Universal Serial Bus (USB) ports have become very popular and most new computers come installed with two or more. Users are comfortable with the advantages of USB’s plug and play and with the variety of peripheral devices that can be easily connected. However, there are still many legacy devices, especially in industrial automation environments, where RS232 (and RS422 / RS485) serial connectivity works just fine. It is for these devices that USB to RS232 converters are ideally suited.
Here are five important features to look out for before choosing a supplier’s USB converter product.
Feature #1: Support for Microsoft Vista and Windows 7 Operating systems.
Although most manufacturers supply drivers for earlier Microsoft system software, as well as for Apple Mac and Linux, there have been performance issues with some manufacturers’ converter products and Microsoft’s newer releases that show up as screen freezes, crashes and connectivity problems.
Solution: Check that the converter comes with drivers that have been optimized for these two Microsoft offerings. (For more detailed information search online for info on Microsoft’s “Windows Hardware Quality Lab” (WHQL) and “Virtual Com Port” (VCP)).
Feature #2: Protection Against Electrostatic Discharge (ESD)
If the operating environment is prone to voltage spikes and surges then a USB converter that protects against ESDs of up to 15 kV and against current surges of up to 600 W/ms is a wise investment. Make sure your USB to RS232 or USB to RS485 converter is designed for these tough conditions.
Feature #3: Supports A Range of Converter Product Offerings
It’s important that your supplier is able to understand the marketplace and provide various converter solutions to satisfy it. For example, some customers require only mini USB to RS232 or USB to RS422 converters, while others insist on multiport, industrial-grade converter hubs. A supplier that can support a range of USB converter products most likely is serious about delivering excellent products and customer service. While this may seem like a ‘soft’ feature, and more on the marketing side, it can be the decider if you have to choose from more than one supplier.
Feature #4: LED ‘Lights On’ Management
While this may not be necessary on the cheaper, single port converters, for multi-port USB to RS232 converter hubs, it’s a useful feature to have when first troubleshooting possible connectivity issues.
Feature #5: Compatible with USB 2.0 and compliant with USB 1.1
Most newer computers come with USB 2.0 ports but there are still those that have only the older USB 1.1 ports. Engineers showing up on-site with older notebook computers may appreciate this backward compatibility one day!
Taken together, when these five features are found in a USB to Serial converter product you can be confident that the device has been engineered to perform to a high standard.
Wednesday, June 23, 2010
Tuesday, June 1, 2010
USB to RS232 Converters – An Introduction
Many people are familiar these days with the use of universal serial bus [USB] ports on their desktop, laptop and notebook computers. The widely used USB 2.0 specification supports a 480 Mbps transfer rate and is popular because computer users can easily connect a wide range of consumer electronics devices and computer peripherals to their computers without having to configure 'dip switches' or install dedicated interface boards.
Although the 'plug'n'play' functionality of USB is its greatest benefit over older and cumbersome ways of connecting and configuring devices, there are still devices that do not support (or physically have installed) USB ports, but do possess RS232 serial ports.
Here is where USB to RS 232 converters have a role to fulfill by connecting computer and RS232 peripheral together.
However, there's more to successfully connecting, for example, an RS232-enabled GPS phone to a computer's USB port, than just manufacturing an appropriate cable. Sophisticated converter electronics plus operating system dependent device driver software are, in addition to the cable itself, what make up a reliable USB to RS-232 converter.
The reason for this complexity lies partly in how software engineers and application programmers have interpreted and coded for the RS232 specification over the years.
The complete details are beyond the scope of this article but in essence the fact that the RS232 specification defines only the interface, and not the protocol to be used, has given implementers a lot of freedom.
Bottom line: application or operating system device driver ways of communicating with RS232 ports introduced a 'flexibility' which does not appear in the more inflexible USB interface specification.
This means that communicating with RS232 via a USB port introduces the requirement for RS232-style UART device driver emulations. So we now have two device drivers involved over a USB Bus with the potential for timing conflicts that can interrupt and delay RS232 communications.
On the hardwire side, there are known issues with various RS232 line driver chips that can result in RS232 input port behavior outside of the original specification.
Another problem that can show up in cheap USB to RS232 converters is an inability to perform the hardware flow control required by some (but no all) applications.
Of course, identifying which applications use software flow control and which use hardware flow control is often beyond the knowledge of the converter manufacturer. And the application itself may make irregular and unclear use of hardware flow control.
The lesson here is to pay careful attention to how the USB to RS232 converter handles application timing, RS232 signaling and hardware flow control. This is particularly important in industrial automation scenarios, although don't be surprised to also experience irregular issues with poorly designed converters in office computing locations.
In contrast, the leading USB to RS232 converter manufacturers use well regarded processor chips in their top end products, such as those from FTDI Semiconductors. They also provide simple to install device drivers supporting popular operating systems such as Windows (including Windows 7 and Vista), Linux and Mac.
Visit USconverters.com to find out more about RS232 to RS485 converter products, free Tools and Diagnostic software.
Although the 'plug'n'play' functionality of USB is its greatest benefit over older and cumbersome ways of connecting and configuring devices, there are still devices that do not support (or physically have installed) USB ports, but do possess RS232 serial ports.
Here is where USB to RS 232 converters have a role to fulfill by connecting computer and RS232 peripheral together.
However, there's more to successfully connecting, for example, an RS232-enabled GPS phone to a computer's USB port, than just manufacturing an appropriate cable. Sophisticated converter electronics plus operating system dependent device driver software are, in addition to the cable itself, what make up a reliable USB to RS-232 converter.
The reason for this complexity lies partly in how software engineers and application programmers have interpreted and coded for the RS232 specification over the years.
The complete details are beyond the scope of this article but in essence the fact that the RS232 specification defines only the interface, and not the protocol to be used, has given implementers a lot of freedom.
Bottom line: application or operating system device driver ways of communicating with RS232 ports introduced a 'flexibility' which does not appear in the more inflexible USB interface specification.
This means that communicating with RS232 via a USB port introduces the requirement for RS232-style UART device driver emulations. So we now have two device drivers involved over a USB Bus with the potential for timing conflicts that can interrupt and delay RS232 communications.
On the hardwire side, there are known issues with various RS232 line driver chips that can result in RS232 input port behavior outside of the original specification.
Another problem that can show up in cheap USB to RS232 converters is an inability to perform the hardware flow control required by some (but no all) applications.
Of course, identifying which applications use software flow control and which use hardware flow control is often beyond the knowledge of the converter manufacturer. And the application itself may make irregular and unclear use of hardware flow control.
The lesson here is to pay careful attention to how the USB to RS232 converter handles application timing, RS232 signaling and hardware flow control. This is particularly important in industrial automation scenarios, although don't be surprised to also experience irregular issues with poorly designed converters in office computing locations.
In contrast, the leading USB to RS232 converter manufacturers use well regarded processor chips in their top end products, such as those from FTDI Semiconductors. They also provide simple to install device drivers supporting popular operating systems such as Windows (including Windows 7 and Vista), Linux and Mac.
Visit USconverters.com to find out more about RS232 to RS485 converter products, free Tools and Diagnostic software.
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