RTD2660 mod for Lilliput 869GL LCD (YPbPr and more)

[moahdib]

This is my worklog on how I've modded my Lilliput 869GL (8 inch 800x480 TTL LCD) for enabling component (YPbPr) input.

It has the RTD2660 chip which is well known in the modding community. The available inputs on this monitor are the standard HDMI, VGA, 2x AV ports.

My intention is to be able to add YPbPr input for a PS2 portable and get rid of the extra conversion from component to hdmi i was using previously.
My initial attempt was to try and find the firmware source to modify an enable the input but I came across another solution.
Upon some research I came across a post on in a russian forum about LCD's about a service menu on this Lilliput. By holding down the "A/V" button for a few sec. on front of the unit, you are able to access it.

The menu that was most intriguing was the input menu which you can turn on and off every input this chip offers.
This includes:
DVI, PC (VGA), HDMI, YPbPr, SVIDEO, VIDEO1, VIDEO2, TV

Sure enough once you turn on the feature, you can switch inputs normally to the ones that are ON. Some of these inputs are shared such as VIDEO1 and TV.

I went about enabling YPbPr and wiring the inputs to the VGA RGB assuming they would be shared but this did not work.

The RTD2660 has 2 sets of analog RGB inputs on the chip. Only the first input was used whilst the unused 2nd port (pins 31-40) were left not connected.
More to come about this....

The LCD has a proprietary port just below the HDMI port. It is a breakout type cable that gives all the other inputs. With that port removed I mapped all the inputs as shown below. The D+, D- are for USB touchscreen and there is also a mono audio input.

To be continued....

 

[moahdib]

Since the VGA and YPbPr are using separate input pins on the RTD2660, we have to connect to them via small wires.
Basically by using the same VGA port inputs I connected them to the 2nd RGB analog input just below it. However after following the datasheet specs, I was only getting a blueish image.

This led me to finding out that the B-/B+ and G-/G+ are switched! So I've gone about wiring them as the diagram below using some 33awg enamel wire.
The wires look messy but it's only because I kinda made them long so they can be handled better.

Now both VGA and YPbPr are sharing the same inputs and this works fine since the values of the resistors, capacitors on both inputs are pretty much the same according to different schematic datasheets I've seen. I've attached a couple here for reference.

There is also S-Video input which could be added as well. I've tried wiring pins 41-44 the same way by using AV1 and AV2, however this did not work for the C(chroma) input. Only got a black and white video image for the Y signal (Luma). I will investigate this later again.

This was no deal breaker as I was already pleased to enable YPbPr. Doing this mod doesn't break the VGA input at all. They will just share the same RGB pin inputs.

I'm not sure if this service menu is present on any other type of LCD. It's probably there from factory to allow easy configuration for Lilliput LCD's.
There are a couple more interesting screens on the service menu. I tried to change some settings on the LOGO but doesn't seem to work.

Anyhow, I am very pleased to get more functionality out of this LCD and make it a beast of a LCD with every input enabled!
Testing with PS2 it can change from 480i ( in the home menu) to 480p without any issues when testing with some games that allow it.

Some info on this "portable". It's an almost finished project with a custom 3D printed rear housing. The front housing is still original.
I'm using an untrimmed PS2 inside as the 8 inch LCD allows for a bigger size PCB. Only the front ports (USB, memory/controller ports) were removed. I can also use the AV, network ports on the back to use it as a regular external console.

There will be more about it later on once it's completely finished but for those who are curious it's pretty similar to my previous mini-PS2 build with a blueretro and a diy RP2040 sd2psxtd gen2. I am using the SD2PSX to load the games on this one.