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I am using a asus N71JQ (came out ~2010 with win7) which did not came with backlit keyboard.

I found that some very similar laptops (asus G73JH and G60) have exactly the same keyboard but with backlit. Those keyboards have an additional FPC for the LED.
I would like to be able to use Fn+F3/Fn+F4 to increase decrease the brightness as you would on G73JH.

So I started to look for N71JQ and G73JH schematics, which unfortunatelly cannot be found anywhere on the web. However I could find N61J schematic. On this schematic I found out that the keyboard backlit is controller with a PWM from the IT8570E embedded controller (= EC = SuperIO):
This PWM goes to a mosfet the mosfet enable/disable the connection of the FPC to ground (5V pin is always connected). By changing the PWM the CPU can vary the brightness of LED.

Then I checked my motherboard (N71JA rev2.1) of which I don't have the schematic. However I found that it has same EC IT8570E. Also to my surprise I found that there is a FPC connector available for the LED backlight! I checked and there is same mosfet as on the schematic I saw. I also checked and the mosfet is connected to the pin 32 for IT8570E which is PWM6 (same as on N61J schematic).

I also checked that the 5V is correctly applied to the FPC.

So all the hardware is already ready to support the backlit keyboard! (Which is strange as no asus N71 serie never had backlit. And the motherboard is not used on other models. So they actually paid for components that never ever have been used.)

So I connected my new keyboard, the keyboard works, previous shortcut I had also worked (Fn+F5/Fn+F6 increase/decrease luminosity of LCD for example) but Fn-F3/F4 does nothing still.

I checked on asus website for drivers, ant installed the ATK of G73JH. Now fn+F3/F4 show the icon OSD of keyboard backlight but it does not work still.

I have thought about 2 possibilities :

• Analyze the two bios (G73JH and N71JQ) and try to find the difference. I tried with AMIBCP, but it does not give any parameter relative to keyboard. Then tried to compare the binary files to see if I can locate some difference regions. Are laptop models are very similar I thought it could be possible, but there are too many differences afterall.




• Make a small driver or .exe at launch to catch when user press fn+F3/F4 and write directly in the SuperIO register. In the datasheet it is said the chip behaves as a LPC/FHW memory device.

Any hint regarding second possibility would be awesome!