Re: [PATCH v3 1/3] dt-bindings: iio: adc: avia-hx711: add avia,hx710b compatible

Jonathan Cameron
2026-04-24T12:00:49Z

On Wed, 22 Apr 2026 23:29:08 +0530
Piyush Patle <piyushpatle228@gmail.com> 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) for the HX711, a rate-gpios property for the HX711 RATE
> pin, and an allOf constraint that forbids HX711-only properties on
> HX710B nodes. Clarify the clock-frequency description to reflect its
> actual purpose: controlling the SCK bit-bang timing.
>
> Signed-off-by: Piyush Patle <piyushpatle228@gmail.com>

Sashikio had some more comments...
https://sashiko.dev/#/patchset/20260422175910.1258579-1-piyushpatle228%40g

First one looks correct to me about the hx710b clearly having a DVDD supply
given we are measuring it.

> ---
> 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 | 50 +++++++++++++++----
> 1 file changed, 41 insertions(+), 9 deletions(-)
>
> diff --git a/Documentation/devicetree/bindings/iio/adc/avia-hx711.yaml b/Documentation/devicetree/bindings/iio/adc/avia-hx711.yaml
> index 9c57eb13f892..0c7c5843b8d2 100644
> --- a/Documentation/devicetree/bindings/iio/adc/avia-hx711.yaml
> +++ b/Documentation/devicetree/bindings/iio/adc/avia-hx711.yaml
> @@ -4,24 +4,24 @@
> $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>
>
> 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. Channel 0 is the
> + differential input and channel 1 measures the DVDD-AVDD supply
> + voltage difference.
How can it be measuring something including DVDD if that supply isn't
allowed for the part?

>
> properties:
> compatible:
> enum:
> + - avia,hx710b
> - avia,hx711
>
> sck-gpios:
> @@ -40,13 +40,44 @@ properties:
>
> 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). HX711 only.
This is the confusing description.
> +
> + vsup-supply:
> + description:
> + Supply voltage for the on-chip regulator (VSUP). HX711 only.
> +
> + 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
I'm fairly sure the sashiko comment on this is wrong given this
looks like standard way of doing this.

> + then:
> + properties:
> + vsup-supply: false
> + dvdd-supply: false
> + rate-gpios: false
> +
> required:
> - compatible
> - sck-gpios
> @@ -62,6 +93,7 @@ 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>;
> };