142 lines
5.4 KiB
Plaintext
142 lines
5.4 KiB
Plaintext
STMicroelectronics STM32 ADC device
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STM32 ADC is a successive approximation analog-to-digital converter.
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It has several multiplexed input channels. Conversions can be performed
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in single, continuous, scan or discontinuous mode. Result of the ADC is
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stored in a left-aligned or right-aligned 32-bit data register.
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Conversions can be launched in software or using hardware triggers.
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The analog watchdog feature allows the application to detect if the input
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voltage goes beyond the user-defined, higher or lower thresholds.
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Each STM32 ADC block can have up to 3 ADC instances.
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Each instance supports two contexts to manage conversions, each one has its
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own configurable sequence and trigger:
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- regular conversion can be done in sequence, running in background
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- injected conversions have higher priority, and so have the ability to
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interrupt regular conversion sequence (either triggered in SW or HW).
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Regular sequence is resumed, in case it has been interrupted.
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Contents of a stm32 adc root node:
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-----------------------------------
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Required properties:
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- compatible: Should be one of:
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"st,stm32f4-adc-core"
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"st,stm32h7-adc-core"
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"st,stm32mp1-adc-core"
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- reg: Offset and length of the ADC block register set.
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- interrupts: One or more interrupts for ADC block. Some parts like stm32f4
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and stm32h7 share a common ADC interrupt line. stm32mp1 has two separate
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interrupt lines, one for each ADC within ADC block.
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- clocks: Core can use up to two clocks, depending on part used:
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- "adc" clock: for the analog circuitry, common to all ADCs.
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It's required on stm32f4.
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It's optional on stm32h7.
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- "bus" clock: for registers access, common to all ADCs.
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It's not present on stm32f4.
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It's required on stm32h7.
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- clock-names: Must be "adc" and/or "bus" depending on part used.
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- interrupt-controller: Identifies the controller node as interrupt-parent
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- vref-supply: Phandle to the vref input analog reference voltage.
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- #interrupt-cells = <1>;
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- #address-cells = <1>;
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- #size-cells = <0>;
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Optional properties:
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- A pinctrl state named "default" for each ADC channel may be defined to set
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inX ADC pins in mode of operation for analog input on external pin.
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Contents of a stm32 adc child node:
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-----------------------------------
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An ADC block node should contain at least one subnode, representing an
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ADC instance available on the machine.
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Required properties:
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- compatible: Should be one of:
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"st,stm32f4-adc"
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"st,stm32h7-adc"
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"st,stm32mp1-adc"
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- reg: Offset of ADC instance in ADC block (e.g. may be 0x0, 0x100, 0x200).
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- clocks: Input clock private to this ADC instance. It's required only on
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stm32f4, that has per instance clock input for registers access.
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- interrupt-parent: Phandle to the parent interrupt controller.
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- interrupts: IRQ Line for the ADC (e.g. may be 0 for adc@0, 1 for adc@100 or
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2 for adc@200).
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- st,adc-channels: List of single-ended channels muxed for this ADC.
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It can have up to 16 channels on stm32f4 or 20 channels on stm32h7, numbered
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from 0 to 15 or 19 (resp. for in0..in15 or in0..in19).
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- st,adc-diff-channels: List of differential channels muxed for this ADC.
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Depending on part used, some channels can be configured as differential
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instead of single-ended (e.g. stm32h7). List here positive and negative
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inputs pairs as <vinp vinn>, <vinp vinn>,... vinp and vinn are numbered
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from 0 to 19 on stm32h7)
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Note: At least one of "st,adc-channels" or "st,adc-diff-channels" is required.
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Both properties can be used together. Some channels can be used as
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single-ended and some other ones as differential (mixed). But channels
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can't be configured both as single-ended and differential (invalid).
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- #io-channel-cells = <1>: See the IIO bindings section "IIO consumers" in
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Documentation/devicetree/bindings/iio/iio-bindings.txt
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Optional properties:
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- dmas: Phandle to dma channel for this ADC instance.
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See ../../dma/dma.txt for details.
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- dma-names: Must be "rx" when dmas property is being used.
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- assigned-resolution-bits: Resolution (bits) to use for conversions. Must
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match device available resolutions:
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* can be 6, 8, 10 or 12 on stm32f4
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* can be 8, 10, 12, 14 or 16 on stm32h7
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Default is maximum resolution if unset.
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- st,min-sample-time-nsecs: Minimum sampling time in nanoseconds.
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Depending on hardware (board) e.g. high/low analog input source impedance,
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fine tune of ADC sampling time may be recommended.
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This can be either one value or an array that matches 'st,adc-channels' list,
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to set sample time resp. for all channels, or independently for each channel.
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Example:
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adc: adc@40012000 {
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compatible = "st,stm32f4-adc-core";
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reg = <0x40012000 0x400>;
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interrupts = <18>;
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clocks = <&rcc 0 168>;
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clock-names = "adc";
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vref-supply = <®_vref>;
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interrupt-controller;
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pinctrl-names = "default";
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pinctrl-0 = <&adc3_in8_pin>;
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#interrupt-cells = <1>;
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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 = "st,stm32f4-adc";
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#io-channel-cells = <1>;
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reg = <0x0>;
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clocks = <&rcc 0 168>;
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interrupt-parent = <&adc>;
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interrupts = <0>;
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st,adc-channels = <8>;
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dmas = <&dma2 0 0 0x400 0x0>;
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dma-names = "rx";
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assigned-resolution-bits = <8>;
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};
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...
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other adc child nodes follow...
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};
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Example to setup:
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- channel 1 as single-ended
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- channels 2 & 3 as differential (with resp. 6 & 7 negative inputs)
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adc: adc@40022000 {
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compatible = "st,stm32h7-adc-core";
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...
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adc1: adc@0 {
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compatible = "st,stm32h7-adc";
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...
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st,adc-channels = <1>;
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st,adc-diff-channels = <2 6>, <3 7>;
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};
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};
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