Re: [PATCH 1/2] dt-bindings: iio: adc: ti,ads1298: add ADS1299 EEG ADC variants

[David Lechner <dlechner@baylibre.com>]

On 6/30/26 9:03 AM, Md Shofiqul Islam wrote:
> The ADS1299, ADS1299-4, and ADS1299-6 share the same SPI interface
> and register map as the ADS1298 ECG ADC family but are designed for
> EEG and biopotential measurement.  Key differences from ADS1298:
> - PGA gain up to 24x (vs 12x for ADS1298)
> - Internal reference is always 2.4V (no 4V option)
> 
> Add compatible strings and update the vref-supply description to
> document the ADS1299 reference voltage behaviour.
> 
> Signed-off-by: Md Shofiqul Islam <shofiqtest@gmail.com>
> ---
>  .../bindings/iio/adc/ti,ads1298.yaml          | 31 ++++++++++++++++---
>  1 file changed, 26 insertions(+), 5 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/iio/adc/ti,ads1298.yaml b/Documentation/devicetree/bindings/iio/adc/ti,ads1298.yaml
> index 71f9f9b745cb..82c5181126df 100644
> --- a/Documentation/devicetree/bindings/iio/adc/ti,ads1298.yaml
> +++ b/Documentation/devicetree/bindings/iio/adc/ti,ads1298.yaml
> @@ -4,11 +4,16 @@
>  $id: http://devicetree.org/schemas/iio/adc/ti,ads1298.yaml#
>  $schema: http://devicetree.org/meta-schemas/core.yaml#
>  
> -title: Texas Instruments' ads1298 medical ADC chips
> +title: Texas Instruments ADS1298/ADS1299 biopotential ADC chips
>  
>  description: |
> -  Datasheet at: https://www.ti.com/product/ADS1298
> -  Bindings for this chip aren't complete.
> +  ADS1298/ADS1298R: 8-channel, 24-bit ECG ADC.
> +  Datasheet: https://www.ti.com/product/ADS1298
> +
> +  ADS1299/ADS1299-4/ADS1299-6: 8/4/6-channel, 24-bit EEG/biopotential ADC.
> +  Identical SPI interface and register map to the ADS1298 family, but with
> +  a higher maximum PGA gain (24x vs 12x) and fixed 2.4V internal reference.
> +  Datasheet: https://www.ti.com/product/ADS1299
>  
>  maintainers:
>    - Mike Looijmans <mike.looijmans@topic.nl>
> @@ -17,6 +22,9 @@ properties:
>    compatible:
>      enum:
>        - ti,ads1298
> +      - ti,ads1299
> +      - ti,ads1299-4
> +      - ti,ads1299-6
>  
>    reg:
>      maxItems: 1
> @@ -33,8 +41,10 @@ properties:
>  
>    vref-supply:
>      description:
> -      Optional reference voltage. If omitted, internal reference is used,
> -      which is 2.4V when analog supply is below 4.4V, 4V otherwise.
> +      Optional reference voltage. If omitted, internal reference is used.
> +      For ADS1298, the internal reference is 2.4V when analog supply is
> +      below 4.4V, 4V otherwise. For ADS1299, the internal reference is
> +      always 2.4V.

Not sure the dt-bindings care about the internal reference. It should
just be a driver implementation detail.

So I would just trim this down to:

	Optional reference voltage. If omitted, internal reference is used.

>  
>    clocks:
>      description: Optional 2.048 MHz external source clock on CLK pin
> @@ -75,5 +85,16 @@ examples:
>            spi-max-frequency = <20000000>;
>            spi-cpha;
>          };
> +
> +        adc@2 {
> +          reg = <2>;
> +          compatible = "ti,ads1299";
> +          label = "ads1299-1-eeg";
> +          avdd-supply = <&reg_iso_5v_a>;
> +          interrupt-parent = <&gpio0>;
> +          interrupts = <79 IRQ_TYPE_EDGE_FALLING>;
> +          spi-max-frequency = <20000000>;
> +          spi-cpha;
> +        };

Since the chips are nearly identical, not sure a 2nd example is
particularly useful.

>      };
>  ...