我考虑尝试编译一个允许通过 USB 控制 Gembird SilverShield 电源插座的 C 程序。在我的安卓 HDMI 电视棒上，这将非常有用。有一个开放的项目。它可以在 Linux 下运行，并且依赖于 libusb。目标平台是android ICS。我想在 Ubuntu Linux 上开发。我让它工作的机会有多大？需要哪些步骤。设置 android SDK、NDK、交叉编译器...这里
有一个较旧的问题，与 android 上的 libusb 相关，但没有关于如何操作的信息。将应用程序移植到 androids 自己的 USB 库是否更容易？
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4 回答
24
Libusb 可以在非 root 的 android 上工作（前提是设备支持 USB 主机......这非常重要，因为并非所有设备都这样做）。您需要使用标准的 android USB 堆栈。然后，您可以从 USBDevice 获取设备描述符并将其传递给 libusb。
不幸的是，您还需要修改 libusb。幸运的是，其他人已经解释了您需要如何修改 LibUSB。
LibUSB 已在此处进行了修改。
祝你好运！
编辑：
首先你需要定义一个广播接收器：
private final BroadcastReceiver mUsbReceiver = new BroadcastReceiver()
{
public void onReceive(Context context, Intent intent)
{
String action = intent.getAction();
if (ACTION_USB_PERMISSION.equals(action))
{
synchronized (this)
{
UsbDevice device = (UsbDevice)intent.getParcelableExtra(UsbManager.EXTRA_DEVICE);
if (intent.getBooleanExtra(UsbManager.EXTRA_PERMISSION_GRANTED, false))
{
if(device != null)
{
UsbDeviceConnection deviceConnection = mUsbManager.openDevice( device );
Log.d( "USB", deviceConnection.getSerial() );
}
}
else
{
Log.d( "USB", "permission denied for device " + device);
}
}
}
}
}
现在您需要创建一个 USBManager 并枚举设备：
mUsbManager = (UsbManager) getSystemService( Context.USB_SERVICE );
HashMap< String, UsbDevice > stringDeviceMap = mUsbManager.getDeviceList();
Collection< UsbDevice > usbDevices = stringDeviceMap.values();
mPermissionIntent = PendingIntent.getBroadcast(this, 0, new Intent( ACTION_USB_PERMISSION ), 0 );
IntentFilter filter = new IntentFilter(ACTION_USB_PERMISSION);
registerReceiver( mUsbReceiver, filter );
Iterator< UsbDevice > usbDeviceIter = usbDevices.iterator();
while( usbDeviceIter.hasNext() )
{
if ( USBDeviceValid( usbDevice ) )
{
// Request permission to access the device.
mUsbManager.requestPermission( usbDevice, mPermissionIntent );
// Open the device.
UsbDeviceConnection connection = mUsbManager.openDevice( usbDevice );
int fd = connection.getFileDescriptor();
// Now pass the file descriptor to libusb through a native call.
