Posts Tagged ‘Modbus’

Ward Systems Inc. Auto-Guided Manufacturing Vehicle

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An industrial automation manufacturing company located in Grass Valley, California, needed to create and design a working communication system to connect multiple devices on auto-guided machines.  Ward Systems Inc., designs manufactures and distributes automated pallet handlers used in warehouse and industrial settings.

Ward Systems AGV auto-guided vehicle

In order for the handlers to be automatically guided through a warehouse with precision, cameras attached to the vehicle itself must be as accurate as possible.  These cameras also need to interact with a PLC running Modbus TCP/IP, which writes and ready data to and from the cameras’ power for efficient battery usage.

As shown to the right, five cameras needed to communicate with a PLC on each handler.  Ward Systems decided to use Comtrol’s DeviceMaster® UP 4-Port and a daisy-chained DeviceMaster UP 1-Port to provide support for each camera.  All of the cameras are directly connected to one network switch, which is then connected to the DeviceMaster switch, which is then connected to the DeviceMaster UP 4-Port and DeviceMaster UP 1-Port.  The PLC is also connected to the network switch, along with a detachable PC used for configuration and programming.  An RFID reader and a custom PCB board connect to the two remaining ports on the DeviceMaster UP 4-Port.

The cameras on the pallet handlers support raw/ASCII data, while the PLC supports Modbus TCP/IP.  Comtrol’s DeviceMaster UP enables communication between the two different protocols to make the entire system a success.

Comtrol’s DeviceMaster UP is designed to provide innovative PLC to device connectivity.  The DeviceMaster UP provides EtherNet/IP, Modbus/TCP, Modbus RTU/ASCII, and PROFINET IO connectivity to a wide variety of devices.  A highly advanced raw/ASCII device interface functionality simplifies PLC programming and ensures robust operation.  These features greatly simplify connecting devices such as bar code scanners, RFID readers, weigh scales, vision systems, printers, encoders and sensors to PLCs.  The DeviceMaster UP’s many unique features provide connectivity options and flexibility not provided by other gateway products.

For more information about Comtrol’s DeviceMaster products, please visit

DeviceMaster® UP Plays Key Role in Oil Pipeline Monitoring

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Modbus Router

System critical automation processes, such as monitoring oil pipelines, can be very demanding on a communication infrastructure.  Performing reliable real-time communication over long distances from multiple Modbus masters to large numbers of remote devices can be a major challenge.  The communication equipment must be highly flexible and robust to perform such a task and the DeviceMaster UP meets that challenge.

oil pipeline monitoring device server modbus

When a major oil company asked Comtrol to help them upgrade their current pipeline infrastructure, Comtrol provided a solution with the DeviceMaster UP running our Modbus Router firmware.  Highly flexible and robust, the Modbus router provided the required communication needs.  Multiple Ethernet and serial Modbus masters were connected to multiple serial Modbus slaves.  The flexible Modbus routing capabilities, the wide operating temperature range, and the robust operation provided by the DeviceMaster UP proved to be the perfect solution.

the process of transporting oil from the oil well to the refining plant must be monitored very closely in order to ensure the total overall health of the system.  Sensors all the way along the length of the pipeline must be constantly checked to ensure safe flow rates, pressure levels and temperatures are maintained.  When a problem is detected, it must be quickly dealt with to avert a possible shutdown or, in worse cases, a catastrophic failure.

Satellite links are used to connect the control center where the SCADA systems reside, to remote Ethernet networks.  It is at those remote Ethernet networks where the DeviceMaster UP provides simultaneous connections between both Ethernet and dial-up modem-based serial Modbus masters to the Modbus slave devices.  In this way, all the individual remote networks, or subnets, are combined to form one large network.  Comtrol’s Modbus Router provides the required real-time connectivity between the Modbus controllers and devices on the network.

Modbus Router Firmware

Modbus router DeviceMaster UP

  • Highly flexible with many Modbus connectivity options
  • Masters: Modbus/TCP, Serial Modbus RTU/ASCII, and Modbus RTU/ASCII over Ethernet TCP/IP
  • Slaves: Modbus/TCP and Serial Modbus RTU/ASCII
  • Automatic protocol conversion and routing
  • Turn serial Modbus masters into Modbus/TCP masters for network wide connectivity
  • Connect Modbus masters to Modbus devices anywhere on a network
  • Simultaneously connect multiple Modbus masters to individual slave devices

Modbus/TCP Master-to-Master Communication

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Modbus/TCP Communication

A large oil and natural gas platform in the North Sea was expanding their facility capabilities by adding a massive system module (over 1.5 million lbs) to the existing platform infrastructure.  In order for the two systems to communicate seamlessly with one another, the proper communication channels needed to be established.

Control systems on each structure were configured to communicate with each other through a serial Modbus RTU RS-232 or RS-485 channel.  However, the Modbus device configuration on each side was designed to communicate as a master, while traditional Modbus communication takes place between a master and a slave.

Each structure’s respective developers had invested substantial resources into their control systems, so the systems integrator needed to find a way to overcome this obstacle by converting one configuration to act as a slave in the most cost-effective way possible – or by making two Modbus master devices communicate with one another.  Many industry experts have expressed that master-to-master Modbus communication is impossible, but Comtrol had already developed an innovative solution to make a Modbus master communicate with another master.

Modbus TCP Master-to-Master Communication

The systems integrator assigned to this task researched master-to-master connectivity and ultimately discovered the DeviceMaster® UP’s capabilities on a respected online forum.  Hesitantly beginning the application, the integrator was highly satisfied with the end result.

As seen in the diagram, Comtrol was able to fix this integrator’s problem using the DeviceMaster UP 2-Port 2E Modbus gateway running Modbus/TCP firmware.  Information coming from each control system/Modbus master device would be routed through serial Modbus/TCP firmware.  Information coming from each control system/Modbus master device would be routed through serial Modbus RTU into the DeviceMaster UP.  Internally, the firmware essentially provides a Modbus slave to respond to each (external) master’s commands.  The slaves are then internally linked to each other to complete the communication process.  Without viewing the internal configuration, the end user only observes that the DeviceMaster UP enables a successful connection from one master to another.

The Modbus/TCP firmware is the original DeviceMaster UP Modbus application.  It has been designed to provide great flexibility for connecting both Modbus serial slaves and Raw/ASCII devices to a variety of Modbus controllers and applications.  Such advanced Raw/ASCII options as filtering, command/response mode, peer-to-peer Modbus communications, and simultaneous connections to multiple Modbus controllers and/or Ethernet TCP/IP applications make the Modbus/TCP firmware the flagship of all Modbus gateways.

For more information on Modbus master-to-master communication please contact support at 763.957.6000

For more information about Comtrol’s DeviceMaster products, please visit

DeviceMaster UP – “Is it really that easy?”

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DeviceMaster UP – Industrial Ethernet Gateway Connectivity

At Comtrol, we believe that gateways should be intelligent, robust and easy to use… and we enjoy explaining that, “Yes, it really is that easy.” With its web-based configuration, example programs, and simplified interfaces, the DeviceMaster UP delivers near plug-and-play Industrial connectivity. To learn more about the DeviceMaster UP’s features including:

DeviceMaster UP industrial ethernet gateway

  • Protocol Flexibility – offering EtherNet/IP, PROFINET IO, Modbus/TCP, Modbus RTU & Modbus/ASCII connectivity
  • DualConnectPlus™ technology
  • Applications
  • Web-based configuration
  • Large received packet support
  • Intelligent packet identification

… and more, (including protocol specifications and highlights) click here!


Industrial Automation – Bar Code Scanning

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As industrial automation continues to develop and make processes such as scanning, packaging, shipping and assembly more efficient, Comtrol’s products have provided the connectivity required to integrate crucial elements in the automation system.

Bar Code Scanner

In conjunction with Compunetics Systems, a Michigan-based company specializing in automated data collection; Comtrol has contributed to a comprehensive communications solution specifically designed for bar code scanning. Compunetics has developed a custom enclosure containing Comtrol’s DeviceMaster® UP and an internal voltage converter to power the scanning system and convert ASCII serial data from the bar code scanner to EtherNet/IPPROFINET IO or Modbus/TCP (industrial network protocols) for the end programmable logic controller (PLC).

As seen in the diagram, the enclosure has three ports, enabling an RS-232 serial connection, a 24VDC power supply connection and an Ethernet connection. Twenty four volts of direct current power are delivered into the enclosure; once inside the enclosure the standard 24VDC of power is stepped down to five volts where +5VDC is wired into pin nine of the serial port, easily powering the attached scanner. The DeviceMaster UP industrial Ethernet gateway has a flexible power input of 5-30VDC thus allowing performance on the enclosure’s five volt circuit. This serial power delivery eliminates the need to introduce an extra power supply for the bar code scanner. The bar code scanner then sends information and process data back through the serial connection to the DeviceMaster, which routes the information over Ethernet (EtherNet/IP, RROFINET IO or Modbus/TCP) to a PLC.

