SD卡动态的mount和unmount问题

发布于 2013-12-18 10:48:23 浏览：3598 订阅该版

版本：RTT-1.2.0RC  stm32f407VG
情景：
系统使用双文件系统，w25q64作为"/", sd卡作为"/SD"
需要的功能：
1）系统上电后先挂w25q64，然后读取sd的cd脚，如果检测到sd卡插入，就挂载sd卡。如果没有，则忽略。
2）配置sd的cd脚为中断，双边沿方式。插入和拔掉sd卡，会触发中断，中断进入后，立即关闭中断使能，清楚标志，发送信号量给sd卡的监控线程，在线程里面延时50ms，然后读取cd脚的状态，判别是插入了sd卡，还是移除了卡。如果拔出了，则dfs_unmount("/SD"),如果插入，则dfs_mount("sd0", "/SD", "elm", 0, 0)。
问题：
1）老是在线程里面dfs_mount失败
sd_mount_flag sd卡是否挂载的标志位  1，已经挂载；0，没有挂载过
g_sdcard_flag sd卡是否插入的标志位，1检测到sd卡，0无sd卡插入

初始化部分
初始化的代码系统上电后先挂w25q64，然后读取sd的cd脚，如果检测到sd卡插入，就挂载sd卡。如果没有，则忽略。    
中断里面的代码
```void EXTI9_5_IRQHandler(void)
{
	NVIC_InitTypeDef NVIC_InitStructure;

rt_kprintf("sdcard detected interrupt handling.
");
    if(EXTI_GetITStatus(EXTI_Line6) == SET)
    {
 
	    NVIC_InitStructure.NVIC_IRQChannel = EXTI9_5_IRQn;
	    NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 2;
	    NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
	    NVIC_InitStructure.NVIC_IRQChannelCmd = DISABLE;
	    NVIC_Init(&NVIC_InitStructure);
			EXTI_ClearITPendingBit(EXTI_Line6);
			//rt_timer_start(&timer_sdmon);
			rt_sem_release(&sdmon_sem);
        
    }

}```
线程里面的代码
```void thread_entry_sdmon(void* parameter)
{
	rt_err_t result;
	NVIC_InitTypeDef NVIC_InitStructure;
	
	result = rt_sem_init(&sdmon_sem, "sdmon_sem", 0, RT_IPC_FLAG_FIFO);
	if (result != RT_EOK)
	{
		DEBUG("sdmon_sem init failed.
");
	}
	while(1)
	{
		rt_sem_take(&sdmon_sem, RT_WAITING_FOREVER);
		rt_thread_delay(20);

//?ò???±?°??????
		EXTI_ClearITPendingBit(EXTI_Line6);
		NVIC_InitStructure.NVIC_IRQChannel = EXTI9_5_IRQn;
		NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 2;
		NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
		NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
		NVIC_Init(&NVIC_InitStructure);
		
		//detect sdcart is exist.
		if(GPIO_ReadInputDataBit(SD_DETECT_GPIO_PORT, SD_DETECT_PIN) != Bit_RESET)
			g_sdcard_flag = 0;
		else
			g_sdcard_flag = 1;

//sdcard????????
		if(g_sdcard_flag == 0)
			{
				if(sd_mount_flag == RT_TRUE)
					{
					if(dfs_unmount("/SD") < 0)
						rt_kprintf("unmount /SD failed.
");
				 	else
						{
							rt_kprintf("sdcard unmounted!
");
							sd_mount_flag = RT_FALSE;
						}
					}
			 	
			}
		//sdcard????????
		else if(g_sdcard_flag == 1)
			{
				rt_kprintf("sdcard detected!
");
				if(sd_mount_flag == RT_FALSE)
				{
					if (dfs_mount("sd0", "/SD", "elm", 0, 0) == 0)
					{
							rt_kprintf("sdcard mounted!
");
							sd_mount_flag = RT_TRUE;
					}
					else
					{
							rt_kprintf("sdcard mount failed.
");
							//sd_mount_flag = RT_FALSE;
					}
				}
		
		}
}

}```

出现的错误：
finsh />
sdcard detected interrupt handling.
sdcard unmounted!
sdcard detected interrupt handling.
sdcard detected!
error detected and set to -2/0 (cmd = 17)
mmcsd request blocks error
-2,0,0, 0x00000002,0x00000000
sdcard mount failed.