LIRC
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This article covers setup and usage of LIRC "Linux Infrared Remote Control" with serial or USB infrared devices.
Contents
Overview
LIRC is a daemon that can translate key presses on a supported remote into program specific commands. In this context, the term, "program specific" means that a key press can do different things depending on which program is running and taking commands from LIRC.
The Central Dogma of LIRC
The list below attempts to show the flow of information from the remote to the application using LIRC:
- User hits a button on the remote causing it to transmit an IR or RF signal.
- The signal is received by the receiver connected to the Linux box.
- The kernel (via the correct module) uses
/dev/lirc0
to characterize the pulse-length information from the receiver. -
/usr/bin/lircd
uses the information from/etc/lirc/lircd.conf.d/foo.conf
to convert the pulse-lengths into button press information. - Programs that use LIRC translate the button press info from
/usr/bin/lircd
into user-defined actions according to~/.lircrc
or to program-specific mappings.
Required Files
-
/etc/lirc/lircd.conf.d/foo.conf
- System-level config translating scancodes --> keys. This directory may contain multiple conf files and each one is specific to each remote control/receiver on the system.
Optional Files
Depending on the application using LIRC, the following are optional. For example, mplayer and mythtv use the these files to define key maps and actions. Not every application will need these. kodi for example, uses its own xml files to achieve these mappings.
-
~/.lircrc
- File containing an include statement pointing to each program's lirc map, i.e.,~/.lirc/foo
,~/.lirc/bar
, etc. -
~/.lirc/foo
- User-level config translating of keys --> actions. Is specific to each remote and to application foo.
Installation
Install the lirc package, which is available in the official repositories.
Setup
Some remotes are identified as keyboards and function as such without LIRC providing input as physical key presses. This is problematic and can result in a doubling of commands. Test if this is the case by opening a shell or a text editor, and by pressing buttons on the remote itself. If letters/numbers appear, or if the up/down/left/right arrow keys behave as the up/down/left/right arrow keys on the physical keyboard, a workaround to disable this is required. See, #Remote functions as a keyboard for a solution before continuing.
The LIRC Config File
The definition of scancodes to keymaps is required to allow LIRC to manage a remote. Copy the corresponding conf file into /etc/lirc/lircd.conf.d
to achieve this mapping.
Option 1. Upstream provided config files
Identify which remote/receiver is to be used and see if /usr/share/lirc/configs
contains a pre-built config file for it. Once identified, copy the needed conf to /etc/lirc/lircd.conf.d
to allow the daemon to initialize support for it.
Option 2. User created config files
Users with unsupported hardware will need to either find a config file someone else has created (i.e. google) or create one. Creating one is fairly straightforward using the included /usr/bin/irrecord
program which guides users along the needed process. If using a detected remote, invoke it like so:
irrecord --device=/dev/lirc0 MyRemote
The program will ask users to begin hitting keys on the remote in an attempt to learn it. If all goes well, the user will be prompted to map out each key press to a specific scancode LIRC uses to identify that specific key press. The process should take no more than 10 minutes. When finished, save the resulting file to /etc/lirc/lircd.conf.d/foo.conf
and proceed.
Testing the Remote
Start lircd.service
and enable it to run at boot time/shutdown (highly recommended).
Test the remote using /usr/bin/irw
, which simply echos anything received by LIRC when users push buttons on the remote to stdout.
Example:
$ irw 000000037ff07bfe 00 One mceusb 000000037ff07bfd 00 Two mceusb 000000037ff07bfd 01 Two mceusb 000000037ff07bf2 00 Home mceusb 000000037ff07bf2 01 Home mceusb
If this does not work (irw gives no output): double check your config files in /etc/lirc/lircd.conf.d/ for errors.
Program Specific Configuration
LIRC has the ability to allow for different programs to use the same keypress and result in unique commands. In other words, mplayer and vlc can respond differently to a given key press.
Decide which programs are to use LIRC commands. Common programs include: mplayer, mythtv, totem, vlc, and kodi.
Users should create the expected files showing LIRC where the various program-specific maps reside:
$ mkdir ~/.lirc $ touch ~/.lircrc
- Populate
~/.lirc
with the program specific config files named for each program.
Example:
$ ls ~/.lirc mplayer mythtv vlc
- Edit
~/.lircrc
to contain an include statement pointing to~/.lirc/foo
and repeat for each program that is to be controlled by LIRC.
Example:
~/.lircrc
include "~/.lirc/mplayer" include "~/.lirc/mythtv" include "~/.lirc/vlc"
Troubleshooting
Remote functions as a keyboard
Xorg detects some remotes, such as the Streamzap USB PC Remote, as a Human Interface Device (HID) which means some or all of the keys will show up as key strokes as if entered from the physical keyboard. This behavior will present problems if LIRC is to be used to manage the device. To disable, create the following file and restart X:
/etc/X11/xorg.conf.d/90-streamzap.conf
Section "InputClass" Identifier "Ignore Streamzap IR" MatchProduct "Streamzap" MatchIsKeyboard "true" Option "Ignore" "true" EndSection
Do not forget to alter the MatchProduct
property according to one shown in Name
from output of
$ cat /proc/bus/input/devices | grep -e IR
For example WinFast
for N: Name="cx88 IR (WinFast DTV2000 H rev."