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A HDMI to Parallel RGB converter.

Robert Grootjans
Prodigy 20 points
Other Parts Discussed in Thread: TFP401A, TFP401

Dear all,

I want to connect a LCD display with parallel RGB, to HDMI (for those interested, I want to connect it to a Raspberry Pi in the future). First of all the LCD is a TFT LCD from a photoframe, with not a standard parallel RGB pinout (e.g. HSYNC/VSYNC/CK). Instead it has some other (for me unknown pins.). The pinout is in the datasheet (page 8, I've marked the pins I don't know about). 2450.CLAA080MB0GCW.pdf. My idea is to use the TFP401A to connect the HDMI to the RGB interface.

My question is, how do I connect these two together(the chip and the display). Or is this not possible?

If this is possible, which pin do I connect to what?

I've made a overview of what I'm planning to make (The device being a computer or a Raspberry Pi for example):

Thank you in advance,

Robert Grootjans

  • 0
    TI__Mastermind 20985 points

    Hi Robert, I'm looking into this and will get back to you shortly.

    Thanks,
    RE

  • 0
    TI__Mastermind 20985 points

    Those certainly are cryptic pin descriptions.  RGB video normally involves the data bus (often 18-bit or 24-bit), Hsync, Vsync, DataEnable, and clock.  DataEnable isn't always needed.

    The TFP401 deserializes DVI data to the standard 27-bit +clock interface.  This panel appears to use something totally different and much less conventional for its input clock and sync, as Page 13 shows "CLKH" and "CLKV".  I suggest either contacting Chunghwa for more info, or selecting a different panel that uses the very common RGB interface.

    Here's one list of panels out there, and here are lots of datasheets.  You might notice that many 800x600 panels use an LVDS interface--that's ok and can be workable, as we have an app note for a 2 chip HDMI-to-LVDS bridge solution:  http://www.ti.com/lit/an/slla325/slla325.pdf

    Thanks,
    RE

  • 0 in reply to RE
    Prodigy 20 points

    Thank you very much for your help. I have sent an email to the Chunghwa, to see if they can clarify this. Once I receive some info I will post it.
    Otherwise I think I have to get another LCD instead indeed. Nevertheless the links and documents you posted are very useful.
    I'll let you know how everything pans out.
    Regards,

    Robert

  • 0 in reply to RE
    Prodigy 10 points

    I'm attempting to complete a similar challenge with the use of the TFP401 and a Raspberry Pi B board.  The posted link for http://www.harbaum.org/till/dvi2par/index.shtml is a good one, and I will end up contacting that person, however I was wondering if anyone had specific advice regarding connecting the infamous (mostly for it's price point) Sharp TFT-LCD LQ038J7DH52 (6406.LQ038J7DH52.pdf) .  As nice as it would be to get the integrated touchscreen working, I'm just focusing on adapting the screen for output (even if it's just 18-bit color with QVGA resolution).  I guess I've been spoiled by modern electronics/connections as I'm unsure how to split the RGB/Grey data up at this point.

  • 0 in reply to Tony Rayo
    Prodigy 40 points

    Hi,

    I'm working in a same project, I need to connect a Raspberry Pi B into a LCD screen 18 bits and put a touchscreen.

    Have you been done your project? Can ou help me?

    Thanks in advance