Re: [PATCH v2 1/7] dt-bindings: iio: adc: Add TI ADS126x ADC family

[Jonathan Cameron <jic23@kernel.org>]

On Tue, 30 Jun 2026 13:38:30 -0500
David Lechner <dlechner@baylibre.com> wrote:

> On 6/30/26 12:14 PM, Kurt Borja wrote:
> > On Mon Jun 29, 2026 at 11:43 AM -05, David Lechner wrote:  
> >> On 6/29/26 11:27 AM, Kurt Borja wrote:  
> >>> On Mon Jun 29, 2026 at 9:21 AM -05, David Lechner wrote:  
> >>>> On 6/28/26 2:12 PM, Kurt Borja wrote:  
> >>>>> On Sun Jun 28, 2026 at 10:45 AM -05, David Lechner wrote:  
> >>>>>> On 6/28/26 12:36 AM, 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:
> >>>>>>> +  "^channel@[0-9]+$":
> >>>>>>> +    $ref: /schemas/iio/adc/adc.yaml#
> >>>>>>> +    unevaluatedProperties: false
> >>>>>>> +
> >>>>>>> +    properties:
> >>>>>>> +      reg:
> >>>>>>> +        maxItems: 1
> >>>>>>> +  
> >>>>>>
> >>>>>> If we want to allow single-ended/pseudo-differential inputs, then we should
> >>>>>> also allow single-channel (positive pin) and common-mode-channel (negative
> >>>>>> pin) properties.
> >>>>>>
> >>>>>> This will also require additional common-mode-<N>-supply properties to allow
> >>>>>> for the negative pin connected to something other than GND.  
> >>>>>
> >>>>> Ah interesting. Why the N though? wouldn't a single supply connected to
> >>>>> AINCOM be enough here?  
> >>>>
> >>>> In theory, any AINx could be a common mode input by connecting it to
> >>>> a constant voltage supply.  
> >>>
> >>> Technically yes, but there is a pin named AINCOM intended for this
> >>> purpose. Can we do a simplification here? I propose having
> >>>
> >>>   common-mode-channel:
> >>>     /* AINCOM pin */
> >>>     const: 10
> >>>
> >>> That way we would only need one common-mode-supply. Would that be okay?
> >>>  
> >>
> >> Ideally, we shouldn't limit how the chip can be wired up in the devicetree
> >> bindings. It doesn't mean that we have to implement everything in the driver
> >> though.  

I'm a bit confused on this.  Arguably you could wire up any side of a differential
pair to a common mode signal, but we haven't had this binding applied more generally
than cases where their is a setup where the intent is a shared common (shielding
on cable in some cases IIRC). 

So why is this case special? I see AIN_COM can be wired up to an internal vbias
but other than that it looks like any other AINX input.

Jonathan

> > 
> > Makes sense.
> > 
> > I just have a doubt: In the ADS112c14 bindings, is there a specific
> > reason why you didn't describe common-mode-<N>-supply?
> >   
> 
> For singled-ended inputs on ADS112c14, there is an internal
> connection to GND, so it isn't possible to have a pseudo-
> differential input like that. I guess technically, it could
> still be possible, but wasn't a typical wiring described in
> the datasheet like it is on ADS1263.
>