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    Subject[PATCH v3 1/2] dt-bindings: iio: afe: add current-sense-shunt and voltage-divider
    Date
    An ADC is often used to measure other quantities indirectly. These
    bindings describe two cases, a current through a shunt resistor, and
    a "big" voltage measured with the help of a voltage divider.

    Signed-off-by: Peter Rosin <peda@axentia.se>
    ---
    .../bindings/iio/afe/current-sense-shunt.txt | 41 ++++++++++++++++++++
    .../bindings/iio/afe/voltage-divider.txt | 45 ++++++++++++++++++++++
    MAINTAINERS | 7 ++++
    3 files changed, 93 insertions(+)
    create mode 100644 Documentation/devicetree/bindings/iio/afe/current-sense-shunt.txt
    create mode 100644 Documentation/devicetree/bindings/iio/afe/voltage-divider.txt

    diff --git a/Documentation/devicetree/bindings/iio/afe/current-sense-shunt.txt b/Documentation/devicetree/bindings/iio/afe/current-sense-shunt.txt
    new file mode 100644
    index 000000000000..4d842aa85040
    --- /dev/null
    +++ b/Documentation/devicetree/bindings/iio/afe/current-sense-shunt.txt
    @@ -0,0 +1,41 @@
    +Current Sense Shunt
    +===================
    +
    +When an io-channel measures the voltage over a current sense shunt,
    +the interesting mesaurement is almost always the current through the
    +shunt, not the voltage over it. This binding describes such a current
    +sense circuit.
    +
    +Required properties:
    +- compatible : "current-sense-shunt"
    +- io-channels : Channel node of a voltage io-channel.
    +- shunt-resistor-micro-ohms : The shunt resistance in microohms.
    +
    +Example:
    +The system current is measured by measuring the voltage over a
    +3.3 ohms shunt resistor.
    +
    +sysi {
    + compatible = "current-sense-shunt";
    + io-channels = <&tiadc 0>;
    +
    + /* Divide the voltage by 3300000/1000000 (or 3.3) for the current. */
    + shunt-resistor-micro-ohms = <3300000>;
    +};
    +
    +&i2c {
    + tiadc: adc@48 {
    + compatible = "ti,ads1015";
    + reg = <0x48>;
    + #io-channel-cells = <1>;
    +
    + #address-cells = <1>;
    + #size-cells = <0>;
    +
    + channel@0 { /* IN0,IN1 differential */
    + reg = <0>;
    + ti,gain = <1>;
    + ti,datarate = <4>;
    + };
    + };
    +};
    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..fd4a215d9e6d
    --- /dev/null
    +++ b/Documentation/devicetree/bindings/iio/afe/voltage-divider.txt
    @@ -0,0 +1,45 @@
    +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.
    +
    +Required properties:
    +- compatible : "voltage-divider"
    +- io-channels : Channel node of a voltage io-channel.
    +
    +Optional properties:
    +- numerator : The io-channel scale is multiplied by this value (default 1).
    +- denominator : The io-channel scale is divided by this value (default 1).
    +
    +Example:
    +The system voltage is circa 12V, but divided down with a 22/200
    +voltage divider to adjust it to the ADC range.
    +
    +SYSV ADC GND
    + + + +
    + | .-----. | .----. |
    + '--| 200 |-+-| 22 |--'
    + '-----' '----'
    +
    +sysv {
    + compatible = "voltage-divider";
    + io-channels = <&maxadc 1>;
    +
    + /* Multiply the ADC voltage by 222/22 to get the system voltage. */
    + numerator = <222>; /* 200 + 22 */
    + denominator = <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 6e950b8b4a41..237fcdfdddc6 100644
    --- a/MAINTAINERS
    +++ b/MAINTAINERS
    @@ -6887,6 +6887,13 @@ F: drivers/staging/iio/
    F: include/linux/iio/
    F: tools/iio/

    +IIO UNIT CONVERTER
    +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>
    M: Stanislaw Gruszka <stf_xl@wp.pl>
    --
    2.11.0
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