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Message-ID: <d2f8e8227022afe411005882cfd269124cd81e01.1744200264.git.marcelo.schmitt@analog.com>
Date: Wed, 9 Apr 2025 09:24:18 -0300
From: Marcelo Schmitt <marcelo.schmitt@...log.com>
To: <linux-iio@...r.kernel.org>, <devicetree@...r.kernel.org>,
<linux-kernel@...r.kernel.org>
CC: <jic23@...nel.org>, <lars@...afoo.de>, <Michael.Hennerich@...log.com>,
<dlechner@...libre.com>, <nuno.sa@...log.com>, <andy@...nel.org>,
<robh@...nel.org>, <krzk+dt@...nel.org>, <conor+dt@...nel.org>,
<marcelo.schmitt1@...il.com>
Subject: [PATCH v1 1/7] dt-bindings: iio: adc: Add AD4170
Add device tree documentation for AD4170 and similar sigma-delta ADCs.
The AD4170 is a 24-bit, multichannel, sigma-delta ADC.
Signed-off-by: Marcelo Schmitt <marcelo.schmitt@...log.com>
---
The AD4170 design has features to aid interfacing with weigh scale and RTD
sensors that are expected to be setup with external circuitry for proper
sensor operation. A key characteristic of those sensors is that the circuit
they are in must be excited with a pair of signals. The external circuit
can be excited either by voltage supply or by AD4170 excitation signals.
The sensor can then be read through a different pair of lines that are
connected to AD4170 ADC.
.../bindings/iio/adc/adi,ad4170.yaml | 527 ++++++++++++++++++
MAINTAINERS | 7 +
2 files changed, 534 insertions(+)
create mode 100644 Documentation/devicetree/bindings/iio/adc/adi,ad4170.yaml
diff --git a/Documentation/devicetree/bindings/iio/adc/adi,ad4170.yaml b/Documentation/devicetree/bindings/iio/adc/adi,ad4170.yaml
new file mode 100644
index 000000000000..93fe3b4648a0
--- /dev/null
+++ b/Documentation/devicetree/bindings/iio/adc/adi,ad4170.yaml
@@ -0,0 +1,527 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/iio/adc/adi,ad4170.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Analog Devices AD4170 and similar Analog to Digital Converters
+
+maintainers:
+ - Marcelo Schmitt <marcelo.schmitt@...log.com>
+
+description: |
+ Analog Devices AD4170 series of Sigma-delta Analog to Digital Converters.
+ Specifications can be found at:
+ https://www.analog.com/media/en/technical-documentation/data-sheets/ad4170-4.pdf
+ https://www.analog.com/media/en/technical-documentation/data-sheets/ad4190-4.pdf
+ https://www.analog.com/media/en/technical-documentation/data-sheets/ad4195-4.pdf
+
+$ref: /schemas/spi/spi-peripheral-props.yaml#
+
+$defs:
+ sensor-node:
+ type: object
+ description: |
+ Common properties of external sensor circuitry connected to the ADC.
+
+ properties:
+ reg:
+ description:
+ Channel number. Connects the sensor to the channel with this number
+ of the device.
+ minimum: 1
+ maximum: 16
+
+ diff-channels:
+ $ref: /schemas/types.yaml#/definitions/uint32-array
+ maxItems: 2
+ minItems: 2
+ description: |
+ ADC analog input pins to which the sensor circuit is connected.
+ The first value specifies the positive input pin, the second
+ specifies the negative input pin. See adc.yaml for details.
+
+ bipolar:
+ $ref: /schemas/types.yaml#/definitions/flag
+ description: If provided, the channel is to be used in bipolar mode.
+
+ adi,sensor-type:
+ description: Type of sensor connected to the device.
+ $ref: /schemas/types.yaml#/definitions/uint8
+
+ adi,ac-excited:
+ type: boolean
+ description: |
+ Whether the external circuit has to be AC or DC excited.
+
+ adi,excitation-pins:
+ $ref: /schemas/types.yaml#/definitions/uint32-array
+ description: |
+ ADC pins used for external circuit excitation. Some applications
+ require optimum matching between excitation currents. Using excitation
+ current pairs minimizes the excitation current mismatch and the
+ excitation current drift matching on the ADC. Must describe either 1
+ or 2 pairs of pins. E.g. <0 1>; <2 3>; <0 1>, <2 3>.
