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    Subject[PATCH v4 2/4] dt-bindings: iio: afe: add binding for voltage-divider
    Date
    An ADC is often used to measure other quantities indirectly. This
    binding describe one cases, a "big" voltage measured with the help
    of a voltage divider.

    Signed-off-by: Peter Rosin <peda@axentia.se>
    ---
    .../bindings/iio/afe/voltage-divider.txt | 53 ++++++++++++++++++++++
    MAINTAINERS | 1 +
    2 files changed, 54 insertions(+)
    create mode 100644 Documentation/devicetree/bindings/iio/afe/voltage-divider.txt

    diff --git a/Documentation/devicetree/bindings/iio/afe/voltage-divider.txt b/Documentation/devicetree/bindings/iio/afe/voltage-divider.txt
    new file mode 100644
    index 000000000000..afb52ce77c27
    --- /dev/null
    +++ b/Documentation/devicetree/bindings/iio/afe/voltage-divider.txt
    @@ -0,0 +1,53 @@
    +Voltage divider
    +===============
    +
    +When an io-channel measures the midpoint of a voltage divider, the
    +interesting voltage is often the voltage over the full resistance
    +of the divider. This binding describes the voltage divider in such
    +a curcuit.
    +
    + Vin ----.
    + |
    + .-----.
    + | R |
    + '-----'
    + |
    + +---- Vout
    + |
    + .-----.
    + | Rout|
    + '-----'
    + |
    + GND
    +
    +Required properties:
    +- compatible : "voltage-divider"
    +- io-channels : Channel node of a voltage io-channel measuring Vout.
    +- output-ohms : Resistance Rout over which the output voltage is measured.
    + See full-ohms.
    +- full-ohms : Resistance R + Rout for the full divider. The io-channel
    + is scaled by the Rout / (R + Rout) quotient.
    +
    +Example:
    +The system voltage is circa 12V, but divided down with a 22/222
    +voltage divider (R = 200 Ohms, Rout = 22 Ohms) and fed to an ADC.
    +
    +sysv {
    + compatible = "voltage-divider";
    + io-channels = <&maxadc 1>;
    +
    + /* Scale the system voltage by 22/222 to fit the ADC range. */
    + output-ohms = <22>;
    + full-ohms = <222>; /* 200 + 22 */
    +};
    +
    +&spi {
    + maxadc: adc@0 {
    + compatible = "maxim,max1027";
    + reg = <0>;
    + #io-channel-cells = <1>;
    + interrupt-parent = <&gpio5>;
    + interrupts = <15 IRQ_TYPE_EDGE_RISING>;
    + spi-max-frequency = <1000000>;
    + };
    +};
    diff --git a/MAINTAINERS b/MAINTAINERS
    index 0f7bec878919..4d534c9321de 100644
    --- a/MAINTAINERS
    +++ b/MAINTAINERS
    @@ -6894,6 +6894,7 @@ M: Peter Rosin <peda@axentia.se>
    L: linux-iio@vger.kernel.org
    S: Maintained
    F: Documentation/devicetree/bindings/iio/afe/current-sense-shunt.txt
    +F: Documentation/devicetree/bindings/iio/afe/voltage-divider.txt

    IKANOS/ADI EAGLE ADSL USB DRIVER
    M: Matthieu Castet <castet.matthieu@free.fr>
    --
    2.11.0
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