UsbDeviceConnection
public
class
UsbDeviceConnection
extends Object
java.lang.Object | |
↳ | android.hardware.usb.UsbDeviceConnection |
This class is used for sending and receiving data and control messages to a USB device.
Instances of this class are created by UsbManager#openDevice
.
Summary
Public methods | |
---|---|
int
|
bulkTransfer(UsbEndpoint endpoint, byte[] buffer, int offset, int length, int timeout)
Performs a bulk transaction on the given endpoint. |
int
|
bulkTransfer(UsbEndpoint endpoint, byte[] buffer, int length, int timeout)
Performs a bulk transaction on the given endpoint. |
boolean
|
claimInterface(UsbInterface intf, boolean force)
Claims exclusive access to a |
void
|
close()
Releases all system resources related to the device. |
int
|
controlTransfer(int requestType, int request, int value, int index, byte[] buffer, int offset, int length, int timeout)
Performs a control transaction on endpoint zero for this device. |
int
|
controlTransfer(int requestType, int request, int value, int index, byte[] buffer, int length, int timeout)
Performs a control transaction on endpoint zero for this device. |
int
|
getFileDescriptor()
Returns the native file descriptor for the device, or -1 if the device is not opened. |
byte[]
|
getRawDescriptors()
Returns the raw USB descriptors for the device. |
String
|
getSerial()
Returns the serial number for the device. |
boolean
|
releaseInterface(UsbInterface intf)
Releases exclusive access to a |
UsbRequest
|
requestWait(long timeout)
Waits for the result of a Note that this may return requests queued on multiple
|
UsbRequest
|
requestWait()
Waits for the result of a Note that this may return requests queued on multiple
|
boolean
|
setConfiguration(UsbConfiguration configuration)
Sets the device's current |
boolean
|
setInterface(UsbInterface intf)
Sets the current |
Protected methods | |
---|---|
void
|
finalize()
Called by the garbage collector on an object when garbage collection determines that there are no more references to the object. |
Inherited methods | |
---|---|
Public methods
bulkTransfer
public int bulkTransfer (UsbEndpoint endpoint, byte[] buffer, int offset, int length, int timeout)
Performs a bulk transaction on the given endpoint. The direction of the transfer is determined by the direction of the endpoint.
Parameters | |
---|---|
endpoint |
UsbEndpoint : the endpoint for this transaction |
buffer |
byte : buffer for data to send or receive |
offset |
int : the index of the first byte in the buffer to send or receive |
length |
int : the length of the data to send or receive. Before
android.os.Build.VERSION_CODES.P Build.VERSION_CODES.P , a value larger than 16384 bytes
would be truncated down to 16384. In API android.os.Build.VERSION_CODES.P Build.VERSION_CODES.P
and after, any value of length is valid. |
timeout |
int : in milliseconds, 0 is infinite |
Returns | |
---|---|
int |
length of data transferred (or zero) for success, or negative value for failure |
bulkTransfer
public int bulkTransfer (UsbEndpoint endpoint, byte[] buffer, int length, int timeout)
Performs a bulk transaction on the given endpoint. The direction of the transfer is determined by the direction of the endpoint.
This method transfers data starting from index 0 in the buffer.
To specify a different offset, use
bulkTransfer(android.hardware.usb.UsbEndpoint, byte[], int, int, int)
.
Parameters | |
---|---|
endpoint |
UsbEndpoint : the endpoint for this transaction |
buffer |
byte : buffer for data to send or receive; can be null to wait for next
transaction without reading data |
length |
int : the length of the data to send or receive. Before
android.os.Build.VERSION_CODES.P Build.VERSION_CODES.P , a value larger than 16384 bytes
would be truncated down to 16384. In API android.os.Build.VERSION_CODES.P Build.VERSION_CODES.P
and after, any value of length is valid. |
timeout |
int : in milliseconds, 0 is infinite |
Returns | |
---|---|
int |
length of data transferred (or zero) for success, or negative value for failure |
claimInterface
public boolean claimInterface (UsbInterface intf, boolean force)
Claims exclusive access to a UsbInterface
.
