ADC device binding
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There are no mandatory properties for ADC. However, if Voltage info is required,
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then there are two options:
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- use microvolts constraint or
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- use regulator phandle to enable/read supply's Voltage
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Properties and constraints:
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*optional and always checked, Voltage polarity info:
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- vdd-polarity-negative: positive reference Voltage has a negative polarity
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- vss-polarity-negative: negative reference Voltage has a negative polarity
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Chose one option, for each supply (Vdd/Vss):
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*optional and always checked, supply Voltage constants:
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- vdd-supply: phandle to Vdd regulator's node
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- vss-supply: phandle to Vss regulator's node
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*optional and checked only if the above corresponding, doesn't exist:
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- vdd-microvolts: positive reference Voltage value [uV]
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- vss-microvolts: negative reference Voltage value [uV]
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Example with constant 'Vdd' value:
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adc@1000000 {
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compatible = "some-adc";
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reg = <0xaabb000 0x100>;
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status = "enabled";
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vdd-microvolts = <1800000>;
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};
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Example of supply phandle usage, for the ADC's VDD/VSS references as below:
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_______ _______
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|Sandbox| |Sandbox|
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: PMIC : : ADC :
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. . . .
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| | (Vdd) | AIN0|-->
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| BUCK2|-------|VDDref |
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| (3.3V)| _|VSSref |
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|_______| | |_______|
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_|_
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For the above PMIC, the node can be defined as follows:
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sandbox_pmic {
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compatible = "sandbox,pmic";
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...
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buck2: buck2 {
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regulator-name = "SUPPLY_3.3V";
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regulator-min-microvolt = <3300000>;
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regulator-max-microvolt = <3300000>;
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};
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...
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};
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For the above ADC, the node can be defined as follows:
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adc@0 {
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compatible = "sandbox,adc";
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vdd-supply = <&buck2>;
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vss-microvolts = <0>;
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};
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The ADC uclass code, will enable the supply before start of the conversion,
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but it will not configure the regulator settings.
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