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Modbus Organization Newsletter, Summer 2012

Bringing Water to the People of

Lara…

Member company ProSoft Technology becomes

involved in a critical water project in Venezuela:

Management of water resources in a state with

large urban areas in addition to many acres of

agriculture isn’t an easy task, no matter what

part of the world you are in.

HidroLara is responsible for administering drink-

ing water in the Venezuelan state of Lara, which

has a population of 2 million people, and includes

Barquisimeto.

continued on page 3

Getting Value from Your

Modbus Org Membership

For many of us, the start of the academic year

is a good time for reflection and assessment.

Planning to gear up for a busy fall?

We thought it would be a good moment to re-

view the benefits of Modbus Organization mem-

bership and remind you of the ways to make

the most of it.

All member organizations should take full ad-

vantage of the various publicity and promotion

opportunities we make available.

Members receive preferential listings in the

Modbus supplier and device directories. These

directories are among the most frequently vis-

ited pages of the Modbus.org site, as users

search the directories for appropriate Modbus

compatible devices for their projects.

Are all your Modbus devices listed? Are spec.

sheets or links to technical data included?

Member companies also publish Modbus appli-

cation stories and product announcements on

both the website and in the newsletter. Two

such stories are in this edition, and we’re al-

ways looking for more content to share about

uses of the ubiquitous Modbus protocol from

around the world.

Were you aware that you can advertise on the

Modbus.org website?

With

a half million pages served to almost 30,000

unique visitors each month,

what better place to ad-

vertise your Modbus devices and software ?

for a rate sheet. A special member's dis-

count makes banner advertising an even better deal for

Modbus Organization member companies.

For general level members, technical benefits include a

free Modbus TCP Developer’s Toolkit, discounts on

Modbus Conformance testing, and eligibility to be-

come a self-testing entity.

if you have questions about your member-

ship or you’re ready to become our newest member.

Hope it’s been a

restful and relaxing

summer!

News about the World’s Most Popular Protocol

Member News

JVL Industri Elektronik A/S

develops and produces electronic

controls for stepper and servo

motors. The company offers a

wide selection of products for mo-

tion control, including integrated

AC-Servo motors and Stepper

motors: AC-Servo motor control-

lers; DC-Servo motor controllers;

Member News

Industrial Data Xchange

(IDX)

is one of the Modbus

Organization’s newest member

companies.

IDX is a South African-based

Industrial IT company, providing

the products and services to Sub-

Saharan Africa. The company

offers industrial communications

expertise and products such as

(industrial gateways, interfaces,

test tools and remote monitoring.

Acting as a distributor for

Anybus, COMsoft, HMS

Industrial Networks &

PROCENTEC, IDX also designs

and manufactures its own

products.

IDX provides training and

support for many industrial

fieldbuses and protocols

including Modbus. The IDX

Academy includes the

PROFIBUS Competence Center

and OPC Competence Center for

the region.

Ewing/Kessler,Inc.,

based in

Hernando , Mississippi,

specializes in providing total

building automation and

integration solutions from

concept and design, to fully

installed and managed systems.

Focusing on the total system

provides innovative, customized,

broad-spectrum plans for the

future based on individual needs

and desires. Committed to

relationships, E|K

AUTOMATION prides itself on

being dedicated to service, and

responsive to the needs of its

clients.

and Motor drivers.

Most recently, JVL announced its

integrated servo motor MAC 141

in a stainless steel version espe-

cially for the food and medical

industry. The MAC 141 has an

option for built-in PLC,

RS232/485, Profibus, CANbus or

industrial Ethernet (including

Modbus TCP and more).

These stainless steel motors are

designed to handle IP67 and

withstand high-pressure wash

down conditions. The concept is

based on a totally sealed

stainless steel tube with

stainless steel front flange and

rear cover.

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

Bringing Water to the People of Lara, cont’d...

Water resources are somewhat

scarce in the state, and special

management is essential.

Besides its urban areas, such as

Barquisimeto, the state of Lara is

largely agrarian.

