On Sat, 29 May 2021 20:59:15 -0400 Liam Beguin <liambeguin@xxxxxxxxx> wrote: > 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> Just one nit pick inline. Hmm. these devices use some 'special' units for their coefficients. Ah well, guess we copy the industry standard. > --- > .../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>; > + }; > + Drop this blank line. Doesn't add anything ;) > +... > 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 >
