skorpien
Posts: 7
Joined: Thu Dec 10, 2015 5:59 am

Using a different LCD panel with KeDei 3.5" HDMI board?

Tue Oct 31, 2017 3:33 pm

I have a 3.5" HDMI TFT LCD (KeDei v1.1, 2017/7/1) that I purchased from eBay.

I've managed to break the LCD panel itself and was wondering if it could be switched with another panel?

I realize it's probably cheaper to go with a new unit entirely, but seeing as the board still works I figured I would at least try to salvage it.

From what I can gather (ie, printing on PCB) it's an 18bit 39pin panel. I was able to source a couple of 39pin panels on Alibaba but I'm not sure they would work.

The Alibaba panels have their pinout listed. I just can't find any documentation on the KeDei pinout to compare.

Any help would be greatly appreciated.


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saper_2
Posts: 232
Joined: Sun Aug 03, 2014 10:08 am
Location: PL

Re: Using a different LCD panel with KeDei 3.5" HDMI board?

Wed Jan 03, 2018 10:47 pm

shahidali55 wrote:
Sun Dec 17, 2017 2:52 pm
You can buy the LCD screen separately:

https://www.aliexpress.com/item/3-5-inc ... 87937.html

Big thanks for replacement :) (and more info about the display) , I have updated my review about this kedei hdmi display and gave you credits for find :) ( viewtopic.php?f=45&t=175616&p=1120533#p1120533 ).

skorpien
Posts: 7
Joined: Thu Dec 10, 2015 5:59 am

Re: Using a different LCD panel with KeDei 3.5" HDMI board?

Wed Jan 17, 2018 5:31 am

Thanks shahidali55. I ended up ordering it but for some reason it's not working. Is it possible they've revised more than just the LCD panel? Or did I just get a dud?

I hooked up the old screen to make sure it wasn't the driver board. The old screen turned on (no picture though, just backlight) but the new one doesn't even light up.

Is there any way to test the board to figure out what the pinout actually is?

floppes
Posts: 3
Joined: Sat Jun 16, 2018 3:35 pm

Re: Using a different LCD panel with KeDei 3.5" HDMI board?

Thu Jan 03, 2019 6:55 pm

This is an old topic, but in case someone stumbles upon it:

The display linked in the second post by shahidali55 works with the KeDei PCB v1.0. That's the PCB with the coil near the USB port:

Image

This display has it's backlight LEDs in row, therefore requiring about 20 V for them. The coil is part of a step-up converter to generate the 20 V from 5 V.

The KeDei PCBs starting with v1.1 use panels that have their LEDs in parallel. They require only 3.3 V for the backlight. Instead of a coil, they use a DS1117 linear voltage regulator to generate 3.3 V from 5 V. Therefore the display from shahidali55's won't work with v1.1 PCBs.

Image

Another thing that makes replacing the display very hard is the different displays KeDei uses. They changed them quite often and you always need the matching firmware for the panel. Some displays have an ILI9481 controller, others a HX8357. They all need the correct parameters for vertical/horizontal number of lines, front/back porch etc. I have created a set of tools to read and write the firmware: RTD266xFlash
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