Re: [PATCH v4 02/10] dt-bindings: iio: adc: support the TI ADS126x ADC family

[Conor Dooley <conor@kernel.org>]

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On Fri, Aug 28, 2026 at 01:38:17AM -0500, Kurt Borja wrote:
> The ADS1262 and ADS1263 are 32-bit, 38.4-kSPS delta-sigma ADCs with an
> integrated PGA, internal reference, excitation and burn-out current
> sources for sensor biasing and diagnostics. The ADS1263 is compatible
> with ADS1262, but includes a second auxiliary ADC (ADC2) to perform main
> channel (ADC1) cross-checking measurements, system background
> measurements, or temperature compensation of the primary sensor.
> 
> Both parts can configure per-channel voltage reference source,
> excitation current sources (IDAC), plus input and IDAC chopping for
> offset and IDAC mismatch cancellation. This lets the device drive and
> ratiometrically measure RTDs and other resistive sensors.
> 
> Signed-off-by: Kurt Borja <kuurtb@gmail.com>
> ---
>  .../devicetree/bindings/iio/adc/ti,ads1262.yaml    | 376 +++++++++++++++++++++
>  MAINTAINERS                                        |   6 +
>  2 files changed, 382 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/iio/adc/ti,ads1262.yaml b/Documentation/devicetree/bindings/iio/adc/ti,ads1262.yaml
> new file mode 100644
> index 000000000000..7e26572388e4
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iio/adc/ti,ads1262.yaml
> @@ -0,0 +1,376 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/iio/adc/ti,ads1262.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: TI ADS1262/ADS1263 analog to digital converter
> +
> +maintainers:
> +  - Kurt Borja <kuurtb@gmail.com>
> +
> +description: |
> +  The ADS1262 and ADS1263 are 38.4-kSPS, delta-sigma (ΔΣ) ADCs with an
> +  integrated PGA, reference, and internal fault monitors. The ADS1263 integrates
> +  an auxiliary, 24-bit, ΔΣ ADC intended for background measurements.
> +
> +  Datasheets:
> +    - ADS126x: https://www.ti.com/lit/ds/symlink/ads1262.pdf
> +
> +properties:
> +  compatible:
> +    oneOf:
> +      - const: ti,ads1262
> +      - items:
> +          - const: ti,ads1263
> +          - const: ti,ads1262
> +
> +  reg:
> +    maxItems: 1
> +
> +  '#address-cells':
> +    const: 1
> +
> +  '#size-cells':
> +    const: 0
> +
> +  spi-max-frequency:
> +    maximum: 8000000
> +
> +  spi-cpha: true
> +
> +  interrupts:
> +    minItems: 1
> +    maxItems: 2
> +    description: Data ready (DRDY) interrupt lines.
> +
> +  interrupt-names:
> +    description:
> +      The data ready (DRDY) signal has two independent interrupt lines. A
> +      dedicated DRDY pin and a pin shared with the serial interface MISO pin,
> +      which is called DOUT/DRDY.
> +    minItems: 1
> +    maxItems: 2
> +    items:
> +      enum: [drdy, doutdrdy]
> +
> +  start-gpios:
> +    description: Start conversion control.
> +    maxItems: 1
> +
> +  reset-gpios:
> +    maxItems: 1
> +
> +  dvdd-supply:
> +    description: Digital power supply.
> +
> +  avdd-supply:
> +    description:
> +      Analog power supply. In bipolar supply configurations, the reported
> +      voltage should be in reference to DGND.
> +
> +  avss-supply:
> +    description:
> +      Negative analog power supply for bipolar configurations. AVSS can only be
> +      at or below the ground reference (DGND). If not described, AVSS is assumed
> +      to be connected to ground (0V).
> +
> +  clocks:
> +    maxItems: 1

clock doesn't appear mandatory, what does it do?

> +
> +  '#io-channel-cells':
> +    minimum: 1
> +    maximum: 2

What's the use case for actually setting this as a single cell? Kinda
confused by it.

Otherwise, quite frankly, the binding is too complicated for me! I'll
have to leave it up to the IIO folks to cover whether what's being done
is sane.

Cheers,
Conor.

