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Modbus Organization Newsletter, Summer 2010

New Open‐Source Modbus

Implementation

A new open-source applications has been

listed on the

Modbus Technical Resources

page:



RModbus

— a free Ruby implementation of

the Modbus protocol. It supports Modbus

RTU and Modbus TCP as master or slave.

For the extensive list of all currently sup-

ported features please refer to the project

web site.

ProSoft’s New Modbus

iPhone Application

ProSoft Technology

announced the support

of the Industrial Hotspot series of radios in

conjunction with Sweet William Automation’s

new ScadaMobile application

for the iPhone/iPod platform.

The application provides engi-

neers with access to live proc-

ess control variables, and the

ability to modify this data re-

motely from their iPhones.

The app. creates a secure

wireless interface between an

iPhone and an existing 802.11

wireless network on the plant-

floor, allowing the iPhone de-

vice to read Modbus TCP and

EtherNet/IP process control variables from

programmable automation controllers/

programmable logic controllers (PAC/PLCs)

distributed throughout the plant. Live values

are displayed in lists and include user-defined

variance allowances and alarms. Engineers

can monitor these variables in real time and

make adjustments on the fly from an iPhone.

The combined security features offered by the

iPhone and ProSoft’s Industrial Hotspot radios

prevent unauthorized access to the network.

ProSoft’s new 802.11n industrial hotspots fea-

ture WPA2-PSK and 802.11i RADIUS security,

which prevent unauthorized access and modifi-

cation to the network. ScadaMobile also pro-

vides a security feature upon configuration

that requires the user to assign a matching

security code as both a password for network

access and as a Security Tag in the CPU.

When ScadaMobile launches, the security code

must match that on the CPU in order to create

a connection.

continued on page 4

Busy Summer for Modbus

Member Companies

It’s been a productive summer for Modbus Or-

ganization member companies. Here is a sam-

pling of the new Modbus products that came

out recently:



Comtrol

released Modbus Server firmware



SCADAmetrics

announced the addition of

the new TRF-W to its line of meter-reading

devices



Danfoss

released the VLT® Soft Starter

MCD 500



Acromag

is offering ActiveX and .NET con-

trols for its Modbus TCP and RTU I/O Mod-

ules

Visit

Modbus.org

to learn more.

Wishing you all a

relaxing summer!

News about the World’s Most Popular Protocol

Member News

∙

Member News

California-based

Actel

Corporation

is a leader in low-

power Field-Programmable Gate

Arrays (FPGAs) and mixed-

signal FPGAs. The company

offers a comprehensive portfolio

of system and power

management solutions.

∙

Member News

Deep Sea Electronics

Established in 1975, Deep Sea

Electronics has over thirty years

experience in creating market-

leading generator controllers.

DSE has a comprehensive range

of products, specializing in

automatic start generator

controllers, automatic mains

failure controllers, and auto

transfer switch controllers. DSE

has a technologically advanced

collection of load share and

electronic engine compatible

solutions.

All products are

manufactured

on-site at the

company's

headquarters in

the UK. DSE

has an

additional office in North

America, as well as a

comprehensive global distributor

network.

DSE has incorporated Modbus

RTU into its product line.

Frontline Test Equipment

is a

leading provider of PC-based

protocol analyzers for special-

purpose data communication

networks. Frontline pioneered

portable and versatile trouble-

Actel implements interface

standards in its products,

including Modbus, PROFIBUS,

WorldFIP, and P-NET.

The company’s products are used

in LCD control signal generation,

battery management, industrial

and medical equipment, and

military and aerospace

applications around the world.

shooting software solutions for

serial and Ethernet network

topologies and communication

protocols.

The growing family of Frontline

Test System (FTS) general-

purpose and industry-specific

protocol analyzers is based on a

common protocol-decoding

engine. FTS products provide a

common user interface, offer

protocol decoding at the bit level,

and enable the rapid

development of custom decodes

for proprietary protocols and

extensions to existing protocol

decoders. Frontline’s Modbus-

related products include

Serialtest® and NetDecoder(TM).

