3.1. Starting the IrDA Stack

There are three sorts of low level drivers: SIR, FIR and dongle.

3.1.1. Standard InfraRed - SIR

Try to find out which serial port is used by the IR device. You may do so by watching the output of dmesg. If serial support is modularized do an modprobe serial first. Look for an entry like:
Serial driver version 4.25 with no serial options enabled ttyS00 at 0x03f8 (irq = 4) is a 16550A #first serial port /dev/ttyS0 ttyS01 at 0x3000 (irq = 10) is a 16550A #e.g. infrared port ttyS02 at 0x0300 (irq = 3) is a 16550A #e.g. PCMCIA modem port
If this is not the case, you either don't have infrared support enabled in the BIOS or the SIR mode of your infrared device is not detected by the kernel. Currently I know only two laptop models with this effect, the HP OmniBook 800 and the Toshiba Libretto models. I am not sure whether PnP support effects the detection of the IR port. If you are unsure try it out and let me know the results. Maybe you can use FIR mode if SIR doesn't work.

In some situations you may have to use setserial /dev/ttyS<0-2> port 0xNNNN irq M to set the values for your infrared serial port, especially if the infrared port is a separate serial line. You usually don't need to change the values! For further information look into the FAQ section below.
If you don't use kerneld or kmod insert the irda module with modprobe irda.
Do lsmod. It should show the modules irda and irtty now.
A look into /var/log/messages should show the entry "Serial connection established" now.

Give irattach some time, e.g. seven seconds, to detect other IR devices. Then watch the output from the kernel that you will hopefully get in /var/log/messages. It should look like the following (I removed some lines, which were not related to Linux/IrDA):
Jan 2 12:57:26 japh kernel: ttyS00 at 0x03f8 (irq = 4) is a 16550A Jan 2 12:57:26 japh kernel: ttyS02 at 0x03e8 (irq = 4) is a 16550A Jan 2 12:57:26 japh kernel: Linux Support for the IrDA (tm) protocols (Dag Bra ttli) Jan 2 12:59:09 japh syslog: executing: 'echo 1 > /proc/sys/net/irda/discovery' Jan 2 12:59:09 japh syslog: Setting discovery to 1 exited with status 1 Jan 2 12:59:09 japh syslog: + 0.1 Fri Jul 25 11:45:26 1997 Dag Brattli Jan 2 12:59:09 japh syslog: + 0.1 Fri Jul 25 11:45:26 1997 Dag Brattli Jan 2 12:59:09 japh syslog: Serial connection established. Jan 2 12:59:09 japh kernel: IrDA irda_device irda0 registered. Jan 2 13:01:22 japh syslog: executing: './drivers start ' Jan 2 13:01:22 japh syslog: Serial connection established. Jan 2 13:01:42 japh syslogd: Printing partial message Jan 2 13:01:42 japh 0.1 Fri Jul 25 11:45:26 1997 Dag Brattli Jan 2 13:02:49 japh kernel: IrDA Discovered: japh Jan 2 13:02:49 japh kernel: Services: Computer

Even more information you can get with cat /proc/net/irda/discovery .

3.1.2. Fast InfraRed - FIR

The IrDA(TM) standard knows three kinds of speeds:

SIR = Standard IrDA, up to 115kbps IrDA,
MIR = Medium Speed IrDA,
FIR = Fast IrDA (4Mbps),
VFIR = Very Fast IrDA(16Mbps), seems to become a future standard

Up to 115.200bps (SIR) many (probably all) infrared controllers work like a serial port and use a RZI (return to zero, inverted) modulation. Not every infrared controller supports 4Mps (FIR), up to 4Mbps they have to use 4PPM (4 pulse position) modulation technique. A list of supported FIR chips is included in /usr/src/linux/drivers/net/irda/Kconfig. You may start the FIR service by loading the according module. Linux/IrDA will probe your hardware then. More drivers are under development.