+
+ adi,excitation-current-microamp:
+ description: |
+ Excitation current in microamperes to be output to each excitation pin
+ specified by adi,excitation-pins property.
+ enum: [0, 10, 50, 100, 250, 500, 1000, 1500]
+ default: 0
+
+ adi,reference-select:
+ description: |
+ Select the reference source to use when converting on the specific
+ channel. Valid values are:
+ 0: Differential reference voltage REFIN+ - REFIN−.
+ 1: Differential reference voltage REFIN2+ - REFIN2−.
+ 2: Internal 2.5V referece (REFOUT) relative to AVSS.
+ 3: Analog supply voltage (AVDD) relative AVSS.
+ If this field is left empty, the first external reference is selected.
+ $ref: /schemas/types.yaml#/definitions/uint8
+ enum: [0, 1, 2, 3]
+ default: 0
+
+ required:
+ - reg
+ - diff-channels
+ - bipolar
+ - adi,sensor-type
+ - adi,excitation-pins
+ - adi,reference-select
+
+properties:
+ compatible:
+ enum:
+ - adi,ad4170
+ - adi,ad4190
+ - adi,ad4195
+
+ avss-supply:
+ description:
+ Referece voltage supply for AVSS. If provided, describes the magnitude
+ (absolute value) of the negative voltage supplied to the AVSS pin. Since
+ AVSS must be −2.625V minimum and 0V maximum, the declared supply voltage
+ must be between 0 and 2.65V. If not provided, AVSS is assumed to be at
+ system ground (0V).
+
+ avdd-supply:
+ description:
+ A supply of 4.75V to 5.25V relative to AVSS that powers the chip (AVDD).
+
+ iovdd-supply:
+ description: 1.7V to 5.25V reference supply to the serial interface (IOVDD).
+
+ refin1p-supply:
+ description: REFIN+ supply that can be used as reference for conversion.
+
+ refin1n-supply:
+ description: REFIN- supply that can be used as reference for conversion. If
+ provided, describes the magnitude (absolute value) of the negative voltage
+ supplied to the REFIN- pin.
+
+ refin2p-supply:
+ description: REFIN2+ supply that can be used as reference for conversion.
+
+ refin2n-supply:
+ description: REFIN2- supply that can be used as reference for conversion. If
+ provided, describes the magnitude (absolute value) of the negative voltage
+ supplied to the REFIN2- pin.
+
+ spi-cpol: true
+
+ spi-cpha: true
+
+ interrupts:
+ maxItems: 1
+
+ interrupt-names:
+ description: |
+ Specify which pin should be configured as Data Ready interrupt.
+ Default if not supplied is sdo.
+ enum:
+ - sdo
+ - dig_aux1
+
+ clocks:
+ maxItems: 1
+ description:
+ Optional external clock source. Can specify either an external clock or
+ external crystal.
+
+ clock-names:
+ enum:
+ - ext-clk
+ - xtal
+
+ '#clock-cells':
+ const: 0
+
+ gpio-controller: true
+
+ "#gpio-cells":
+ const: 2
+ description: |
+ The first cell is for the GPIO number: 0 to 3.
+ The second cell takes standard GPIO flags.
+
+ ldac-gpios:
+ description:
+ GPIO connected to DIG_AUX2 pin to be used as LDAC toggle to control the
+ transfer of data from the DAC_INPUT_A register to the DAC.
+ maxItems: 1
+
+ '#address-cells':
+ const: 1
+
+ '#size-cells':
+ const: 0
+
+patternProperties:
+ "^channel@[0-9a-f]$":
+ $ref: adc.yaml
+ type: object
+ unevaluatedProperties: false
+ description: |
+ Represents the external channels which are connected to the ADC.
+
+ properties:
+ reg:
+ description: |
+ The channel number.
+ items:
+ minimum: 0
+ maximum: 15
+
+ diff-channels:
+ description: |
+ This property is used for defining the inputs of a differential
+ voltage channel. The first value is the positive input and the second
+ value is the negative input of the channel.
