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-rw-r--r--Documentation/devicetree/bindings/iio/afe/current-sense-amplifier.yaml54
-rw-r--r--Documentation/devicetree/bindings/iio/afe/current-sense-shunt.yaml68
-rw-r--r--Documentation/devicetree/bindings/iio/afe/temperature-sense-rtd.yaml101
-rw-r--r--Documentation/devicetree/bindings/iio/afe/temperature-transducer.yaml114
-rw-r--r--Documentation/devicetree/bindings/iio/afe/voltage-divider.yaml86
5 files changed, 423 insertions, 0 deletions
diff --git a/Documentation/devicetree/bindings/iio/afe/current-sense-amplifier.yaml b/Documentation/devicetree/bindings/iio/afe/current-sense-amplifier.yaml
new file mode 100644
index 000000000..527501c1d
--- /dev/null
+++ b/Documentation/devicetree/bindings/iio/afe/current-sense-amplifier.yaml
@@ -0,0 +1,54 @@
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/iio/afe/current-sense-amplifier.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Current Sense Amplifier
+
+maintainers:
+ - Peter Rosin <peda@axentia.se>
+
+description: |
+ When an io-channel measures the output voltage from a current sense
+ amplifier, the interesting measurement is almost always the current
+ through the sense resistor, not the voltage output. This binding
+ describes such a current sense circuit.
+
+properties:
+ compatible:
+ const: current-sense-amplifier
+
+ io-channels:
+ maxItems: 1
+ description: |
+ Channel node of a voltage io-channel.
+
+ sense-resistor-micro-ohms:
+ description: The sense resistance.
+
+ sense-gain-mult:
+ $ref: /schemas/types.yaml#/definitions/uint32
+ description: Amplifier gain multiplier. The default is <1>.
+
+ sense-gain-div:
+ $ref: /schemas/types.yaml#/definitions/uint32
+ description: Amplifier gain divider. The default is <1>.
+
+required:
+ - compatible
+ - io-channels
+ - sense-resistor-micro-ohms
+
+additionalProperties: false
+
+examples:
+ - |
+ sysi {
+ compatible = "current-sense-amplifier";
+ io-channels = <&tiadc 0>;
+
+ sense-resistor-micro-ohms = <20000>;
+ sense-gain-mult = <50>;
+ };
+...
diff --git a/Documentation/devicetree/bindings/iio/afe/current-sense-shunt.yaml b/Documentation/devicetree/bindings/iio/afe/current-sense-shunt.yaml
new file mode 100644
index 000000000..f8a112c9a
--- /dev/null
+++ b/Documentation/devicetree/bindings/iio/afe/current-sense-shunt.yaml
@@ -0,0 +1,68 @@
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/iio/afe/current-sense-shunt.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Current Sense Shunt
+
+maintainers:
+ - Peter Rosin <peda@axentia.se>
+
+description: |
+ When an io-channel measures the voltage over a current sense shunt,
+ the interesting measurement is almost always the current through the
+ shunt, not the voltage over it. This binding describes such a current
+ sense circuit.
+
+properties:
+ compatible:
+ const: current-sense-shunt
+
+ io-channels:
+ maxItems: 1
+ description: |
+ Channel node of a voltage io-channel.
+
+ "#io-channel-cells":
+ const: 0
+
+ shunt-resistor-micro-ohms:
+ description: The shunt resistance.
+
+required:
+ - compatible
+ - io-channels
+ - shunt-resistor-micro-ohms
+
+additionalProperties: false
+
+examples:
+ - |
+ i2c {
+ #address-cells = <1>;
+ #size-cells = <0>;
+ tiadc: adc@48 {
+ compatible = "ti,ads1015";
+ reg = <0x48>;
+ #io-channel-cells = <1>;
+
+ #address-cells = <1>;
+ #size-cells = <0>;
+
+ channel@0 { /* IN0,IN1 differential */
+ reg = <0>;
+ ti,gain = <1>;
+ ti,datarate = <4>;
+ };
+ };
+ };
+ sysi {
+ compatible = "current-sense-shunt";
+ io-channels = <&tiadc 0>;
+ #io-channel-cells = <0>;
+
+ /* Divide the voltage by 3300000/1000000 (or 3.3) for the current. */
+ shunt-resistor-micro-ohms = <3300000>;
+ };
+...