This joint industrial hardened solution not only enables the automation system, but the enclosure decreases necessary cabling and is customizable upon customer request. Installation is easy; all that is required is the enclosure, a 24VDC power supply, Ethernet cabling, DeviceMaster UP configuration and scanner connection.

Comtrol’s DeviceMaster UP is designed to provide innovative PLC to device connectivity. The DeviceMaster UP provides EtherNet/IP, Modbus/TCP, Modbus RTU/ASCII, and PROFINET IO connectivity to a wide variety of devices. A highly advanced raw/ASCII device interface functionality simplifies PLC programming and ensures robust operation. These features greatly simplify connecting devices such as bar code scanners, RFID readers, weigh scales, vision systems, printers, encoders and sensors to PLCs. The DeviceMaster UP’s many unique features provide connectivity options and flexibility not provided by other gateway products.

DeviceMaster® UP Alternative Configuration: “The Serial Port Splitter”

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DeviceMaster UP

At times we have had customers request the ability to take a signal from one serial port and split it into many serial ports, like a simple sort of “Y cable.”  Officially, our classic serial products like DeviceMaster and RocketPort have never been marketed with the ability to behave as serial splitters.  In conventional wisdom, RS-485 and RS-422 are discussed as point-to-point or multidrop and RS-232 as exclusively point-to-point, with neither really being commonly thought to be suitable for splitting.

Well, as it happens, the DeviceMaster UP (DMUP) with Modbus/TCP firmware can be configured as a “serial splitter.”

One rarely discussed feature of Modbus/TCP firmware has NOTHING to do with Modbus – the user can configure just the serial port settings and an application TCP connection and basically ignore all the other parameters that may typically be involved when configuring Modbus/TCP firmware; In this sense the DMUP is doing just what we would do with an RTS running socket server.

However, the “application TCP connection” interface in Modbus/TCP firmware allows up to SIX connections to one serial port:

I have tested this arrangement and it works beautifully.

Secure Port Redirector, which is of course a free download from our website, can be used to send those 6 socket data streams to virtual COM ports.  (I.E. If you are running apps on a PC or Server, using Secure Port Redirector to obtain virtual COM ports is going to be nearly the same as having real serial ports installed on the PC.  There are small differences that may matter in some cases, contact Comtrol Technical Support if you need details.)  So now you have one ASCII device going to SIX virtual COM ports!

DeviceMaster UP serial port splitter gateway

IN ADDITION, if the you need a serial port split into multiples and those multiples need to be REAL HARDWARE, not virtual COM ports (say there is no computer involved, or any other reason to avoid virtual,) you CAN USE, for example, a DeviceMaster UP 4-Port:

One serial port is fed to the other 3 using internal socket connections, so that you have a 1 to 3 split, bidirectional.  Anything coming out the 1 port goes to all 3, anything coming out any of the 3 just goes to the 1.

If you need a splitter, and the serial devices are scattered all over the place, just buy one DMUP 1P to implement the “serial – 6 sockets” application described above, and use individual DMRTS (or UP) at each endpoint to convert the socket back to serial.  Now you’ve got a DISTRIBUTED Serial port Splitter- pure hardware based.

Note: Any of the six connected applications (on sockets) can write back to the one serial port at any time.  If they attempt to write to the serial port simultaneously, there will be no control over which socket is writing at a given moment and therefore the data streams may be improperly mixed.  In this sense, the configuration behaves like a literal (physical) splitter.  The user must be able to control which socket applications are writing at any given moment, or else use the configuration in a “monitor only” fashion.  Alternatively, the system could be designed so that there is only ONE read-write connection with the others all running as “read only.”  There is no provision in the Devicemaster UP to explicitly configure a path as read only or read-write, but the user must simply be aware of what the application CAN and CANNOT do.  It CAN allow one serial port to send data to six sockets.  It CANNOT control which of those sockets replies back to the serial port; The user must take responsibility to ensure that simultaneous writes from multiple sockets to one serial port DO NOT occur.

Long story short, if you need to run an application involving serial port splitting- we can do it!

– Nolan Kariniemi

Wide-Area Network Performance Diagnostics

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DeviceMaster® RTS & Modbus Server

Modbus ServerA research and natural resource development company in remote northern Canada was experiencing some unexpected performance issues between devices in their wide-area wireless network.  Diagnostics information provided by the Modbus server firmware for this company’s system indicated specific problems with some of the devices. With help from the diagnostic information and Comtrol’s technical team, read how the company was able to determine solutions to the system failures.


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