dt-bindings: iio: document dpot-dac bindings

[linux-2.6-microblaze.git] / Documentation / devicetree / bindings / iio / dac / dpot-dac.txt

diff --git a/Documentation/devicetree/bindings/iio/dac/dpot-dac.txt b/Documentation/devicetree/bindings/iio/dac/dpot-dac.txt
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+Bindings for DAC emulation using a digital potentiometer
+
+It is assumed that the dpot is used as a voltage divider between the
+current dpot wiper setting and the maximum resistance of the dpot. The
+divided voltage is provided by a vref regulator.
+
+                  .------.
+   .-----------.  |      |
+   | vref      |--'    .---.
+   | regulator |--.    |   |
+   '-----------'  |    | d |
+                  |    | p |
+                  |    | o |  wiper
+                  |    | t |<---------+
+                  |    |   |
+                  |    '---'       dac output voltage
+                  |      |
+                  '------+------------+
+
+Required properties:
+- compatible: Should be "dpot-dac"
+- vref-supply: The regulator supplying the voltage divider.
+- io-channels: Channel node of the dpot to be used for the voltage division.
+- io-channel-names: Should be "dpot".
+
+Example:
+
+       &i2c {
+               dpot: mcp4651-503@28 {
+                       compatible = "microchip,mcp4651-503";
+                       reg = <0x28>;
+                       #io-channel-cells = <1>;
+               };
+       };
+
+       dac {
+               compatible = "dpot-dac";
+               vref-supply = <&reg_3v3>;
+               io-channels = <&dpot 0>;
+               io-channel-names = "dpot";
+       };