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

∙

Member News

∙

Member News

Saving the Famous Bellagio Las Vegas Water Fountains from Extinction

Dancing water is the signature

trademark of the Bellagio Ho-

tel, and last year it became

clear that keeping the water

show running might require a

major investment in an entire

new control system. The origi-

nal system was built around

several hundred pumps driven

by obsolete Danfoss 2200

drives using a proprietary pro-

tocol. The Bellagio avoided a

major investment by using a

Real Time Automation

gate-

way to interface Rockwell Auto-

mation POWERFLEX drives

with the legacy water fountain

control system.

In early 2009 it became clear that

the dancing water show at the

Bellagio Hotel, one of the most

renowned attractions on the Las

Vegas strip, was in peril due to

the obsolescence of the Danfoss

2200 drives used to build it in

1998.

The Bellagio was created to be

the pinnacle of opulence. Modeled

after the extravagant Lake Como

Resort in Bellagio Italy, the Las

Vegas Bellagio is a must-see for

every visitor.

With over 200 fountains, the Bel-

lagio fountain show is considered

the largest and most technologi-

cally advanced show of its kind in

the world.

The fountains are literally an

oasis in the desert. Fed by a well

once used to water the Dunes

Golf Course, which used to reside

on the same grounds, the foun-

tains use only 10% of the water

the golf course once used.

The fountains are powered by

220 pump houses located at the

bottom of the eight-acre lake.

The obsolete Danfoss 2200 drives

power pumps that send some of

the over 1,200 streams of water

as high as 460 feet in the air.

Over the years, the engineers at

the Bellagio scoured the globe

gathering all the 2200 drives

they could find, but by early 2009

it was clear that the supply was

simply running dry. Without a

replacement for the drives, the

show would soon come to a halt.

To make matters worse, the eco-

nomic recession had left Los Ve-

gas in a deep freeze as the num-

ber of visitors to Sin City plum-

meted. A low-cost replacement

option was needed to keep the

fountains up and running.

The possibility of simply replac-

ing the drives with more current

drives was quickly discarded.

Any other drive would have a

different communication protocol,

necessitating major changes to

the water show’s hardware and/

or software system. That would

be high risk and expensive, as

extensive time and testing would

be required. Plus there would be

no mechanism to phase in a few

at a time. The entire show would

have to go dark while all drives

and software were updated.

Instead, Real Time Automation

proposed a solution based on an

existing RTA gateway product.

RTA proposed customizing one of

its gateways to emulate the de-

funct drive so that none of the

show control software or hard-

ware would require modification.

Real Time Automation created a

solution that talked Modbus RTU

over an RS-232 port to a Rock-

well Automation POWERFLEX

drive, while communicating with

the legacy water fountain control

system using the DF2200 drive’s

proprietary serial protocol.

Using this module the Bellagio

solution was delivered within

days and functioned nearly per-

fectly during commissioning and

dry testing on land. The custom

protocol and logic for the DF2200

drive was added directly on top of

the established and tested Mod-

bus RTU code. This led to a much

shorter testing period and very

rapid advancement from beta to

production. The gateway module

made the POWERFLEX drive

appear to be a Danfoss 2200

drive, allowing seamless and effi-

cient integration — a true plug

and play replacement solution.

continued on page 4

Member News

Modbus iPhone App.

∙

Member News

Bellagio Fountains

Once testing was

completed on land,

the solution had to

perform under wa-

ter. Installation in

this environment

was a daunting

three-day task.

∙

Member News

cont’d from pg 3

cont’d from pg 1

By using the ScadaMobile

application in conjunction with

ProSoft Technology’s Industrial

Hotspot series of radios,

engineers can manage their

industrial processes remotely.

The Industrial Hotspots are

certified for hazardous

environments and optimized for

plant-wide network integration,

particularly the new 802.11n

series, which is designed to meet

the specific needs of industrial

customers who demand ease of

deployment, ruggedness, and

reliable industrial

communication.

