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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 <mazziesaccount@gmail.com> Reviewed-by: Conor Dooley <conor.dooley@microchip.com> Link: https://patch.msgid.link/2a4c65ee35cb79c6b29dbc59cfd9bc7d615a08ac.1744022065.git.mazziesaccount@gmail.com Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
69 lines
1.5 KiB
YAML
69 lines
1.5 KiB
YAML
# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
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%YAML 1.2
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---
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$id: http://devicetree.org/schemas/iio/adc/rohm,bd79104.yaml#
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$schema: http://devicetree.org/meta-schemas/core.yaml#
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title: ROHM Semiconductor BD79104 ADC
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maintainers:
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- Matti Vaittinen <mazziesaccount@gmail.com>
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description: |
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12 bit SPI ADC with 8 channels.
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properties:
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compatible:
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const: rohm,bd79104
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reg:
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maxItems: 1
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vdd-supply: true
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iovdd-supply: true
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# The component data-sheet says the frequency is 20M. I, however, found
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# that the ROHM evaluation board BD79104FV-EVK-001 had problems with 20M.
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# I have successfully used it with 4M. My _assumption_ is that this is not
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# the limitation of the component itself, but a limitation of the EVK.
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spi-max-frequency:
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maximum: 20000000
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"#io-channel-cells":
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const: 1
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spi-cpha: true
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spi-cpol: true
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required:
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- compatible
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- reg
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- vdd-supply
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- iovdd-supply
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- spi-cpha
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- spi-cpol
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allOf:
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- $ref: /schemas/spi/spi-peripheral-props.yaml#
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unevaluatedProperties: false
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examples:
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- |
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#include <dt-bindings/interrupt-controller/irq.h>
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spi {
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#address-cells = <1>;
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#size-cells = <0>;
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adc@0 {
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compatible = "rohm,bd79104";
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reg = <0>;
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vdd-supply = <&vdd_supply>;
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iovdd-supply = <&iovdd_supply>;
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spi-max-frequency = <4000000>;
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spi-cpha;
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spi-cpol;
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#io-channel-cells = <1>;
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};
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};
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...
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