Keyboard Backlight for Zenbook S16 (2024) - too bright on lowest setting

[user45876]

Hi,

after searching around a lot and probing all kind of ways (icluding asking ASUS), I am struggling with the keyboard backlight brightness of the Zenbook S16. It is way too bright on the lowest setting.

I tried poking at an UEFI image, I tried using Device Monitor to see any commands / Packets, peeking into the drivers and the registry. Until now, I can not find a way to control the brightness of the keyboard backlight besides the three supplied levels. Also changing the color as a trick to get it to be darker does not work (expectedly). Also here, I could not find a silimar question. Is is being discucced on reddit but without any success so far.

Is there any way to make the keyboard backlight less bright than the darkest of the three levels? Can i provide anything to help discovering it?

Thanks a lot :)
Hubert

[seerge]

@user45876 hello, usually brightness is set in a discreet single-byte values. And mostly it's 4 levels in total - i.e. 0 - 1 - 2 - 3

So if 1 is too bright, you can't set it to be 0.3 anyhow :)

Does your device support backlight colors ? If so - try to set it to grey instead of white.

[user45876]

Aha. It was a different Controlpoint and a different value ;)

PS C:\WINDOWS\system32> Invoke-CimMethod (Get-CimInstance -Namespace root/wmi -ClassName AsusAtkWmi_WMNB) -MethodName DEVS -Arguments @{Device_ID= 0x00050021; Control_status=129}

result ReturnValue PSComputerName
------ ----------- --------------
     1        True


PS C:\WINDOWS\system32> Invoke-CimMethod (Get-CimInstance -Namespace root/wmi -ClassName AsusAtkWmi_WMNB) -MethodName DEVS -Arguments @{Device_ID= 0x00050021; Control_status=130}

result ReturnValue PSComputerName
------ ----------- --------------
     1        True


PS C:\WINDOWS\system32> Invoke-CimMethod (Get-CimInstance -Namespace root/wmi -ClassName AsusAtkWmi_WMNB) -MethodName DEVS -Arguments @{Device_ID= 0x00050021; Control_status=131}

result ReturnValue PSComputerName
------ ----------- --------------
     1        True


PS C:\WINDOWS\system32> Invoke-CimMethod (Get-CimInstance -Namespace root/wmi -ClassName AsusAtkWmi_WMNB) -MethodName DEVS -Arguments @{Device_ID= 0x00050021; Control_status=132}
Invoke-CimMethod : Allgemeiner Fehler
In Zeile:1 Zeichen:1
+ Invoke-CimMethod (Get-CimInstance -Namespace root/wmi -ClassName Asus ...
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : NotSpecified: (AsusAtkWmi_WMNB...PNP0C14\ATK_0"):CimInstance) [Invoke-CimMethod], CimException
    + FullyQualifiedErrorId : HRESULT 0x80041001,Microsoft.Management.Infrastructure.CimCmdlets.InvokeCimMethodCommand

PS C:\WINDOWS\system32> Invoke-CimMethod (Get-CimInstance -Namespace root/wmi -ClassName AsusAtkWmi_WMNB) -MethodName DEVS -Arguments @{Device_ID= 0x00050021; Control_status=132}

So, giving it above 132 leads to an error. Will play around.

[seerge]

@user45876 oh, my bad, I linked you a wrong endpoint (the one responsible for RGB mode actually ...)

g-helper/app/AsusACPI.cs

Line 118 in f1353aa

public const int TUF_KB_BRIGHTNESS = 0x00050021;

0x00050021 is indeed correct one for brightness

It also adds couple of control bits to it (as this is what AC / asus apps send to device too)

g-helper/app/AsusACPI.cs

Line 792 in f1353aa

int param = 0x80 | (brightness & 0x7F);

But most likely w/o them it also won't work

[user45876]

Yes, I saw that as well ;) How would I change the control bits / send different ones?

[seerge]

@user45876 effectively it just adds 128 to the desired level. so 0 = 128, 1 = 128 + 1, etc

You can try any value from 0 to 255 :) but it won't make a difference most likely

[user45876]

Ah, I see, so it is already sending it - oh man... Yeah, does not help. Well, I have pleaded Asus to change it - if they do not want to, I will put stickers under the keycaps - did a POC while we were writing, it kind if works - but it is a lot to do and I might break thnigs on a brand new device, otherwhise perfect at this point in time.

Has Asus ever done a change wanted by its users? ;)

Thanks, dear Seerge, for taking the time to help me here, very much appreciated!

[user45876]

@seerge

Dear seerge, just wanted to tell about the solution I found.

I used a 22-ohm resistor in series to the KB backlight to adjust the keyboard backlight. Measurements yielded the following currents and voltages (measured behind the resistor) for different resistance values:

0 Ohm (original):
Current: 104mA, 170mA, 259mA
Voltage: 3.26V, 3.79V, 4.48V

10 Ohm:
Current: 46mA, 75mA, 113mA
Voltage: 2.8V, 3.0V, 3.36V

22 Ohm:
Current: 28mA, 45mA, 68mA
Voltage: 2.67V, 2.83V, 3.04V

At maximum brightness, the voltage drop across the 22-ohm resistor (4.48V - 3.04V) at 68mA results in approximately 100mW.