This must be done before sending or receiving data on any
UsbEndpoint
s belonging to the interface.
Parameters | |
---|---|
intf |
UsbInterface : the interface to claim |
force |
boolean : true to disconnect kernel driver if necessary |
Returns | |
---|---|
boolean |
true if the interface was successfully claimed |
close
public void close ()
Releases all system resources related to the device.
Once the object is closed it cannot be used again.
The client must call UsbManager#openDevice
again
to retrieve a new instance to reestablish communication with the device.
controlTransfer
public int controlTransfer (int requestType, int request, int value, int index, byte[] buffer, int offset, int length, int timeout)
Performs a control transaction on endpoint zero for this device.
The direction of the transfer is determined by the request type.
If requestType & UsbConstants#USB_ENDPOINT_DIR_MASK
is
UsbConstants#USB_DIR_OUT
, then the transfer is a write,
and if it is UsbConstants#USB_DIR_IN
, then the transfer
is a read.
Parameters | |
---|---|
requestType |
int : request type for this transaction |
request |
int : request ID for this transaction |
value |
int : value field for this transaction |
index |
int : index field for this transaction |
buffer |
byte : buffer for data portion of transaction,
or null if no data needs to be sent or received |
offset |
int : the index of the first byte in the buffer to send or receive |
length |
int : the length of the data to send or receive |
timeout |
int : in milliseconds |
Returns | |
---|---|
int |
length of data transferred (or zero) for success, or negative value for failure |
controlTransfer
public int controlTransfer (int requestType, int request, int value, int index, byte[] buffer, int length, int timeout)
Performs a control transaction on endpoint zero for this device.
The direction of the transfer is determined by the request type.
If requestType & UsbConstants#USB_ENDPOINT_DIR_MASK
is
UsbConstants#USB_DIR_OUT
, then the transfer is a write,
and if it is UsbConstants#USB_DIR_IN
, then the transfer
is a read.
This method transfers data starting from index 0 in the buffer.
To specify a different offset, use
controlTransfer(int, int, int, int, byte[], int, int, int)
.
Parameters | |
---|---|
requestType |
int : request type for this transaction |
request |
int : request ID for this transaction |
value |
int : value field for this transaction |
index |
int : index field for this transaction |
buffer |
byte : buffer for data portion of transaction,
or null if no data needs to be sent or received |
length |
int : the length of the data to send or receive |
timeout |
int : in milliseconds |
Returns | |
---|---|
int |
length of data transferred (or zero) for success, or negative value for failure |
getFileDescriptor
public int getFileDescriptor ()
Returns the native file descriptor for the device, or -1 if the device is not opened. This is intended for passing to native code to access the device.
Returns | |
---|---|
int |
the native file descriptor |
getRawDescriptors
public byte[] getRawDescriptors ()
Returns the raw USB descriptors for the device. This can be used to access descriptors not supported directly via the higher level APIs.
Returns | |
---|---|
byte[] |
raw USB descriptors |
getSerial
public String getSerial ()
Returns the serial number for the device. This will return null if the device has not been opened.
Returns | |
---|---|
String |
the device serial number |
releaseInterface
public boolean releaseInterface (UsbInterface intf)
Releases exclusive access to a UsbInterface
.
Parameters | |
---|---|
intf |
UsbInterface |
Returns | |
---|---|
boolean |
true if the interface was successfully released |
requestWait
public UsbRequest requestWait (long timeout)
Waits for the result of a UsbRequest.queue(ByteBuffer)
operation
Note that this may return requests queued on multiple
UsbEndpoint
s. When multiple endpoints are in use,
UsbRequest.getEndpoint()
and UsbRequest.getClientData()
can be useful in determining how to process
the result of this function.