So what speeds can you expect? Using SIR, you should be able to get about 10 Kbytes/s. Using FIR (4Mbps) you can get over 300 Kbytes/s (if you are lucky).

3.1.3. Dongle Connection - Infrared Adapters for the Serial Port

A survey of supported dongles is included in /usr/src/linux/drivers/net/irda/Kconfig.

Dag Brattli wrote (modified by wh): "To use dongles you have to do something like this:
modprobe tekram # or esi or actisys irattach -d tekram # or -d esi or -d actisys
modprobe is not necessary, if /etc/modules.conf is correct. As you can see, you must still use the -d option with irattach since it is possible to have two serial ports using different dongles at the same time (so the tty you are binding must know which dongle it is supposed to use). So if you have two dongles and two serial ports, you could do something like this:
modprobe tekram modprobe esi irattach /dev/ttyS0 -d esi & irattach /dev/ttyS1 -d tekram &
PS: I would not try to turn the two dongles against each other, since I really don't know how the stack would react :-) ... Since I don't have any of these new ACTiSYS 220L+ dongles, I'm not able to test it. Since the new dongle has support for one extra speed (38400bps), you must specify the dongles differently with irattach so that the kernel knows which dongle you are using (and what QoS can be used):
irattach /dev/ttyS0 -d actisys # for the 220L dongle irattach /dev/ttyS0 -d actisys+ # for the 220L+ dongle
The current implementation of dongle support does not have any state associated with it, so its not possible to use both ACTiSYS dongles (220L and 220L+) at the same time (connected to two serial ports) for now. If someone needs to be able to do so, please mail me (Dag Brattli) and I will think about it!"

Note: When I tried to use an infrared modem (Swissmod 56Ki, manufactured by Telelink AG) connected to my laptop (IrDA works with Microsoft-Window$95 only, due to non-standard hardware) I had to remove the infrared support in the BIOS to get it working!

Dag Brattli: "It is now possible to use irport instead of irtty! I have moved all the dongle stuff out of irtty and into irda_device, so it will also be possible to attach dongles to irport. Need however to make a small user-space utility dongle_attach that can be used to attach dongles to a specific driver instance. BTW: irattach is still working as before, and you will not notice the difference even when attaching dongles to irtty (I've just redirected the dongle ioctl to irda_device). Irport may be interesting since you avoid one software interrupt (bh) level, and it's also forced to work in half duplex mode so you don't get any echo if the irda port itself don't have echo-cancellation (Girbil dongle and HP-4000 etc) ... To use it, you must supply the parameters to modprobe like this: modprobe irport io=0x3f8 irq=4, or whichever values you use. You can also add these parameters to /etc/modprobe.conf (kernel 2.6) or /etc/modules.conf (kernel 2.4) like this: options irport io=0x3f8 irq=4, but then you must remember to do a depmod -a and use modprobe irport instead of modprobe."

Alvin Loh: "Anyone with a ESI 9680C can use both parallax's and ESI's signalling scheme, meaning they can use Parallax's driver with ESI9680C to work. "

3.1.4. Dongle Connection - Infrared Adapters for the USB Port

Not every USB dongle does work. For details see the dedicated chapter below IrDA and USB.

3.1.5. Dongle Connection - Infrared Motherboard Adapter

Support for e.g. the ACTiSYS IR2000 dongle has been implemented.

From James I have this description about setting up the hardware: There are two configurations, a five pin in line connector and a 6 pin DIL (at the end of a 18 pin DIL header). Basically any IrDA compatible transceiver will work (I have a stack of old IRM3001 these are now obselete) you need to hook a capacitor (use a tantalum about ~1uF) between 5V and 0V near the transceiver and then connect everthing else up (RX->RX, TX->TX, 5V->5V, and 0V-0V). If you don't like soldering irons, lots of companies do sell IR modules for the 5 pin connectors that fit into a hole in your case.