Re: [PATCH v3 1/9] dt-bindings: iio: adc: support the TI ADS126x ADC family

[Kurt Borja]

On Sat Aug 8, 2026 at 1:38 PM -05, David Lechner wrote:
> On 8/7/26 10:58 PM, 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 adds a second,
>> 24-bit delta-sigma ADC (ADC2) for background measurements.
>> 
>
> ...
>
>> +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 not described, its assumed to be connected to ground
>> +      (0V).
>
> Would we really have a case with a negative only reference? I would say if not
> described, assume the pin is free for other use.

In bipolar supply configurations, I believe it would make sense to wire
the negative reference to -2.5V and ground the positive. Also we have
the ti,reference-reversal case, where you may wire the "negative"
reference to say 2.5V and the positive to ground.

>
>> +
>> +  "^refn[1-3]-supply$":
>> +    description:
>> +      Negative voltage reference connected to REFN1 (AIN1), REFN2 (AIN3) or
>> +      REFN3 (AIN5). If not described, its assumed to be connected to ground
>> +      (0V).
>
> Assumption is only true when corresponding refp supply is described. Otherwise
> we should assume the pin is free for other uses.

I'll clarify it.

>
>> +
>> +  "^ti,refp[1-3]-refn[1-3]-resistor-ohms$":
>> +    description:
>> +      Magnitude of the external reference resistor connected between REFP<N>
>> +      and REFN<M>. In ratiometric configurations, such as RTD measurements, the
>> +      IDAC excitation current returns through this resistor, generating the
>> +      reference voltage for the conversion.
>> +
>> +  "^channel@[0-9]+$":
>> +    $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:
>> +        description: |
>> +          In addition to the analog input pins 0 (AIN0) - 10 (AINCOM), there are
>> +          special inputs that can be selected from the following values:
>> +          11: Temperature sensor monitor
>> +          12: Analog power supply monitor
>> +          13: Digital power supply monitor
>> +          14: TDAC test signal
>
> For reasons mentioned in the reply to the cover letter, I'm not a fan of the
> monitor channels here.
>
>> +        items:
>> +          minimum: 0
>> +          maximum: 14
>> +
>
> ...
>
>> +      input-chopping: true
>> +
>> +      ti,idac-rotation:
>
> Should we make this one a standard property like input-chopping?

Maybe excitation-current-chopping or excitation-channel-chopping?

>
>> +        $ref: /schemas/types.yaml#/definitions/flag
>> +        description:
>> +          Automatically swap the IDAC1 and IDAC2 connections of alternate
>> +          conversions. The ADC averages the alternate conversions to eliminate
>> +          IDAC mismatch.
>> +
>
> ...
>
>> +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 {
>> +                    regulator-name = "vbias";
>
> The node name is already "vbias" so giving regulator-name is redundant.

Is it okay to leave it empty?

    ads1262_vbias: vbias { };

>
>> +                };
>> +            };
>> +
>> +            channel@0 {
>> +                reg = <0>;
>> +                single-channel = <0>;
>> +                /* The VBIAS is enabled on pin 10 (AINCOM) */
>> +                common-mode-channel = <10>;
>> +            };
>> +        };
>> +    };
>> +

-- 
Thanks,
 ~ Kurt