Re: [PATCH v4 1/7] dt-bindings: iio: adc: avia-hx711: add avia,hx710b compatible

[David Lechner]

On 4/27/26 5:09 AM, Piyush Patle wrote:
> The HX710B shares the same two-wire interface as the HX711 but differs
> in its channel and gain model: gain is fixed at 128 and the number of
> trailing PD_SCK pulses selects the input channel rather than the gain.
> 
> Add avia,hx710b to the compatible enum. Document the chip differences
> in the description and add chip-specific supply properties (dvdd-supply,
> vsup-supply, vref-supply) and a rate-gpios property for the HX711 RATE
> pin. Add allOf constraints that forbid HX711-only properties on HX710B
> nodes and vice versa. Clarify the clock-frequency description to
> reflect its actual purpose: controlling the SCK bit-bang timing.

Krzysztof gave a Reviewed-by on the last revision [1], so you need to
include that here or explain why you didn't pick it up. If you just make
a trivial change, you can still pick it up. In this case though, I think
that enough changes were made that it is worth having a DT maintainer have
another look.

https://lore.kernel.org/linux-iio/20260423-famous-tody-of-opposition-73c8af@quoll/

> 
> Signed-off-by: Piyush Patle <piyushpatle228@xxxxxxxxx>
> ---
> Changes in v4:
> - Add vref-supply for the HX710B VREF reference voltage pin.
> - Remove dvdd-supply from the HX710B forbidden properties list; the
>   HX710B has a DVDD supply and the DVDD-AVDD channel relies on it.
> - Add allOf block forbidding vref-supply on HX711 nodes.
> - Add an HX710B example showing vref-supply.
> - Update description: avoid specific channel-number references in
>   hardware text.
> 
> Changes in v3:
> - Drop the vref-supply mention from avdd-supply; no such binding
>   property exists.
> - Drop the clock-frequency sentence that repeated the schema default.
> - Restore the example node name to weight.
> - Remove the separate HX710B example.
> 
> Changes in v2:
> - Remove driver implementation details from the description and describe
>   hardware behaviour only.
> - Drop unrelated punctuation cleanup.
> - Add dvdd-supply and vsup-supply optional properties for HX711.
> - Add rate-gpios optional property for the HX711 RATE pin and forbid it
>   on HX710B.
> - Add the allOf if/then block forbidding HX711-only properties on
>   HX710B nodes.
> - Clarify clock-frequency as SCK bit-bang timing, not a crystal or
>   external clock input.
> - Sort compatible enum alphabetically.
> - Remove redundant example comments.
> - Update the HX711 example to exercise rate-gpios.
> ---
>  .../bindings/iio/adc/avia-hx711.yaml          | 82 +++++++++++++++----
>  1 file changed, 67 insertions(+), 15 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/iio/adc/avia-hx711.yaml b/Documentation/devicetree/bindings/iio/adc/avia-hx711.yaml
> index 9c57eb13f892..fddd296bfaca 100644
> --- a/Documentation/devicetree/bindings/iio/adc/avia-hx711.yaml
> +++ b/Documentation/devicetree/bindings/iio/adc/avia-hx711.yaml
> @@ -4,49 +4,91 @@
>  $id: http://devicetree.org/schemas/iio/adc/avia-hx711.yaml#
>  $schema: http://devicetree.org/meta-schemas/core.yaml#
>  
> -title: AVIA HX711 ADC chip for weight cells
> +title: AVIA HX711 and HX710B ADCs
>  
>  maintainers:
>    - Andreas Klinger <ak@xxxxxxxxxxxxx>
>  
>  description: |
> -  Bit-banging driver using two GPIOs:
> -  - sck-gpio gives a clock to the sensor with 24 cycles for data retrieval
> -    and up to 3 cycles for selection of the input channel and gain for the
> -    next measurement
> -  - dout-gpio is the sensor data the sensor responds to the clock
