Re: [PATCH v1 1/2] dt-bindings: iio: adc: avia-hx711: add avia,hx710b compatible

[David Lechner <dlechner@baylibre.com>]

On 4/18/26 12:05 PM, Piyush Patle wrote:
> Add the HX710B compatible to the binding and describe the variant-specific
> channel and gain model.
> 
> Also add an example node for HX710B so the schema covers both supported
> parts.
> 
> Signed-off-by: Piyush Patle <piyushpatle228@gmail.com>
> ---
>  .../bindings/iio/adc/avia-hx711.yaml          | 36 +++++++++++++++----
>  1 file changed, 30 insertions(+), 6 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/iio/adc/avia-hx711.yaml b/Documentation/devicetree/bindings/iio/adc/avia-hx711.yaml
> index 9c57eb13f892..19318c4dd994 100644
> --- a/Documentation/devicetree/bindings/iio/adc/avia-hx711.yaml
> +++ b/Documentation/devicetree/bindings/iio/adc/avia-hx711.yaml
> @@ -4,7 +4,7 @@
>  $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@it-klinger.de>
> @@ -12,9 +12,19 @@ maintainers:
>  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
> +    and 1 to 3 additional cycles for selection of the input channel and gain
> +    for the next measurement
> +  - dout-gpio is the sensor data output the sensor drives in response to
> +    the clock
> +
> +  HX711: 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.
> +
> +  HX710B: 24-bit ADC with fixed gain of 128. Channel 0 is the differential
> +  input and channel 1 measures the DVDD-AVDD supply voltage difference.
> +  Channel selection for the next conversion is controlled by the number of
> +  trailing PD_SCK pulses.

The bits about "bit-banging" and "channel selection" sound like driver
implementation details that don't belong in the DT bindings.

>  
>    Specifications about the driver can be found at:
>    http://www.aviaic.com/ENProducts.aspx
> @@ -23,11 +33,12 @@ properties:
>    compatible:
>      enum:
>        - avia,hx711
> +      - avia,hx710b
>  
>    sck-gpios:
>      description:
>        Definition of the GPIO for the clock (output). In the datasheet it is
> -      named PD_SCK
> +      named PD_SCK.

Save the cleanups for a separate patch to keep the adding HX710B changes clear.

I'm guessing the existing binding for HX711 is quite old because it is quite
incomplete.

It has avdd-supply, but is missing vsup-supply and dvdd-supply.

It should probably also have a way to describe how the rate pin is wired.

And it should have a clocks property instead of clock-frequency.

It would make sense to have two clocks, on for XI/XO and one for PD_SCK.
The second one being optional because of sck-gpios.

HX710B has many fewer pins, so we will need an:

allOf:
  - if:
      properties:
	compatible:
	  const: avia,hx710b

section that sets anything for pins that chip doesn't have to false, like
vsup-supply.

HX710B also has a vref-supply that HX711 doesn't have. (Unless these are the
same thing by a different name?)


>      maxItems: 1
>  
>    dout-gpios:
> @@ -43,6 +54,9 @@ properties:
>        Definition of the regulator used as analog supply
>  
>    clock-frequency:
> +    description:
> +      Bit-bang clock frequency on PD_SCK. Keep the PD_SCK high time below
> +      the chip power-down threshold.

I suspect that this was meant to be the crystal frequency (XI/XO), not PD_SCK
since sck-gpios already exists for PD_SCK

>      minimum: 20000
>      maximum: 2500000
>      default: 400000
> @@ -58,10 +72,20 @@ additionalProperties: false
>  examples:
>    - |
>      #include <dt-bindings/gpio/gpio.h>
> -    weight {
> +    /* HX711 example */

The compatible string already has the part number, so this comment
doesn't really and any new info.

> +    weight0 {
>          compatible = "avia,hx711";
>          sck-gpios = <&gpio3 10 GPIO_ACTIVE_HIGH>;
>          dout-gpios = <&gpio0 7 GPIO_ACTIVE_HIGH>;
>          avdd-supply = <&avdd>;
>          clock-frequency = <100000>;
>      };
> +  - |
> +    #include <dt-bindings/gpio/gpio.h>
> +    /* HX710B example */
> +    weight1 {
> +        compatible = "avia,hx710b";
> +        sck-gpios = <&gpio3 11 GPIO_ACTIVE_HIGH>;
> +        dout-gpios = <&gpio0 8 GPIO_ACTIVE_HIGH>;
> +        avdd-supply = <&avdd>;
> +    };

There is nothing significantly different about this example, so it
isn't particularly useful.