Copernicus | # 1 | 2012-02-24, 17:06 | Report

Question for N900 hardware experts: is there any way to control the brightness of the infrared LED? I'm working on a program that uses infrared (Pierogi), and it appears that the brightness of the LED can vary somewhat between N900s. I don't see any brightness controls in the lirc_rx51 device driver, but maybe there is some other mechanism to adjust it? Thanks!

Mike Fila | # 2 | 2012-02-27, 04:56 | Report

iirc the ir port was tied in some way to the kernel, maybe the use of a different kernel like kp could affect it's output.

ajack | # 3 | 2012-02-27, 07:54 | Report

@Copernicus: May I suggest you ask Pali!

sulu | # 4 | 2012-02-27, 08:17 | Report

Just a wild guess (I don't have my N900 here atm):
Have a look at:IF there are any devices listed, one of them MIGHT be the IR LED.
If so you should find a file called brightness which accepts values of 0-255.
Assuming the LED supports different brightness levels (most of them only switch on and off) you can check the result with any digital camera (photo, video, webcam) pointing at the N900's IR emitter since their sensors partially cover the IR spectrum.

reinob | # 5 | 2012-02-27, 12:40 | Report

@sulu,

Unfortunately I only see the R/G/B, the keyboard leds and the vibrator.. so no IR there

Copernicus | # 6 | 2012-02-27, 18:22 | Report

Hey, poking around in the rest of the /sys directory turned up a /sys/devices/platform/lirc_rx51 directory. I have no clue what the contents signify, but it even has a subdirectory called "power" (although it contains just one file called "wakeup", and that looks empty).

I guess I should ask, might there be any documentation around for any of this?

blue_led | # 7 | 2012-02-27, 23:02 | Report

CIR output is PWM type so there is no brightness control, just only on ( maximum ) and off
but between "always on" and off state can be a lot of average brightness values.

from datasheet :
• Transmit mode only (receive mode is not supported)
• Free data format (supports any remote-control private standards)
• Selectable bit rate
• Configurable carrier frequency
• 1/2, 5/12, 1/3, or 1/4 carrier duty cycle

dani846 | # 8 | 2012-02-28, 19:48 | Report

please come up with something soon guys.people like me,who don't wanna mess around with their lovely N900s so much,would all be very grateful.Pierogi is a great programme,but the fault lies in my mobile phone.The Infra red LED brightness is very low.There HAS to be a way to adjust this somehow.its an open challenge to all you good people who're good at crackin' stuff.cheers people.

davdav | # 9 | 2012-02-29, 09:09 | Report

just an idea
why we dont connect an infrared usb chip to the n900 via hen
and make pierogi transmit via it ?

Copernicus | # 10 | 2012-02-29, 13:37 | Report

Actually, make it a transmitter and a receiver, and I could turn the N900 into a "learning" remote. (And it might be useful for the N9 too, if it has USB host mode.)

I'm not a hardware guy, so I don't really do this sort of thing, but I think it'd be easy to rework the Pierogi back-end to tie it to other IR devices...