How to make use of IrDA

The purpose of this document is to get the IrDA hardware in your ThinkPad operational, setting up communication to other devices is not covered. However, the external links section can prove useful for this.

Serial IR (SIR)

SIR is limited to serial datarates up to 115.2Kb/s

On modern distributions all configuration might be taken care of automatically by starting the irda service # service irda start. If not try the following;

To use it, run # irattach /dev/ttyS1 -s; modprobe ircomm-tty

Then turn on your IrDA-capable device and put it within range, and point your software (e.g., minicom) to /dev/irda0.

Kernel configuration

Edit /etc/modprobe.conf and add the following lines

alias tty-ldisc-11 irtty-sir
alias char-major-161 ircomm-tty

Fast IR (FIR)

FIR is the preferred mode of IrDA operation and operates at a maximum bandwidth of 4 Mbps

On modern distributions this should all be automatically handled by simply starting the idra service # service irda start. If not try the following;

Kernel configuration

Edit /etc/modprobe.conf and add the following lines

alias irda0 nsc-ircc

Make sure that setserial is in right directory (e.g not in /usr/bin/setserial).After that if irdadump still gives nothing try:

echo 1 > /proc/sys/net/irda/discovery

Known problems

• If you read something like "ttyS1: LSR safety check engaged!" and "irattach: tcgetattr: Input/output error" in the system log, try limiting the FIR max baud rate (echo 57600 > /proc/sys/net/irda/max_baud_rate). This did the trick for me when I was trying to synchronize my Ericsson T39m with my Thinkpad R51 (multisync, evolution-2.8, KDE 3.5.5, openSUSE 10.2).

Some other things you might want to do with IrDA

• add fast PPP support:

# modprobe irnet

• if needed, limit further the size of the transmit window

# echo 1 > /proc/sys/net/irda/max_tx_window

• set the connection speed to 4Mbit in FIR mode:

# echo 4000000 > /proc/sys/net/irda/max_baud_rate

LIRC and IrDA

LIRC allows the use of infrared remote controls with Linux. Usually, IrDA ports are not compatible with LIRC, but you may have luck using lirc_sir, as follows;

Configuring lirc_sir

Go into your BIOS setup, and ensure that Infrared is fully enabled and that resources are assigned. I suggest using IO 2f8 and IRQ 3.

Boot into Linux, and first ensure the setserial program is installed. Running # /bin/setserial /dev/ttyS1 should return at this point:

/dev/ttyS1, UART: undefined, Port: 0x02f8, IRQ: 3

If setserial cannot be found, install the setserial package with your distributions package management software

Then create a file /etc/modprobe.d/lirc.conf with the following content:

# prevent nsc_ircc from loading (blacklist might not be enough)
blacklist nsc_ircc
install nsc_ircc /bin/true
# pass options to lirc_sir to load it on ttyS1
options lirc_sir io=0x2f8 irq=3
# ensure serial resources are cleared before loading lirc_sir
# not doing so can result in a device busy error, or can even hang your system
install lirc_sir /bin/setserial /dev/ttyS1 uart none port 0 irq 0; /sbin/modprobe --ignore-install lirc_sir

At this point it is best to reboot, to ensure that nsc_ircc was never loaded. Several things can go wrong if the steps are not followed accurately. You might get an error when loading lirc_sir that the device is busy, or your system may even hang.

Now do a # modprobe lirc_sir and check # dmesg output. You should see something like this:

lirc_dev: IR Remote Control driver registered, major 61
lirc_dev: lirc_register_plugin: sample_rate: 0
lirc_sir: I/O port 0x02f8, IRQ 3.
lirc_sir: Installed.

Configuring LIRC

If you did not yet install LIRC, then do so now using your distributions package management system.

Make sure your /etc/lirc/hardware.conf looks like this:

REMOTE="SIR IrDA (built-in IR ports)"
REMOTE_MODULES="lirc_dev lirc_sir"
REMOTE_DRIVER=""
REMOTE_DEVICE="/dev/lirc0"
REMOTE_LIRCD_CONF="generic/devinput.conf"
REMOTE_LIRCD_ARGS=""
TRANSMITTER="None"
TRANSMITTER_MODULES=""
TRANSMITTER_DRIVER=""
TRANSMITTER_DEVICE=""
TRANSMITTER_LIRCD_CONF=""
TRANSMITTER_LIRCD_ARGS=""
START_LIRCD="true"
START_LIRCMD=""
LOAD_MODULES=""
LIRCMD_CONF=""
FORCE_NONINTERACTIVE_RECONFIGURATION="false"

After this, start (or re-start) the lirc daemon, and set it to automatically start on bootup. The way you do this varies depending on your distribution.

Starting lircd on Ubuntu

# service lirc restart
# update-rc.d lirc defaults

Starting lircd on Fedora

# service lircd restart
# chkconfig lircd on

Testing LIRC

Now we are ready to test if we can receive IR data from a remote control.

Try running # irrecord -d /dev/lirc0 foo and follow the onscreen instructions. When asked keep a button on a remote pressed while pointing at the ThinkPad IR port and you should see dots appear.

You are now able to start configuring LIRC for your specific remote control, which you can then use to control applications like mplayer, xine, mythtv or boxee.

Configuring remote controls is out of scope for this document and you should check the LIRC website for detailed instructions.

External Sources

• Linux-IrDA Project (External)
• Linux PCMCIA Project (External)
• tpctl homepage (External)
• Linux Infrared Remote Control (External)