Dell N7110 backlit keyboard in an N5110 - Page 1
Forum section: electronics / projects

author: IMI4tth3w
author_rank: Contributor
timestamp: December 23, 2015, 08:47:52 pm
content: So i've been wanting a backlit keyboard in my Inspiron N5110 for ages and google has told me this just isn't possible. Well i'm not ready to accept that. Plus this seems like a fun project to keep my busy this winter break while i'm out of class (studying Electrical Engineering)Looking at the N5110 motherboard, there are blank, unpopulated input tabs for the KBLIT1 spot. I believe this only exists because the Vostro 3550 uses the same motherboard, with slightly different populated components.Looking at the N7110 backlit keyboard, the flat flex input that powers the backlit keyboard would line up perfectly. (the larger flat flex bends over on the n5110. it will fit). The keyboards are identical other than the back light capabilities.Now some more google searching found the schematic for the backlit keyboard and the circuit components. This is from the Dell Inspiron N5110 Schematic pdf.Parts as follows:Component Location # | Part # | Description4 Pin FFC (flat flex connector, need to whip out the micrometer to determine pin pitch. either 0.5mm or 1mm)Components for the +5 volt line:F6901 FUSE-D5A6V-2-GP (0.5A 6V surface mount fuse)R6902 0R2J-2-GP (Resistor, not sure what value resistance)C6905 SCD1U10V2KX-5GP (1uF 10V surface mount capacitor)Components for the KB_LED_DET line:R6904 51KR2J-1-GP (51k surface mount resistor)R6903 100KR2J-1-GP (100K surface mount resistor)C6906 SCD1U10V2KX-5GP (1uF 10V surface mount capacitor)Components for the KB_BL_CTRL line:Q6901 P8503BMG-GP (N-Channel FEThttp://www.cheertech.com.tw/Niko-sem/Datasheet\P8503BMG.pdf)R6901 100KR2J-1-GP (100k surface mount resistor)Here's a picture where i circled each component and its associated location on the boardSome things i'm worried about are the EC labeled parts. As an inexperienced EE, i'm not sure what those are, and i don't see them mentioned in the datasheet schematic, but i'm assuming they are some type of capacitor. EC4103 is already populated while EC9732 and EC9726 are unpopulated. Also R6902's resistance is a mystery.And here's a (blurry, sorry) picture of the Vostro 3550 motherboard where the led backlight keyboard components live.zooming in on the vostro motherboard, you can see that the EC9732 and EC9726 are non existent. So i probably don't need to worry about them.. Also, its hard to tell, but it appears they don't bother with the fuse either.Wish i could find a better picture of this thing. But this is the best i could findIf anyone has any tips or clues about those parts, please feel free to chime in.I have an extra motherboard that my N5110 originally came with, as i swapped it with one that has discrete graphics. Will be using it to test this out and see what happens. Worse comes to worse i'll kill a motherboard i don't need. Best case, for those determined enough and willing to solder a few surface mount parts, will be able to finally get a back lit keyboard functioning on an N5110.

author: amyk
author_rank: Super Contributor
timestamp: December 24, 2015, 04:08:31 am
content: (Make sure you have the version of the schematic that shows both the DN15 and DQ15 variants, since the one with only DQ15 doesn't have the values for the backlight components.)R6902 is a 0.2 ohm resistor, presumably to limit current. The alternative is a 0.5A fuse.I think the biggest problem you'll have is actually enabling the backlight, since it's controlled by the EC (via KB_BL_CTRL signal) and if the firmware thinks there's no backlight available, then it won't do anything with that.On the other hand, it seems you can control which model the EC firmware thinks the board is by changing the R2710 which controls the voltage of the "MODEL_ID_DET" signal; there's options for DN15 and DQ15 with various GPUs. (See page 27 of the schematic.)

author: IMI4tth3w
author_rank: Contributor
timestamp: December 24, 2015, 09:15:13 am
content: Quote from: amyk on December 24, 2015, 04:08:31 amMy N5110 motherboard has NVIDIA discrete graphics, and since there's only one listed in this chart with NVIDIA, i'm guessing my MODEL_ID_DET is DQ15_NVIDIA with a 33.0K pull-high resistorFrom my understanding, what i want is one that has the DN15 prefix with the nvidia software, but i don't see one listed. I suppose i could still test its functionality with my other board that just has integrated graphics and try the DN15_UMA (assuming the UMA mean integrated graphics) and just see what happens

author: amyk
author_rank: Super Contributor
timestamp: December 24, 2015, 12:08:52 pm
content: That's right, UMA = Unified Memory Architecture and means GPU shares memory with CPU.I suppose that means there are no Vostros with the same backlit keyboard and nVidia graphics.How is the backlight controlled from the user point of view? Extra button on keyboard, via software, or does it just stay on all the time?

author: PA0PBZ
author_rank: Super Contributor
timestamp: December 24, 2015, 01:43:38 pm
content: Here is a better picture of the schematic. If you are a bit creative and leave some parts out it will be always on

author: IMI4tth3w
author_rank: Contributor
timestamp: December 24, 2015, 01:50:32 pm
content: Quote from: amyk on December 24, 2015, 12:08:52 pmIts a button on the keyboard. you can see it on the F6 key. I believe multiple presses change the brightness/turn it off.Quote from: PA0PBZ on December 24, 2015, 01:43:38 pmNow this i wouldn't mind either.