+
+ Besides the analog input pins AIN0 to AIN8, there are special inputs
+ that can be selected with the following values:
+ 17: Internal temperature sensor
+ 18: (AVDD-AVSS)/5
+ 19: (IOVDD-DGND)/5
+ 20: DAC output
+ 21: ALDO
+ 22: DLDO
+ 23: AVSS
+ 24: DGND
+ 25: REFIN+
+ 26: REFIN-
+ 27: REFIN2+
+ 28: REFIN2-
+ 29: REFOUT
+ For the internal temperature sensor, use the input number for both
+ inputs (i.e. diff-channels = <17 17>).
+ items:
+ enum: [0, 1, 2, 3, 4, 5, 6, 7, 8, 17, 18, 19, 20, 21, 22, 23, 24, 25,
+ 26, 27, 28, 29]
+
+ single-channel: true
+
+ common-mode-channel: true
+
+ bipolar: true
+
+ adi,sensor-type:
+ description: Sensor type for direct ADC sensors.
+ $ref: /schemas/types.yaml#/definitions/uint8
+ const: 0
+
+ adi,buffered-positive:
+ description: |
+ Enable precharge buffer, full buffer, or skip reference buffering of
+ the positive voltage reference. Because the output impedance of the
+ source driving the voltage reference inputs may be dynamic, RC
+ combinations of those inputs can cause DC gain errors if the reference
+ inputs go unbuffered into the ADC. Enable reference buffering if the
+ provided reference source has dynamic high impedance output. Note the
+ absolute voltage allowed on positive reference inputs (REFIN+,
+ REFIN2+) is from AVSS − 50 mV to AVDD + 50 mV when the reference
+ buffers are disabled but narrows to AVSS to AVDD when reference
+ buffering is enabled or in precharge mode.
+ 0: Reference precharge buffer.
+ 1: Full Buffer.
+ 2: Bypass reference buffers (buffering disabled).
+ $ref: /schemas/types.yaml#/definitions/uint8
+ enum: [0, 1, 2]
+ default: 0
+
+ adi,buffered-negative:
+ description: |
+ Enable precharge buffer, full buffer, or skip reference buffering of
+ the negative voltage reference. Because the output impedance of the
+ source driving the voltage reference inputs may be dynamic, RC
+ combinations of those inputs can cause DC gain errors if the reference
+ inputs go unbuffered into the ADC. Enable reference buffering if the
+ provided reference source has dynamic high impedance output. Note the
+ absolute voltage allowed on negative reference inputs (REFIN-,
+ REFIN2-) is from AVSS − 50 mV to AVDD + 50 mV when the reference
+ buffers are disabled but narrows to AVSS to AVDD when reference
+ buffering is enabled or in precharge mode.
+ 0: Reference precharge buffer.
+ 1: Full Buffer.
+ 2: Bypass reference buffers (buffering disabled).
+ $ref: /schemas/types.yaml#/definitions/uint8
+ enum: [0, 1, 2]
+ default: 0
+
+ adi,reference-select:
+ description: |
+ Select the reference source to use when converting on the specific
+ channel. Valid values are:
+ 0: Differential reference voltage REFIN+ - REFIN−.
+ 1: Differential reference voltage REFIN2+ - REFIN2−.
+ 2: Internal 2.5V referece (REFOUT) relative to AVSS.
+ 3: Analog supply voltage (AVDD) relative AVSS.
+ If this field is left empty, the internal reference is selected.
+ $ref: /schemas/types.yaml#/definitions/uint8
+ enum: [0, 1, 2, 3]
+ default: 2
+
+ required:
+ - reg
+
+ allOf:
+ - oneOf:
+ - required: [single-channel]
+ properties:
+ diff-channels: false
+ - required: [diff-channels]
+ properties:
+ single-channel: false
+ common-mode-channel: false
+
+ "^weighscale@":
+ $ref: '#/$defs/sensor-node'
+ unevaluatedProperties: false
+
+ properties:
+ diff-channels: true
+ bipolar: true
+
+ adi,sensor-type:
+ description: Weigh scale sensor.
+ $ref: /schemas/types.yaml#/definitions/uint8
+ const: 1
+
+ adi,excitation-pins:
+ description: |
+ ADC pins to use for weigh scale bridge circuit excitation. Must
+ describe either 1 or 2 pairs of pins. E.g. <0 1>; <2 3>; <0 1>, <2 3>.
