AN169

2

Rev. 2.3

2. USBXpress Versions

The USBXpress v4.0 and above driver incorporates Microsoft's WinUSB driver rather than the proprietary driver of

v3.x, and both the underlying driver and the DLL have changed. To use USBXpress v4.0, install the latest driver

from the website (www.silabs.com/interface-software) and upgrade the DLL.

The API to the DLL remains unchanged, but there is one new API call added to the library: SI_CancelIo(). This API

call replaces CancelIo() and should be used if the software calls SI_Read() or SI_Write() in overlapped mode and

the software needs to cancel I/O operations. The SI_CancelIo() function cancels read and write requests in both

the DLL buffer and the driver buffer, whereas CancelIo() only cancels requests in the driver buffer, leaving

outstanding requests in the DLL.

The AN220 Driver Customization software provides an option to customize either the v4.0 and above driver or the

v3.x driver for legacy applications. Customizations of the v4.0 and above WinUSB driver will still require

recertification through Microsoft. The AN220 software can be found here: www.silabs.com/interface-appnotes.