From: Liam Beguin <lvb@xxxxxxxxxx> An ADC is often used to measure other quantities indirectly. This binding describe one cases, the measurement of a temperature through the voltage across an RTD resistor such as a PT1000. Signed-off-by: Liam Beguin <lvb@xxxxxxxxxx> --- .../iio/afe/temperature-sense-rtd.yaml | 65 +++++++++++++++++++ MAINTAINERS | 1 + 2 files changed, 66 insertions(+) create mode 100644 Documentation/devicetree/bindings/iio/afe/temperature-sense-rtd.yaml 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 000000000000..4798eda6e533 --- /dev/null +++ b/Documentation/devicetree/bindings/iio/afe/temperature-sense-rtd.yaml @@ -0,0 +1,65 @@ +# 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 <lvb@xxxxxxxxxx> + +description: | + 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. + +properties: + compatible: + const: temperature-sense-rtd + + io-channels: + maxItems: 1 + description: | + Channel node of a voltage io-channel. + + '#io-channel-cells': + const: 1 + + excitation-current-microamp: + description: The current fed through the RTD sensor. + + alpha-micro-ohms-per-ohm-celsius: + description: | + Linear approximation of the resistance versus temperature relationship + between 0 and 100 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 and 1000 for PT1000. + +additionalProperties: false +required: + - compatible + - io-channels + - excitation-current-microamp + - alpha-micro-ohms-per-ohm-celsius + - r-naught-ohms + +examples: + - | + pt1000_1: iio-rescale0 { + compatible = "temperature-sense-rtd"; + #io-channel-cells = <1>; + io-channels = <&temp_adc1 0>; + + excitation-current-microamp = <1000>; + alpha-micro-ohms-per-ohm-celsius = <3908>; + r-naught-ohms = <1000>; + }; + +... diff --git a/MAINTAINERS b/MAINTAINERS index d3ab0ccc34ab..a7279af85adb 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -8721,6 +8721,7 @@ L: linux-iio@xxxxxxxxxxxxxxx S: Maintained F: Documentation/devicetree/bindings/iio/afe/current-sense-amplifier.yaml F: Documentation/devicetree/bindings/iio/afe/current-sense-shunt.yaml +F: Documentation/devicetree/bindings/iio/afe/temperature-sense-rtd.yaml F: Documentation/devicetree/bindings/iio/afe/voltage-divider.yaml F: drivers/iio/afe/iio-rescale.c -- 2.30.1.489.g328c10930387
