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Diffstat (limited to 'Documentation/devicetree/bindings/iio/afe')
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..dddf97b50 --- /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 circuit. + + 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 */ + }; +... |