LIRC
This article covers setup and usage of LIRC with serial or USB infrared devices.
From the official website:
- LIRC (Linux Infrared Remote Control) is a package that decodes and sends infra-red signals of many (but not all) commonly used remote controls.
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.
- A button on the remote is pressed causing it to transmit an IR or RF signal.
- The signal is received by the receiver connected to the Linux computer.
- The kernel (via the correct module) use presents pulse data from the remote on a device like
/dev/lirc0,/dev/input/eventX,/dev/ttyUSBXor/dev/ttyS0. /usr/bin/lircduses the information from/etc/lirc/lircd.conf.d/foo.confto convert the pulse data into button press information.- Programs that use LIRC translate the button press info from
/usr/bin/lircdinto user-defined actions according to or to program-specific mappings.
Installation
Install the package. If you need audio driver, install .
Configuration
Receiver and transmitter configuration
The driver and/or the device for the LIRC service may need to be specified in order to run properly. Look for messages like these in the journalctl output if the service abruptly stops while running LIRC-dependent programs such as irrecord:
Driver `devinput' not found or not loadable (wrong or missing -U/--plugindir?). readlink() failed for "auto": No such file or directory
Set these in the configuration file and then restart the service.
Serial port
Modern kernel has serial_ir module, which supersedes older lirc_serial driver. It supports even DIY receivers and transmitters, connected to the motherboard's serial port. Install and run:
# setserial /dev/ttyS0 uart none # modprobe serial_ir
After loading serial_ir module, device /dev/lirc0 will be created by kernel. If not, check the journal for any relevant errors. An LIRC configuration example for serial device:
Sound card
Sound card with connected external DIY circuits can be used to receive and transmit IR codes.
audio_alsa driver included in , but supports only reception.
Unmute microphone input with and set enough gain. You can check waveform and gain with . There should be distinguishable square pulses: not flatlined, nor overloaded. Also good demodulated pulses easily perceptible by ear. Note that LIRC and reads positive pulses in right audio channel. Negative pulses will not work.
audio driver included in and supports both reception and transmission. Note, that default latency around 0.02 can cause "Warning: Output underflow" and corrupted transmission - receiver will not respond to it. Try a higher value like 0.05.
Increase sound card output loudness, otherwise LED signal will be weak and range is low. LED flash can be detected with smartphone camera, as it sensitive to infrared wavelengths.
Remote configuration
Directory /etc/lirc/lircd.conf.d/ contains system-wide configuration files for remotes. Each *.conf file corresponds to one device and describes its protocol, scancodes and keycodes. It allows LIRC receive and send signals for specific hardware. These files are not included in package and should be found somewhere or created by user.
Searching for remote configuration
Plenty of configuration files can be found in the LIRC remotes database. Follow the url or use irdb-get(1) to search the database.
An example using to find a configuration file for a "Streamzap" remote:
Once identified, copy the needed .conf to /etc/lirc/lircd.conf.d/ to allow the daemon to initialize support for it.
# cp streamzap.lircd.conf /etc/lirc/lircd.conf.d/
Creating remote configuration
Remote control configurations can be created using , which guides users trough the process. If using a detected remote, invoke it like so:
# irrecord --device=/dev/lirc0 MyRemote
The program will instruct user to begin hitting keys on the remote in an attempt to learn it, ultimately mapping out every button and its corresponding scancode. When finished, save the resulting file to /etc/lirc/lircd.conf.d/foo.conf and proceed. Consider sharing configuration file with others.
Application-specific actions
Bind keycodes to application-specific actions by placing their respective configuration files in which should be created manually if desired, see . This only works for LIRC-aware applications, like MPlayer, VLC, MythTV and (Kodi also supports LIRC but does so in a non-standard way, see Kodi#Using a remote control).
Define these application-specific configurations in separate files and include them in lircrc, like:
include "~/.config/lircrc/mplayer" include "~/.config/lircrc/mythtv" include "~/.config/lircrc/vlc"
Running as a regular user
By default, lircd runs as root. For increased stability and security, upstream recommends running it as a regular user. See Appendix 14 at this link.
User the AUR package for lirc-user-service
lirc-user-serviceAUR is offered which does everything automatically.
Testing
Receiving commands
Run irw(1), point remote to the receiver and press some buttons. Received codes will be printed to stdout.
If gives no output:
- Run mode2 or xmode2 to see if LIRC actually read something from IR sensor, if no - check the hardware
- If mode2 receives pulse data, check the configuration files in
/etc/lirc/lircd.conf.d/for errors
Transmitting commands
List registered remotes (configuration files):
List available codes for the specific device:
Choose discovered device and send command :
$ irsend SEND_ONCE LG_6710CMAP01A KEY_POWER
Troubleshooting
When using Xorg
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:
Do not forget to alter the property according to one shown in Name from output of
$ cat /proc/bus/input/devices | grep -e IR
For example for
Not using Xorg
Blacklist the offending modules by creating to suppress this behavior. An example is provided for the Streamzap remote.
install ir_sharp_decoder /bin/false install ir_xmp_decoder /bin/false install ir_rc5_decoder /bin/false install ir_nec_decoder /bin/false install ir_sony_decoder /bin/false install ir_mce_kbd_decoder /bin/false install ir_jvc_decoder /bin/false install ir_rc6_decoder /bin/false install ir_sanyo_decoder /bin/false
Changing default configuration
Users not getting any output from may have the default configuration in incorrectly setup (or might have been overwritten by an update).
First, check if /dev/lirc0 is present:
$ mode2 --driver default --device /dev/lirc0
Watch the output while pressing buttons on the remote. If output is present, edit changing the driver and device appropriately.
If no output is presented, the task becomes locating the correct driver/device combination. First check what combination lirc detected by default. Run from the v4l-utils package. and check the output. It will look similar to this:
Found /sys/class/rc/rc0/ (/dev/input/event5) with:
Driver ite-cir, table rc-rc6-mce
Supported protocols: unknown other lirc rc-5 jvc sony nec sanyo mce-kbd rc-6 sharp xmp
Enabled protocols: lirc
Extra capabilities: <access denied>
In this case, LIRC automatically detected as the IR device, which uses the driver. Check if this combination is working by running:
$ mode2 --driver devinput --device /dev/input/event5
Now try pressing buttons on the remote. If there is no output, try different driver and device combinations. Once a working combination has been identified, change driver and device in appropriately.
Example
An example configuration for a MCE RC6 compatible receiver: