Fieldservers and protocol converters

A FieldServer is a type of communications bridge or gateway that is designed to either convert one protocol to another as the messages are sent or map tags from different devices and handle communications.

03/05/2016


While programmable logic controllers (PLCs) are common in the industrial world, when it comes to controlling buildings and campuses in the commercial space the landscape looks a bit different. Instead of production machinery, the equipment and facilities involve environmental controls; boiler rooms, chilling plants, lighting controllers, security systems etc. HVAC systems, computer uninterruptible power supply (UPS) systems and gas monitoring are also tied into the network.

There are many different manufacturers and vendors in this space that may use different protocols for communications between systems and devices. Some may be the same as those in industry; Profibus and Modbus are common. Others, such as BACnet, are specific to the building automation and control world.

Back in the 1990s I did a few projects where data had to be exchanged and converted. It involved working with things like Allen-Bradley’s SLC based BASIC module and writing computer code on a dedicated PC. This was very time-consuming and expensive. Now, the cost and time involved has been reduced significantly due to devices like FieldServers. 

A FieldServer is a type of communications bridge or gateway. Some are designed to simply convert one protocol to another as the messages are sent. Others actually map tags from different devices to one another and handle communications in both directions. This involves onboard memory and some configuration.

A cool thing about this device is that it uses three different sets of registers; the server side mapped to the PLC and specific to it's names and structures, an intermediate internal register which can be manipulated by doing math or swapping bytes with each tag or group, and the client side mapped via BACnet to the building control system. This allows the naming conventions and structures to be dictated by both parties involved.

The FieldServer can only read "flat" tags, which means that the tags all have to be mapped from their structured form into basic BOOLs, DINTs and REALs. While this is pretty easy, tags still have to be entered manually into the code by browsing for their location in the software. They also have to be typed into the FieldServer configuration file. That means a lot of copy and paste from Excel.

Frank Lamb is the founder of Automation Consulting Services Inc. This article originally appeared on the Automation Primer blog. Automation Primer is a CFE Media content partner. Edited by Chris Vavra, production editor, Control Engineering, CFE Media, cvavra@cfemedia.com.

ONLINE extra

For more articles on PLCs and programming, see related articles below.



No comments
The Engineers' Choice Awards highlight some of the best new control, instrumentation and automation products as chosen by...
The System Integrator Giants program lists the top 100 system integrators among companies listed in CFE Media's Global System Integrator Database.
The Engineering Leaders Under 40 program identifies and gives recognition to young engineers who...
This eGuide illustrates solutions, applications and benefits of machine vision systems.
Learn how to increase device reliability in harsh environments and decrease unplanned system downtime.
This eGuide contains a series of articles and videos that considers theoretical and practical; immediate needs and a look into the future.
Robotic safety, collaboration, standards; DCS migration tips; IT/OT convergence; 2017 Control Engineering Salary and Career Survey
Integrated mobility; Artificial intelligence; Predictive motion control; Sensors and control system inputs; Asset Management; Cybersecurity
Big Data and IIoT value; Monitoring Big Data; Robotics safety standards and programming; Learning about PID
Featured articles highlight technologies that enable the Industrial Internet of Things, IIoT-related products and strategies to get data more easily to the user.
This article collection contains several articles on how automation and controls are helping human-machine interface (HMI) hardware and software advance.
This digital report will explore several aspects of how IIoT will transform manufacturing in the coming years.

Find and connect with the most suitable service provider for your unique application. Start searching the Global System Integrator Database Now!

Mobility as the means to offshore innovation; Preventing another Deepwater Horizon; ROVs as subsea robots; SCADA and the radio spectrum
Future of oil and gas projects; Reservoir models; The importance of SCADA to oil and gas
Big Data and bigger solutions; Tablet technologies; SCADA developments
Automation Engineer; Wood Group
System Integrator; Cross Integrated Systems Group
Jose S. Vasquez, Jr.
Fire & Life Safety Engineer; Technip USA Inc.
This course focuses on climate analysis, appropriateness of cooling system selection, and combining cooling systems.
This course will help identify and reveal electrical hazards and identify the solutions to implementing and maintaining a safe work environment.
This course explains how maintaining power and communication systems through emergency power-generation systems is critical.
click me