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How to connect of C6748 's 16 bit display data pins to 24 bit RGB of TFT /LCD Display

Anil Sudhakaran
Expert 1125 points
Other Parts Discussed in Thread: TMS320C6748

Hi,

Designing a board  with TMS320C6748 with TFT LCD  Display.

TFT Display used  is one with  24 bit RGB parallel data and  Hsync, Vsync, Pclk, DEN .

Processor has only 16  display data pins  >>  VPIF_DOUT0/LCD_D_[15:0].

Please let me know how this 16 display pins should be  mapped to 24  ( 8X RGB ) data pins of the LCD.

Regards,

Anil

  • 0
    TI__Mastermind 43660 points

    Hello Anil,

    Since the C6748 device having 16 bit data bus, you can use RGB565 interface to connect with 24 bit RGB888 TFT LCD display.

    GND        ->  B0                                       GND         ->  G0                                    GND          ->   R0

    GND        ->  B1                                       GND         ->  G1                                    GND          ->   R1

    GND        ->  B2                                       LCD_D5   ->  G2                                    GND          ->   R2 

    LCD_D0  ->  B3                                       LCD_D6   ->  G3                                    LCD_D11  ->   R3

    LCD_D1  ->  B4                                       LCD_D7   ->  G4                                    LCD_D12  ->   R4 

    LCD_D2  ->  B5                                       LCD_D8   ->  G5                                    LCD_D13  ->   R5

    LCD_D3  ->  B6                                       LCD_D9   ->  G6                                    LCD_D14  ->   R6

    LCD_D4  ->  B7                                       LCD_D10 ->  G7                                    LCD_D15  ->   R7

    The LCD with only 16 bits or source color (5 red, 6 green and 5 blue) see severe banding artifacts when displaying smooth shaded regions or color gradients. This is not an issue for things like menu displays but looks terrible for video applications. 

     

    Regards,

    Senthil

  • 0 in reply to Senthilkumar Srinivasan
    Expert 1125 points

    Thanks Senthil.    

    When  we  look at P1,P2 display interface connector  of the eval board schematic and   BB-xM-LCD7-01 Display Board schematic,  the lower bit RGB  connections are different as below. (For eg. P2.7 and P2.13  are shorted in schematic ) Can you comment  on this please ?

    LCD_1V8_D_13 >> R0
    LCD_1V8_D_14 >> R1
    LCD_1V8_D_15 >> R2

    LCD_1V8_D_9 >> G0
    LCD_1V8_D_10 >> G1

    LCD_1V8_D_3 >> B1
    LCD_1V8_D_4 >> B2

    Regards,

    Anil

  • 0 in reply to Anil Sudhakaran
    TI__Mastermind 43660 points

    Hello Anil,

    There are two ways to interface RGB565 to RGBB888.

    1. Connect the RGB888 unused LSB's (B - D0, D1, D2, G - D8, D9, R - D16, D17, D18) to GND. In this configuration, the mentioned portions are always black in pixels.

    2. Connect the RGB888 unused LSB's to MSB's (B - D0 to D5, D1 to D6, D2 to D7, G - D8 to D14, D9 to D15, R - D16 to D21, D17 to D22, D18 to D23). In this configuration, the mentioned LSB portion replicates the color of MSB to which it is connected.

    In C6748 LCDK board, they have followed the second method of interface. 

    Regards,

    Senthil

  • 0 in reply to Senthilkumar Srinivasan
    Expert 1125 points

    Hi Senthil,

    I was aware of (1) you mentioned , not (2).   Do you have  any details of performance comparison of these two methods?

    Regards,

    Anil

  • 0 in reply to Anil Sudhakaran
    TI__Mastermind 43660 points

    Hello Anil,

    Sorry, we do not have any performance comparison between the two methods.

    Since we used second method in our LCDK board, I guess the second method might produce better image quality. 

    Regards,

    Senthil

  • 0 in reply to Senthilkumar Srinivasan
    Expert 1125 points

    Thanks Senthil. So will go with option 2. 

    Regards,

    Anil