DMA2D Blend ARGB8888 with RGB565

[mwp]

Hi all,

I would like to blend a ARGB8888 image onto my RGB565 frame buffer. Is this possible?

The code I'm currently testing (that does not work) is the following:

	//configure DMA2D options
	LL_DMA2D_SetMode(DMA2D, LL_DMA2D_MODE_M2M_BLEND);
	LL_DMA2D_SetOutputColorMode(DMA2D, LL_DMA2D_OUTPUT_MODE_RGB565);
	LL_DMA2D_SetOutputRBSwapMode(DMA2D, LL_DMA2D_RB_MODE_REGULAR);
	//output
	LL_DMA2D_SetOutputMemAddr(DMA2D, (uint32_t)OutAddr);
	LL_DMA2D_SetLineOffsetMode(DMA2D, LL_DMA2D_LINE_OFFSET_PIXELS);
	LL_DMA2D_SetLineOffset(DMA2D, 0);
	LL_DMA2D_SetNbrOfLines(DMA2D, LCD_HEIGHT);
	LL_DMA2D_SetNbrOfPixelsPerLines(DMA2D, LCD_WIDTH);
	//background config (same as output)
	LL_DMA2D_BGND_SetColorMode(DMA2D, LL_DMA2D_INPUT_MODE_RGB565);
	LL_DMA2D_BGND_SetMemAddr(DMA2D, (uint32_t)OutAddr);
	LL_DMA2D_BGND_SetLineOffset(DMA2D, 0);
	LL_DMA2D_BGND_SetAlpha(DMA2D, 0xFF);
	LL_DMA2D_BGND_SetAlphaInvMode(DMA2D, LL_DMA2D_ALPHA_REGULAR);
	//foreground (input)
	LL_DMA2D_FGND_SetColorMode(DMA2D, LL_DMA2D_INPUT_MODE_ARGB8888);
	LL_DMA2D_FGND_SetMemAddr(DMA2D, (uint32_t)SrcAddr);
	LL_DMA2D_FGND_SetLineOffset(DMA2D, 0);
	LL_DMA2D_FGND_SetAlphaMode(DMA2D, LL_DMA2D_ALPHA_MODE_COMBINE);
	LL_DMA2D_FGND_SetAlphaInvMode(DMA2D, LL_DMA2D_ALPHA_REGULAR);
	LL_DMA2D_FGND_SetAlpha(DMA2D, AlphaValue);
	//go
	LL_DMA2D_Start(DMA2D);

Thanks in advance.

[KDJEM.1]

Hello @mwp ,

Could you please precise which STM32 MCUs devices are you using?

Concerning the first question about the conversion from YCBCR to RGB. I think that  AN4996 can help in this conversion case.

Concerning the second issue how to configure DMA2D with blending transfer mode. 

I advise you to get inspired from an available DMA2D_MemToMemWithBlending example by following the steps shared in readme.txt.

Thank you.

Kaouthar

[mwp]

Thanks for the reply. I worked out the YCBCR problem, but couldn't delete this forum post, so edited it with a new question instead.
The mcu is a STM32H7A3.
I have blending working fine for other colour modes, like ARGB4444 to RGB565, but ARGB8888 to RGB565 give me unexpected results.