STM32F7 LTDC 学习

因为STM32F7的探索板上因为各种原因,也没有手册.只能按照他给的参数来了.因为RK043FN48H型号到处有,手册看不到.
这是从官方的配置里面抄的参数:

/**
  * @brief  RK043FN48H Size
  */
#define  RK043FN48H_WIDTH    ((uint16_t)480)          /* LCD PIXEL WIDTH            */
#define  RK043FN48H_HEIGHT   ((uint16_t)272)          /* LCD PIXEL HEIGHT           */
/**
  * @brief  RK043FN48H Timing
  */
#define  RK043FN48H_HSYNC            ((uint16_t)41)   /* Horizontal synchronization */
#define  RK043FN48H_HBP              ((uint16_t)13)   /* Horizontal back porch      */
#define  RK043FN48H_HFP              ((uint16_t)32)   /* Horizontal front porch     */
#define  RK043FN48H_VSYNC            ((uint16_t)10)   /* Vertical synchronization   */
#define  RK043FN48H_VBP              ((uint16_t)2)    /* Vertical back porch        */
#define  RK043FN48H_VFP              ((uint16_t)2)    /* Vertical front porch       */

LTDC的初始化复杂程度,并不比SDRAM简单.首先SDRAM先自行初始化上,首先我定义了一下RGB565_480x272的变量在SDRAM,SDRAM的空间因此被我占用了480*272*2个字节,也就是65280个32位.定义方法需要特别提醒一下:

uint32_t RGB565_480x272[65280] __attribute__((at(0xC0000000)));

然后250K的空间,突然就被分割掉了,好可惜呢.然后初始化这个变量.

    for(tmpmrd = 0; tmpmrd < 65280; tmpmrd++)
    {
        RGB565_480x272[tmpmrd] = 0xFFFFFFFF;
    }

特别要注意的是,自己新建工程,要添加MSP初始化,初始化各种时钟,比如下面的SAI1时钟,也是LTDC时钟.

    PeriphClkInitStruct.PeriphClockSelection = RCC_PERIPHCLK_LTDC;
    PeriphClkInitStruct.PLLSAI.PLLSAIN = 192;
    PeriphClkInitStruct.PLLSAI.PLLSAIR = 5;
    PeriphClkInitStruct.PLLSAIDivR = RCC_PLLSAIDIVR_4;
    HAL_RCCEx_PeriphCLKConfig(&PeriphClkInitStruct);

其他参数只能照搬,接着有层次设置.第一层第二层什么的,这是为了LTDC才引入的吧.其他Layer(只有一层)按照默认先配置一下.逐步试验功能.默认设置:

 /* Layer1 Configuration ------------------------------------------------------*/
    /* Windowing configuration */
    /* In this case all the active display area is used to display a picture then :
       Horizontal start = horizontal synchronization + Horizontal back porch = 43
       Vertical start   = vertical synchronization + vertical back porch     = 12
       Horizontal stop = Horizontal start + window width -1 = 43 + 480 -1
       Vertical stop   = Vertical start + window height -1  = 12 + 272 -1      */
    pLayerCfg.WindowX0 = 0;
    pLayerCfg.WindowX1 = 480;
    pLayerCfg.WindowY0 = 0;
    pLayerCfg.WindowY1 = 272;
    /* Pixel Format configuration*/
    pLayerCfg.PixelFormat = LTDC_PIXEL_FORMAT_RGB565;
    /* Start Address configuration : frame buffer is located at FLASH memory */
    pLayerCfg.FBStartAdress = (uint32_t)&RGB565_480x272;
    /* Alpha constant (255 == totally opaque) */
    pLayerCfg.Alpha = 255;
    /* Default Color configuration (configure A,R,G,B component values) : no background color */
    pLayerCfg.Alpha0 = 0; /* fully transparent */
    pLayerCfg.Backcolor.Blue = 0;
    pLayerCfg.Backcolor.Green = 0;
    pLayerCfg.Backcolor.Red = 0;
    /* Configure blending factors */
    pLayerCfg.BlendingFactor1 = LTDC_BLENDING_FACTOR1_CA;
    pLayerCfg.BlendingFactor2 = LTDC_BLENDING_FACTOR2_CA;
    /* Configure the number of lines and number of pixels per line */
    pLayerCfg.ImageWidth  = 480;
    pLayerCfg.ImageHeight = 272;

如果改变得更小的一点的范围呢?比如如下:

    pLayerCfg.WindowX0 = 0;
    pLayerCfg.WindowX1 = 320;
    pLayerCfg.WindowY0 = 0;
    pLayerCfg.WindowY1 = 240;

同时记得修改:

    pLayerCfg.ImageWidth  = 320;
    pLayerCfg.ImageHeight = 240;

发现实际情况是:

设置一下全局背景颜色:

    hltdc_F.Init.Backcolor.Blue = 0;
    hltdc_F.Init.Backcolor.Green = 255;
    hltdc_F.Init.Backcolor.Red = 0;

再设置一下透明度:

    pLayerCfg.Alpha = 100;

大概变成这样:

如果透明度是240,背景颜色更难看得到,前景黄色越明显,可见层1是层叠在背景上的.LTDC不算困难,如何做漂亮的图,才是困难.