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@xxxxxxxxxx>
---
.../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@xxxxxxxxxx>
L: linux-iio@xxxxxxxxxxxxxxx
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@xxxxxxx>
--
2.11.0
--
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