From 085831cfce61fc5e326f31eec1976414e71f4c17 Mon Sep 17 00:00:00 2001 From: Matti Vaittinen Date: Mon, 7 Apr 2025 13:45:06 +0300 Subject: [PATCH] dt-bindings: ROHM BD79104 ADC The ROHM BD79104 is a 12-bit, 8-channel ADC with two power supply pins, connected to SPI. It's worth noting the IC requires SPI MODE 3, (CPHA = 1, CPOL = 1). I used an evaluation board "BD79104FV-EVK-001" from ROHM. With this board I had problems to have things working correctly with higher SPI clock frequencies. I didn't do thorough testing for maximum frequency though. First attempt was 40M, then 20M and finally 4M. With 20M it seemed as if the read values were shifted by 1 bit. With 4M it worked fine. The component data-sheet is not exact what comes to the maximum SPI frequency. It says SPI frequency is 20M - "unless othervice specified". Additionally, it says that maximum sampling rate is 1Mhz, and since reading a sample requires writing the channel (16 bits) and reading data (16 bits) - we get some upper limit from this. >From the "frequency is 20M, unless othervice specified" I picked the maximum frequency 20M - and did assumption that my problems with 20M weren't related to the BD79104 - but to the evaluation board "BD79104FV-EVK-001". Add bindings for the ROHM BD79104 ADC. Signed-off-by: Matti Vaittinen Reviewed-by: Conor Dooley Link: https://patch.msgid.link/2a4c65ee35cb79c6b29dbc59cfd9bc7d615a08ac.1744022065.git.mazziesaccount@gmail.com Signed-off-by: Jonathan Cameron --- .../bindings/iio/adc/rohm,bd79104.yaml | 69 +++++++++++++++++++ 1 file changed, 69 insertions(+) create mode 100644 Documentation/devicetree/bindings/iio/adc/rohm,bd79104.yaml diff --git a/Documentation/devicetree/bindings/iio/adc/rohm,bd79104.yaml b/Documentation/devicetree/bindings/iio/adc/rohm,bd79104.yaml new file mode 100644 index 0000000000000..2a8ad4fdfc6b1 --- /dev/null +++ b/Documentation/devicetree/bindings/iio/adc/rohm,bd79104.yaml @@ -0,0 +1,69 @@ +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause) +%YAML 1.2 +--- +$id: http://devicetree.org/schemas/iio/adc/rohm,bd79104.yaml# +$schema: http://devicetree.org/meta-schemas/core.yaml# + +title: ROHM Semiconductor BD79104 ADC + +maintainers: + - Matti Vaittinen + +description: | + 12 bit SPI ADC with 8 channels. + +properties: + compatible: + const: rohm,bd79104 + + reg: + maxItems: 1 + + vdd-supply: true + iovdd-supply: true + +# The component data-sheet says the frequency is 20M. I, however, found +# that the ROHM evaluation board BD79104FV-EVK-001 had problems with 20M. +# I have successfully used it with 4M. My _assumption_ is that this is not +# the limitation of the component itself, but a limitation of the EVK. + spi-max-frequency: + maximum: 20000000 + + "#io-channel-cells": + const: 1 + + spi-cpha: true + spi-cpol: true + +required: + - compatible + - reg + - vdd-supply + - iovdd-supply + - spi-cpha + - spi-cpol + +allOf: + - $ref: /schemas/spi/spi-peripheral-props.yaml# + +unevaluatedProperties: false + +examples: + - | + #include + spi { + #address-cells = <1>; + #size-cells = <0>; + + adc@0 { + compatible = "rohm,bd79104"; + reg = <0>; + vdd-supply = <&vdd_supply>; + iovdd-supply = <&iovdd_supply>; + spi-max-frequency = <4000000>; + spi-cpha; + spi-cpol; + #io-channel-cells = <1>; + }; + }; +... -- 2.47.2