bindings/hwmon/ntc-thermistor.yaml

1 # SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
2 ---
3 $id: http://devicetree.org/schemas/hwmon/ntc-thermistor.yaml#
4 $schema: http://devicetree.org/meta-schemas/core.yaml#
9   - Linus Walleij <linus.walleij@linaro.org>
13   vary in resistance in an often non-linear way in relation to temperature.
14   The negative temperature coefficient means that the resistance decreases
15   as the temperature rises. Since the relationship between resistance and
16   temperature is non-linear, software drivers most often need to use a look
17   up table and interpolation to get from resistance to temperature.
20   pull-up resistor or/and a pull-down resistor and a fixed voltage like this:
22       + e.g. 5V = pull-up voltage (puv)
24      +-+
26      | | Pull-up resistor
28      +-+
29       |-------------------------o
30      +-+ |                      ^
36      +-+                        |
37       |-------------------------o
38      +-+                        ^
40      | | Pull-down resistor     | Measured voltage (mv)
42      +-+                        |
49   the cases when either pull-up or pull-down resistance is zero.
51   If the pull-up resistance is 0 one end of the thermistor is connected to the
52   positive voltage and we get the thermistor on top of a pull-down resistor
53   and we take the measure between the thermistor and the pull-down resistor.
55   Conversely if the pull-down resistance is zero, one end of the thermistor is
56   connected to ground and we get the thermistor under the pull-up resistor
57   and we take the measure between the pull-up resistor and the thermistor.
59   We can use both pull-up and pull-down resistors at the same time, and then
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
80       - const: ntc,ncp15wb473
82       - const: ntc,ncp18wb473
84       - const: ntc,ncp21wb473
86       - const: ntc,ncp03wb473
88       - const: ntc,ncp15wl333
91   "#thermal-sensor-cells":
95   pullup-uv:
97     description: Pull-up voltage in micro volts. Must always be specified.
99   pullup-ohm:
101     description: Pull-up resistance in ohms. Must always be specified, even
104   pulldown-ohm:
106     description: Pull-down resistance in ohms. Must always be specified, even
109   connected-positive:
112       a pull-up and/or a pull-down resistor. See the description above for
114       to be connected-ground, which usually means a pull-down resistance of
118   io-channels:
124   - compatible
125   - pullup-uv
126   - pullup-ohm
127   - pulldown-ohm
128   - io-channels
133   - |
136       io-channels = <&gpadc 0x06>;
137       pullup-uv = <1800000>;
138       pullup-ohm = <220000>;
139       pulldown-ohm = <0>;
140       #thermal-sensor-cells = <0>;