# Linux Input Binding
This binding allows to you use a keyboard to control your openHAB instance. It works by exposing all keys on the keyboard as channels.
As indicated by the name of the binding this only works on Linux. (It uses the libevdev library the receive events from the kernel) As all the low-level protocols are handled by the Linux kernel it works for any kind of keyboard; USB, Bluetooth, etc.
# Supported Things
All keyboards supported by the Linux kernel.
# Discovery
The discovery feature finds all cold- or hotplugged keyboards by watching the
/dev/input/ directory.
The discovery uses the numeric ids for the devices. (/dev/input/event0,
etc...).
This can lead to issues when the kernel autodiscovery enumerates devices in a
nondeterministic order. This problem can be circumvented by using predictable
device names in /dev/input/by-id/ or /dev/input/by-path/ or by using Udev
facilities (out of scope for this document).
# Binding Configuration
openHAB will need rights on the /dev/input/ files it is supposed to access.
This can be implemented by group-memberships, (custom) initscripts or Udev
rules.
The exact configurations possible depend on your system (out of scope for this document).
The libevdev library has to be installed for this plugin to work.
(It should be available via your package manager)
# Thing Configuration
Each thing has has to be explicitly enabled after it is configured. While it is enabled all of the generated events will be consumed by openHAB. The device will not be available for normal input processing!
# Static configuration
# Thing
Thing linuxinput:input-device:some-keyboard [ enable=true, path="/dev/input/eventXX" ]
# Item
Contact SomeButton "Some Button" { channel="linuxinput:input-device:event17:keypresses#KEY_0" }
# Channels
Each Thing provides multiple channels
- A
keychannel that aggregates all events. - Per physical key channels.
# Events
The following happens when pressing and releasing a key:
# Press
- State of global key channel updated to new key.
- State of per-key channel updated to
"CLOSED". - Global key channel triggered with the current key name.
- Per-key channel triggered with
"PRESSED"". - State of global key channel updated to
""(Empty string)
# Release
- State of per-key channel updated to
"OPEN" - Per-key channel triggered with
"RELEASED"
# Rationale
Channel states are updated first to allow rules triggered by channel triggers to access the new state.
# Channel names
The binding tries to translate the numeric event codes to their symbolic names; KEY_1, KEY_A, KEY_BACKSPACE etc.
If the currently installed version of libevdev does not know the symbolic name of a key, the numeric value is used. Please note that future versions of libevdev may start translating the symbolic names.
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