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Interfacing LCD to Omapl138 baseboard

Nanou
Prodigy 230 points
Other Parts Discussed in Thread: OMAPL138, OMAP-L138

Good Morning,

I want to connect a TFT panel to the Omapl138 baseboard and I found an interesting document :

" Interfacing LCDs to OMAP-L138 eXperimenter and EVM Baseboards"

Application Note 418.

 

But I need to know the description of each pin, they used abbreviations for all signals and I need pins to connect to a :

  • scan direction control pin on the panel
  • Led backlight (I have 1 pin for cathode and 1 for anode on the panel) 

Plus on the panel I have 1 pin for Data Enable and another one for Display on/off and on the OMAP baseboard I found only the LCD_MDISP, I guessed this one should be connected to the Display on/off pin, am I right? If yes, which one should go the Data Enable then?

If someone can help me. Excuse my bad english.

Thank you,

Nanou

  • 0
    TI__Mastermind 27585 points

    The Data Enable pin should be connected to LCD_AC_ENB_CS (for active TFT displays), which is labeled LCD_MDISP on the baseboard.

    The Display on/off can either be tied to ON, or connected to a GPIO if you want the ability to turn the panel on and off.

    The scan direction control bit can simply be tied high or low depending on which mode you want it to operate in.

    For the LED backlight, we would need to know the part number for the panel. Based on the fact that it has inputs for anode and cathode, its probably directly hooked up to the LEDs, which means you will need some external circuitry to provide the right inputs.

    Jeff

     

  • 0 in reply to jc-ti
    Prodigy 230 points

    Thank you Jeff for your help,

     the part number of the display is T-55423GD050J-LW-A-AAN, 5"  from Optrex.

     

    Nanou

  • 0 in reply to Nanou
    TI__Mastermind 27585 points

    For this panel the datasheet specifies the current and voltage specs for the LED backlight. These power signals are not provided from the baseboard and will have to be done on additional interface board.

    Jeff

  • 0 in reply to jc-ti
    Prodigy 230 points

    Hi Jeff,

    I still have one more problem to connect the display, I just found out that :

    the pin R_LCD_R0 is connected to the R_LCD_R5 pin and,

    the pin R_LCD_B0 is connected to the R_LCD_B5 pin. Why are they connected ? And should I just use for example the pins R_LCD_R0 to R_LCD_R4 ?

  • 0 in reply to Nanou
    TI__Mastermind 27585 points

    This device outputs in RGB565 format, and the panel is RGB666. This means we are lacking one red and one blue bit to output to the panel.

    See the below graphic, which shows 2 different approaches, in the case of attaching 6-bit output to 8-bit input.

    Tying off the lower bits gives the most linear color range, but you lose the full color range of the panel.

    The standard way is connecting the MSB outputs to the missing LSBs of the panel, which is what we did on the EVM.

    Jeff