Update fatfs_drv.c

增加异常处理，防止错误cmd值导致返回RES_OK

board/STM32F103_SIM800A/Hardware/fatfs_drv.c

@@ -8,6 +8,7 @@
 
 #define SPI_FLASH_SECTOR_SIZE   (4 * 1024)
 #define SPI_FLASH_PAGE_SIZE     256
+
  DSTATUS w25q64_fatfs_status(BYTE lun)
 {
     DSTATUS status = STA_NOINIT;
@@ -64,13 +65,13 @@ DRESULT w25q64_fatfs_write(BYTE lun, const BYTE *buff, DWORD sector, UINT count)
     case GET_BLOCK_SIZE:
         *(DWORD *)buff = 1;
         break;
-    }
-    res = RES_OK;
+    default:
         return res;
     }
+    res = RES_OK;
   
-
-
+    return res;
+}
 
 DWORD get_fattime (void)
 {