}
}
编辑 2：
构建 libusb 只需将文件放在方便的地方（我将它们放在 jni/libusb 中），然后将以下行添加到您的 Android.mk 中：
include $(CLEAR_VARS)
LOCAL_MODULE := libusb
LOCAL_SRC_FILES := libusb/core.c libusb/descriptor.c libusb/io.c libusb/sync.c libusb/os/linux_usbfs.c
LOCAL_LDLIBS := -llog
include $(BUILD_SHARED_LIBRARY)
于 2013-04-26T10:25:24.203 回答
4
我实现的解决方案是使用 Java API 打开 USB 设备，然后使用带有 libusb 的文件描述符。我使用了 primesense 的 openni 项目中的 libusb（https://github.com/OpenNI/OpenNI2）
代码位：
打开设备（使用 swig）：
int LibUsbAndroid::android_open(libusb_device *device, libusb_device_handle **devHandle)
{
int fd = USBJNICallbacks::getCallback()->getDeviceFd(device->bus_number, device->device_address);
__android_log_print(ANDROID_LOG_VERBOSE,"USB","Got FD:%d",fd);
if(fd==-1)
{
__android_log_print(ANDROID_LOG_ERROR,"USB","android_open, bad fd");
return -1;
}
return libusb_open(device, devHandle, fd);
}
用 JAVA 代码打开设备（不在主线程上运行！）：
public int getDeviceFd(int busNumber, int deviceAddress) {
UsbDevice device = findDevice(busNumber, deviceAddress);
if(device!=null)
{
mReceivedPermission = false;
PermissionRequester pr = new PermissionRequester(device);
pr.run();
if(!mUsbManager.hasPermission(device))
{
Log.v("USB", "Requesting permissiom to device");
mPermissionIntent = PendingIntent.getBroadcast(mContext, 0, new Intent(ACTION_USB_PERMISSION), 0);
IntentFilter filterPermission = new IntentFilter(ACTION_USB_PERMISSION);
mContext.registerReceiver(mUsbPermissionReceiver, filterPermission);
mUsbManager.requestPermission(device, mPermissionIntent);
}
else
{
Log.v("USB", "Already has permission");
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
mReceivedPermission = true;
Log.v("USB", "Opening device");
OpenDevice od = openDevice(device);
Log.v("USB", "Adding to open devices");
mOpenDevices.put(""+busNumber+"/"+deviceAddress, od);
}
Log.v("USB", "Waiting for permission");
waitForPermissionResult();
OpenDevice od = mOpenDevices.get(""+busNumber+"/"+deviceAddress);
if(od!=null)
{
Log.v("USB", "Getting FD");
int result = od.mConnection.getFileDescriptor();
Log.i("USB","USB File desc:"+result);
return result;
}
else
{
Log.v("USB", "Error getting FD");
return -1;
}
}
return -1;
}
权限处理代码：
私有 BroadcastReceiver mUsbPermissionReceiver=new BroadcastReceiver(){
@Override
public void onReceive(Context context, Intent intent) {
Log.v("USB", "Received permission result");
String action = intent.getAction();
if (ACTION_USB_PERMISSION.equals(action)) {
synchronized (this) {
UsbDevice device = (UsbDevice)intent.getParcelableExtra(UsbManager.EXTRA_DEVICE);
if (intent.getBooleanExtra(UsbManager.EXTRA_PERMISSION_GRANTED, false)) {
Log.v("USB", "Received permission result OK");
if(device != null){
Log.v("USB", "Device OK");
mContext.unregisterReceiver(this);
Log.v("USB", "Openning device");
OpenDevice od = openDevice(device);
Log.v("USB", "Adding to open device list");
mOpenDevices.put(""+od.mBus+"/"+od.mAddress,od);
Log.v("USB", "Received permission is true");
mReceivedPermission = true;
}
else {
Log.d(TAG, "permission denied for device " + device);
}
}
}
}
}
};
开启功能：
public OpenDevice openDevice(UsbDevice device) {
UsbDeviceConnection connection = mUsbManager.openDevice(device);
Log.i("USB","Device name="+device.getDeviceName());
int bus = getBusNumber(device.getDeviceName());
int address = getAddress(device.getDeviceName());
return new OpenDevice(device, connection, bus, address);
}
USB 库更改（core.c）：
int API_EXPORTED libusb_open(libusb_device *dev,
