# USB Usage Guidelines The following procedure uses bulk transfer as an example. ## Procedure 1. Obtain a USB service instance. ```cpp static OHOS::USB::UsbSrvClient &g_usbClient = OHOS::USB::UsbSrvClient::GetInstance(); ``` 2. Obtain the USB device list. ```cpp std::vector deviceList; int32_t ret = g_usbClient.GetDevices(deviceList); ``` 3. Apply for device access permissions. ```cpp int32_t ret = g_usbClient.RequestRight(device.GetName()); ``` 4. Open the USB device. ```cpp USBDevicePipe pip; int32_t et = g_usbClient.OpenDevice(device, pip); ``` 5. Configure the USB interface. ```cpp ret = g_usbClient.ClaimInterface(pip, interface, true); // **interface** indicates an interface of the USB device in **deviceList**. ``` 6. Transfer data. ```cpp srvClient.BulkTransfer(pipe, endpoint, vdata, timeout); ``` Parameter description: - **pipe**: pipe for data transfer of the USB device opened. - **endpoint**: endpoint for data transfer on the USB device. - **vdata**: binary data block to be transferred or read. - **timeout**: timeout duration of data transfer. 7. Close the USB device. ```cpp ret = g_usbClient.Close(pip); ```