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Message-ID: <5dc08b622dac1db561f26034c93910ccff75e965.1758916484.git.marcelo.schmitt@analog.com>
Date: Fri, 26 Sep 2025 17:40:47 -0300
From: Marcelo Schmitt <marcelo.schmitt@...log.com>
To: <linux-iio@...r.kernel.org>, <devicetree@...r.kernel.org>,
<linux-doc@...r.kernel.org>, <linux-spi@...r.kernel.org>,
<linux-kernel@...r.kernel.org>
CC: <jic23@...nel.org>, <michael.hennerich@...log.com>, <nuno.sa@...log.com>,
<eblanc@...libre.com>, <dlechner@...libre.com>, <andy@...nel.org>,
<robh@...nel.org>, <krzk+dt@...nel.org>, <conor+dt@...nel.org>,
<corbet@....net>, <marcelo.schmitt1@...il.com>
Subject: [PATCH v3 7/8] dt-bindings: iio: adc: adi,ad4030: Add ADAQ4216 and ADAQ4224
ADAQ4216 and ADAQ4224 are similar to AD4030 except that ADAQ devices have a
PGA (programmable gain amplifier) that scales the input signal prior to it
reaching the ADC inputs. The PGA is controlled through a couple of pins (A0
and A1) that set one of four possible signal gain configurations.
Signed-off-by: Marcelo Schmitt <marcelo.schmitt@...log.com>
---
Change log v2 -> v3
- PGA gain now described in decibels.
The PGA gain is not going to fit well as a channel property because it may
affect more than one channel as in AD7191.
https://www.analog.com/media/en/technical-documentation/data-sheets/AD7191.pdf
I consulted a very trustworthy source [1, 2] and learned that describing signal
gains in decibels is a common practice. I now think it would be ideal to describe
these PGA and PGA-like gains with properties in decibel units and this patch
is an attempt of doing so. The only problem with this approach is that we end up
with negative values when the gain is lower than 1 (the signal is attenuated)
and device tree specification doesn't support signed integer types. As the
docs being proposed fail dt_binding_check, I guess I have to nack the patch myself.
Any chance of dt specification eventually support signed integers?
Any suggestions appreciated.
[1] https://en.wikipedia.org/wiki/Decibel
[2] https://en.wikipedia.org/wiki/Gain_(electronics)
Thanks,
Marcelo
.../bindings/iio/adc/adi,ad4030.yaml | 84 +++++++++++++++++--
1 file changed, 79 insertions(+), 5 deletions(-)
diff --git a/Documentation/devicetree/bindings/iio/adc/adi,ad4030.yaml b/Documentation/devicetree/bindings/iio/adc/adi,ad4030.yaml
index 564b6f67a96e..20462fa6c39d 100644
--- a/Documentation/devicetree/bindings/iio/adc/adi,ad4030.yaml
+++ b/Documentation/devicetree/bindings/iio/adc/adi,ad4030.yaml
@@ -19,6 +19,8 @@ description: |
* https://www.analog.com/media/en/technical-documentation/data-sheets/ad4030-24-4032-24.pdf
* https://www.analog.com/media/en/technical-documentation/data-sheets/ad4630-24_ad4632-24.pdf
* https://www.analog.com/media/en/technical-documentation/data-sheets/ad4630-16-4632-16.pdf
+ * https://www.analog.com/media/en/technical-documentation/data-sheets/adaq4216.pdf
+ * https://www.analog.com/media/en/technical-documentation/data-sheets/adaq4224.pdf
$ref: /schemas/spi/spi-peripheral-props.yaml#
@@ -31,6 +33,8 @@ properties:
- adi,ad4630-24
- adi,ad4632-16
- adi,ad4632-24
+ - adi,adaq4216
+ - adi,adaq4224
reg:
maxItems: 1
@@ -54,6 +58,14 @@ properties:
description:
Internal buffered Reference. Used when ref-supply is not connected.
+ vddh-supply:
+ description:
+ PGIA Positive Power Supply.
+
+ vdd-fda-supply:
+ description:
+ FDA Positive Power Supply.
+
cnv-gpios:
description:
The Convert Input (CNV). It initiates the sampling conversions.
@@ -64,6 +76,26 @@ properties:
The Reset Input (/RST). Used for asynchronous device reset.
maxItems: 1
+ pga-gpios:
+ description:
+ A0 and A1 pins for gain selection. For devices that have PGA configuration
+ input pins, pga-gpios should be defined if adi,gain-milli is absent.
+ minItems: 2
+ maxItems: 2
+
+ adi,pga-gain-db:
+ description: |
+ Should be present if PGA control inputs are pin-strapped. The values
+ specify the rounded decibel gain calculated from the voltage gain.
+ Possible values:
+ -10 (A1=0, A0=0), (1/3 V/V gain)
+ -5 (A1=0, A0=1), (5/9 V/V gain)
+ 7 (A1=1, A0=0), (20/9 V/V gain)
+ 16 (A1=1, A0=1), (20/3 V/V gain)
+ If defined, pga-gpios must be absent.
+ enum: [-10, -5, 7, 16]
+ default: -10
+
pwms:
description: PWM signal connected to the CNV pin.
maxItems: 1
@@ -86,11 +118,33 @@ required:
- vio-supply
- cnv-gpios
-oneOf:
- - required:
- - ref-supply
- - required:
- - refin-supply
+allOf:
+ - oneOf:
+ - required:
+ - ref-supply
+ - required:
+ - refin-supply
+ # ADAQ devices require a gain property to indicate how hardware PGA is set
+ - if:
+ properties:
+ compatible:
+ contains:
+ pattern: ^adi,adaq
+ then:
+ allOf:
+ - required: [vddh-supply, vdd-fda-supply]
+ properties:
+ ref-supply: false
+ - oneOf:
+ - required:
+ - adi,pga-value
+ - required:
+ - pga-gpios
+ else:
+ properties:
+ adi,pga-value: false
+ pga-gpios: false
+
unevaluatedProperties: false
@@ -114,3 +168,23 @@ examples:
reset-gpios = <&gpio0 1 GPIO_ACTIVE_LOW>;
};
};
+ - |
+ #include <dt-bindings/gpio/gpio.h>
+ spi {
+ #address-cells = <1>;
+ #size-cells = <0>;
+
+ adc@0 {
+ compatible = "adi,adaq4216";
+ reg = <0>;
+ spi-max-frequency = <80000000>;
+ vdd-5v-supply = <&supply_5V>;
+ vdd-1v8-supply = <&supply_1_8V>;
+ vio-supply = <&supply_1_8V>;
+ ref-supply = <&supply_5V>;
+ cnv-gpios = <&gpio0 0 GPIO_ACTIVE_HIGH>;
+ reset-gpios = <&gpio0 1 GPIO_ACTIVE_LOW>;
+ adi,pga-gain-db = <-5>;
+ };
+ };
+...
--
2.39.2
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