1# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
2%YAML 1.2
3---
4$id: http://devicetree.org/schemas/iio/afe/voltage-divider.yaml#
5$schema: http://devicetree.org/meta-schemas/core.yaml#
6
7title: Voltage divider
8
9maintainers:
10  - Peter Rosin <peda@axentia.se>
11
12description: |
13  When an io-channel measures the midpoint of a voltage divider, the
14  interesting voltage is often the voltage over the full resistance
15  of the divider. This binding describes the voltage divider in such
16  a circuit.
17
18    Vin ----.
19            |
20         .-----.
21         |  R  |
22         '-----'
23            |
24            +---- Vout
25            |
26         .-----.
27         | Rout|
28         '-----'
29            |
30           GND
31
32
33properties:
34  compatible:
35    const: voltage-divider
36
37  io-channels:
38    maxItems: 1
39    description: |
40      Channel node of a voltage io-channel.
41
42  output-ohms:
43    description:
44      Resistance Rout over which the output voltage is measured. See full-ohms.
45
46  full-ohms:
47    description:
48      Resistance R + Rout for the full divider. The io-channel is scaled by
49      the Rout / (R + Rout) quotient.
50
51required:
52  - compatible
53  - io-channels
54  - output-ohms
55  - full-ohms
56
57additionalProperties: false
58
59examples:
60  - |
61    #include <dt-bindings/interrupt-controller/irq.h>
62    /*
63     * The system voltage is circa 12V, but divided down with a 22/222
64     * voltage divider (R = 200 Ohms, Rout = 22 Ohms) and fed to an ADC.
65     */
66    spi {
67        #address-cells = <1>;
68        #size-cells = <0>;
69        maxadc: adc@0 {
70            compatible = "maxim,max1027";
71            reg = <0>;
72            #io-channel-cells = <1>;
73            interrupt-parent = <&gpio5>;
74            interrupts = <15 IRQ_TYPE_EDGE_RISING>;
75            spi-max-frequency = <1000000>;
76        };
77    };
78    sysv {
79        compatible = "voltage-divider";
80        io-channels = <&maxadc 1>;
81
82        /* Scale the system voltage by 22/222 to fit the ADC range. */
83        output-ohms = <22>;
84        full-ohms = <222>; /* 200 + 22 */
85    };
86...
87