> +    description: |
> +      The first cell selects the channel by its reg. The second cell selects
> +      between the main ADC (ADC1) and the auxiliary ADC (ADC2) as follows:
> +        0: ADC1
> +        1: ADC2
> +
> +  '#gpio-cells':
> +    const: 2
> +
> +  gpio-controller: true
> +
> +  regulators:
> +    type: object
> +    description:
> +      List of regulators provided by this chip.
> +
> +    properties:
> +      vbias:
> +        $ref: /schemas/regulator/regulator.yaml#
> +        type: object
> +        description:
> +          Level-shift voltage output on the AINCOM pin. Its output is the
> +          mid-voltage of the analog supply, (AVDD + AVSS) / 2, and is used to
> +          shift floating sensors to within the ADC input range.
> +        unevaluatedProperties: false
> +
> +      refout:
> +        $ref: /schemas/regulator/regulator.yaml#
> +        type: object
> +        description:
> +          Buffered internal voltage reference output on the REFOUT pin.
> +        unevaluatedProperties: false
> +
> +    additionalProperties: false
> +
> +patternProperties:
> +  "^ain([0-9]|com)-supply$":
> +    description:
> +      Common-mode voltage supply connected to AIN<N> or AINCOM.
> +
> +  "^refp[1-3]-supply$":
> +    description:
> +      Positive voltage reference connected to REFP1 (AIN0), REFP2 (AIN2) or
> +      REFP3 (AIN4). If this regulator is not described and a channel selects
> +      it as a reference source, then it's assumed to be connected to ground
> +      (0V).
> +
> +  "^refn[1-3]-supply$":
> +    description:
> +      Negative voltage reference connected to REFN1 (AIN1), REFN2 (AIN3) or
> +      REFN3 (AIN5). If this regulator is not described and a channel selects
> +      it as a reference source, then it's assumed to be connected to ground
> +      (0V).
> +
> +  "^ti,refp[1-3]-refn[1-3]-resistor-ohms$":
> +    description:
> +      Magnitude of the external reference resistor connected between REFP<N>
> +      and REFN<M>. In ratiometric configurations, such as RTD measurements, the
> +      IDAC excitation current returns through this resistor, generating the
> +      reference voltage for the conversion.
> +
> +  "^channel@[0-9a-f]+$":
> +    $ref: /schemas/iio/adc/adc.yaml#
> +    unevaluatedProperties: false
> +
> +    properties:
> +      reg:
> +        maxItems: 1
> +
> +      single-channel:
> +        minimum: 0
> +        maximum: 10
> +
> +      common-mode-channel:
> +        minimum: 0
> +        maximum: 10
> +        default: 10
> +
> +      diff-channels:
> +        items:
> +          minimum: 0
> +          maximum: 10
> +
> +      input-chopping: true
> +
> +      reference-sources:
> +        minItems: 2
> +        description:
> +          Indicates the reference sources for this channel. The first and second
> +          items are the positive (REFP) and negative (REFN) sources of the main
> +          ADC (ADC1). The third item is the reference source of the secondary
> +          ADC (ADC2) and must always have a positive differential voltage.
> +        items:
> +          - enum: [internal-p, refp1, refp2, refp3, avdd]
> +          - enum: [internal-n, refn1, refn2, refn3, avss]
> +          - enum: [internal, refp1-refn1, refp2-refn2, refp3-refn3, avdd-avss]
> +
> +      ti,reference-reversal:
> +        $ref: /schemas/types.yaml#/definitions/flag
> +        description:
> +          Indicates that the ADC1 (this has no effect on ADC2) reference voltage
> +          for this channel has negative polarity and thus should be internally
> +          reversed.
> +
> +      excitation-channels:
> +        minItems: 1
> +        maxItems: 2
> +        description:
> +          Selects the pins for the IDAC sources from 0 (AIN0) to 10 (AINCOM).
> +          The first value corresponds to IDAC1 and the second to IDAC2.
> +        items:
> +          minimum: 0
> +          maximum: 10
> +
> +      excitation-current-nanoamp:
> +        minItems: 1
> +        maxItems: 2
> +        description:
> +          The first value corresponds to IDAC1 and the second to IDAC2.
> +        items:
> +          enum: [50000, 100000, 250000, 500000, 750000, 1000000, 1500000,
> +                 2000000, 2500000, 3000000]
> +
> +      excitation-current-chopping: true
> +
> +      burn-out-current-nanoamp:
> +        description:
> +          Selects current magnitude for the sensor bias current source.
> +        enum: [500, 2000, 10000, 50000, 200000]
> +
> +      ti,burn-out-resistor:
> +        $ref: /schemas/types.yaml#/definitions/flag
> +        description:
> +          Instead of a fixed current, the sensor bias (burn-out) current source
> +          can be pulled using an internal 10 MΩ resistor.
> +
> +      ti,burn-out-polarity:
> +        $ref: /schemas/types.yaml#/definitions/string
> +        description:
> +          The sensor bias can be configured to either pull-up or pull-down mode.
