1 # SPDX-License-Identifier: (GPL-2.0 OR BSD-2-C
2 ---
3 $id: http://devicetree.org/schemas/hwmon/ntc-t
4 $schema: http://devicetree.org/meta-schemas/co
5
6 title: NTC thermistor temperature sensors
7
8 maintainers:
9 - Linus Walleij <linus.walleij@linaro.org>
10
11 description: |
12 Thermistors with negative temperature coeffi
13 vary in resistance in an often non-linear wa
14 The negative temperature coefficient means t
15 as the temperature rises. Since the relation
16 temperature is non-linear, software drivers
17 up table and interpolation to get from resis
18
19 When used in practice, a thermistor is often
20 pull-up resistor or/and a pull-down resistor
21
22 + e.g. 5V = pull-up voltage (puv)
23 |
24 +-+
25 | |
26 | | Pull-up resistor
27 | | (puo)
28 +-+
29 |-------------------------o
30 +-+ | ^
31 | |/ |
32 | / |
33 |/| Thermistor | Measured vol
34 / | | "connected g
35 /| | |
36 +-+ |
37 |-------------------------o
38 +-+ ^
39 | | |
40 | | Pull-down resistor | Measured vol
41 | | (pdo) | "connected p
42 +-+ |
43 | |
44 | v
45 + GND GND
46
47 The arrangements of where we measure the vol
48 called "connected ground" and "connected pos
49 the cases when either pull-up or pull-down r
50
51 If the pull-up resistance is 0 one end of th
52 positive voltage and we get the thermistor o
53 and we take the measure between the thermist
54
55 Conversely if the pull-down resistance is ze
56 connected to ground and we get the thermisto
57 and we take the measure between the pull-up
58
59 We can use both pull-up and pull-down resist
60 the figure illustrates where the voltage wil
61 ground" and "connected positive" cases.
62
63 properties:
64 $nodename:
65 pattern: "^thermistor(.*)?$"
66
67 compatible:
68 oneOf:
69 - const: epcos,b57330v2103
70 - const: epcos,b57891s0103
71 - const: murata,ncp15wb473
72 - const: murata,ncp18wb473
73 - const: murata,ncp21wb473
74 - const: murata,ncp03wb473
75 - const: murata,ncp15wl333
76 - const: murata,ncp03wf104
77 - const: murata,ncp15xh103
78 - const: samsung,1404-001221
79 # Deprecated "ntp," compatible strings
80 - const: ntc,ncp15wb473
81 deprecated: true
82 - const: ntc,ncp18wb473
83 deprecated: true
84 - const: ntc,ncp21wb473
85 deprecated: true
86 - const: ntc,ncp03wb473
87 deprecated: true
88 - const: ntc,ncp15wl333
89 deprecated: true
90
91 "#thermal-sensor-cells":
92 description: Thermal sensor cells if used
93 const: 0
94
95 pullup-uv:
96 $ref: /schemas/types.yaml#/definitions/uin
97 description: Pull-up voltage in micro volt
98
99 pullup-ohm:
100 $ref: /schemas/types.yaml#/definitions/uin
101 description: Pull-up resistance in ohms. M
102 if zero.
103
104 pulldown-ohm:
105 $ref: /schemas/types.yaml#/definitions/uin
106 description: Pull-down resistance in ohms.
107 if zero.
108
109 connected-positive:
110 $ref: /schemas/types.yaml#/definitions/fla
111 description: Indicates how the thermistor
112 a pull-up and/or a pull-down resistor. S
113 an illustration. If this flag is NOT spe
114 to be connected-ground, which usually me
115 zero but complex arrangements are possib
116
117 # See /schemas/iio/adc/adc.yaml
118 io-channels:
119 maxItems: 1
120 description: IIO ADC channel to read the v
121 always be specified.
122
123 required:
124 - compatible
125 - pullup-uv
126 - pullup-ohm
127 - pulldown-ohm
128 - io-channels
129
130 additionalProperties: false
131
132 examples:
133 - |
134 thermistor {
135 compatible = "murata,ncp18wb473";
136 io-channels = <&gpadc 0x06>;
137 pullup-uv = <1800000>;
138 pullup-ohm = <220000>;
139 pulldown-ohm = <0>;
140 #thermal-sensor-cells = <0>;
141 };
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.