这个例程测试了在连续串行模式下配置imx335相机斌且配置为800*480分辨率 RGB565模式将像素数据通过ISP推流到LTDC屏幕上，这里我们使用GPIO翻转和示波器来测量ISP处理图像数据的性能。由于屏幕接口为LTDC

所以这个项目的瓶颈在于屏幕显示速度而非ISP本身的性能限制

首先使能D-CACHE和I-CACHE 这两个cache缓存功能可以极大提升代码运行效率

  /* Enable I-Cache---------------------------------------------------------*/
  SCB_EnableICache();

  /* Enable D-Cache---------------------------------------------------------*/
  SCB_EnableDCache();

将STLINK连接的串口配置为115200波特率，并使能LED1

BSP_LED_Init(LED_GREEN);
  BSP_LED_Init(LED_RED);
    /* UART log */
#if USE_COM_LOG
  COM_InitTypeDef COM_Init;

  /* Initialize COM init structure */
  COM_Init.BaudRate   = 115200;
  COM_Init.WordLength = COM_WORDLENGTH_8B;
  COM_Init.StopBits   = COM_STOPBITS_1;
  COM_Init.Parity     = COM_PARITY_NONE;
  COM_Init.HwFlowCtl  = COM_HWCONTROL_NONE;

  BSP_COM_Init(COM1, &COM_Init);

  if (BSP_COM_SelectLogPort(COM1) != BSP_ERROR_NONE)
  {
    Error_Handler();
  }
#endif

调用BSP支持包 初始化IMX335摄像头

IMX335_Probe(IMX335_R2592_1944, IMX335_RAW_RGGB10);

查阅IMX335手册可知 摄像头像素格式为RGGB模式

初始化屏幕，并配置像素

LCD_Init(FRAME_WIDTH, FRAME_HEIGHT);

使能ISP模块 并通过CSI接口将图像经过ISP模块推流到屏幕帧缓冲区并显示

if(ISP_Init(&hcamera_isp, &hdcmipp, 0, &appliHelpers, ISP_IQParamCacheInit[0]) != ISP_OK)
  {
    Error_Handler();
  }

  if (HAL_DCMIPP_CSI_PIPE_Start(&hdcmipp, DCMIPP_PIPE1, DCMIPP_VIRTUAL_CHANNEL0 , BUFFER_ADDRESS, DCMIPP_MODE_CONTINUOUS) != HAL_OK)
  {
    Error_Handler();
  }

  /* Start the Image Signal Processing */
  if (ISP_Start(&hcamera_isp) != ISP_OK)
  {
    Error_Handler();
  }

其中关键的部分为上文中的LCD_INIT函数

static void LCD_Init(uint32_t Width, uint32_t Height)
{
  LTDC_LayerCfgTypeDef pLayerCfg ={0};

  hltdc.Instance = LTDC;

  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     = RK050HR18_HSYNC - 1;
  hltdc.Init.AccumulatedHBP     = RK050HR18_HSYNC + RK050HR18_HBP - 1;
  hltdc.Init.AccumulatedActiveW = RK050HR18_HSYNC + Width + RK050HR18_HBP -1;
  hltdc.Init.TotalWidth         = RK050HR18_HSYNC + Width + RK050HR18_HBP + RK050HR18_HFP - 1;
  hltdc.Init.VerticalSync       = RK050HR18_VSYNC - 1;
  hltdc.Init.AccumulatedVBP     = RK050HR18_VSYNC + RK050HR18_VBP - 1;
  hltdc.Init.AccumulatedActiveH = RK050HR18_VSYNC + Height + RK050HR18_VBP -1 ;
  hltdc.Init.TotalHeigh         = RK050HR18_VSYNC + Height + RK050HR18_VBP + RK050HR18_VFP - 1;

  hltdc.Init.Backcolor.Blue  = 0x0;
  hltdc.Init.Backcolor.Green = 0xFF;
  hltdc.Init.Backcolor.Red   = 0x0;

  if(HAL_LTDC_Init(&hltdc) != HAL_OK)
  {
    Error_Handler();
  }

  pLayerCfg.WindowX0       = 0;
  pLayerCfg.WindowX1       = Width;
  pLayerCfg.WindowY0       = 0;
  pLayerCfg.WindowY1       = Height;
  pLayerCfg.PixelFormat    = LTDC_PIXEL_FORMAT_RGB565;
  pLayerCfg.FBStartAdress  = BUFFER_ADDRESS;
  pLayerCfg.Alpha = LTDC_LxCACR_CONSTA;
  pLayerCfg.Alpha0 = 0;
  pLayerCfg.BlendingFactor1 = LTDC_BLENDING_FACTOR1_PAxCA;
  pLayerCfg.BlendingFactor2 = LTDC_BLENDING_FACTOR2_PAxCA;
  pLayerCfg.ImageWidth = Width;
  pLayerCfg.ImageHeight = Height;
  pLayerCfg.Backcolor.Blue = 0;
  pLayerCfg.Backcolor.Green = 0;
  pLayerCfg.Backcolor.Red = 0;
  if(HAL_LTDC_ConfigLayer(&hltdc, &pLayerCfg, LTDC_LAYER_1))
  {
    Error_Handler();
  }
}

在这里开辟了一个帧缓冲区的buffer 即BUFFER_ADDRESS

ISP将数据处理完成之后来内需的搬运到这里，LTDC控制器将buffer中的数据连续搬运到屏幕中 完成了现实的过程

 while (1)
  {
    /* USER CODE END WHILE */
    BSP_LED_Toggle(LED_GREEN);
    if (ISP_BackgroundProcess(&hcamera_isp) != ISP_OK)
    {
      BSP_LED_Toggle(LED_RED);
    }
    /* USER CODE BEGIN 3 */
  }

在while中翻转io引脚 用示波器观察

平均处理时间为1.85us处理完一幅图像数据 整个画面表现得十分丝滑流畅