更新 'DOC/21_FATFS_MSC.md'

DOC/21_FATFS_MSC.md

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+###  解决fatfs   msc 冲突
+
+sd_diskio.c增加两个函数,  msc usb中断时关闭消息
+```C
+void SD_Delet_Queue(void) {
+	osMessageDelete(SDQueueID);
+}
+
+void SD_Create_Queue(void) {
+    SDQueueID = osMessageQueueNew(QUEUE_SIZE, 2, NULL);
+}
+```
+
+启用或禁用  SD FatFS 0禁止
+```C
+static void Set_SD_WriteOrRead(uint8_t en) {
+	if (en == 1) {
+		SD_Create_Queue();
+		SDCard_EN = 1;
+	} else {
+		SD_Delet_Queue();
+		SDCard_EN = 0;
+	}
+}
+
+```
+
+
+USB回调
+```C
+void OTG_FS_IRQHandler(void)
+{
+ 
+  HAL_PCD_IRQHandler(&hpcd_USB_OTG_FS);
+ 
+  FILE_MGT_USB_CHECK(); // 自定义的函数
+ 
+}
+```
+
+
+两个任务，一个是FatFs 读写任务，一个是 USB 状态连接任务
+FatFS  读写放到任务里面取， 等待信号量执行读写
+两个任务互斥信号量     		osMutexWait(sdFreeMutexHandle, osWaitForever);
+```C
+static void FILE_MGT_SD_TEST_TASK(const void *arg) {
+	osDelay(500);
+	for (;;) {
+		osDelay(500);
+		osMutexWait(sdFreeMutexHandle, osWaitForever);
+		if (SDCard_EN) {
+			FatFs_FileTest();
+		} else {
+			printf("禁止使用SD卡\n");
+		}
+		osMutexRelease(sdFreeMutexHandle);
+
+	}
+}
+
+```
+
+USB 状态连接检测任务， 检测到USB 关闭 SD  FATFS
+需要提供 信号量   usbStateQueueHandle
+
+```C
+static void FILE_MGT_USB_CHECK_TASK(const void *arg) {
+	uint8_t dev_state = 0;
+	osEvent event;
+	FatFs_Check();
+	for (;;) {
+
+		event = osMessageGet(usbStateQueueHandle, osWaitForever);  // 改osMessageQueueGet
+		if (event.status == osEventMessage) {
+			osMutexWait(sdFreeMutexHandle, osWaitForever);
+			printf("hUsbDeviceFS:%d\n", (uint8_t) event.value.v);
+			if ((uint8_t) event.value.v == USBD_STATE_ADDRESSED) {
+				dev_state = USBD_STATE_ADDRESSED;
+			} else if ((dev_state == USBD_STATE_ADDRESSED)
+					&& ((uint8_t) event.value.v == USBD_STATE_CONFIGURED)) {
+				Set_SD_WriteOrRead(0);
+				printf("usb connect\n");
+			} else {
+				dev_state = 0;
+				Set_SD_WriteOrRead(1);
+				printf("usb disconnect\n");
+			}
+			osMutexRelease(sdFreeMutexHandle);
+		}
+
+	}
+}
+```