I placed the resistor in series with one of the two lines of the 8-pin FFC cable and connected it to the original backlight connector on the board. To save space, I plan to use a flatter FFC connector and a 1206 SMD resistor (250mW).

Recommended components:

FFC Connector: 1-row, bottom contact, 8-pin, 0.5mm pitch
FFC Cable: 8-pin, 0.5mm, 0.3mm thick
SMD Resistor: 1206, 22 Ohm

[seerge]

That's great :) It looks like backlight on this laptop bothered you a lot! :)

[user45876]

You bet ;) It is OK now. I also learned so much in the process. And now I look differently at every PCB-shot of laptops, always looking for that golden cable for the KB backlight ;) Also spotted it in Lenovo Laptops.

Here's the lovestory. I just wanted to share it, in case some poor sould like me (poor I mean with OCD) wants to do this as well.

The whole process does not touch or alter the board or device in any electrical way. When refining, my goal would be to build an intermediate cable with a slimmer connector and an SMD resistor, which can be put above the original connector, thus even less work is needed and really no modifications at all are needed.



From some research and schematics and boardviews of older models, I came to the conclusion, that this connector is for the kwyboard backlight.

I then measured voltage and current in different backlight situations (off, low, med, high) with different resistors (0 Ohm, 10 Ohm, 22 Ohm in serial) to decide, which resistor I want to use.

All values are for low, med, high brightness.

0 Ohm (original):
Current: 104mA, 170mA, 259mA
Voltage: 3.26V, 3.79V, 4.48V

10 Ohm:
Current: 46mA, 75mA, 113mA
Voltage: 2.8V, 3.0V, 3.36V

22 Ohm:
Current: 28mA, 45mA, 68mA
Voltage: 2.67V, 2.83V, 3.04V

Built a first prototype to proof the concept ;)

The final connector looks like this.

I moved the keybpoard cable to come close to the cavity north of the loudspeaker

I put the connector there - finished and no more glaring lights at night where not needed or wanted.

FFC Connector: 1-row, bottom contact, 8-pin, 0.5mm pitch
FFC Cable: 8-pin, 0.5mm, 0.3mm thick
SMD Resistor: 1206, 22 Ohm

[user45876]

See #3731 (reply in thread) for hardware mod.

[dylan-works]

Is there a way to lower it with software/BIOS change? I really don't feel comfortable building a connector like this, or do you sell them? thanks

[seerge]

@dylan-works do you have same device ? Or something else ? If it supports RGB you can set dimmer color.

If not - the only way would be (somehow?) modifying firmware, but I'm not sure if that's doable :)

[dylan-works]

Thanks for the quick reply. I have the ProArt P16 (2024), the lowest brightness keyboard setting is like double the highest setting on my MacBook Pro (2024), it's definitely weird and makes this laptop difficult to use comfortably in dark situations. The slider you have for brightness seems to values [0,1,2,3], do decimal value work here like 0.3? Is there a way I could test that out locally? Thanks

[user45876]

Is there a way to lower it with software/BIOS change? I really don't feel comfortable building a connector like this, or do you sell them? thanks

I agree with seerge - it could be easy with a bios change but I have no idea.

I could probably build a contraption for you - I should get slimmer connectors and smaller resistors in a week or so. Are you based in Europe? Would you be able to put it in?
I will not sell anything for profit, parts cost only and a provided label. I can not take any responsibilities.

[seerge]

@dylan-works it's a byte values that you set :) You can't set 0.3.

[user45876]

Thanks for the quick reply. I have the ProArt P16 (2024), the lowest brightness keyboard setting is like double the highest setting on my MacBook Pro (2024), it's definitely weird and makes this laptop difficult to use comfortably in dark situations. The slider you have for brightness seems to values [0,1,2,3], do decimal value work here like 0.3? Is there a way I could test that out locally? Thanks

Nice device - almost bought that as well but I think, it had a 60Hz display and a dGPU - I wanted a slimmer profile ;)

As said before, I can build one for you - it is a light thing to ship. You can have a look into your device right now, if it has the same connector - I would think so. I can also send you the parts I ordered from Ali, of you are based far away, maybe you can order them and find somebody who can build it and put it in.

EDIT::
From this, it seems to be a 12 pin connector, not 8 pin. So you can not use my solution 1:1. https://www.notebookcheck.com/Asus-ProArt-P16-Laptop-im-Test-AMD-Zen-5-trifft-auf-RTX-4070-Laptop-und-4K-OLED.869326.0.html

Look at the picture https://www.notebookcheck.com/fileadmin/_processed_/6/b/csm_IMG_6012_8c30433289.jpg - the smaller connector on the left even says KB BL. You would need to measure a little, but if you know somebody nerdy, they could do it. You only need a 12 pin connector and a 12 pin cable and a resistor.

EDIT2:
I wonder, where the touchpad connector is. But never mind.