Motorola USB08 - Manual (Page 137)

Universal USB Device Driver (USBIO)
Overview
USB08 Evaluation Board Designer Reference Manual
MOTOROLA Universal USB Device Driver (USBIO) 137
• Multiple USB devices can be controlled by USBIO at the same
time
• Multiple applications can use USBIO at the same time
The USBIO device driver can be used to control any USB device from a
Win32 application running in user mode. Examples of such devices are
• telephone and fax devices
• telephone network switches
• audio and video devices (e.g. cameras)
• measuring devices (e.g. oscilloscopes, logic analyzers)
• sensors (e.g. temperature, pressure)
• data converters (e.g. A/D converters, D/A converters)
• bus converters or adapters (e.g. RS 232, IEEE 488)
• chip card devices
If a particular kernel mode interface (e.g. WDM Kernel Mode Streaming,
NDIS) has to be supported in order to integrate the device into the
operating system, it is not possible to use the generic USBIO driver.
However, in such a case it is possible to develop a custom device driver
based on the source code of the USBIO though. Please contact
Thesycon if you need support on such kind of project.
Although the USBIO device driver fully supports isochronous data pipes,
there are some limitations with respect to isochronous data transfers.
They result from the fact that the processing of the isochronous data
streams has to be performed by the application which runs in user mode.
There is no guaranteed response time for threads running in user mode.
This may be critical for the implementation of some synchronization
methods, for example when the data rate is controlled by loop-back
packets (see the USB Specification, Chapter 5 for synchronization
issues of isochronous data streams).
However, it is possible to support all kinds of isochronous data streams
using the USBIO driver. But the delays that might be caused by the
thread scheduler of the operating system should be taken into
consideration.