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Modbus Organization Newsletter, December 2012

Wireless Communications in the

Industrial Space

Member company connectBlue brings its expertise

in wireless communications to bear every day for its

customers. In this issue, connectBlue’s chief tech-

nology officer, Mats Andersson, offers a bird’s eye

view of the role of wireless in industrial communica-

tions. Links to a longer paper can be found at the

end of this article.

Wireless communication has been used in industrial

applications for more than 30 years. Among its first

applications was the wireless control of Automated

Guided Vehicles (AGV) and cranes in warehouses

where proprietary radios were used to achieve flexi-

ble control of the moving devices. During the last 10

years, standardized radio technologies such as

Wireless LAN (IEEE 802.11),

continued on page 3

Modbus Protocol V1.1b3 Posted

on Modbus Web Site

The Modbus Organization has posted a new ver-

sion of the Modbus protocol specification on the

web site. Modbus Protocol v1.1b3 corrects some

acronym misnomers and replaces the traditional

master/slave language with the more appropriate

client/server construct.

Expect similar changes to the implementation

guides in short order. Other updates are under-

way as well.

New Addition to Modbus

Resources Page

The Modbus Organization’s Technical Resources

page

list of resources

for Modbus developers and

users continues to grow.

The newest listing is an open-source multi-

platform Modbus library for .Net. Cet Electronics

offers a series of open-source Modbus libraries

written in C#. They support RTU (binary only),

TCP and UDP, both client and server. The librar-

ies target .Net Micro Framework, Windows

Phone, and standard .Net (incoming). High ab-

straction for easy pluggability, and extensibility.

Multi-threading and C# 5 are supported. Very

easy to use.

Wishing you all

the best in 2013!

News about the World’s Most Popular Protocol

Member News

Since 1990,

Hjelmslund Elec-

tronics

has been completing

industrial automation projects

according to customers’ specifica-

tions. Today the company works

with smaller and more complex

technologies, using ARM micro-

processors (Primarily ARM7),

USB, Bluetooth and other tech-

nologies in customer-specified

projects.

Member News

Elecsys Corporation

provides

innovative machine-to-machine

(M2M) communication

technology solutions, custom

electronic equipment and

displays for critical industrial

applications worldwide. The

company’s primary markets

include energy production and

distribution, agriculture, water

management, aerospace,

military, safety and security

systems, and transportation. The

company’s culture and

philosophy place a high emphasis

on innovation, quality, reliability,

and customer support.

Elecsys Corporation’s

Director

Industrial Communications

Gateway

is a cost-effective

remote field data

communications device designed

for data acquisition and control

applications, which

communicates via Modbus TCP

or Modbus over serial line.

Toronto-based

Accuenergy

was

founded in 1998. The company is

a research, design and

manufacturing organization,

specializing in power

measurement meters and

software for the distribution,

control and management of

electric energy and other

dynamic processes.

Accuenergy’s Acuvim series of

energy meters include three-

phase multifunction power

meters, multi-circuit power and

energy meters, multifunctional

DC power meters, and single-

phase multifunction power

meters — used in energy

management, industrial

automation, wide area power

monitoring, power quality

analysis, substation automation,

and many other applications.

Hjelmslund Electronics’ own

products include the USB485

family of Modbus RTU-

compatible USB-to-RS485 con-

verters — unique because of

their isolation barrier and com-

pactness, typically found only in

much larger converters.

Modbus Newsletter

This is the newsletter of the Modbus

Organization, the international nonprofit

organization devoted to the evolution and

support of the Modbus protocols.

The Modbus Organization Mission

The Modbus Organization, Inc. is a group of

independent users and suppliers of automation

devices that seeks to drive the adoption of the

Modbus communication protocol suite and the

evolution to address architectures for distributed

automation systems across multiple market

segments. Modbus Organization also provides the

infrastructure to obtain and share information about

the protocols, their application, and certification to

simplify implementation by users resulting in

reduced costs.

For more information about membership and

other services, please refer to our website:

www.modbus.org

Newsletter Editor:

Lenore Tracey (lenore@modbus.org)

Modbus Organization, Inc.

PO Box 628

Hopkinton, MA 01748 USA

ph +1-508-435-7170

Member News

Applications where rapid roam-

ing is required. Bluetooth tech-

nology is used for Human Ma-

chine Interfaces (HMI), program-

ming, service/maintenance as

well as real-time control tasks.

During the last few years, other

technologies such as IEEE

802.15.4 (ZigBee, Wireless Hart,

etc.) and Bluetooth low-energy

technology have become increas-

ingly used for sensors, actuators

and other small devices.