HidroLara began a pilot project

in 2011 at its Los Dos Cerritos

water substation, which collects

water and distributes it from the

Los Dos Cerritos reservoir: The

company installed a supervisory

system based on Rockwell Auto-

mation’s Factory Talk coupled

with wireless communication. At

the time, the Venezuelan water

company was having a difficult

time integrating the supervisory

system and end devices, because

of the multiple communication

protocols involved, including

Modbus and PROFIBUS DP.

Gathering data from the Los Dos

Cerritos Reservoir and its aptly

named substation is critical. “It’s

a fundamental part of the city, as

a large amount of water is taken

through these two facilities,” said

Juan de Sousa of LS Innova-

ciones, the integrator who de-

vised the solution.

LS Innovaciones proposed a new

communications architecture at

the Los Dos Cerritos Water Sub-

station using ProSoft Technol-

ogy’s gateways to communicate

between the PROFIBUS DP and

Modbus RTU network. Their so-

lution involved both wired and

wireless communication. On one

end, radios were transmitting

signals from pumps into the

Hidrolara network, while the

gateway was controlling and

gathering data for the discharge

valves on the other end of the

network via PROFIBUS and

Modbus.

De Sousa said. “Our company

often connects different devices,

and having a platform like Pro-

Soft is very important. We have

used different ProSoft gateways

with different protocols including

Modbus, Profibus, DNP 3.0,

Ethernet/IP and Modbus TCP,

and they all work correctly. We

have also used ProSoft wireless

devices, which have given us very

good results.”

HidroLara can see all the vari-

ables in the water substation and

check important variables, such

as the flow levels from the Los

Cerritos Reservoir.

“Hidrolara is very happy with

this project,” de Sousa said.

“They can see all the variables in

the substation. They want to do

this project in five additional sub-

stations.”

De Sousa chose ProSoft Technol-

ogy’s gateways, because they sup-

port a variety of protocols that

can be used in many different

applications.

“ProSoft Technology offers sev-

eral products that interface dif-

ferent communication protocols,”

De Sousa also added that ProSoft

Technology products are easy to

configure and its technical sup-

port is top notch. “Latin-

American Support Engineer Jose

Victor provides excellent support

when there is any question about

the product.”

Victor Garcia,

ProSoft Technology

Products such as ProSoft’s ProLinx

family Modbus Master/Slave to

PROFIBUS Master communications

gateway (5104-MCM-PDPMV1) create

a connection between devices on a

Modbus network and PROFIBUS DP

Slave devices. The module is a stand-

alone DIN-rail mounted protocol gate-

way that provides one serial port and

one PROFIBUS Master DB9F port.

Member News

to this task researched client-to-

client connectivity, and ulti-

mately discovered the Device-

Master UP’s capabilities on a

respected online forum. Hesi-

tantly beginning the application,

the integrator was highly satis-

fied with the end result.

As seen in the diagram, Comtrol

was able to address this integra-

tor’s problem using the Device-

Master UP 2-Port 2E Modbus

gateway running Modbus TCP

firmware. Information coming

from each control system/Modbus

client device would be routed

through serial Modbus RTU into

the DeviceMaster UP.

Internally, the firmware essen-

tially provides a Modbus server

to respond to each (external) cli-

ent’s commands. The servers are

then internally linked to each

Member News

Modbus TCP Master-to-Master Communication ...

A large oil and natural gas plat-

form in the North Sea was ex-

panding its facility capabilities

by adding a massive system mod-

ule (over 1.5 million lbs) to the

existing platform infrastructure.

In order for the two systems to

communicate seamlessly with

one another, the proper commu-

nication channels needed to be

established.

other to complete the communi-

cation process. Unless one views

the DeviceMaster UP’s internal

configuration, the end user only

observes that he/she is able to

connect one client to another suc-

cessfully .

The Modbus TCP firmware is the

original DeviceMaster UP Mod-

bus application. It was designed

to provide great flexibility for

connecting both Modbus serial

servers and Raw/ASCII devices

to a variety of Modbus control-

lers and applications. Such ad-

vanced Raw/ASCII options as

filtering, command/response

mode, peer-to-peer Modbus com-

munications, and simultaneous

connections to multiple Modbus

controllers and/or Ethernet TCP/

IP applications make the Modbus

TCP firmware the flagship of all

Modbus gateways.

