Globally Serial: Extending the Reach of your Serial Devices Around the World
Incorporating embedded server technology to connect RS232 devices to high-speed Ethernet eliminates the distance limitations of serial communications
Integration of serial devices into a business network infrastructure offers distinct advantages for businesses seeking to centralize their operations, overcome the distance limitations of standard serial communications or lower costs associated with hands-on administration of these devices. However, integrating serial communications into a network is difficult as Ethernet topology is not capable of directly transmitting serial data from one device to another. In order for a business to take advantage of simplifying their overall operations, this limitation needs to be overcome.
Most devices used in data acquisition or control applications, such as time clocks, traffic control signals, data collectors and alarm panels are usually serial based because it is a reliable and low-cost technology. Some manufacturers are beginning to offer Ethernet integration by modifying the design of their products to provide Ethernet connectivity. Unfortunately, these Ethernet-capable serial devices are often expensive. Because of the higher cost of new Ethernet-capable devices any cost benefits realized from enabling serial communications over longer distances is often overshadowed by new equipment costs.
An alternative to purchasing the higher priced Ethernet-capable serial equipment is simply to install an external device that enables serial data communications to be directly integrated into the Ethernet topology.
"The simplest way to transfer serial RS232 data over an Ethernet network is to use an external device that can directly connect the equipment to a network," explains Russ Straayer, President of Data Comm for Business (DCB), a leading manufacturer and distributor of a diverse line of data communication devices. "The device needs to simply convert the serial data into IP packets for transport over the networkeither a corporate intranet or the Internet. It needs to do this efficiently, and reliably. Our EtherPath will directly connect any serial device to an Ethernet network and enable serial communications over long distances. And with our newest firmware employing Ethermodem technology, a client Etherpath can be made to dial a server Etherpath using modem type AT commands and IP addresses."
The EtherPath is a single port serial server that can provide an RS-232 connection over an Ethernet LAN and will support TCP/IP, SNMP, as well as HTML configuration. It will connect serial management ports directly to an Ethernet network via either the 10BaseT or the 10Base2 connector to allow a "remote" serial port via telnet. The EtherPath also can connect any two asynchronous serial devices when used in client-server mode to provide a point-to-point connection between the devices. About the client-server mode, Russ Straayer says "We call this a nailed up connection. This path can be totally transparent to the end devices".
Once the serial device is accessible through an Ethernet, there are several common uses that applications can be grouped into.
The first is providing direct access to a serial device to manage it or collect its data. "One of the most common uses is telnet to the Etherpath from a PC, which gives you the equivalent of a remote PC serial port," relates Straayer. "Perhaps there is a PC sitting on your desk connected to the LAN. Elsewhere you may have one or more devices you need to control, normally through an RS232 port. If its too far away for a regular serial cable, or you want to reduce the wiring in your office, or maybe multiple people need to get at the same serial device, an EtherPath on the device would enable anybody to access it over the network. COM: port redirector software could also be used. This allows un-modified PC software to access that remote device as if it were directly connected to a local COM: port on the PC."
A second prime application is configuring two devices in a mode that creates a "nailed" connection. Each time the devices are powered up, a connection is forced between the two EtherPaths, and the devices attached to them. These serial devices can now communicate with each other over any network just as if they were connected to each other by a standard serial cable. This type of connection creates a virtual serial cable that can "piggy-back" over the Internet to any place on the globe.
"Someone may need a plain old RS232 path and theyd like to use the in-place high speed Ethernet wiring thats already there. Configure two EtherPaths with a "nailed-up" connection. One is configured as a server and the other as a client," explains Straayer. "A nailed up, dedicated EtherPath connection between two EtherPath devices, one configured as a server and one as a client, basically turns the Ethernet into a long RS232 cable. With a pair of EtherPaths, one client and one server, now have a virtual serial cable that literally reaches to anywhere in the world."
DCBs customer applications illustrate the convenience and versatility connecting serial devices into the network can give a business:
Factory Floor Data Acquisition
Many data recorders and collectors that monitor the critical processes of manufacturing operations are RS-232/RS-485 serial devices. Industrial automation brought wired LAN capability to most factory floors. The EtherPath enables these devices to connect in a multi-drop capability directly to the LAN network.
Quality control operations that use mechanical devices to test products on the manufacturing line are also usually RS-485 serial bus-driven. With EtherPath, these devices can be connected in a multi-drop configuration using the existing factory floor LAN network instead of RS-485.
"The EtherPath lets you take an Ethernet network and use it in place of the old multi-drop RS485 system," affirms Straayer. "This helps provide integration between factory floor and office environments".
Time clocks are used in almost every business, and are usually placed in different locations within a company. Reaching them to retrieve their data for payroll without network connectivity is time consuming.
"Connectivity into the Ethernet LAN allows for easy retrieval of the information from the time clocks to do payroll and so on," explains Straayer. "Without network connectivity, access to their data is often attained by dialing into the time clocks through individual modems attached to each clock, or somebody has to walk around to manually dump the data onto a disk. Since the time clocks already have a serial port, rather than re-engineering the time clocks, an EtherPath can be attached to it and the data can be pulled right over the network to wherever it needs to be."
Security Door Access Devices
Security door access devices can be programmed to only allow authorized employees to enter buildings, rooms or other restricted areas and are now quite common.
"An international corporation uses the EtherPath to centralize the management of their security access devices located in all of their subsidiary offices," says Straayer. "You can go to New York from their headquarters, San Francisco, or a plant or sales office, wherever it might be. They can allow you in or not allow you in based on your employee ID card. All of the information is updated centrally, because they use the EtherPath to piggy-back over the corporate network."
More and more cities are relying on LANs to connect all of their departments. An EtherPath that can add RS232 devices such as traffic lights and the entire traffic control system, into their LAN systems enables them to get rid of individual dial-up modems or leased lines for each device, which is a cost savings. In addition, the remote management of traffic control devices can streamline resetting or reprogramming the devices when they malfunction.
Automatic scanners and test readers that score students tests are usually RS-232 driven. Like almost every other serial device, if you dont have a direct connection to the device, a dial-up modem has to be installed to gain access. The EtherPath allows the school to connect the scanners to the LAN network so that a user can communicate over the LAN to any or all of the graders and retrieve their data.
Hospitals rely on devices that can monitor patient functions and trigger alarms to alert hospital staff of a dangerous condition. Historically, these monitors and alarms are usually serial-port based, especially most of the code alarms. The addition of an EtherPath to the monitoring device or code alarm can allow access to the data and code alarms through the LAN infrastructure of the hospital.
Most alarm control panels are RS232-controlled. Without a question alarm companies must monitor and manage devices that may be at customer sites in their service areas at great distances from each other. For companies that have an Ethernet connection to their various locations, access to their RS232-controlled alarm panels can be achieved by attaching the EtherPath to their alarm control panels.
Integrating serial communications into an Ethernet pathway can streamline a business operations by bringing data to or from locations not reachable through other means. The simplest solution, a device like the EtherPath, makes this goal achievable without the costs of replacement serial devices that are Ethernet-capable.
For more information on serial-to-Ethernet connectivity, remote LAN management and the EtherPath, contact Data Comm for Business (DCB) at (217) 897-6600 or (800) 4-DCB-NET; write to them at 2949 County Road 1000 N, Dewey,IL. 61840; or visit their web site at http://www.dcbnet.com.
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Written by Julie Lugar, a Technical Writer based in Torrance, CA. She has been a freelance writer and on-line journalist in the past 10 years.
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