Android processes UsbRequests
asynchronously. Hence it is not
guaranteed that requestWait(0)
returns a request that has been
queued right before even if the request could have been processed immediately.
Parameters | |
---|---|
timeout |
long : timeout in milliseconds. If 0 this method does not wait. |
Returns | |
---|---|
UsbRequest |
a completed USB request, or null if an error occurred |
Throws | |
---|---|
BufferOverflowException |
if the number of bytes read or written is more than the
limit of the request's buffer. The number of bytes is
determined by the length parameter of
UsbRequest#queue(ByteBuffer, int) |
TimeoutException |
if no request was received in timeout milliseconds. |
requestWait
public UsbRequest requestWait ()
Waits for the result of a UsbRequest.queue(ByteBuffer)
operation
Note that this may return requests queued on multiple
UsbEndpoint
s. When multiple endpoints are in use,
UsbRequest.getEndpoint()
and UsbRequest.getClientData()
can be useful in determining how to process
the result of this function.
Returns | |
---|---|
UsbRequest |
a completed USB request, or null if an error occurred |
Throws | |
---|---|
IllegalArgumentException |
Before API android.os.Build.VERSION_CODES.O Build.VERSION_CODES.O : if the number of
bytes read or written is more than the limit of the
request's buffer. The number of bytes is determined by the
length parameter of
UsbRequest#queue(ByteBuffer, int) |
BufferOverflowException |
In API android.os.Build.VERSION_CODES.O Build.VERSION_CODES.O and after: if the
number of bytes read or written is more than the limit of the
request's buffer. The number of bytes is determined by the
length parameter of
UsbRequest#queue(ByteBuffer, int) |
setConfiguration
public boolean setConfiguration (UsbConfiguration configuration)
Sets the device's current UsbConfiguration
.
Parameters | |
---|---|
configuration |
UsbConfiguration |
Returns | |
---|---|
boolean |
true if the configuration was successfully set |
setInterface
public boolean setInterface (UsbInterface intf)
Sets the current UsbInterface
.
Used to select between two interfaces with the same ID but different alternate setting.
Parameters | |
---|---|
intf |
UsbInterface |
Returns | |
---|---|
boolean |
true if the interface was successfully selected |
Protected methods
finalize
protected void finalize ()
Called by the garbage collector on an object when garbage collection
determines that there are no more references to the object.
A subclass overrides the finalize
method to dispose of
system resources or to perform other cleanup.
The general contract of finalize
is that it is invoked
if and when the Java virtual
machine has determined that there is no longer any
means by which this object can be accessed by any thread that has
not yet died, except as a result of an action taken by the
finalization of some other object or class which is ready to be
finalized. The finalize
method may take any action, including
making this object available again to other threads; the usual purpose
of finalize
, however, is to perform cleanup actions before
the object is irrevocably discarded. For example, the finalize method
for an object that represents an input/output connection might perform
explicit I/O transactions to break the connection before the object is
permanently discarded.
The finalize
method of class Object
performs no
special action; it simply returns normally. Subclasses of
Object
may override this definition.
The Java programming language does not guarantee which thread will
invoke the finalize
method for any given object. It is
guaranteed, however, that the thread that invokes finalize will not
be holding any user-visible synchronization locks when finalize is
invoked. If an uncaught exception is thrown by the finalize method,
the exception is ignored and finalization of that object terminates.
After the finalize
method has been invoked for an object, no
further action is taken until the Java virtual machine has again
determined that there is no longer any means by which this object can
be accessed by any thread that has not yet died, including possible
actions by other objects or classes which are ready to be finalized,
at which point the object may be discarded.
The finalize
method is never invoked more than once by a Java
virtual machine for any given object.
Any exception thrown by the finalize
method causes
the finalization of this object to be halted, but is otherwise
ignored.
Throws | |
---|---|
Throwable |