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Modbus Organization Newsletter, Spring 2011

Modbus Joins Wireless

Cooperation Team

We are delighted to announce that the Modbus

Organization has become the fourth member of

the Wireless Cooperation Team (WCT). Mod-

bus has joined with Fieldbus Foundation,

PROFIBUS Nutzerorganisation e.V., and the

HART Communication Foundation to work

cooperatively on the development of wireless

gateway specifications based on WirelessHART

and the emerging

ISA SP 100.11a

standard.

In the course of the

project the team is de-

veloping use cases, re-

quirements, and specifi-

cations for wireless

communication with

intelligent field de-

vices in process

New Set-up Video for

ProSoft i-View

ProSoft Technology is of-

fering a

new tutorial

demonstrate how to imple-

ment the ProSoft i-View

for use on a Modbus TCP

network quickly and eas-

ily. The ProSoft i-View

transforms iPad, iPhone,

or iPod touch devices into mobile human ma-

chine interfaces, enabling live monitoring of

process control data for engineers and plant

floor operators. The mobile app uses ProSoft

Technology’s industrial 802.11 or cellular wire-

less solutions to grant access to control

information by authorized users from virtually

anywhere.

Another Project on Modbus

Technical Resources Page

According to developer Petri Tuomio, Ananas

— technically Modbus TCP Server — is a

mighty fruit supporting two simultaneous TCP

connections. Full scale of 16-bit input and hold-

ing registers are supported (0-65535). Modbus

TCP client is also included (using the server's

address space). Server and client can be used

independently. Ananas also

supports DDE connection to

registers. Why the project is

called Ananas, which means

pineapple in German, remains

a mystery.

measurement and control applications in the

automation industry. The goal of the project is

to design specifications as common as possible,

while ensuring complete compatibility with the

existing wired versions of each participant’s

technology.

As the newcomer to the Wireless Cooperation

Team, the Modbus Organization’s initial work

will be to map the Modbus protocol to

WirelessHART to support the development of a

specification for a gateway whose field side will

accommodate WirelessHART field devices and

whose output uses the Modbus protocol.

News about the World’s Most Popular Protocol

Member News

MatrikonOPC

provides

equipment data connectivity

software based on the OPC

standard. The MatrikonOPC

promise is to empower customers

with reliable data access to all

major automation vendors’

systems, provide practical OPC

training, and deliver superior

client care.

Member News

Based in the north of Spain,

Ingeteam's industry division

integrates mechanical

engineering, electrical, and

automation companies. With over

30 years experience in the

industrial sector,

Ingeteam

has a

long history of developing

products for diverse automation

industries.

The company's INGESYS® family

of products are used in a wide

range of applications including

continuous processes, power

generation, energy distribution

and transport, rail and marine

transport, water treatment and

distribution, and the chemical

sector.

Ingeteam works closely with

qualified integrator and

distributor companies to offer its

INGESYS® automation solutions

around the world.

PiiGAB

develops, markets, and

sells software and hardware for

data communication, data

acquisition and tracking for both

industrial settings and building

automation.

The company introduced its

M-Bus 900 gateway series in

June 2010. The product allows

simultaneous remote reading of

M-Bus meters with up to four

clients. Meter reading can be

mixed using local network, city

network, Internet, normal serial

communication or using an

existing M-Bus master.

The M-Bus 900 gateway allows

parallel connection to a Modbus

client to read values from the M-

Bus meter to a remote device or

to be shown on a local display.

The M-Bus reads all types of

meters including electricity,

heat, and water meters.

With offices in North America,

Europe, Asia-Pacific, and the

Middle East, MatrikonOPC

provides local presence on a

global scale. MatrikonOPC is a

vendor-neutral connectivity

supplier.

The company's Modbus OPC

Server provides secure, real-time

data access between Modbus

devices and any OPC-enabled

applications such as historians,

HMIs, and SCADA.

Modbus Newsletter

This is the newsletter of the

Modbus Organization, the

international nonprofit

organization devoted to the

evolution and support of the

Modbus protocols.

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.

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.