The adoption of wireless in an

industrial environment is typi-

cally a gradual process. Initial

requirements include the crea-

tion of islands of wireless en-

abled devices connected to an

existing wired network. The

wired network may be a stan-

dard IP-based network or a field-

bus network, such as Modbus

TCP, Profinet, Devicenet,

Controlnet or Interbus-S.

connectBlue’s white paper

describes some of the specific

requirements for wireless com-

munication technology in indus-

trial applications. The paper con-

siders the following topics in

more detail:



Serial cable replacement

Ethernet cable replacement

and Ethernet infrastructure

Seamless roaming

Fieldbus cable replacement

Smart phone/other mobile

device applications

Wireless sensors and actua-

tors network

Industrial requirements for

wireless technologies

Coexistence of multiple wire-

less technologies.

Member News

Wireless Communications, cont’d...

IEEE 802.15.4 and Bluetooth

technology (IEEE 802.15.1) have

become the dominant technolo-

gies.

Wireless solutions offer several

advantages in industrial applica-

tions. They are used to increase

mobility, eliminate expensive and

high-maintenance transmission

media (such as flexible cables

and swivels), and overcome the

problems associated with large or

problematic zones, such as public

roadways.

Moxa’s new Profibus-to

-Modbus TCP gateway

Moxa recently released its MGate

5101-PBM-MN Profibus-to-

Modbus TCP gateways series with

PI certification. The MGate 5101-

PBM-MN gateway features enable

bridging Profibus devices

(Profibus drives or masters) to

Modbus TCP masters (SCADA or

PLCs) with ease.

Industrial plants typically consist

of multiple devices intercon-

nected in different ways. These

devices may include simple I/Os,

intelligent sensors, single-loop

controllers or programmable con-

trollers, and devices for data log-

ging and supervisory control.

The devices may be intercon-

nected using different communi-

cation protocols and media types,

which, in some cases, can be re-

placed by wireless technologies.

No one wireless technology offers

all the features and strengths

that fit the various industrial

application requirements; there-

fore, standardized wireless tech-

nologies Wireless LAN, Bluetooth

technology and IEEE 802.15.4, as

well as number of proprietary

technologies, are all used. The

main requirement could be high

data throughput, robustness or

low power (the latter especially

for battery-operated devices).

Wireless LAN is often used for

production planning and data

acquisition, as well as

Its rugged design with optional

built-in optical isolation, and -40

to 75°C wide-temperature opera-

tion, ensure reliable performance

for use in industrial applications

such as oil/gas, power, process

automation and factory automa-

tion.

With a little help from

our friends...

Modbus member company

Acromag, recently pointed out a

helpful Wiki page

with explicit

instructions for taking raw Mod-

bus data and uploading it to

iDigi as “Dia Data” for access by

Web services.

Many thanks to Lynn Linse at

Digi for his continuous support to

the Modbus community. A fre-

quent contributor to the Modbus

discussion forums, he seems to

always be there with useful

advice for those with Modbus

questions and quandaries.

Member News

Modbus Discussion

Member News

Modbus Discussion

Q&A from the Modbus Discussion Forum...

Using Modbus data packets and setting up the

registers to be read from a Modbus master...

New user posted this message

to the forum:

I’m new using Modbus and would

like some help, if possible. I have

an application where I need to

output data in Modbus format

over Ethernet to Experion Soft-

ware. I believe Automation Di-

rect’s H2-ECOM 100 module is

all I need, but not sure.

Once the PLC process is done, I

need to download all my user in-

puts (recipe data) to Experion. It

appears all I need is to use a con-

version sheet that targets V

memory. Specifically, I just enter

the V memory into the spread-

sheet and it tells me the Modbus

number to use.

I have not worked with Experion,

but am assuming this Modbus

“number” is what the Master

needs to pull that data. From a

PLC ladder logic point of view I

don’t have to write any additional

logic beside the Load and Output

for assigning user inputs to re-

ceipt V memory. Correct?

William Sturm replied:

Sounds to me like you have the

overall right idea...

Steve Myres concurred:

Correct. With the 205 PLC, Mod-

bus/TCP comms to an H2-

ECOM100 (or Modbus RTU

comms to Port 2) target the same

block of V-Memory you address

in ladder, so you don’t have to

move the data you’re interested

in to a special location or any-

thing like that.

To make it even easier, the ad-

dresses (for Modbus FCs 3 and

16) are even the same, once you

allow for the fact that ADC mem-

ory addresses are in octal. V2000

is Modbus 1024, for example (you

might see it as 1025, depending

on Experion’s implementation of

Modbus).

