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Thread: Sega Nomad replacement RGB screen

  1. #1
    Road Rasher Bibin's Avatar
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    Default Sega Nomad replacement RGB screen

    I picked up one of those cheapo 3.5" LCDs off eBay with the intent of screwing around with it. I won't replace a nomad LCD with those since they all take composite video and look really muddy as a result. What I'd like is to give one of these screens S-video or RGB.

    The one I received has an AMT630 controller chip, a clone of an MST703 controller. This controller *does* take S-video, and RGB - two inputs of each, actually! It's a matter of rewriting the configuration EEPROM or using an MCU/CPLD to talk to it and set the appropriate registers.

    The datasheet is here: http://csh.rit.edu/~moffitt/MST703.pdf

    If anyone else wants to have a stab at this, we could make something great here - no more composite video on a Nomad. Imagine it with an active-matrix RGB display!

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    Raging in the Streets xelement5x's Avatar
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    Sounds promising! Good luck
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  3. #3
    Co-Creator of the MegaAmp Raging in the Streets villahed94's Avatar
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    I am working together with Ace on the same issue but with a different approach.
    Taking the bog standard LCD mod screen and disassembling it, we can see it uses a LCD panel like this one: http://www.3605buy.com/images/s/ali/134214842847736.jpg the LQ035NC111.
    According to the datasheet (http://videotechnology.com/lcd/CHE--...S_20071205.pdf) it has an 8 bit per colour parallel RGB interface. In order to make up for this we have the the Motorola MC44251, a parallel, 8 bit per colour ADC.
    Combined with sync strippers, this should be enough for RGB.


    Mega Amp: The reference audio circuit for the Sega Genesis/Mega Drive.

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    Master of Shinobi evilevoix's Avatar
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    Very interested in the outcome.

  5. #5
    Road Rasher Bibin's Avatar
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    Quote Originally Posted by villahed94 View Post
    I am working together with Ace on the same issue but with a different approach.
    Taking the bog standard LCD mod screen and disassembling it, we can see it uses a LCD panel like this one: http://www.3605buy.com/images/s/ali/134214842847736.jpg the LQ035NC111.
    According to the datasheet (http://videotechnology.com/lcd/CHE--...S_20071205.pdf) it has an 8 bit per colour parallel RGB interface. In order to make up for this we have the the Motorola MC44251, a parallel, 8 bit per colour ADC.
    Combined with sync strippers, this should be enough for RGB.
    Sounds like you guys are already on your way so perhaps there's no need for me to do anything with this. If you clock the ADC using the master clock in the Nomad then captures will smoothly be done on pixel transitions and it will be very sharp (in both H32 and H40). I have a similar LCD that came with the display - standard parallel RGB interface, and simple 3.3V-level Hsync / Vsync / Clk signals. Shouldn't be too complicated. Let me know what progress you make! I'd love to see a higher quality nomad image.

  6. #6
    Extreme Procrastinator Master of Shinobi Flygon's Avatar
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    What is the resolution of the screen you guys are using? If you can somehow find a 1280*960 3.5in panel, you should be able to make a replacement screen that'll have zero scaling problems going between 256 and 320 wide modes. You'll still have issues with bars on the top and bottom of the screen unless it's one of those rare PAL games that actually uses those bits, but most PAL peeps are used to these things anyway.

  7. #7
    Hedgehog-in-Training Hedgehog-in-Training
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    I'm interested to hear if anyone makes progress on this! Getting one of those cheap car backup cam monitors to play nice with RGB would benefit more than just the nomad!

  8. #8
    Mega Driven Raging in the Streets cleeg's Avatar
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    If anyone gets this going count me in, my composite (*sicks in mouth*) screen looks quite good, and has a nifty remote but RGB is of course preferable.

  9. #9
    Road Rasher Bibin's Avatar
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    The crappy screen I got the other week had trouble syncing to 240p. I did manage to feed it an (unstable) S-video signal, though. Even that would be a huge benefit if it was stable...

  10. #10
    Hedgehog-in-Training Hedgehog-in-Training
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    Yeah, from what I've seen, the composite screens really don't look terrible, especially compared to the original nomad screen which, colors completely aside, has such bad ghosting it is a detriment to some popular fast paced sega games. I have one of the 3.5 inch screens with the blue driver board, as those seem to give the best results I've seen around, but it's definitely composite input. Figuring out a process for inputting RGB to small LCD's like that would be a big deal for portabilizing consoles in general I think. From what I've seen though, it may be wishful thinking, as driving LCD displays gets to be quite a confusing topic, sometimes with detailed information about hardware drivers being hidden by licencing and non disclosure stuff on the business side of things.

    Out of curiosity, I wonder if there is any such thing as small LCD displays that take RGB video input out of the box as an intended and supported feature? At any price point really. Mostly just curious as I don't think I've ever run into such a thing.

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    Nameless One GreasyWolverine's Avatar
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    I want to say I will pledge to pay someone for this mod. I have waited and hoped for the day I could replace my nomad screen but I want nothing to do with composite!!! I want to reserve a spot on the waiting list. I will gladly pay well for this mod!

  12. #12
    Mega Driven Raging in the Streets cleeg's Avatar
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    If there is ever a waiting list then me too.

  13. #13
    Road Rasher Bibin's Avatar
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    Planning on screwing around with directly driving one of these LCDs this weekend.

  14. #14
    Road Rasher Bibin's Avatar
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    So I just got a Nomad, and holy crap, the LCD is really bad at some things! If you give it a repeating 1px pattern of white/black, it will slowly fade to black, and then leave the screen affected for minutes afterwards... The appeal of a modern LCD is stronger now. It might be nice to just manufacture a new front PCB for it, incorporating the controller, sound amp, A/V output, etc as well. That would make the install job much more professional.

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    Video Game Modder Outrunner segasonicfan's Avatar
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    Quote Originally Posted by GreasyWolverine View Post
    I want to say I will pledge to pay someone for this mod. I have waited and hoped for the day I could replace my nomad screen but I want nothing to do with composite!!! I want to reserve a spot on the waiting list. I will gladly pay well for this mod!
    Same here! People say Composite video is not noticeable on small screens...so not true! We need an RGB solution for our beloved Sega Nomads 640 x480 would be damn nice too.

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