Member News

ProSoft Technology Gives NASA a Boost

Adrienne Lutovsky & Danetta

Bramhall

On July 20, 1969, Apollo 11 suc-

cessfully touched down on the

moon’s surface and people sat

glued to their television sets

waiting for Neil Armstrong and

Buzz Aldrin to be the first men to

walk on the moon. The unflappa-

ble news anchor, Walter Cronkite

took off his glasses, rubbed his

hands together and shot a boyish

grin at the camera. His body lan-

guage spoke volumes to the mil-

lions of people watching with

bated breath to see what is con-

sidered by many to be one of

man’s greatest feats.

In April 1981, the first Space

Shuttle, Columbia, launched and

orbited the earth 37 times before

landing on a runway at Edwards

Airforce Base in California. It

was also the first U.S. manned

space vehicle launched without

an unmanned powered test

flight. NASA described the mis-

sion as: "The boldest test flight in

history.”

The NASA space program has

accomplished feats that have

sparked the imaginations of chil-

dren and writers for the past half

century. But each of these mis-

sions is preceded by years of

stringent adherence to safety and

production requirements.

Safety, Precision & Accuracy

After each countdown to ignition,

a shuttle is propelled into space

by trademark twin flames

streaming from Solid Rocket

Boosters (SRB), which provide 80

percent of the shuttle launch

thrust before they burn out, sepa-

rate, and jettison into the

ocean. NASA recovery

ships retrieve the boosters

and tow them to Hangar

A/F Cape Canaveral Air

Force Station (CCAFS) in

Florida, where they are

disassembled.

The refurbishing of the

boosters for reuse takes

place in two locations. The

entire process from re-

trieval to completion takes

approximately a year.

Refurbishment & Reuse

The engineering teams at

the Assembly and Refur-

bishment Facility are

bound by incredibly rigid

production specifications,

because anything more

than a hairline deviation

can severely affect the

safety of a mission. Of the

SRB’s total weight of 1.25

million pounds, propellant

accounts for 1.1 million

pounds, which burns hot enough

to damage the structural integ-

rity of the boosters.

One of the materials used to pro-

tect the rocket boosters during

ascent, descent and splashdown,

is a USA-developed thermal pro-

tection system called booster

trowelable ablative (BTA). Its

consistency resembles that of

automotive body filler, but it has

much better thermal properties,

which is important because it

protects the booster components

from damage, enabling them to

be reused time and time again.

The mixing of the insulation used

on the flight components is auto-

mated. The batching process is

handled by two functionally iden-

tical machines, using

Micro Motion flow meters to

release precise measures of

resin and catalyst into a mix-

ing vessel, where a Charles

Ross mixer blends them to

form the BTA insulation. The

Kennedy facility sees an av-

erage of five 3000 gram batch

cycles per day.

Controlling the process for

each machine are a Rockwell

Automation Allen-Bradley

ControlLogix PAC and an

SLC-500, respectively. USA

tried using a 4-20 mA feed-

back between the controller

and the flow meters, but

found they were unable to

obtain the required level of

accuracy and precision.

Member News

NASA...

Member News

cont’d from pg 3

“We contacted Micro Motion and

they pointed us to ProSoft Tech-

nology’s Modbus communication

modules, which integrate directly

into the ControlLogix and SLC-

500 platforms,” explained Dan

Dermody, Control Systems Engi-

neer at USA and the machine

builder for this application. “We

tested them out and quickly dis-

covered that they provided the

accuracy and precision we

needed.”

The initial challenge was reach-

ing the data transfer rates re-

quired, which could not be ac-

complished using a standard 4-

20 mA analog input module.

Once we brought the information

over digitally it was a night-and-

day difference. Still, we were

only barely achieving our goal,

and I knew something wasn’t

right with the update rate. So we

worked with ProSoft to identify a

controller programming problem

that essentially caused the con-

troller to write over data within

a millisecond of when I was try-

ing to read it. We now have the

performance we need.”

“Now we’re getting millisecond

update times and we can control

down to the gram level in a 2000

gram batch.”

Because of the level of repeatable

precision USA is able to accom-

plish with this solution, it is not

required to continually test the

adhesive delivery system to

prove its accuracy.