Coils are almost as easy. Convert

the “C” address to decimal and

add 3072, IIRC.

You don’t even need to use ADC’s

spreadsheet if you don’t want to.

Excel has the DEC2OCT() func-

tion in the Analysis Toolkit, and

between that and drag-and-fill,

you pretty much have everything

you need.

Read more or add your com-

ments

to this thread.

Modbus comms &

total time scan...

VSS asked:

Both analog and discrete values

are fetched from a PLC via

RS485 2W Modbus. How much

time does it take to read value

for analog (numeric) value and

digital (holding register) value

till the values are displayed in

DCS system?

I read somewhere that it takes 5

sec for numeric and 1 sec for dis-

crete value.

What effect it will have if sev-

eral devices are put using multi-

drop?

Can anyone confirm this?

The Modbus Community



Active technical discussions



Knowledge aggregation



Contact with Modbus users

Discussion supported by...

Join!

Design!

Test!

Promote!

Apply!

We’re with you. The Modbus Or-

ganization is there to help suppli-

ers and users of the Modbus proto-

col succeed. Our members range

from Modbus device suppliers, to

system integrators, end users, and

educational institutions.

The common link? They all value

the information and services pro-

vided by the Modbus Organization,

and they all play a role in deter-

mining the future of the world’s

most broadly applied protocol.

Visibility: Your Company &

Your Products

Your membership in the Modbus

Organization also opens the door

to a powerful range of visibility

options to highlight your company

as a supplier of Modbus-based

products.

Exposure on our website, our

newsletter, and through our vari-

ous trade show appearances are

all options that allow you to make

the most of your Modbus Organi-

zation membership.

Your company will also value the

opportunity to participate in our

technical committees. There, your

company’s knowledge, experience

and technology can help guide

future enhancements, extensions,

and adaptations of Modbus to

keep it the world’s leader for dec-

ades to come.

Modbus TCP Toolkit v3.0

The Modbus TCP Toolkit provides

all the necessary pieces to develop

a Modbus-compliant device, in-

cluding documentation, diagnostic

tools, sample source code, and pre-

test software to prepare for Mod-

bus conformance certification.

Designing with Modbus

Modbus developers rely on the

Modbus Organization for valued

assistance with their projects:



Start by downloading specifica-

tions and other design documents

from the modbus.org website.



To save time,

purchase the Mod-

bus TCP Toolkit

CD (FREE to

general members); it contains

source code and a myriad of other

resources.



If you come across technical is-

sues that have you stumped, post

your question on the

modbus.org

forum.

One of the many experi-

enced Modbus implementers who

frequent this forum will likely

have your answer.

Time to Apply

When it comes time to get your

Modbus network up and running,

it’s comforting to know that hun-

dreds of thousands of applications

have preceded yours. But what if

things don’t go as planned?

Again, the

modbus.org forum

ready to answer your questions

and provide guidance. Thousands

of users from diverse backgrounds

participate in the forum, giving

you a powerful base of experience

from which to draw.

The Future is Yours

Whatever your role in the use of

Modbus, consider joining the Mod-

bus Organization. You’ll get the

support you need today, and have

opportunities to help guide Mod-

bus to a dynamic future.

Download the Modbus Organiza-

tion Membership Application

learn about the different member-

ship levels and their associated

benefits.

The toolkit is available as a bene-

fit of corporate-level membership

in the Modbus Organization or can

be purchased separately for

US$500 plus shipping and han-

dling. The toolkit contains the fol-

lowing items:

Modbus Documentation



Modbus Application Protocol

Specification, v1.1b



Modbus Messaging on TCP Im-

plementation Guide, v1.0b

Tools



Modbus TCP Client & Server

Diagnostic Tools

Conformance Testing

When your project’s done, how do

you know it really conforms to the

Modbus specification? How do your

users know?

The answer starts with running the

conformance test suite included

with your Modbus TCP Toolkit.

This self-test helps you check your

design assumptions and catch the

subtle “gotchas” that might other-

wise slip through your design re-

view.

Then

submit your product for test-

ing

to the Modbus Organization for

conformance testing. We’ll certify

your product as compliant, and

post that information on the Mod-

bus website for the world to see.

Sample Source Code



Modbus TCP Sample Client

Code for Visual Basic Win32



Modbus TCP Sample Client

Code for C/C++ Win32



Modbus TCP Sample Server

Code for C/C++ Win32



Modbus TCP Sample Server

Code for C VxWorks



Modbus TCP Sample Server

Code for C++ VxWorks

Modbus Conformance Testing



Conformance Test Tool v3.0



Conformance Test Tool v2.1

Additional Resources

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