I'm planning to use N900 as light beacon for infrared-camera (e.g. as wiimote's sensor bar replacement). So I'm looking way to just turn infrared led on. Not transmitting any IR-codes.

I made first test with lirc and it's irsend, but it is targeted for IR-signaling, so it is not very suitable as it (maybe with very special config-file).

That little tx led is not enough to illuminate something in the dark . You better try a case mod on your N900 with a separated circuit for an ir torch . Just like that guy modded n900 case with bigger lens for camera .

It is enough if infrared-camera can see it.

it is probably much stronger than any of those cheap wii wireless sensor bars
althou two candles still give the best results

That camera sees it because is oriented face to face and at few meters distance it will see it like a white dot . You better think about making a torchlight that could illuminate your whole room with infrared light so you will be able to record anything with your camera .

I agree, the IRED is not going to illuminate much.
It is not designed for this purpose.

My opening post was too vague and general. I'm planning to use N900 as Wiimote's sensor bar. (Sensor bar is bold name for 12 infrared leds). I have used two candles, but they emits too much visible light when playing/surfing/watching on dark room. And they are not safe when there are children and animals running on the same room. Self made battery+IR-led would work but I'm not handy to make it nice looking. (I almost bought wii wireless sensor bar, but seller didn't know how often battery must be changed).

And I'm Maemo-hacker so I'm looking software solution

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With lirc and endless bash loop I can blink IR-led forever. With one N900 this is enough for wiimote to work (under Ubuntu and open source driver it needs only one led), but it lags/jitters (I think it is because of blinking).

I also test with two N900's side by side, but they are not blinking in same sync, so mouse cursor is continously waving/jumping left to rigth (=not usable).

The dev of Pierogi is the man to ask about this.
Not seen him about for a while tho.

Thanks, documentation of Pierogi: Light led for 999ms: echo 999 > /dev/lirc0
999 is biggest it accepts. Next step would be tuning driver: http://svn.jacekowski.org/host_mode/...rc/lirc_rx51.c

So far this is my best:
(And then it uses continuously 4-5% CPU)

When looking trough another N900's camera there aren't blinking at all.

[EDIT]
Simple modification to the driver:
So the value is totally skipped (it must still be in range[100,999]). Led will be then ON ~3.5 minutes (which is not INT_MAX), wrap it inside bash-loop.

If echo is stopped (ctrl+c) led is dimmed OFF.

When infrared is in use, device can't go deep sleep states, so bash loop is not heavy addition.
[/EDIT]

Can i record lightless with infrared with n900 camera ? Are infrared torches available what about a tiny infrared module on back of n900?
If this can happen then lets sue estel to put one on his mod