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