> +          In pull-up mode, the current flows into the positive input and flows
> +          out of the negative input. In pull-down mode, the polarities are
> +          reversed.
> +        enum: [pull-up, pull-down]
> +        default: pull-up
> +
> +    dependencies:
> +      excitation-channels: [excitation-current-nanoamp]
> +      excitation-current-nanoamp: [excitation-channels]
> +      burn-out-current-nanoamp:
> +        not:
> +          required:
> +            - ti,burn-out-resistor
> +
> +    required:
> +      - reg
> +
> +    allOf:
> +      - if:
> +          properties:
> +            excitation-channels:
> +              maxItems: 1
> +          required:
> +            - excitation-channels
> +        then:
> +          properties:
> +            excitation-current-nanoamp:
> +              maxItems: 1
> +        else:
> +          properties:
> +            excitation-current-nanoamp:
> +              minItems: 2
> +
> +    oneOf:
> +      - required: [single-channel]
> +      - required: [diff-channels]
> +
> +dependencies:
> +  interrupts: [interrupt-names]
> +  interrupts-extended: [interrupt-names]
> +
> +required:
> +  - compatible
> +  - reg
> +  - spi-cpha
> +  - avdd-supply
> +  - dvdd-supply
> +  - '#address-cells'
> +  - '#size-cells'
> +
> +allOf:
> +  - $ref: /schemas/spi/spi-peripheral-props.yaml#
> +  - if:
> +      properties:
> +        compatible:
> +          contains:
> +            const: ti,ads1263
> +    then:
> +      properties:
> +        '#io-channel-cells':
> +          minimum: 1
> +          maximum: 2
> +      patternProperties:
> +        "^channel@[0-9]+$":
> +          properties:
> +            reference-sources:
> +              minItems: 3
> +              maxItems: 3
> +              default: [internal-p, internal-n, internal]
> +    else:
> +      properties:
> +        '#io-channel-cells':
> +          const: 1
> +      patternProperties:
> +        "^channel@[0-9]+$":
> +          properties:
> +            reference-sources:
> +              minItems: 2
> +              maxItems: 2
> +              default: [internal-p, internal-n]
> +
> +unevaluatedProperties: false
> +
> +examples:
> +  - |
> +    #include <dt-bindings/gpio/gpio.h>
> +    #include <dt-bindings/interrupt-controller/irq.h>
> +
> +    spi {
> +        #address-cells = <1>;
> +        #size-cells = <0>;
> +
> +        adc@0 {
> +            compatible = "ti,ads1262";
> +            reg = <0>;
> +            spi-max-frequency = <8000000>;
> +            spi-cpha;
> +            avdd-supply = <&avdd>;
> +            dvdd-supply = <&dvdd>;
> +            #address-cells = <1>;
> +            #size-cells = <0>;
> +
> +            interrupts-extended = <&gpio 0 IRQ_TYPE_EDGE_FALLING>;
> +            interrupt-names = "drdy";
> +
> +            /* Typical common mode voltage configuration */
> +            aincom-supply = <&ads1262_vbias>;
> +
> +            regulators {
> +                ads1262_vbias: vbias { };
> +            };
> +
> +            channel@0 {
> +                reg = <0>;
> +                single-channel = <0>;
> +                /* The VBIAS is enabled on pin 10 (AINCOM) */
> +                common-mode-channel = <10>;
> +            };
> +        };
> +    };
> +
> +  - |
> +    #include <dt-bindings/gpio/gpio.h>
> +    #include <dt-bindings/interrupt-controller/irq.h>
> +
> +    spi {
> +        #address-cells = <1>;
> +        #size-cells = <0>;
> +
> +        adc@0 {
> +            compatible = "ti,ads1263", "ti,ads1262";
> +            reg = <0>;
> +            spi-max-frequency = <8000000>;
> +            spi-cpha;
> +            avdd-supply = <&avdd>;
> +            dvdd-supply = <&dvdd>;
> +            #address-cells = <1>;
> +            #size-cells = <0>;
> +
> +            interrupts-extended = <&gpio 0 IRQ_TYPE_EDGE_FALLING>;
> +            interrupt-names = "drdy";
> +
> +            ti,refp2-refn2-resistor-ohms = <3520>;
> +
> +            channel@0 {
> +                reg = <0>;
> +                diff-channels = <4 5>;
> +                reference-sources = "refp2", "refn2", "refp2-refn2";
> +                excitation-channels = <1 6>;
> +                excitation-current-nanoamp = <500000 500000>;
> +            };
> +        };
> +    };
> diff --git a/MAINTAINERS b/MAINTAINERS
> index f3be900e5b9d..7593e33c5346 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -27019,6 +27019,12 @@ S:	Maintained
>  F:	Documentation/devicetree/bindings/iio/adc/ti,ads1018.yaml
>  F:	drivers/iio/adc/ti-ads1018.c
>  
> +TI ADS1262 ADC DRIVER
> +M:	Kurt Borja <kuurtb@gmail.com>
> +L:	linux-iio@vger.kernel.org
> +S:	Maintained
> +F:	Documentation/devicetree/bindings/iio/adc/ti,ads1262.yaml
> +
>  TI ADS7924 ADC DRIVER
>  M:	Hugo Villeneuve <hvilleneuve@dimonoff.com>
>  L:	linux-iio@vger.kernel.org
> 
> -- 
> 2.55.0
> 

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