[PATCH v2 1/2] dt-bindings: iio: afe: add current-sense-cuicuit and voltage-divider

Peter Rosin
2018-04-03T15:36:34Z

An ADC is often used to measure other quantities indirectly. These
bindings describe two cases, a current through a sense 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-circuit.txt | 45 ++++++++++++++++++++++
.../bindings/iio/afe/voltage-divider.txt | 45 ++++++++++++++++++++++
MAINTAINERS | 7 ++++
3 files changed, 97 insertions(+)
create mode 100644 Documentation/devicetree/bindings/iio/afe/current-sense-circuit.txt
create mode 100644 Documentation/devicetree/bindings/iio/afe/voltage-divider.txt

diff --git a/Documentation/devicetree/bindings/iio/afe/current-sense-circuit.txt b/Documentation/devicetree/bindings/iio/afe/current-sense-circuit.txt
new file mode 100644
index 000000000000..0bc7d89387c0
--- /dev/null
+++ b/Documentation/devicetree/bindings/iio/afe/current-sense-circuit.txt
@@ -0,0 +1,45 @@
+Current Sense Curcuit
+=====================
+
+When an io-channel measures the voltage over a current sense resistor,
+the interesting mesaurement is often the current through the resistor,
+not the voltage over it. This binding describes such a current sense
+curcuit.
+
+Required properties:
+- compatible : "current-sense-circuit"
+- 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 current is measured by measuring the voltage over a
+3.3 ohms sense resistor.
+
+sysi {
+ compatible = "current-sense-circuit";
+ io-channels = <&tiadc 0>;
+
+ /* Divide the ADC voltage by 33/10 (i.e. 3.3) to get the current. */
+ numerator = <10>;
+ denominator = <33>;
+};
+
+&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 36a28e979e9a..9dbe5019c6bd 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -6889,6 +6889,13 @@ 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-circuit.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