Introduction
Introduction
Thank you for choosing QuickUSB
®
. QuickUSB makes your product a well-
connected USB device quickly and with a minimum of hassle. Not only is
QuickUSB a quick way to get connected to USB, it also offers great Hi-Speed
USB 2.0 performance with a wide variety of target interface options.
We hope this guide will answer all of your questions about QuickUSB. However,
if you have a question that you cannot find an answer for in this guide, please
check the web site at
and please use the QuickUSB online
support forum. Our support team will do our best get you the answer you need.
QuickUSB and the Big USB Picture
Please take some time to understand the big picture as it relates to USB
connections. USB has gained the success it has because it is a well-designed
bus specifically designed to easily, and reliably connect peripherals to a PC.
Part of that design defines the relationship between your PC and the device.
Although with QuickUSB you do not need to learn the inner workings of USB, you
do need to understand the basics of USB. We will explain the basics here and if
you want to learn more, you can browse
and learn just about
everything that there is to know about USB. Just be careful, because you can
easily get distracted from what you really need to accomplish.
USB Nomenclature
Conveying the big picture requires defining some key words. The first is
USB
and it is an acronym for Universal Serial Bus.
Host
means your PC.
Device
means the QuickUSB module and/or the subsystem you need to connect to the
PC. A
pipe
is a unidirectional virtual connection between a host and the device.
Every pipe has a direction attribute of either
IN
or
OUT
to indicate the direction
of data flow
with respect to the host
. An
endpoint
is the device side connection
of a pipe. When a device is connected to a host, the host automatically senses
this and
enumerates
the bus to find it.
USB System Architecture
The USB is a master/slave bus. This means that the master initiates all traffic
on the bus and the slave can only respond to the master. For the USB, the
master is the host computer (your PC) and the slave is the device. This
master/slave relationship means that interrupts are not possible on the USB.
The USB supports a pseudo-interrupt scheme involving low-latency
interrupt
endpoints
so the host can perform low-latency device polling to emulate an
interrupt. QuickUSB does not currently support interrupt endpoints.
USB
Nomenclature
1