For plant engineers, this solution

enables:



Live monitoring of process data

for engineers and plant floor

operators



Secure remote monitoring and

modification of live process

data



Real-time alarm management

First divers dove to

the bottom of Lake

Bellagio to discon-

nect the pump plat-

form from its power

and network connections. Then a small crane was floated over and the

15′ high structure was lifted out of the water and onto a raft. After it

was moved inside the facility, the platform was given 24 hours to dry.

Once dry, the drive solution was installed and tested. Finally the unit

was sealed, moved back, lowered into the lake, and connected to power

and the show controller.

With shows as often as 15 minutes a day, one day of testing confirmed

that the solution saved the dancing waters from extinction.

Real Time Automation supplies EtherNet/IP, Modbus TCP, Modbus

RTU and DeviceNet gateways to system integrators and end users

around the world. RTA also tailors these gateways for specific applica-

tions like the Bellagio Fountains. For more information on the com-

pany’s many Modbus gateways or for information on tailored applica-

tions like this, please visit the

Real Time Automation’s website.

Modbus humor courtesy of our

friends at

Automation.com

Member News

Modbus Discussion

∙

Modbus Discussion

Q&A from the Modbus Discussion Forum...

Most used Modbus Functions...

Luca Gallina wrote to the fo-

rum:

I am developing a software Mod-

bus driver for S7-300/-400 PLCs,

getting rid of expensive

CP341/441 and their external

loadable drivers.

My personal experience on a few

cases tells me that almost no real

field applications require access

to memory area others than reg-

isters 30001.. and 40001.. (Most

requests are instrumentation and

DCS interfacing).

I am therefore focusing only on

Modbus functions FC03, FC04,

FC06 and FC16.

My question: In your real world

applications do you often (or

never) need to access Modbus

functions other than the ones I

listed above?

M Griffin replied:

I think it depends on the applica-

tion. If you are logging produc-

tion data then it’s usually just

registers. However, if you are

dealing with a simple HMI or

reporting status (is the machine

in auto, are there any faults,

etc.), then coils and (to a lesser

extent) discrete inputs get used a

lot.

If the software on the other end

is flexible, then it might be able

to use data in registers rather

than coils. However, some soft-

ware insists on having coils for

some functionality. That would

mean 1, 2, 5, and 15.

On the other hand, having regis-

ter-only access is still better than

having none at all.

Will you be doing a TCP version

as well as RTU? I’m assuming

this is RTU as you mentioned a

CP341.

Harvard offered:

[Function] codes 1, 2, and 5 are

also a common offering on any

generic host. IMO.

Lynn August Linse suggested:

The other replies are good — but

I would avoid FC04. Some com-

mon client/hosts cannot issue

FC04 requests.

The bit functions FC01 and FC02

can be complex to create in a lan-

guage without shifts, because

literally you can read the 3rd to

6th bits, which must be shifted

over 3 places to return as-if the

1st to 3rd bits of a byte.

So I’d suggest:

1) FC 3, 6, 16

2) Make FC04 look like 3 (but not

sure the value of FC04)

3) Assuming all bits are READ-

ABLE via FN 03, then you don't

really need FN 1 & 2. I can't

think of any normal client/host

which could NOT handle bits re-

turned as packed blocks of 16 in

holding registers.

4) You could still do FN 05 to

write a single bit, as it is hard to

do bit writes via the FN16 since

you’d over-write 15 bits to

write 1.

∙

Member News

Modbus Discussion

5) You could do FC15, but then

you are back to needing bit-

shifts. If they are easy to do fine,

otherwise skip the hassle.

Luca Gallina shared more in-

formation about his project:

Thank you for replies and opin-

ions.

1. Yes, I’m doing the RTU flavor.

2. My aim is to sell the S7 blocks

as communication libraries.

I haven’t planned a TCP driver

since I suppose it’s fairly simple

to send Modbus PDUs over

Ethernet. Most of the people

seem to have difficulties in creat-

ing the S7 code for generating the

CRC used in serial Modbus com-

munication.

Modbus users & suppliers

get together on the

Modbus Community for:



Interactivity



Knowledge aggregation



Contact with other

Modbus users

Discussion supported by...

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