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

[Kurt Borja]

On Mon Aug 10, 2026 at 11:42 AM -05, David Lechner wrote:
> On 8/9/26 3:26 AM, Kurt Borja wrote:
>> 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.
>> 
>
> OK. I guess the better wording for both of these would be that if any
> channel references one of these in reference-sources and it is not present
> assume it is connected to ground (0V).

I'll go for this wording.

>
>>>
>>>> +
>>>> +  "^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?
>
> I suppose. All of the TI literature seems to call it "rotation" rather
> than "chopping", but I did find a few other sources that call it
> "chopping" and that would be consistent with input-chopping.

Yes, IMO it makes more sense to go for the chopping term.

>
> I would go with excitation-channel-chopping since we are swapping
> the current generators, not just the current magnitude.

I'll add the patch.

-- 
Thanks,
 ~ Kurt