xref: /linux/Documentation/devicetree/bindings/iio/adc/adc.yaml (revision 3a2c4d55e32ad65efebdb6de44eef3bfa08bb49d) 
1# SPDX-License-Identifier: GPL-2.0
2%YAML 1.2
3---
4$id: http://devicetree.org/schemas/iio/adc/adc.yaml#
5$schema: http://devicetree.org/meta-schemas/core.yaml#
6
7title: IIO Common Properties for ADC Channels
8
9maintainers:
10  - Jonathan Cameron <jic23@kernel.org>
11
12description:
13  A few properties are defined in a common way ADC channels.
14
15properties:
16  $nodename:
17    pattern: "^channel(@[0-9a-f]+)?$"
18    description:
19      A channel index should match reg.
20
21  reg:
22    maxItems: 1
23
24  label:
25    description: Unique name to identify which channel this is.
26
27  bipolar:
28    $ref: /schemas/types.yaml#/definitions/flag
29    description: If provided, the channel is to be used in bipolar mode.
30
31  diff-channels:
32    $ref: /schemas/types.yaml#/definitions/uint32-array
33    maxItems: 2
34    minItems: 2
35    description:
36      Many ADCs have dual Muxes to allow different input pins to be routed
37      to both the positive and negative inputs of a differential ADC.
38      The first value specifies the positive input pin, the second
39      specifies the negative input pin.
40      There are also some ADCs, where the differential channel has dedicated
41      positive and negative inputs which can be used to measure differential
42      voltage levels. For those setups, this property can be configured with
43      the 'reg' property for both inputs (i.e. diff-channels = <reg reg>).
44
45  single-channel:
46    $ref: /schemas/types.yaml#/definitions/uint32
47    description:
48      When devices combine single-ended and differential channels, allow the
49      channel for a single element to be specified, independent of reg (as for
50      differential channels). If this and diff-channels are not present reg
51      shall be used instead.
52
53  common-mode-channel:
54    $ref: /schemas/types.yaml#/definitions/uint32
55    description:
56      Some ADCs have differential input pins that can be used to measure
57      single-ended or pseudo-differential inputs. This property can be used
58      in addition to single-channel to signal software that this channel is
59      not differential but still specify two inputs.
60
61      The input pair is specified by setting single-channel to the positive
62      input pin and common-mode-channel to the negative pin.
63
64  settling-time-us:
65    description:
66      Time between enabling the channel and first stable readings.
67
68  oversampling-ratio:
69    $ref: /schemas/types.yaml#/definitions/uint32
70    description:
71      Oversampling is used as replacement of or addition to the low-pass filter.
72      In some cases, the desired filtering characteristics are a function the
73      device design and can interact with other characteristics such as
74      settling time.
75
76  reference-sources:
77    $ref: /schemas/types.yaml#/definitions/string-array
78    description:
79      Indicates the voltage reference source or sources for this channel. Some
80      ADCs usually allow choosing between internal reference sources or a pair
81      of external pins.
82
83  input-chopping:
84    type: boolean
85    description:
86      If set, the positive and negative input channels are swapped on every
87      other conversion to reduce offset error. This generally comes at the
88      expense of added settling time between conversions, so should be omitted
89      on systems with high-frequency signals or high data rate requirements.
90
91  excitation-channels:
92    $ref: /schemas/types.yaml#/definitions/uint32-array
93    description:
94      Excitation current sources provide current to resistive temperature
95      devices (RTDs), thermistors, diodes and other resistive sensors that
96      require constant current biasing.
97
98      This array describes the mux configuration of the excitation current
99      sources. The values correspond to pins similar to the diff-channels and
100      single-channel properties.
101
102  excitation-current-nanoamp:
103    description:
104      Excitation current sources provide current to resistive temperature
105      devices (RTDs), thermistors, diodes and other resistive sensors that
106      require constant current biasing.
107
108      This array describes the current configuration of the excitation current
109      sources. The index in the array corresponds to the same index in the
110      excitation-channels array.
111
112  burn-out-current-nanoamp:
113    description:
114      Burn-out current sources provide current to the channel's input pins for
115      open-circuit or short-circuit detection.
116
117anyOf:
118  - oneOf:
119      - required:
120          - reg
121          - diff-channels
122      - required:
123          - reg
124          - single-channel
125  - required:
126      - reg
127
128additionalProperties: true
129