E.5.3 data transfer requests, E.5.3.1 bulk and interrupt transfers, E.5.3 – Motorola USB08 User Manual
Page 182: Data transfer requests, E.5.3.1, Bulk and interrupt transfers, Universal usb device driver (usbio)
Designer Reference Manual
USB08 Evaluation Board
182
Universal USB Device Driver (USBIO)
MOTOROLA
Universal USB Device Driver (USBIO)
E.5.3 Data Transfer Requests
The USBIO device driver exports an interface to USB pipes that is similar
to files. For that reason the Win32 API functions
ReadFile
and
WriteFile
are used to transfer data from or to a pipe. The handle that
is associated with the USB pipe is passed as
hFile
to this function.
The
ReadFile
function is defined as follows:
BOOL ReadFile (
HANDLE hFile,
// handle of file to read
LPVOID lpBuffer,
// pointer to buffer that receives data
DWORD nNumberOfBytesToRead,
// number of bytes to read
LPDWORD lpNumberOfBytesRead,
// pointer to number of bytes read
LPOVERLAPPED lpOverlapped
// pointer to OVERLAPPED structure
);
The
WriteFile
function is defined as follows:
BOOL WriteFile (
HANDLE hFile,
// handle of file to write
LPVOID lpBuffer,
// pointer to data to write to file
DWORD nNumberOfBytesToWrite,
// number of bytes to write
LPDWORD lpNumberOfBytesWritten,// pointer to number of bytes written
LPOVERLAPPED lpOverlapped
// pointer to OVERLAPPED structure
);
By using these functions it is possible to implement both synchronous
and asynchronous data transfer operations. Both methods are fully
supported by the USBIO driver. Refer to the Microsoft Platform SDK
documentation for more information on using the
ReadFile
and
WriteFile
functions.
E.5.3.1 Bulk and Interrupt Transfers
For interrupt and bulk transfers the buffer size can be larger than the
maximum packet size of the endpoint (physical FIFO size) as reported
in the endpoint descriptor. But the buffer size has to be equal or smaller
than the value specified in the MaximumTransferSize field of the
USBIO_INTERFACE_SETTING (
) structure on the Set
Configuration call.