STM32H750B-DK LTC example
After tinkering with some of those cheap SPI displays, I would like to use the LTDC controller of the STM32H7 MCU. From my current research, I understand that the LCD controller controls the attached display, allowing me to push data stored in a frame buffer, much like I already did with my SPI displays.
Therefore, I looked at one of the demo projects provided by ST displaying an image on the integrated LCD display. Since the demo project didn't run because of a debugger error, I would like to come up with my own example. I therefore intend:
- Let the LCD display custom data.
At this point, I would consider the noise pattern from an uninitialized RAM section a success. I set up a new project and configured clocks and the LTDC according to the demo project from ST:
static void MX_LTDC_Init(void)
{
/* USER CODE BEGIN LTDC_Init 0 */
/* USER CODE END LTDC_Init 0 */
LTDC_LayerCfgTypeDef pLayerCfg = {0};
/* USER CODE BEGIN LTDC_Init 1 */
/* USER CODE END LTDC_Init 1 */
hltdc.Instance = LTDC;
hltdc.Init.HSPolarity = LTDC_HSPOLARITY_AL;
hltdc.Init.VSPolarity = LTDC_VSPOLARITY_AL;
hltdc.Init.DEPolarity = LTDC_DEPOLARITY_AL;
hltdc.Init.PCPolarity = LTDC_PCPOLARITY_IPC;
hltdc.Init.HorizontalSync = 40;
hltdc.Init.VerticalSync = 9;
hltdc.Init.AccumulatedHBP = 53;
hltdc.Init.AccumulatedVBP = 11;
hltdc.Init.AccumulatedActiveW = 533;
hltdc.Init.AccumulatedActiveH = 283;
hltdc.Init.TotalWidth = 565;
hltdc.Init.TotalHeigh = 285;
hltdc.Init.Backcolor.Blue = 0;
hltdc.Init.Backcolor.Green = 0;
hltdc.Init.Backcolor.Red = 0xFF;
if (HAL_LTDC_Init(&hltdc) != HAL_OK)
{
Error_Handler();
}
pLayerCfg.WindowX0 = 0;
pLayerCfg.WindowX1 = 480;
pLayerCfg.WindowY0 = 0;
pLayerCfg.WindowY1 = 272;
pLayerCfg.PixelFormat = LTDC_PIXEL_FORMAT_ARGB8888;
pLayerCfg.Alpha = 255;
pLayerCfg.Alpha0 = 255;
pLayerCfg.BlendingFactor1 = LTDC_BLENDING_FACTOR1_CA;
pLayerCfg.BlendingFactor2 = LTDC_BLENDING_FACTOR2_CA;
pLayerCfg.FBStartAdress = 0;
pLayerCfg.ImageWidth = 480;
pLayerCfg.ImageHeight = 272;
pLayerCfg.Backcolor.Blue = 255;
pLayerCfg.Backcolor.Green = 0;
pLayerCfg.Backcolor.Red = 0;
if (HAL_LTDC_ConfigLayer(&hltdc, &pLayerCfg, 0) != HAL_OK)
{
Error_Handler();
}
/* USER CODE BEGIN LTDC_Init 2 */
/* USER CODE END LTDC_Init 2 */
}
Then allocated the frame buffer. Since the display used features a resolution of 480 x 272 pixels and 3 bytes of color per pixel, I allocated 391680 bytes in the RAM_D1 region. Then I assigned the frame buffer in main.c:
/* USER CODE BEGIN PV */
__attribute__((section(".FrameBuffer"))) uint8_t framebuffer[FB_BUFFER_NBR][FRAMEBUFFER_SIZE];
/* USER CODE END PV */
MX_GPIO_Init();
MX_FMC_Init();
MX_LTDC_Init();
/* USER CODE BEGIN 2 */
//memset(frame_buffer, 0x1F, 0xFF);
if (HAL_OK != HAL_LTDC_SetAddress(&hltdc, (uint32_t)&framebuffer, 0))
{
Error_Handler();
}
if (HAL_OK != HAL_LTDC_Reload(&hltdc, LTDC_RELOAD_VERTICAL_BLANKING))
{
Error_Handler();
}
while (1)
{
HAL_GPIO_TogglePin(LD1_GPIO_Port,LD1_Pin);
HAL_Delay(250);
/* USER CODE END WHILE */
/* USER CODE BEGIN 3 */
}
The project was compiled and loaded to the demo board. While to code seems to work, as the Error_Handler() isn't called, the display still shows a blank page. So I would like to know, how the HAL LTDC can be used and which prerequisites need to be fulfilled, in order to run this simple example.