> +  The HX711 is a 24-bit ADC with selectable gain (32/64/128) and two
> +  differential input channels. Channel A supports gain 64 and 128;
> +  channel B supports gain 32.
>  
> -  Specifications about the driver can be found at:
> -  http://www.aviaic.com/ENProducts.aspx
> +  The HX710B is a 24-bit ADC with fixed gain of 128. One input measures
> +  the differential voltage between the two input pins; a second measures
> +  the DVDD-AVDD supply voltage difference for battery level detection.
>  
>  properties:
>    compatible:
>      enum:
> +      - avia,hx710b
>        - avia,hx711
>  
>    sck-gpios:
>      description:
> -      Definition of the GPIO for the clock (output). In the datasheet it is
> -      named PD_SCK
> +      GPIO for the clock output (PD_SCK in the datasheet).
>      maxItems: 1
>  
>    dout-gpios:
>      description:
> -      Definition of the GPIO for the data-out sent by the sensor in
> -      response to the clock (input).
> -      See Documentation/devicetree/bindings/gpio/gpio.txt for information
> -      on how to specify a consumer gpio.
> +      GPIO for the data output from the sensor (DOUT in the datasheet).
>      maxItems: 1
>  
>    avdd-supply:
>      description:
> -      Definition of the regulator used as analog supply
> +      Analog supply voltage (AVDD). Also serves as the voltage reference on
> +      both chips.
> +
> +  dvdd-supply:
> +    description:
> +      Digital supply voltage (DVDD). For the HX710B, DVDD must be greater
> +      than or equal to AVDD. When DVDD is a battery rail and AVDD is a
> +      regulated supply, one channel monitors the DVDD-AVDD difference for
> +      battery level detection.
> +
> +  vsup-supply:
> +    description:
> +      Supply voltage for the on-chip regulator (VSUP). HX711 only.
> +
> +  vref-supply:
> +    description:
> +      Reference voltage input (VREF). HX710B only. When omitted, the driver
> +      assumes VREF is tied to AVDD on the board.
> +
> +  rate-gpios:
> +    description:
> +      GPIO connected to the RATE pin (HX711 only). When driven low the
> +      output data rate is 10 SPS; when driven high it is 80 SPS. If
> +      omitted the RATE pin state is determined by the board wiring.
> +    maxItems: 1
>  
>    clock-frequency:
> +    description:
> +      Controls the SCK bit-bang timing. The value is used to derive the
> +      delay between SCK edges; keep the SCK high time below 60 us to
> +      avoid triggering chip power-down mode.
>      minimum: 20000
>      maximum: 2500000
>      default: 400000
>  
> +allOf:
> +  - if:
> +      properties:
> +        compatible:
> +          const: avia,hx710b
> +    then:
> +      properties:
> +        vsup-supply: false
> +        rate-gpios: false
> +
> +  - if:

Could just be else:

Probably OK either way though.

> +      properties:
> +        compatible:
> +          const: avia,hx711
> +    then:
> +      properties:
> +        vref-supply: false
> +
>  required:
>    - compatible
>    - sck-gpios
> @@ -62,6 +104,16 @@ examples:
>          compatible = "avia,hx711";
>          sck-gpios = <&gpio3 10 GPIO_ACTIVE_HIGH>;
>          dout-gpios = <&gpio0 7 GPIO_ACTIVE_HIGH>;
> +        rate-gpios = <&gpio0 9 GPIO_ACTIVE_HIGH>;
>          avdd-supply = <&avdd>;
>          clock-frequency = <100000>;
>      };
> +  - |
> +    #include <dt-bindings/gpio/gpio.h>
> +    weight {
> +        compatible = "avia,hx710b";
> +        sck-gpios = <&gpio3 10 GPIO_ACTIVE_HIGH>;
> +        dout-gpios = <&gpio0 7 GPIO_ACTIVE_HIGH>;
> +        avdd-supply = <&avdd>;
> +        vref-supply = <&vref>;
> +    };