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java – 在Android平板电脑和相机之间的USB bulkTransfer

我想使用bulkTransfer功能在相机和Android平板电脑设备之间交换数据/命令.我写了这个Activity,但是bulkTransfer方法返回-1(错误状态).为什么会返回错误？

public class MainActivity extends Activity {

    private TextView text;
    private int TIMEOUT = 1000;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        text = (TextView) findViewById(R.id.txt);
        usbTest();
    }

    private void usbTest() {
        UsbDevice device = (UsbDevice) getIntent().getParcelableExtra(
                                                                      UsbManager.EXTRA_DEVICE);
        if (device == null)
            text.setText("device null");
        else
            text.setText("device not null");

        UsbManager manager = (UsbManager) getSystemService(Context.USB_SERVICE);
        HashMap<String, UsbDevice> deviceList = manager.getDeviceList();
        text.setText(text.getText() + "/nDevices connected: "
                     + deviceList.values().size());
        Iterator<UsbDevice> deviceIterator = deviceList.values().iterator();

        while (deviceIterator.hasNext()) {
            device = deviceIterator.next();
            text.setText(text.getText() + "/nDevice name: "
                         + device.getDeviceName());
            text.setText(text.getText() + "/nDevice protocol: "
                         + device.getDeviceProtocol());
            text.setText(text.getText() + "/nDevice id: "
                         + device.getDeviceId());
            text.setText(text.getText() + "/nDevice product id: "
                         + device.getProductId());
            text.setText(text.getText() + "/nDevice vendor id: "
                         + device.getVendorId());
            text.setText(text.getText() + "/nDevice class: "
                         + device.getDeviceClass());
            text.setText(text.getText() + "/nDevice subclass: "
                         + device.getDeviceSubclass());
            text.setText(text.getText() + "/nDevice interface count: "
                         + device.getInterfaceCount());
            text.setText(text.getText() + "/n/n");
        }

        // communicate with device
        UsbInterface intf = device.getInterface(0);
        UsbEndpoint endpoint = intf.getEndpoint(0);
        UsbDeviceConnection connection = manager.openDevice(device);
        connection.claimInterface(intf, true);

        for (int i = 0; i < intf.getEndpointCount(); i++) {
            UsbEndpoint ep = intf.getEndpoint(i);
            if (ep.getType() == UsbConstants.USB_ENDPOINT_XFER_BULK) {
                if (ep.getDirection() == UsbConstants.USB_DIR_OUT) {
                    endpoint = ep;
                    text.setText("Found: "+i);
                }
            }
        }


        // byte[] opensession = { 0x0C, 0x00, 0x00, 0x00, 0x01, 0x00, 0x02,
        // 0x10,
        // 0x00, 0x00, 0x00, 0x00 };
        // connection.bulkTransfer(endpoint, opensession, opensession.length,
        // TIMEOUT);

        byte[] getEvent = { 0x0C, 0x00, 0x00, 0x00, 0x01, 0x00, toByte(0xC7),
            toByte(0x90), 0x00, 0x00, 0x00, 0x00 };
        int status = connection.bulkTransfer(endpoint, getEvent,
                                             getEvent.length, TIMEOUT);
        //text.setText("Status: " + status);

        byte[] capture = { 0x14, 0x00, 0x00, 0x00, 0x10, 0x00, 0x0E, 0x10,
            0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
            0x00, 0x00 };
        connection.bulkTransfer(endpoint, capture, capture.length, TIMEOUT);

        // teminate communication
        BroadcastReceiver mUsbReceiver = new BroadcastReceiver() {
            @Override
            public void onReceive(Context context, Intent intent) {
                String action = intent.getAction();
                if (UsbManager.ACTION_USB_DEVICE_DETACHED.equals(action)) {
                    UsbDevice device = (UsbDevice) intent
                    .getParcelableExtra(UsbManager.EXTRA_DEVICE);
                    if (device != null) {
                        // call your method that cleans up and closes
                        // communication with the device
                    }
                }
            }
        };

    }

    public static byte toByte(int c) {
        return (byte) (c <= 0x7f ? c : ((c % 0x80) - 0x80));
    }

}

我怀疑你没有正确地搜索界面和端点.

见下面的说明.

建议：测试端点是否有效,并尝试将其与设备描述符进行匹配.

一个界面可以有多个设置.

AFAIK,对于相机,他们应该是相机接口的三个替代设置.

>零带宽 – 内部没有端点 – 最可能的替代设置0

>同步(如果相机支持它) – 等时端点在里面

>批量 – 您感兴趣的地方内的批量端点

(我不知道实际的USB相机规格,但是这应该适用于所有通过USB的流式传输协议(正如我在Audio Class中看到的)

您需要搜索批量交替设置,然后在其中的端点上执行通信.

http://stackoverflow.com/questions/13982264/usb-bulktransfer-between-android-tablet-and-camera

原文 https://codeday.me/bug/20181015/296651.html