LTDC pixel format RGB565 produces output only when CLUT is enabled

[yusuf1809]

I am using LTDC for interfacing with a TFT LCD. The LCD is connected with 18 bit (RGB666) interface. I have selected the pixel format as RGB565, and I am using a frame buffer stored in the internal SRAM. The frame buffer has been populated with 16 bit RGB values. The problem is, I can only see the output when I enable the CLUT and populate the CLUT with RGB values. Otherwise, if CLUT is not enabled, I cannot see the output. As far as I know, CLUT is used in L8 pixel format, but for RGB565 CLUT is not used. I am confused about this situation. Any idea what may be happening here?

[LouisB]

Hello @yusuf1809,

TouchGFX doesn't support RGB666 framebuffer format. You did the proper conversion from rgb565 to rgb666 for the screen ?

Br,

[yusuf1809]

Hi @LouisB thanks for your reply. I am not using touch gfx. I have configured the frame buffer manually. The rgb666 interface is working as I have been able to pass data using L8 pixel format with the CLUT. But when I changed the pixel format from L8 to rgb565, nothing shows up on the LCD unless I enable the CLUT. Note that when I was using the L8 format, my frame buffer was 8 bit. When I changed to rgb565, I have updated the frame buffer size to 16 bit. Even if I put 16 bit rgb values in the frame buffer nothing shows up on the LCD without enabling the CLUT.

[MM..1]

You ask in TouchGFX area and changing generated code from one format to other isnt simple click... If you first generate L8 setup , changing to 565 require more as one regenerate code and chceck all settings LTDC ...

Try show what and where you change, normal is only Layer type change. (without touchgfx)