STM32H743 LTDC with no framebuffer

[AlexSmart]

Is it possible to use STM32H743's LTDC with no frambuffer and fill its FIFO "on the fly"?

[MM..1]

Maybe yes with line interrupts, but you dont fill FIFO, you set one line buffer address

[AlexSmart]

Seemed doable until I find out that there could be only one line interrupt per frame

[MM..1]

Tgfx uses more as one line int on frame to past blanking area , then i mean you can refresh on interrupt next line interrupt , but for efective i recomm use more as one line buffer.

[AlexSmart]

Ok, I managed to do that, Im using 32 lines buffer. But I see no output from that buffer. I see background color, black rectangle where buffer output should be, but no data inside...

unsigned short framebuffer[32][1280] __attribute__((used,aligned(4),at(0x30000000))); 
int main(void)
{
  GPIO_InitTypeDef GPIO_InitStruct = {0};
  HAL_Init();
  SystemClock_Config();
 
  MX_GPIO_Init();
  MX_LTDC_Init();
	__HAL_RCC_D2SRAM1_CLK_ENABLE();
	__HAL_RCC_D2SRAM2_CLK_ENABLE();
	__HAL_RCC_D2SRAM3_CLK_ENABLE();
	for (int line=0;line<32;line++)
	{
		for (int i=0;i<1280;)
		{
			if (line & 0x01)
			{
				framebuffer[line][i++] = 0x5555;
				framebuffer[line][i++] = 0xAAAA;
			}
			else
			{
				framebuffer[line][i++] = 0xAAAA;
				framebuffer[line][i++] = 0x5555;
			}
		}
	}
	HAL_NVIC_SetPriority(LTDC_IRQn, 0, 0);
	HAL_NVIC_EnableIRQ(LTDC_IRQn);
	HAL_LTDC_ProgramLineEvent(&hltdc, 0);
  while (1)
  {
  }
}
static void MX_LTDC_Init(void)
{
  LTDC_LayerCfgTypeDef pLayerCfg = {0};
  hltdc.Instance = LTDC;
  hltdc.Init.HSPolarity = LTDC_HSPOLARITY_AH;
  hltdc.Init.VSPolarity = LTDC_VSPOLARITY_AH;
  hltdc.Init.DEPolarity = LTDC_DEPOLARITY_AL;
  hltdc.Init.PCPolarity = LTDC_PCPOLARITY_IPC;
  hltdc.Init.HorizontalSync = 19;
  hltdc.Init.VerticalSync = 4;
  hltdc.Init.AccumulatedHBP = 29;
  hltdc.Init.AccumulatedVBP = 9;
  hltdc.Init.AccumulatedActiveW = 1309;
  hltdc.Init.AccumulatedActiveH = 729;
  hltdc.Init.TotalWidth = 1319;
  hltdc.Init.TotalHeigh = 749;
  hltdc.Init.Backcolor.Blue = 0;
  hltdc.Init.Backcolor.Green = 0xff;
  hltdc.Init.Backcolor.Red = 0;
  if (HAL_LTDC_Init(&hltdc) != HAL_OK)
  {
    Error_Handler();
  }
  pLayerCfg.WindowX0 = 0;
  pLayerCfg.WindowX1 = 1280;
  pLayerCfg.WindowY0 = 72;
  pLayerCfg.WindowY1 = 692;
  pLayerCfg.PixelFormat = LTDC_PIXEL_FORMAT_RGB565;
  pLayerCfg.Alpha = 255;
  pLayerCfg.Alpha0 = 255;
  pLayerCfg.BlendingFactor1 = LTDC_BLENDING_FACTOR1_CA;
  pLayerCfg.BlendingFactor2 = LTDC_BLENDING_FACTOR2_CA;
  pLayerCfg.FBStartAdress = 0x30000000;
  pLayerCfg.ImageWidth = 1280;
  pLayerCfg.ImageHeight = 32;
  pLayerCfg.Backcolor.Blue = 0;
  pLayerCfg.Backcolor.Green = 0xff;
  pLayerCfg.Backcolor.Red = 0;
  if (HAL_LTDC_ConfigLayer(&hltdc, &pLayerCfg, 0) != HAL_OK)
  {
    Error_Handler();
  }
}

[MM..1]

Show IRQ too and start with only 32 line test ...

  pLayerCfg.WindowY0 = 72;
  pLayerCfg.WindowY1 = 72+32;

[AlexSmart]

Here is code for interrupt - no buffer or window manipulation here, just test signal output.

void LTDC_IRQHandler(void)
{
       static unsigned int line_num = 10;
	__HAL_LTDC_CLEAR_FLAG(&hltdc, LTDC_FLAG_LI);
	__HAL_LTDC_DISABLE_IT(&hltdc, LTDC_IT_LI);
	LTDC->LIPCR = line_num;
	__HAL_LTDC_ENABLE_IT(&hltdc, LTDC_IT_LI);
 
	line_num +=5;
	if (line_num>=720)
		line_num = 10;
	LED1_GPIO_Port->ODR ^=LED1_Pin;
}

window size now is 0..1280 and 72..692. Buffer size - 32. Shouldnt I excpect buffer output at line 72 to 104?

[MM..1]

Hmm lines is numbered with porch and irq on 0 maybe isnt good choice.

Inspire from touchgfx code

    lcd_int_active_line = (LTDC->BPCR & 0x7FF) - 1;
    lcd_int_porch_line = (LTDC->AWCR & 0x7FF) - 1;

[AlexSmart]

I disabled interrupt for now. My goal is to see the buffer on the screen...

[MM..1]

Trry explain for what you plan this because i dont see real use.