libusb_device_handle **handle, int fd)
{
struct libusb_context *ctx = DEVICE_CTX(dev);
struct libusb_device_handle *_handle;
size_t priv_size = usbi_backend->device_handle_priv_size;
int r;
usbi_dbg("open %d.%d", dev->bus_number, dev->device_address);
_handle = malloc(sizeof(*_handle) + priv_size);
if (!_handle)
return LIBUSB_ERROR_NO_MEM;
r = usbi_mutex_init(&_handle->lock, NULL);
if (r) {
free(_handle);
return LIBUSB_ERROR_OTHER;
}
_handle->dev = libusb_ref_device(dev);
_handle->claimed_interfaces = 0;
memset(&_handle->os_priv, 0, priv_size);
r = usbi_backend->open(_handle,fd);
if (r < 0) {
usbi_dbg("open %d.%d returns %d", dev->bus_number, dev->device_address, r);
libusb_unref_device(dev);
usbi_mutex_destroy(&_handle->lock);
free(_handle);
return r;
}
usbi_mutex_lock(&ctx->open_devs_lock);
list_add(&_handle->list, &ctx->open_devs);
usbi_mutex_unlock(&ctx->open_devs_lock);
*handle = _handle;
/* At this point, we want to interrupt any existing event handlers so
* that they realise the addition of the new device's poll fd. One
* example when this is desirable is if the user is running a separate
* dedicated libusb events handling thread, which is running with a long
* or infinite timeout. We want to interrupt that iteration of the loop,
* so that it picks up the new fd, and then continues. */
usbi_fd_notification(ctx);
return 0;
}
op_open(libusb_fs.c) 更改：
static int op_open(struct libusb_device_handle *handle, int fd)
{
struct linux_device_handle_priv *hpriv = _device_handle_priv(handle);
char filename[PATH_MAX];
_get_usbfs_path(handle->dev, filename);
usbi_dbg("opening %s", filename);
hpriv->fd = fd;
if (hpriv->fd < 0) {
if (errno == EACCES) {
usbi_err(HANDLE_CTX(handle), "libusb couldn't open USB device %s: "
"Permission denied.", filename);
usbi_err(HANDLE_CTX(handle),
"libusb requires write access to USB device nodes.");
return LIBUSB_ERROR_ACCESS;
} else if (errno == ENOENT) {
usbi_err(HANDLE_CTX(handle), "libusb couldn't open USB device %s: "
"No such file or directory.", filename);
return LIBUSB_ERROR_NO_DEVICE;
} else {
usbi_err(HANDLE_CTX(handle),
"open failed, code %d errno %d", hpriv->fd, errno);
return LIBUSB_ERROR_IO;
}
}
return usbi_add_pollfd(HANDLE_CTX(handle), hpriv->fd, POLLOUT);
}
于 2014-08-28T14:03:58.000 回答
1
即使你编译了它，Android 也可能不会让你通过 libusb 访问 USB 设备，除非你的设备是 root 的。如果将您的应用程序移植到Android 的本机 USB 堆栈是可行的，那几乎肯定是一个更稳定的解决方案。
于 2013-04-25T21:01:19.560 回答
1
也可以尝试使用android串口api
这是串行端口初始化的示例。
private FileDescriptor mFd;
private FileInputStream mFileInputStream;
private FileOutputStream mFileOutputStream;
public SerialPort(File device, int baudrate, int flags) throws SecurityException, IOException {
/* Check access permission */
if (!device.canRead() || !device.canWrite()) {
try {
/* Missing read/write permission, trying to chmod the file */
Process su;
su = Runtime.getRuntime().exec("/system/bin/su");
String cmd = "chmod 666 " + device.getAbsolutePath() + "\n"
+ "exit\n";
su.getOutputStream().write(cmd.getBytes());
if ((su.waitFor() != 0) || !device.canRead()
|| !device.canWrite()) {
throw new SecurityException();
}
} catch (Exception e) {
e.printStackTrace();
throw new SecurityException();
}
}
mFd = open("/dev/ttyACM0", 9600, 0);
if (mFd == null) {
Log.e(TAG, "native open returns null");
throw new IOException();
}
mFileInputStream = new FileInputStream(mFd);
mFileOutputStream = new FileOutputStream(mFd);
}
使用 USB 主机上的设备也是如此。
于 2013-04-26T12:28:02.703 回答