Re: [PATCH v2 1/2] dt-bindings: staging: iio: cdc: ad7746: add binding documentation for AD7746

[Lars-Peter Clausen]

On 4/22/21 9:16 PM, Lucas Stankus wrote:
> On Tue, Apr 20, 2021 at 4:37 PM Rob Herring <robh@xxxxxxxxxx> wrote:
> > On Sun, Apr 18, 2021 at 07:49:51PM -0300, Lucas Stankus wrote:
> > > Add device tree binding documentation for AD7746 cdc in YAML format.
> > >
> > > Signed-off-by: Lucas Stankus <lucas.p.stankus@xxxxxxxxx>
> > > ---
> > >
> > > A minor note about the adi,excitation-vdd-permille property. Jonathan
> > > suggested the name to be adi,excitation-vdd-milicent, but I was unsure of
> > > the milicent naming. With a quick search I found out that the common way to
> > > call a thousandth is 'per mille'[1], but I didn't find any use of it in the
> > > kernel documentation. Any thoughts about it?
> > Seems okay to me.
> >
> > > [1] https://en.wikipedia.org/wiki/Per_mille
> > >
> > >   .../bindings/iio/cdc/adi,ad7746.yaml          | 73 +++++++++++++++++++
> > >   1 file changed, 73 insertions(+)
> > >   create mode 100644 Documentation/devicetree/bindings/iio/cdc/adi,ad7746.yaml
> > >
> > > diff --git a/Documentation/devicetree/bindings/iio/cdc/adi,ad7746.yaml b/Documentation/devicetree/bindings/iio/cdc/adi,ad7746.yaml
> > > new file mode 100644
> > > index 000000000000..a2a7eee674ba
> > > --- /dev/null
> > > +++ b/Documentation/devicetree/bindings/iio/cdc/adi,ad7746.yaml
> > > @@ -0,0 +1,73 @@
> > > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > > +%YAML 1.2
> > > +---
> > > +$id: http://devicetree.org/schemas/iio/cdc/adi,ad7746.yaml#
> > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > +
> > > +title: AD7746 24-Bit Capacitance-to-Digital Converter with Temperature Sensor
> > > +
> > > +maintainers:
> > > +  - Michael Hennerich <michael.hennerich@xxxxxxxxxx>
> > > +
> > > +description: |
> > > +  AD7746 24-Bit Capacitance-to-Digital Converter with Temperature Sensor
> > > +
> > > +  Specifications about the part can be found at:
> > > +  https://www.analog.com/media/en/technical-documentation/data-sheets/ad7291.pdf
> > > +
> > > +properties:
> > > +  compatible:
> > > +    enum:
> > > +      - adi,ad7745
> > > +      - adi,ad7746
> > > +      - adi,ad7747
> > > +
> > > +  reg:
> > > +    maxItems: 1
> > > +
> > > +  adi,excitation-vdd-permille:
> > > +    description: |
> > > +      Set VDD per mille to be used as the excitation voltage.
> > > +    $ref: /schemas/types.yaml#/definitions/uint32
> > > +    enum: [125, 250, 375, 500]
> > > +
> > > +  adi,exca-output-en:
> > > +    description: Enables the EXCA pin as the excitation output.
> > > +    type: boolean
> > > +
> > > +  adi,exca-output-invert:
> > > +    description: Inverts the excitation output in the EXCA pin.
> > > +    type: boolean
> > 'invert' assumes I know what the non-inverted signal is. Sometimes that
> > makes sense, but if you can define in terms of the inverse that would be
> > better. For example, for a normally active low signal, name the property
> > 'foo-active-high'.
> Thanks for the feedback!
>  From reading the data sheet I couldn't quite grasp what would be an inverted
> excitation output, but I don't have a lot of experience with CDCs. Maybe someone
> with more experience could help out with a better suggestion.

This is the only thing I could find 
https://www.analog.com/media/en/technical-documentation/application-notes/AN-1585.pdf.

The datasheet also says that only at most one of them should be 
inverted. So maybe only a single property which selects which of the two 
is inverted.