diff --git a/Documentation/devicetree/bindings/iio/afe/temperature-sense-rtd.yaml b/Documentation/devicetree/bindings/iio/afe/temperature-sense-rtd.yaml
new file mode 100644
index 000000000..336ce9637
--- /dev/null
+++ b/Documentation/devicetree/bindings/iio/afe/temperature-sense-rtd.yaml
@@ -0,0 +1,101 @@
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/iio/afe/temperature-sense-rtd.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Temperature Sense RTD
+
+maintainers:
+ - Liam Beguin <liambeguin@gmail.com>
+
+description: |
+ RTDs (Resistance Temperature Detectors) are a kind of temperature sensors
+ used to get a linear voltage to temperature reading within a give range
+ (usually 0 to 100 degrees Celsius).
+
+ When an io-channel measures the output voltage across an RTD such as a
+ PT1000, the interesting measurement is almost always the corresponding
+ temperature, not the voltage output. This binding describes such a circuit.
+
+ The general transfer function here is (using SI units)
+
+ V = R(T) * iexc
+ R(T) = r0 * (1 + alpha * T)
+ T = 1 / (alpha * r0 * iexc) * (V - r0 * iexc)
+
+ The following circuit matches what's in the examples section.
+
+ 5V0
+ -----
+ |
+ +---+----+
+ | R 5k |
+ +---+----+
+ |
+ V 1mA
+ |
+ +---- Vout
+ |
+ +---+----+
+ | PT1000 |
+ +---+----+
+ |
+ -----
+ GND
+
+properties:
+ compatible:
+ const: temperature-sense-rtd
+
+ io-channels:
+ maxItems: 1
+ description: |
+ Channel node of a voltage io-channel.
+
+ '#io-channel-cells':
+ const: 0
+
+ excitation-current-microamp:
+ description: The current fed through the RTD sensor.
+
+ alpha-ppm-per-celsius:
+ description: |
+ alpha can also be expressed in micro-ohms per ohm Celsius. It's a linear
+ approximation of the resistance versus temperature relationship
+ between 0 and 100 degrees Celsius.
+
+ alpha = (R_100 - R_0) / (100 * R_0)
+
+ Where, R_100 is the resistance of the sensor at 100 degrees Celsius, and
+ R_0 (or r-naught-ohms) is the resistance of the sensor at 0 degrees
+ Celsius.
+
+ Pure platinum has an alpha of 3925. Industry standards such as IEC60751
+ and ASTM E-1137 specify an alpha of 3850.
+
+ r-naught-ohms:
+ description: |
+ Resistance of the sensor at 0 degrees Celsius.
+ Common values are 100 for PT100, 500 for PT500, and 1000 for PT1000
+
+additionalProperties: false
+required:
+ - compatible
+ - io-channels
+ - excitation-current-microamp
+ - alpha-ppm-per-celsius
+ - r-naught-ohms
+
+examples:
+ - |
+ pt1000_1: temperature-sensor0 {
+ compatible = "temperature-sense-rtd";
+ #io-channel-cells = <0>;
+ io-channels = <&temp_adc1 0>;
+
+ excitation-current-microamp = <1000>; /* i = U/R = 5 / 5000 */
+ alpha-ppm-per-celsius = <3908>;
+ r-naught-ohms = <1000>;
+ };
+...
diff --git a/Documentation/devicetree/bindings/iio/afe/temperature-transducer.yaml b/Documentation/devicetree/bindings/iio/afe/temperature-transducer.yaml
new file mode 100644
index 000000000..cfbf5350d
--- /dev/null
+++ b/Documentation/devicetree/bindings/iio/afe/temperature-transducer.yaml
@@ -0,0 +1,114 @@
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/iio/afe/temperature-transducer.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Temperature Transducer
+
+maintainers:
+ - Liam Beguin <liambeguin@gmail.com>
+
+description: |
+ A temperature transducer is a device that converts a thermal quantity
+ into any other physical quantity. This binding applies to temperature to
+ voltage (like the LTC2997), and temperature to current (like the AD590)
+ linear transducers.
+ In both cases these are assumed to be connected to a voltage ADC.
+
+ When an io-channel measures the output voltage of a temperature analog front
+ end such as a temperature transducer, the interesting measurement is almost
+ always the corresponding temperature, not the voltage output. This binding
+ describes such a circuit.
