Ideas to hack NC4200 LCD ambient light sensor?

Hi,

I have the business HP NC4200 laptop, which has a great ambient light sensor.

I generally disable it, because the screen gets too dim in nearly every situation, in my opinion.

But I noticed something strange. When the ambient light sensor is disabled, it is possible to adjust the screen's brightness at your own taste. This is logical.

But you cannot get the screen to 100% brightness. The only way to get 100% brightness is to actually ACTIVATE the ambient light sensor and get a very bright light source right into the ambient light sensor. Then the screen gets MUCH brighter.

Don't bother saying, I've used the Fn keys to control the LCD brightness. That's they way it works.

I use notebook hardware control, and with the nc4200 I can monitor the power consumption of the system in Watts. When the screen is maxed out without the ambient light sensor (which is approx. 50% of the LCD brightness, in reality) the system consumes around 10 watts of power.

When I max the screen with the trick mentioned above, the screen consumes +2 Watts! No need to mention battery life drops a lot.

But I do like that brightness! I'd like to keep it all the time. But it's impossible to apply the trick all the time.

I've tried tweaking the display driver to get more brightness, but that just degrades the LCD display quality.

Just a side note, I've bought an asus EEE pc maybe a year ago, and I remember that the LCD was kind of crippled too, in order to get acceptable battery life ratings. At that time, I had used a utility specifically for the asus EEE to crank up the brightness, more than it was allowed by the hardware.

I'd like to do the same... I've searched and searched, I never ever came across somebody that reported the same behavior for this family of laptop.

If you have nc2400, nc4200, tc4200, nc4400, tc4400, nc6xxxx (?C??? models) etc you all have the ambient light sensors, try the trick. It works.

Could it be that HP crippled the LCD to get a better figure in regards to battery life ? If you lock the max brightness to 50%, reviews will report a much better battery life than if you allowed up to 100%. Makes sense to me.

I’m not sure how the light sensor technology works, how about if I disconnect it? If I short it? Does it have only two wires? I’m an electrical engineer, I have my tools, so I’m ready to work on the issue, any input appreciated!

 

Have you turned your battery setting from balanced/power saver to high performance? That could be crippling your screen brightness.

 

Already tried that, no go.

It really seems to be hardware-based, since I can get the same behavior when I enter the BIOS setup.

 

To my surprise, I tried the software for the asus EEE, which is called EEECTL.

That software could control the fan, CPU speed, and LCD brightness (on the EEE)

Well, the software can control the LCD brightness! I can crank up the brightness all the way up just like if I had activated the ambient light sensor and put a strong light source on it ! The rest doesn't work.

The software could maybe work on all the HP business line (or maybe others?), so if you want to give it a try and see if you like your new brightness levels, you can download here: http://www.cpp.in/dev/eeectl/

Please post your impression if you try.

Goodbye

 

The software reports that the LCD is capped at 75% max brightness.

I'm working on the source code of EEEctl to remove all the cpu speed and fan control modules, to avoid messing with (maybe) incompatible registers. I didn't find any problem so far, except the "garbage from PLL" message box on startup, which I removed by commenting the popup on the source code

 

Hi,

Here's the modified version of Eeectl that does not have the speed, fan and temp modules.

It allows you to control the brightness of your laptop LCD via software ! Note that you have to disable the ambient light sensor in order for it to work (it's Fn+f11 on my model)

http://pages.infinit.net/thief/Eeectl.zip

I have included the modified source code so you can take a look. I basically have commented the modules' header and removed the corresponding .c and .h from the project.

The default configuration file (the .ini file) has the system tray icon display the current brightness in %, you can adjust the brightness using CTRL+UP and CTRL+DOWN. The program starts at 100%.

If you have any NCxxxx or TCxxxx laptop, I suggest you give it a try, you might have a display that is crippled at 75%.

I'm curious to see if it works on many laptops. Maybe just on intel video ?

I hope this thread helps somebody else that is looking for an answer regarding this issue.

 

I can get full brightness with my ambient light sensor disabled (at least to HP's max settings-verified by shining a tactical torch on the sensor). I can also adjust the degree of "dimness" with the ambient light sensor enabled by using the function key and the f8 & f9 keys. IMO the max brightness settings are pretty bright as is.

 

That's interesting. Which model do you have ?

Can you also look for which bios version you have ? My BIOS is date 10/30/2007 F.0F

 

I tried using this with the laptop in my sig (I used your modded version) and the program didn't work, Error 00000006:000004FB initizlizing IO Driver.

 

OK, thanks for trying, Harper.

I've tried on a friend's compaq V2000 (which is similar in many ways to my nc4200), the program started but didn't have control of brightness.

I guess I've been lucky, the asus EEE 700/701 (which is the model the original program is supposed to work on) has the intel 915 chipset (same as nc4200). The Compaq V2000 had the intel 845 (which is one generation older) and it didn't work.

Not to mention your laptop, Harper, which is completely different !

 

You do not have to hack it and fooling around with power settings does do do all that we want. Just hold down "fn" key & repeatedly tap on "F2" key to brighten screen or "F1" to dim. Notice the brightness symbol on those keys...

 

Another user reported the following:

The strange thing about my two - one (1.73 ghz cpu 1 yr warranty), had the LCD "fixed" at 75%, just like yours, but the other ( 1.86 ghz and 3 yr warranty marked on back) the LCD could go to the full 100% without any tricks. Both have the same bios. I even swapped the inverters around and it made no difference.

This may explain the various reviews at the time of its release- some moaned about the dim lcd, whereas some seemed quite happy.

 

A user reported that the software works on his NX6110, which has the same chipset.

EDIT: so does the HP nx7300(/nx7400)

 

thanks wipeout! used your control on a tc4400 running win7 pro - works great with ambient sensor toggled off. Definitely better than shining a light on the sensor before disabling it.

wish i looked when you posted this two years ago

 

Great

I'm surprised it works on win 7.

 

"dci

Error 0000002:00000005 initializing IO driver. "

Running Windows 7 Ultimate 32bit in my tc4400.
I tried this in my 8510w with Win7 x64 and similar error was produced.