rtt的io设备框架面向对象学习-电阻屏LCD设备

1.8080电阻屏LCD设备

以stm32f407-atk-explorer为例，该bsp支持电阻触摸屏LCD，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
然后它就调用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。

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。

void xpt2046_entry(void *parameter)
{
    ……  
    while (1)
    {        
        ……  
        #ifdef PKG_USING_LVGL            
        lv_port_indev_input(read_data.x_coordinate, read_data.y_coordinate, ((read_data.event == RT_TOUCH_EVENT_DOWN) ? LV_INDEV_STATE_PR : LV_INDEV_STATE_REL));
        #else /* PKG_USING_LVGL */            
         const rt_uint32_t black = 0x0;            
         rt_graphix_ops(lcd)->set_pixel((const char *)(&black),                                        read_data.x_coordinate,                                         read_data.y_coordinate);
         #endif 
         rt_thread_mdelay(1);     
    }        
   
}

如上线程，若是lvgl读到触摸坐标则调用lv_port_indev_input通知lvgl事件，/bsp / stm32 / stm32f407-atk-explorer / board / ports/drv_lcd.c中的函数lcd_fill_array作为对接lvgl的绘图回调函数:

void lcd_fill_array(rt_uint16_t x_start, rt_uint16_t y_start, rt_uint16_t x_end, rt_uint16_t y_end, void *pcolor)
{    
rt_uint16_t *pixel = RT_NULL;    
rt_uint16_t cycle_y, x_offset = 0;    
pixel = (rt_uint16_t *)pcolor;    
for(cycle_y = y_start; cycle_y <= y_end; )    {        
LCD_SetCursor(x_start, cycle_y);        LCD_WriteRAM_Prepare();        
for(x_offset = 0;x_start + x_offset <= x_end; x_offset++)        
{            
LCD->RAM = *pixel++;       
 }        
 cycle_y++;    
 }
}

可以看到通过绘点来实现显示刷新。

但是如果没有开启lvgl，则直接调用rt_graphix_ops(lcd)->set_pixel，它是/ 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,
};

并在构造函数drv_lcd_hw_init中赋给了设备基类的user_data 成员

device->user_data = &fsmc_lcd_ops;

这样就能直接操作lcd绘图。

2.spi电阻屏LCD

spi通信的电阻屏LCD是怎么操作的，可以参照官方开发板麻雀一号开发板。
它的实现是没有创建新的lcd设备对象的，它是直接操作spi设备＋DC（命令/数据控制引脚）进行结合来通信控制lcd显示的。

在麻雀一号开发板sdk的samples/lcd_test/samples/drv_lcd.c中封装了如下函数:

static struct rt_spi_device *spi_dev_lcd;
static int rt_hw_lcd_config(void)
{    
spi_dev_lcd = (struct rt_spi_device *)rt_device_find("spi3");
return RT_EOK
}

static rt_err_t lcd_write_cmd(const rt_uint8_t cmd)
{    
rt_size_t len;    
rt_pin_write(LCD_DCx_PIN, PIN_LOW);    
len = rt_spi_send(spi_dev_lcd, &cmd, 1);    
if (len != 1)    
{        
LOG_I("lcd_write_cmd error. %d", len);        
return -RT_ERROR;    
}    
else    
{      
  return RT_EOK;  
}
}


static rt_err_t lcd_write_data(const rt_uint8_t data)
{    
rt_size_t len;    
rt_pin_write(LCD_DCx_PIN, PIN_HIGH);   
 len = rt_spi_send(spi_dev_lcd, &data, 1);    
 if (len != 1)    
 {        
 LOG_I("lcd_write_data error. %d", len);        
 return -RT_ERROR;    
 }    
 else    
 {        
 return RT_EOK;    
 }
 }
 
……