rtt的io设备框架面向对象学习-电阻屏LCD设备

news2024/11/23 17:06:14

1.8080通信的电阻屏LCD设备

rtt没有实现的设备驱动框架层，那么是在驱动层直接实现的，以stm32f407-atk-explorer为例，在/bsp / stm32 / stm32f407-atk-explorer / board / ports /drv_lcd.c中定义了该设备类：

struct drv_lcd_device
{
    struct rt_device parent;
    struct rt_device_graphic_info lcd_info;
};

其中struct rt_device_graphic_info是在/ components / drivers / include / drivers /classes/graphic.h定义的：

struct rt_device_graphic_info
{
    rt_uint8_t  pixel_format;                           /**< graphic format */
    rt_uint8_t  bits_per_pixel;                         /**< bits per pixel */
    rt_uint16_t pitch;                                  /**< bytes per line */

    rt_uint16_t width;                                  /**< width of graphic device */
    rt_uint16_t height;                                 /**< height of graphic device */

    rt_uint8_t *framebuffer;                            /**< frame buffer */
    rt_uint32_t smem_len;                               /**< allocated frame buffer size */
};

然后实例化了该设备类

static struct drv_lcd_device _lcd;

1.1 构造流程

并实现了其构造函数drv_lcd_hw_init：

int drv_lcd_hw_init(void)
{
    rt_err_t result = RT_EOK;
    struct rt_device *device = &_lcd.parent;
    /* memset _lcd to zero */
    memset(&_lcd, 0x00, sizeof(_lcd));

    _lcd.lcd_info.bits_per_pixel = 16;
    _lcd.lcd_info.pixel_format = RTGRAPHIC_PIXEL_FORMAT_RGB565;

    device->type = RT_Device_Class_Graphic;
#ifdef RT_USING_DEVICE_OPS
    device->ops = &lcd_ops;
#else
    device->init = drv_lcd_init;
    device->control = drv_lcd_control;
#endif
    device->user_data = &fsmc_lcd_ops;
    /* register lcd device */
    rt_device_register(device, "lcd", RT_DEVICE_FLAG_RDWR | RT_DEVICE_FLAG_STANDALONE);

    return result;
}
INIT_DEVICE_EXPORT(drv_lcd_hw_init);

可以看到其重写了父类——设备基类的方法——但是只是重写了init方法和control方法。
其对象图如下
请添加图片描述
从上面代码可以知道它是调用在/ components / drivers / core /device.c中设备基类的构造函数rt_device_register，将电阻屏LCD设备对象放到对象容器里管理。

详细参见io设备管理层。
https://blog.csdn.net/yhb1206/article/details/136440373

1.2 使用

在/bsp / stm32 / stm32f407-atk-explorer / board / ports / touch /drv_xpt2046_init.c中，

static int touch_xpt2046_init(void)
{
    xpt2046_init_hw();
    rt_thread_t tid = rt_thread_create("xpt2046", xpt2046_entry, RT_NULL, 1024, 8, 20);
    RT_ASSERT(tid != RT_NULL);
    rt_thread_startup(tid);
    return RT_EOK;
}
INIT_COMPONENT_EXPORT(touch_xpt2046_init);


void xpt2046_init_hw(void)
{
  	……
    lcd = rt_device_find("lcd");
    rt_device_init(lcd);
}

在rtt的io设备框架面向对象学习-touch设备中说过，因为此bsp的LCD是电阻触摸LCD屏，所以在xpt2046_init_hw中初始化触摸设备，最后也初始化了LCD，如上代码。
在xpt2046_entry线程中，读取到触摸坐标点，若开启了lvgl绘图，则通知lvgl绘图，否则直接调用rt_graphix_ops(lcd)->set_pixel在LCD上绘制点的轨迹。

lvgl对接有lcd的绘点接口，暂忽略。

rt_graphix_ops(lcd)->set_pixel是/ components / drivers / include / drivers /classes/graphic.h定义的lcd操作接口：

struct rt_device_graphic_ops
{
    void (*set_pixel) (const char *pixel, int x, int y);
    void (*get_pixel) (char *pixel, int x, int y);

    void (*draw_hline)(const char *pixel, int x1, int x2, int y);
    void (*draw_vline)(const char *pixel, int x, int y1, int y2);

    void (*blit_line) (const char *pixel, int x, int y, rt_size_t size);
};
#define rt_graphix_ops(device)          ((struct rt_device_graphic_ops *)(device->user_data))

而之前drv_lcd.c中实现了该接口：

struct rt_device_graphic_ops fsmc_lcd_ops =
    {
        LCD_Fast_DrawPoint,
        LCD_ReadPoint,
        LCD_HLine,
        LCD_VLine,
        LCD_BlitLine,
};