+ $ref: /schemas/types.yaml#/definitions/uint32-array
+ minItems: 2
+ maxItems: 4
+ items:
+ minimum: 0
+ maximum: 20
+
+ adi,excitation-current-microamp:
+ description: |
+ Excitation current in microamperes to be output to each excitation pin
+ specified by adi,excitation-pins property. If not provided and
+ adi,ac-excited is true, use predefined ACX1, ACX1 negated, ACX2, and
+ ACX2 negated signals to AC excite the weigh scale bridge. Those
+ singals are output on GPIO2, GPIO0, GPIO3, and GPIO1, respectively.
+ enum: [0, 10, 50, 100, 250, 500, 1000, 1500]
+
+ adi,power-down-switch-pin:
+ description: |
+ Number of the GPIO used as power-down switch for the bridge circuit.
+ $ref: /schemas/types.yaml#/definitions/uint8
+ enum: [0, 1]
+
+ "^thermocouple@":
+ $ref: '#/$defs/sensor-node'
+ unevaluatedProperties: false
+
+ properties:
+ diff-channels: true
+ bipolar: true
+
+ adi,sensor-type:
+ description: Thermocouple sensor.
+ $ref: /schemas/types.yaml#/definitions/uint8
+ const: 2
+
+ adi,excitation-pins:
+ description: |
+ ADC pins to use for bridge circuit excitation. Must describe either 1
+ or 2 pairs of pins. E.g. <0 1>; <2 3>; <0 1>, <2 3>.
+ $ref: /schemas/types.yaml#/definitions/uint32-array
+ minItems: 2
+ maxItems: 4
+ items:
+ minimum: 0
+ maximum: 20
+
+ adi,excitation-current-microamp:
+ description: |
+ Excitation current in microamperes to be output to each excitation pin
+ specified by adi,excitation-pins property. If not provided and
+ adi,ac-excited is true, use predefined ACX1, ACX1 negated, ACX2, and
+ ACX2 negated signals to AC excite the bridge circuit. Those singals
+ are output on GPIO2, GPIO0, GPIO3, and GPIO1, respectively.
+ enum: [0, 10, 50, 100, 250, 500, 1000, 1500]
+
+ adi,vbias:
+ type: boolean
+ description: |
+ For unbiased thermocouple applications, the voltage generated by the
+ thermocouple must be biased around some DC voltage. When present, this
+ property specifies a bias voltage of (AVDD + AVSS)/2 to be applied as
+ common-mode voltage for the sensor.
+
+ adi,power-down-switch-pin:
+ description: |
+ Number of the GPIO used as power-down switch for the bridge circuit.
+ $ref: /schemas/types.yaml#/definitions/uint8
+ enum: [0, 1]
+
+ "^rtd@":
+ $ref: '#/$defs/sensor-node'
+ unevaluatedProperties: false
+
+ properties:
+ diff-channels: true
+ bipolar: true
+
+ adi,sensor-type:
+ description: RTD sensor.
+ $ref: /schemas/types.yaml#/definitions/uint8
+ const: 3
+
+ adi,excitation-pins:
+ description: |
+ ADC pins to use for RTD circuit excitation. Must describe a pair of
+ pins. E.g. <0 1>; <2 3>.
