Well, years ago I bought a little irDA adaptor for USB.
I guess it was also possible to make own yourself using the RS232 and a some photo diodes/transistors or so.
Wait, here's a tutorial..
http://www.meblin.karoo.net/IrDAbuild.htm
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If I understand correctly, there's supposed to be a 5pin header on the motherboard for irDA.
Maybe it can also connected (with some modifications) to the serial port headers ?
From a software point of view, it connects to serial ports, anyway..
Edit: There's also a kit beeing sold.
The schematics and required parts are mentioned here: https://www.voti.nl/ir-2/index_1.html
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Edit: Never mind. 🙁 Seems like that this one isn't irDA compatible yet.
Maybe in the future the LIRC software will support it.
http://www.lirc.org/irda.html
Edit: Another edit, sorry. Fixed some typos, too.
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