŒraw_enabled”KŒline_length_limit”M'Œpep_references”NŒpep_base_url”Œhttps://peps.python.org/”Œpep_file_url_template”Œpep-%04d”Œrfc_references”NŒrfc_base_url”Œ&https://datatracker.ietf.org/doc/html/”Œ	tab_width”KŒtrim_footnote_reference_space”‰Œsyntax_highlight”Œlong”Œsmart_quotes”ˆŒsmartquotes_locales”]”Œcharacter_level_inline_markup”‰Œdoctitle_xform”‰Œdocinfo_xform”KŒsectsubtitle_xform”‰Œimage_loading”Œlink”Œembed_stylesheet”‰Œcloak_email_addresses”ˆŒsection_self_link”‰Œenv”NubŒreporter”NŒindirect_targets”]”Œsubstitution_defs”}”Œsubstitution_names”}”Œrefnames”}”Œrefids”}”Œnameids”}”(jB  j?  hïhìj:  j7  j’  j  j'  j$  jŠ  j‡  j«  j¨  jj  jg  j£  j   j2  j/  j£  j   j*  j'  uŒ	nametypes”}”(jB  ‰hï‰j:  ‰j’  ‰j'  ‰jŠ  ‰j«  ‰jj  ‰j£  ‰j2  ‰j£  ‰j*  ‰uh}”(j?  h¶hìhÉj7  hòj  jB  j$  ja  j‡  j*  j¨  j•  jg  j´  j   jm  j/  j®  j   jß  j'  j¦  uŒfootnote_refs”}”Œcitation_refs”}”Œautofootnotes”]”Œautofootnote_refs”]”Œsymbol_footnotes”]”Œsymbol_footnote_refs”]”Œ	footnotes”]”Œ	citations”]”Œautofootnote_start”KŒsymbol_footnote_start”K Œ
id_counter”Œcollections”ŒCounter”“”}”…”R”Œparse_messages”]”Œtransform_messages”]”Œtransformer”NŒinclude_log”]”Œ
decoration”Nhžhub.