+ $ref: /schemas/types.yaml#/definitions/uint32-array
+ minItems: 2
+ maxItems: 2
+ items:
+ minimum: 0
+ maximum: 20
+
+ adi,excitation-current-microamp: true
+
+ required:
+ - adi,excitation-current-microamp
+
+required:
+ - compatible
+ - reg
+ - avdd-supply
+ - iovdd-supply
+ - spi-cpol
+ - spi-cpha
+
+allOf:
+ # Some devices don't have integrated DAC
+ - if:
+ properties:
+ compatible:
+ contains:
+ enum:
+ - adi,ad4190
+ - adi,ad4195
+ then:
+ properties:
+ ldac-gpios: false
+
+unevaluatedProperties: false
+
+examples:
+ - |
+ #include <dt-bindings/interrupt-controller/irq.h>
+ spi {
+ #address-cells = <1>;
+ #size-cells = <0>;
+
+ adc@0 {
+ compatible = "adi,ad4170";
+ reg = <0>;
+ spi-max-frequency = <20000000>;
+ spi-cpol;
+ spi-cpha;
+ avdd-supply = <&avdd>;
+ iovdd-supply = <&iovdd>;
+ interrupt-parent = <&gpio_in>;
+ interrupts = <0 IRQ_TYPE_EDGE_FALLING>;
+ #address-cells = <1>;
+ #size-cells = <0>;
+
+ // Sample AIN0 with respect to AIN1 throughout AVDD/AVSS input range
+ // Differential bipolar. If AVSS < 0V, differential true bipolar
+ channel@0 {
+ reg = <0>;
+ bipolar;
+ diff-channels = <0 1>;
+ adi,sensor-type = /bits/ 8 <0>;
+ adi,reference-select = /bits/ 8 <3>;
+ };
+ // Sample AIN2 with respect to DGND throughout AVDD/DGND input range
+ // Pseudo-differential unipolar (fig. 2a)
+ channel@1 {
+ reg = <1>;
+ single-channel = <2>;
+ common-mode-channel = <24>;
+ adi,sensor-type = /bits/ 8 <0>;
+ adi,reference-select = /bits/ 8 <3>;
+ };
+ // Sample AIN3 with respect to 2.5V throughout AVDD/AVSS input range
+ // Pseudo-differential bipolar (fig. 2b)
+ channel@2 {
+ reg = <2>;
+ bipolar;
+ single-channel = <3>;
+ common-mode-channel = <29>;
+ adi,sensor-type = /bits/ 8 <0>;
+ adi,reference-select = /bits/ 8 <3>;
+ };
+ // Sample AIN4 with respect to DGND throughout AVDD/AVSS input range
+ // Pseudo-differential bipolar (fig. 2c)
+ channel@3 {
+ reg = <3>;
+ bipolar;
+ single-channel = <4>;
+ common-mode-channel = <24>;
+ adi,sensor-type = /bits/ 8 <0>;
+ adi,reference-select = /bits/ 8 <3>;
+ };
+ // Sample AIN5 with respect to 2.5V throughout AVDD/AVSS input range
+ // Pseudo-differential unipolar (AD4170 datasheet page 46 example)
+ channel@4 {
+ reg = <4>;
+ single-channel = <5>;
+ common-mode-channel = <29>;
+ adi,sensor-type = /bits/ 8 <0>;
+ adi,reference-select = /bits/ 8 <3>;
+ };
+ // Sample AIN6 with respect to 2.5V throughout REFIN+/REFIN- input range
+ // Pseudo-differential bipolar
+ channel@5 {
+ reg = <5>;
+ bipolar;
+ single-channel = <6>;
+ common-mode-channel = <29>;
+ adi,sensor-type = /bits/ 8 <0>;
+ adi,reference-select = /bits/ 8 <0>;
+ };
+ // Weigh scale sensor
+ weighscale@6 {
+ reg = <6>;
+ bipolar;
+ diff-channels = <7 8>;
+ adi,sensor-type = /bits/ 8 <1>;
+ adi,ac-excited;
+ adi,excitation-pins = <17 18>, <19 20>;
+ adi,reference-select = /bits/ 8 <0>;
+ };
+ };
+ };
+...
+
diff --git a/MAINTAINERS b/MAINTAINERS
index 030d90d38341..991b6e2e373a 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -1337,6 +1337,13 @@ F: Documentation/ABI/testing/sysfs-bus-iio-adc-ad4130
F: Documentation/devicetree/bindings/iio/adc/adi,ad4130.yaml
F: drivers/iio/adc/ad4130.c
+ANALOG DEVICES INC AD4170 DRIVER
+M: Marcelo Schmitt <marcelo.schmitt@...log.com>
+L: linux-iio@...r.kernel.org
+S: Supported
+W: https://ez.analog.com/linux-software-drivers
+F: Documentation/devicetree/bindings/iio/adc/adi,ad4170.yaml
+
ANALOG DEVICES INC AD4695 DRIVER
M: Michael Hennerich <michael.hennerich@...log.com>
M: Nuno Sá <nuno.sa@...log.com>
--
2.47.2
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