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https://github.com/AsahiLinux/u-boot
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68 lines
2 KiB
Text
68 lines
2 KiB
Text
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ADC attached resistor ladder buttons
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------------------------------------
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Required properties:
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- compatible: "adc-keys"
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- io-channels: Phandle to an ADC channel
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- io-channel-names = "buttons";
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- keyup-threshold-microvolt: Voltage above or equal to which all the keys are
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considered up.
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Optional properties:
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- poll-interval: Poll interval time in milliseconds
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- autorepeat: Boolean, Enable auto repeat feature of Linux input
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subsystem.
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Each button (key) is represented as a sub-node of "adc-keys":
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Required subnode-properties:
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- label: Descriptive name of the key.
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- linux,code: Keycode to emit.
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- press-threshold-microvolt: voltage above or equal to which this key is
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considered pressed.
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No two values of press-threshold-microvolt may be the same.
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All values of press-threshold-microvolt must be less than
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keyup-threshold-microvolt.
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Example:
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#include <dt-bindings/input/input.h>
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adc-keys {
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compatible = "adc-keys";
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io-channels = <&lradc 0>;
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io-channel-names = "buttons";
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keyup-threshold-microvolt = <2000000>;
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button-up {
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label = "Volume Up";
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linux,code = <KEY_VOLUMEUP>;
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press-threshold-microvolt = <1500000>;
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};
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button-down {
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label = "Volume Down";
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linux,code = <KEY_VOLUMEDOWN>;
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press-threshold-microvolt = <1000000>;
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};
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button-enter {
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label = "Enter";
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linux,code = <KEY_ENTER>;
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press-threshold-microvolt = <500000>;
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};
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};
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+--------------------------------+------------------------+
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| 2.000.000 <= value | no key pressed |
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+--------------------------------+------------------------+
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| 1.500.000 <= value < 2.000.000 | KEY_VOLUMEUP pressed |
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+--------------------------------+------------------------+
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| 1.000.000 <= value < 1.500.000 | KEY_VOLUMEDOWN pressed |
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+--------------------------------+------------------------+
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| 500.000 <= value < 1.000.000 | KEY_ENTER pressed |
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+--------------------------------+------------------------+
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| value < 500.000 | no key pressed |
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+--------------------------------+------------------------+
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