Control systems on each struc-

ture were configured to commu-

nicate 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 com-

municate as a master (client),

while traditional Modbus com-

munication takes place between

a master and a slave (server).

Each structure’s respective de-

velopers had invested substan-

tial resources into their control

systems, so the systems integra-

tor needed to find a way to over-

come this obstacle by converting

one configuration to act as a

server in the most cost-effective

way possible – or by making two

Modbus client devices communi-

cate with one another.

Many industry experts have e

pressed that client-to-client

Modbus communication is impos-

sible, but Comtrol had developed

an innovative process to make a

Modbus client communicate with

another client.

The systems integrator assigned

Member News

Modbus Discussion

Member News

Modbus Discussion

Q&A from the Modbus Discussion Forum...

Firmware Update an Embedded System over Modbus RTU using UART...

Vee posted this message to

the forum :

Can I update the firmware of an

embedded system using Modbus

RTU over UART? If yes, what

function code needs to be used for

firmware update? and how?

Currently, my system supports 1,

2, 3, 4, 5, 6, 15, 16, 23 function

codes.

A quick reply will be highly ap-

preciated.

David replied:

I’m aware of one control device

that uses Modbus for download

and upload of configurations. It

uses function codes 20 and 21 to

transfer the configuration data.

That same device applies firm-

ware updates with a Windows

based “loader” application that

manages the firmware data

download.

My gut feeling is that if you have

to ask how to accomplish a firm-

ware update, you’re not in a posi-

tion to execute an update suc-

cessfully.

Vee responded:

Can you please name that control

device? [In] what format [do] you

receive a file on the device; how

does it get stored in memory?

I’m a novice programmer for

Modbus and firmware update.

I’ve implemented Modbus using

some function codes as men-

tioned.

Your response refers to function

codes 20 (0x14) & 21 (0x15)

which are Read File Reference &

Write File Reference respectively.

I feel that there is no file read or

write function under Modbus.

Does the use of the function code

16 (0x10), which would allow to

write 200 bytes of data per mes-

sage, from PC to device resolve

my problem?

Following are the steps I would

like to implement for firmware

update through Modbus RTU

over serial (loading device with a

new image file):

1. Break down the image file (FW

update) into groups of bytes not

to exceed 200 bytes per group.

2. Encapsulate each of the 200

byte groups as write register

commands (i.e., add destination

Modbus Address 1-249), function

code (16 (0x10) = write multiple

registers), starting address (two

bytes, value depends on how you

are managing the counting of

groups), qty = 2 bytes value 200

decimal, and than the error check

(CRC-16 two bytes).

3. Transmit the groups of bytes

from PC to device ONE group at

a time. As the response indicates

that group of bytes is received,

send the next one.

4. Assemble the file from the re-

ceived groups on the other end

(slave).

Please correct me if I’m wrong.

Lynn August Linse jumped in:

As someone else pointed out,

most vendors either use proprie-

tary functions like 0x7D, or the

file read/write. Using standard

functions like 16 will be prob-

lematic since Modbus holding

registers have no notion of mov-

ing 128Kbytes as a whole, which

is why the file read/write is pre-

ferred.

Plus how are you going to pre-

vent missing a block or duplicat-

ing a blocks? Imagine this situa-

tion — you write block #75, the

slave sends a response so now

expects block #76, but your mas-

ter misses the response and re-

sends block #75.

In your design you are already

demanding a custom “master”

tool breaking up the file and

sending it, as well as a custom

“slave” function — why bother

misusing using function 16?

What does it buy you? Problems

is all that I can see you gaining.

The file read/write include off-

sets, plus if I understand the

standard correctly the 10000

‘records’ can be, for example, 200

bytes each, so one could move a

file of up to 2 MB. If your prod-

uct has different text/code seg-

ments, those could be different

files which allow you to replace

the code in phases.

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