+
+ The general transfer function here is (using SI units)
+ V(T) = Rsense * Isense(T)
+ T = (Isense(T) / alpha) + offset
+ T = 1 / (Rsense * alpha) * (V + offset * Rsense * alpha)
+
+ When using a temperature to voltage transducer, Rsense is set to 1.
+
+ The following circuits show a temperature to current and a temperature to
+ voltage transducer that can be used with this binding.
+
+ VCC
+ -----
+ |
+ +---+---+
+ | AD590 | VCC
+ +---+---+ -----
+ | |
+ V proportional to T +----+----+
+ | D+ --+ |
+ +---- Vout | LTC2997 +--- Vout
+ | D- --+ |
+ +---+----+ +---------+
+ | Rsense | |
+ +---+----+ -----
+ | GND
+ -----
+ GND
+
+properties:
+ compatible:
+ const: temperature-transducer
+
+ io-channels:
+ maxItems: 1
+ description: |
+ Channel node of a voltage io-channel.
+
+ '#io-channel-cells':
+ const: 0
+
+ sense-offset-millicelsius:
+ description: |
+ Temperature offset.
+ This offset is commonly used to convert from Kelvins to degrees Celsius.
+ In that case, sense-offset-millicelsius would be set to <(-273150)>.
+ default: 0
+
+ sense-resistor-ohms:
+ description: |
+ The sense resistor.
+ By default sense-resistor-ohms cancels out the resistor making the
+ circuit behave like a temperature transducer.
+ default: 1
+
+ alpha-ppm-per-celsius:
+ description: |
+ Sometimes referred to as output gain, slope, or temperature coefficient.
+
+ alpha is expressed in parts per million which can be micro-amps per
+ degrees Celsius or micro-volts per degrees Celsius. The is the main
+ characteristic of a temperature transducer and should be stated in the
+ datasheet.
+
+additionalProperties: false
+
+required:
+ - compatible
+ - io-channels
+ - alpha-ppm-per-celsius
+
+examples:
+ - |
+ ad950: temperature-sensor-0 {
+ compatible = "temperature-transducer";
+ #io-channel-cells = <0>;
+ io-channels = <&temp_adc 3>;
+
+ sense-offset-millicelsius = <(-273150)>; /* Kelvin to degrees Celsius */
+ sense-resistor-ohms = <8060>;
+ alpha-ppm-per-celsius = <1>; /* 1 uA/K */
+ };
+ - |
+ znq_tmp: temperature-sensor-1 {
+ compatible = "temperature-transducer";
+ #io-channel-cells = <0>;
+ io-channels = <&temp_adc 2>;
+
+ sense-offset-millicelsius = <(-273150)>; /* Kelvin to degrees Celsius */
+ alpha-ppm-per-celsius = <4000>; /* 4 mV/K */
+ };
+...
diff --git a/Documentation/devicetree/bindings/iio/afe/voltage-divider.yaml b/Documentation/devicetree/bindings/iio/afe/voltage-divider.yaml
new file mode 100644
index 000000000..df2589f21
--- /dev/null
+++ b/Documentation/devicetree/bindings/iio/afe/voltage-divider.yaml
@@ -0,0 +1,86 @@
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/iio/afe/voltage-divider.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Voltage divider
+
+maintainers:
+ - Peter Rosin <peda@axentia.se>
+
+description: |
+ 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
+
+
+properties:
+ compatible:
+ const: voltage-divider
+
+ io-channels:
+ maxItems: 1
+ description: |
+ Channel node of a voltage io-channel.
+
+ output-ohms:
+ description:
+ Resistance Rout over which the output voltage is measured. See full-ohms.
+
+ full-ohms:
+ description:
+ Resistance R + Rout for the full divider. The io-channel is scaled by
+ the Rout / (R + Rout) quotient.
+
+required:
+ - compatible
+ - io-channels
+ - output-ohms
+ - full-ohms
+
+additionalProperties: false
+
+examples:
+ - |
+ #include <dt-bindings/interrupt-controller/irq.h>
+ /*
+ * 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.
+ */
+ spi {
+ #address-cells = <1>;
+ #size-cells = <0>;
+ 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>;
+ };
+ };
+ 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 */
+ };
+...