 USB Converters – Essential Components for
Today’s Industrial Connections
The Challenge of Industrial Disconnect
Finding a new computer today that will ship with the once standard DB-9
and DB-25 connections, and that will communicate with your RS-232
and RS-422/485 devices is a significant challenge.
As the high-speed Universal Serial Bus (USB) has progressively
dominated the consumer market, these slower and more cumbersome
connections have become obsolete to the masses. Following typical
supply and demand procedures, PC manufacturers have simply stopped
providing them as standard hardware, replacing them with USB
components.
This shift in the marketplace represents somewhat of an obstacle for
industrial players, as most of their current electronic equipment utilizes
RS-232 and RS-422/485 interfaces to communicate with their computer
systems.
Consequently, a major connectivity gap has emerged between industrial
electronics and today’s computers.
Understanding How and Why
USB Dominance Came to Be
USB was officially introduced to the world in 1995, although the concept
had been in the works since before 1994. The concept was the brainchild
of a consortium of seven companies that combined their resources to
advance the ways computers connect to peripherals and other
components.
The original consortium of seven companies, now called the USB
Implementers Forum, Inc (USB-IF), has grown to include over 1000
members that help steer the promotion and development of USB
technologies. Leading participants within the USB-IF include industry
players such as Intel, Hewlett Packard, Microsoft, NEC and Phillips.
It is little wonder that USB has so quickly obtained such a dominant
market presence. Prior to USB technologies, adding and subtracting
peripherals to your computer system or network required powering down
the system, making the adjustment, rebooting the system and then
installing necessary drivers. This process took time and consumed
valuable human resources. Additionally, more often than not, additional
internal components, such as PCI cards, were required to make the
addition, further complicating installation procedures and expenditures.
USB technologies have radically changed this process. USB allows users
to “hot swap” components – or add and subtract peripherals such as printers, cameras, scanners, and a
wide range of Human Interface Devices
(HID’s) without rebooting. And while device drivers are still necessary,
the installation process has been expedited and simplified, especially
considering that drivers are only installed once when a device is first
connected.
A final aspect of USB technologies that have made it so appealing is its
expansion capacities. A standard DB-9 connection has little flexibility in
controlling multiple external components and peripherals. One
connection controls one piece of equipment. In stark contrast, when
combined with USB hubs, adequate PC resources, and proper wiring, a
single USB port can manage as many as 127 devices. This feature
instantly frees up internal computer space, saves on buying additional
hardware, eliminates the need for setting COM ports and IRQ’s, and
provides for almost instant installation of new peripherals.
The Technical Capacities and Specifications of USB
Supported Operating Systems
Windows 98 was the first OS to support USB connections right out of the
box. Since then, virtually every OS on the market is USB enabled.
Support for Windows 95 has since been added and third party solutions
have been created for support in NT 4.0.
Logos and Terms
There are various USB logos, each with different meanings and
corresponding product specifications.
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Standard USB Logo – Current logo that designates the existence of
a USB connection. Can be USB 1.0, 1.1, or USB 2.0. Data transfer
rates can vary from 1.5Mbps to12 Mbps. |
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High-Speed USB Logo – Indicates the presences of USB 2.0 with
transfer capacities of up to 480Mbps. |
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USB On-the-Go Logo – A unique version of USB technology, this allows
certain types of peripherals, such as PDA’s and cell phones to connect
directly to each other, without a computer acting as host. Can be USB
1.0, 1.1, or 2.0 with speeds varying from 1.5Mbps to 12Mbps |
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USB On-the-Go High Speed Logo – Always USB 2.0 technology
with transfer speeds of up to 480Mbps. |
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USB Wireless Logo – The latest in USB technology that allows
peripherals and computers to communicate without a hard connection at
distances of up to 30 meters and at speeds of up to 12Mbps. |
All version types are backward compatible and will support previous
versions by slowing down transfer rates. Baud and version rates can coexist
on the same bus, but it is recommended that high-speed and low
speed devices be separated for maximum performance.
Data Transfer Rates and Terms
- Low or Normal Speed 1.5Mbps
- Full Speed 12Mbps
- High Speed 480Mbps (USB 2.0)
Note: Not all USB 2.0 devices are certified for High Speed transfer rates. Look for the USB High Speed Logo to ensure maximum capacity.
Technical Specifications
- Max wire length -- 5 meters
Note: Can be extended to 30 meters
by adding a series of hubs.
- Max number of hubs -- 5
- Max number of devices per USB port -- 127
Note: Hubs count as a device
- Low power device -- 100mA
- High power device -- 500mA
- Wiring Configuration -- Star topology
- Signal Levels (volts)
-- 0.0-0.3 (low), 2.8-3.6 (high)
- Communication type -- Half-duplex
Wiring Types
There are 4 types of wiring systems used with USB. All use Shielded
Twisted Pair (STP) cabling.
USB Type A
 
USB Type B
 
Pin Numbers and Function
1 = VBUS (4.75-5.25 volts)
2 = D-
3 = D+
4 = GND
Bridging the Gap - Connecting to USB
The technology gap between existing industrial equipment and today’s
computers does create a challenge for many companies. Fortunately, it is
an obstacle that is quickly and inexpensively solved.
The solution lies in the emergence of a wide range of USB converters.
These converters give companies the freedom and flexibility to utilize the
latest computer power and resources, while maintaining their fully
operational, legacy peripherals and equipment.
What To Look For
USB converters come in a wide variety of shapes and sizes. The
challenge is that many connectors of the same pin configuration do not
necessarily make the necessary conversions or meet the required baud
rates.
For example, a USB to serial converter connecting a 9-pin DB9, will
typically only have the capacity to connect to RS-232 devices. However,
supported operating systems, baud rates, cable types, buffer rates,
duplexing capabilities and a number of other factors can vary greatly.
The same type of variables hold true with USB to RS-422 and RS-485
converters.
Because of these differences, it is essential that you know the exact
specifications needed for the conversion process. Here are seven
essential elements to consider:
- Are you converting from RS-232, RS-422, RS-485 or do
you have a need to move all of them through on USB host?
- What transfer rates are required?
- What duplex do you need for your RS-485 communications?
- Are you dealing with DB9 or DB25 connectors? Male or
female?
- When making the conversion, do you need optical isolation
to withstand harsh environments?
- What handshake requirements
do you have and does the converter meet those needs?
- Does the converter meet the voltage needs of your RS-232, 422, 485 device?
Installation
Once these fundamental questions have been answered and the
appropriate converter selected, bridging the gap is a very simply process.
Simply plug in the converter to USB port on the computer and connect
your peripheral to the other end. On the first connection, all necessary
drivers will need to be installed, but after that you can freely hot swap
elements and components as necessary.
An Overview of USB Converter Benefits & Features
- Is a low cost solution for connecting existing equipment to
today’s computer systems
- Frees up computer’s internal hardware space
- Eliminates time consuming set up of confusing IRQ’s, I/O
addresses and COM Ports
- Allows hot swap so numerous peripherals can be added and/or
subtracted instantly
- Up to 127 devices can be added and controlled by a single USB
port. This minimizes costs and maximizes resources
- Automatic and seamless adjustments for various version types
and baud rates
- Converters available for virtually every industrial situation and
application.
- Readily converts RS-232, RS-422 and RS-485 to USB,
regardless of connector pin configuration
- Peripherals can be up to 30 meters away from controlling
computer system
- USB converters allow companies to save valuable resources of
time, money, and human resources by avoiding costly hardware
upgrades, and moving to a true “plug and play” hot swap
environment
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