The Future

NASA and the space program are

currently undergoing a major

directional shift with the end of

the space shuttle program.

Presently, USA is building up

the parts for a second test flight

for the Ares Program. While

there has been no official deci-

sion on the exact architecture of

the post shuttle human space-

flight program, one fact will re-

main; the demanding environ-

ment in which rockets must per-

form will require materials with

the highest quality standards

made possible by innovative

solutions.

New ASComm.NET

Modbus Master Driver

Automated Solutions

recently

announced its new

AS-

Comm.NET Modbus Master

Driver.

The package provides

high-performance connectivity to

Modbus RTU and ASCII slave

devices via serial port, encapsu-

lated TCP/IP and encapsulated

UDP/IP, and allows .NET appli-

cation to read/write registers on

Modbus RTU and Modbus ASCII

slave devices.

Key benefits include:



No requirement for third-party

drivers.



x86, x64, and any CPU com-

patible



Visual Studio.NET 2005, 2008

and 2010 compatible



Most .NET targets supported,

including Web, Windows, con-

sole, and service apps.



10-15 mSec typical transaction

time



Optimizes multiple register

configurations into minimal

transactions



Tag database can be configured

via code or visual designer



Abstract base classes allow you

to write generic code that

works with all drivers



Synchronous and asynchro-

nous read/write methods



Data change notifications



Common user interface across

all driver classes

“The module collects flow data

and feeds it directly into the Con-

trolLogix data tables,” Dermody

continued. “This type of flow con-

trol system maintains all the

process parameters, ensuring

that nothing goes out of specifi-

cation during mixing. The Pro-

Soft module made the architec-

ture we wanted to use possible,

and we’ve stuck with that type of

philosophy on our flow meters

ever since.”

Challenges

With specifications allowing for

only plus or minus 2% deviation

on any given batch, USA has a

challenging job.

“In normal industry you can pro-

duce a similar product and get

away with being 10 - 15% off and

it wouldn’t make any difference.

But because of the environment

that these Solid Rocket Boosters

operate in, there is absolutely no

room for error.”

Member News

Modbus Discussion

Member News

Modbus Discussion

Member News

Modbus Discussion

Q&A from the Modbus Discussion Forum...

How to calculate silent interval in Modbus RTU?

Satoshi Sakai asked:

I assume the calculation of silent

interval in 9600 bps is as below.

1/9600(bps) * 11(bits)*3.5(ct) =

4.01 [ms].

A certain manufacturer's slave

device calculates as below be-

cause Modbus RTU is binary.

1/9600(bps) * 4(bits)*3.5(ct) =

1.46 [ms].

Both seem to be reasonable, but I

would like to know which is [the]

correct calculation.

Jerry Miille answered:

Your first calculation is correct,

4.01 msec.

But beware that there are some

implementations that may not do

their timing so precisely! If you

are implementing a new Modbus

driver, then you should consider

making this time "adjustable."

In the end, if your device strictly

adheres to 4.01 msec and my de-

vice does as well, then there will

certainly be synchronization

problems because your clock and

mine are not synchronized ex-

actly. My recommendation is to

have default timing values calcu-

lated as you have shown them

but also be able to override them.

Lynn Linse concurred:

Jerry speaks from experience:

Suppose your customer uses a

cheap "packet radio" to bridge

your 9600 baud signal across a

25-mile gap, then you could find

gaps of from 50 to 500 msec be-

tween every 32 or 50 bytes, and if

satellite is used, these gaps can

be five minutes or more!



Sure it violates the Modbus RTU

spec., but if you cannot handle

these gaps, then your product

cannot be used by the customer;

you don't make the sale.

Not sure about you, but my wife

certainly likes me get paid every

two weeks.

Remember that by watching the

bytes arrive you can estimate the

expected size of the message. For

example, a Modbus RTU function

code 3 request will always be 8

bytes. The response will be five

bytes plus the byte count in third

byte.

You really only need this idle-gap

for unknown function codes.

Any other way of expressing ad-

dresses is simply some manufac-

turer's idea of how to write their

manuals or software user inter-

face. It has nothing to do with

what actually gets sent through

the wires.

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