update zh-cn/device-dev/subsystems/subsys-usbservice-guide.md.

Signed-off-by: NAustin23 <liaozhiqi7@huawei.com>

zh-cn/device-dev/subsystems/subsys-usbservice-guide.md

@@ -13,40 +13,40 @@
 
 2. 获取usb设备列表
 
-  ```cpp
-  std::vector<OHOS::USB::UsbDevice> deviceList;
-  int32_t ret = g_usbClient.GetDevices(deviceList);
-  ```
+   ```cpp
+   std::vector<OHOS::USB::UsbDevice> deviceList;
+   int32_t ret = g_usbClient.GetDevices(deviceList);
+   ```
 
 3. 申请设备权限
 
-  ```cpp
-  int32_t ret = g_usbClient.RequestRight(device.GetName());
-  ```
+   ```cpp
+   int32_t ret = g_usbClient.RequestRight(device.GetName());
+   ```
 
 4. 打开设备
 
-  ```cpp
-  USBDevicePipe pip;
-  int32_t et = g_usbClient.OpenDevice(device, pip);
-  ```
+   ```cpp
+   USBDevicePipe pip;
+   int32_t et = g_usbClient.OpenDevice(device, pip);
+   ```
 
 5. 配置设备接口
 
-  ```cpp
-  ret = g_usbClient.ClaimInterface(pip, interface, true);
-  interface为deviceList中device的interface。
-  ```
+   ```cpp
+   ret = g_usbClient.ClaimInterface(pip, interface, true);
+   interface为deviceList中device的interface。
+   ```
 
 6. 数据传输
 
-  ```cpp
-  srvClient.BulkTransfer(pipe, endpoint, vdata, timeout);
-  ```
-  pipe为打开设备后的数据传输通道，endpoint为device中数据传输的端点，vdata是需要传输或读取的二进制数据块，timeout为传输超时时长。
+   ```cpp
+   srvClient.BulkTransfer(pipe, endpoint, vdata, timeout);
+   ```
+   pipe为打开设备后的数据传输通道，endpoint为device中数据传输的端点，vdata是需要传输或读取的二进制数据块，timeout为传输超时时长。
 
 7. 关闭设备
- 
-  ```cpp
-  ret = g_usbClient.Close(pip);
-  ```
+  
+   ```cpp
+   ret = g_usbClient.Close(pip);
+   ```