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。 this 有一个开放项目。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 ...
有一个较旧的问题 here，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 android 自己的 USB 库是否更容易？
【问题讨论】：
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。如果将您的应用移植到Android's native USB stack 是可行的，那几乎肯定是一个更稳定的解决方案。
【讨论】：
Libusb 可以在非 root 的 android 上运行（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已修改here。
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：
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)
【讨论】：
你也可以试试android serial port api
这里是串口初始化的例子。
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。
【讨论】：
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：
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);
}
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;
}
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);
}
}
}
}
}
};
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);
}
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;
}
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);
}
【讨论】：