| Marek Szyprowski | 32238f0 | 2021-02-18 11:33:14 +0100 | [diff] [blame] | 1 | ADC attached resistor ladder buttons |
| 2 | ------------------------------------ |
| 3 | |
| 4 | Required properties: |
| 5 | - compatible: "adc-keys" |
| 6 | - io-channels: Phandle to an ADC channel |
| 7 | - io-channel-names = "buttons"; |
| 8 | - keyup-threshold-microvolt: Voltage above or equal to which all the keys are |
| 9 | considered up. |
| 10 | |
| 11 | Optional properties: |
| 12 | - poll-interval: Poll interval time in milliseconds |
| 13 | - autorepeat: Boolean, Enable auto repeat feature of Linux input |
| 14 | subsystem. |
| 15 | |
| 16 | Each button (key) is represented as a sub-node of "adc-keys": |
| 17 | |
| 18 | Required subnode-properties: |
| 19 | - label: Descriptive name of the key. |
| 20 | - linux,code: Keycode to emit. |
| 21 | - press-threshold-microvolt: voltage above or equal to which this key is |
| 22 | considered pressed. |
| 23 | |
| 24 | No two values of press-threshold-microvolt may be the same. |
| 25 | All values of press-threshold-microvolt must be less than |
| 26 | keyup-threshold-microvolt. |
| 27 | |
| 28 | Example: |
| 29 | |
| 30 | #include <dt-bindings/input/input.h> |
| 31 | |
| 32 | adc-keys { |
| 33 | compatible = "adc-keys"; |
| 34 | io-channels = <&lradc 0>; |
| 35 | io-channel-names = "buttons"; |
| 36 | keyup-threshold-microvolt = <2000000>; |
| 37 | |
| 38 | button-up { |
| 39 | label = "Volume Up"; |
| 40 | linux,code = <KEY_VOLUMEUP>; |
| 41 | press-threshold-microvolt = <1500000>; |
| 42 | }; |
| 43 | |
| 44 | button-down { |
| 45 | label = "Volume Down"; |
| 46 | linux,code = <KEY_VOLUMEDOWN>; |
| 47 | press-threshold-microvolt = <1000000>; |
| 48 | }; |
| 49 | |
| 50 | button-enter { |
| 51 | label = "Enter"; |
| 52 | linux,code = <KEY_ENTER>; |
| 53 | press-threshold-microvolt = <500000>; |
| 54 | }; |
| 55 | }; |
| 56 | |
| 57 | +--------------------------------+------------------------+ |
| 58 | | 2.000.000 <= value | no key pressed | |
| 59 | +--------------------------------+------------------------+ |
| 60 | | 1.500.000 <= value < 2.000.000 | KEY_VOLUMEUP pressed | |
| 61 | +--------------------------------+------------------------+ |
| 62 | | 1.000.000 <= value < 1.500.000 | KEY_VOLUMEDOWN pressed | |
| 63 | +--------------------------------+------------------------+ |
| 64 | | 500.000 <= value < 1.000.000 | KEY_ENTER pressed | |
| 65 | +--------------------------------+------------------------+ |
| 66 | | value < 500.000 | no key pressed | |
| 67 | +--------------------------------+------------------------+ |