Re: [foxboro] Use of FBM232 to communicate with 20 devices via one IP address

Kevin,
 

Thanks for the quick reply.

 

The vendor had setup the MODBUS scanner on his laptop (after assigning
his laptop an IP within the domain), and connect it to the HVAC PC via a
small hub.

The MODBUS scanner application has the ability to open multiple windows
each is configured with a different device MODBUS address.

We are on the same track, I mean that I expected also that the
application on the HVAC PC would combine/pack the data collected over
the RS-485 network and passes it to my FBM in an appropriate memory map
addresses, but the vendor claimed that the use of MODBUS device address
is enough (from his point of view) to establish the communication.

 

Ahmed Khaled

 

-----Original Message-----
From: foxboro-bounce@xxxxxxxxxxxxx [mailto:foxboro-bounce@xxxxxxxxxxxxx]
On Behalf Of Fitzgerrell, Kevin
Sent: Wednesday, April 29, 2009 8:52 AM
To: foxboro@xxxxxxxxxxxxx
Subject: Re: [foxboro] Use of FBM232 to communicate with 20 devices via
one IP address

 

 

Ahmed,

 

The Modbus TCP FDSI you are using can communicate with one or more
Modbus

slave devices on an Ethernet network.  If that device is your HVAC PC,

there must be some application running on that PC to provide register

data to the FDSI via Modbus TCP.

 

It sounds like you are expecting the PC to act as a bridge from your

Ethernet connection to the RS485 serial Modbus - it can't do that

directly.  There needs to be some application running on the HVAC PC

which simulates a Modbus device, and your FDSI will communicate with

that application.  That application will poll your RTUs independent of

it's communication with the FDSI.  

 

The application on your HVAC computer should have contiguously

addressable  register space, rather than a patchwork of addressable

registers, for use with the FDSI.  If you need to address specific small

ranges of registers, an FBM224 may work better for you, as that

capability has not been available in the FDSI (although it has been

requested by a number of customers - maybe Foxboro has fixed this).

 

Did your vendor set up the Modbus Scanner software on the HVAC PC, on a

separate computer connected to the HVAC PC via Ethernet?

 

Foxboro does have serial Modbus devices that can communicate directly

with devices on a serial Modbus link.  The serial Modbus FDSI would

likely have problems if your address map is not complete.

 

Regards,

 

Kevin FitzGerrell

 

 

 

-----Original Message-----

From: foxboro-bounce@xxxxxxxxxxxxx [mailto:foxboro-bounce@xxxxxxxxxxxxx]

On Behalf Of Ahmed K. Sayed

Sent: Wednesday, April 29, 2009 2:18 PM

To: foxboro@xxxxxxxxxxxxx

Subject: [foxboro] Use of FBM232 to communicate with 20 devices via one

IP address

 

Dear Gents,

 

 

First of all, I wish you are fine and healthy.

 

 

 

I would like to ask about something regarding our FDSI - MODBUS TCP/IP

communication.

 

We have an HVAC system that is supposed to be linked to our DCS via

FDSI, as a MODBUS TCP/IP link on a single mode FBM232.

 

 

 

The HVAC system itself includes multiple RTUs that are connected

together via MODBUS RS-485 link, this also includes one converter

RS485-RS232 to connect to the HVAC computer (normal PC with a MODBUS

processing application). This HVAC computer then is connected to my

FBM232 via a normal RJ45 Ethernet cable.

 

 

 

Typically, I assigned an IP address for that computer (within the same

domain of my FBM IP), configured one ECB201 as a MODBUS device with that

IP.

 

 

 

The problem is that this HVAC application is not sending a combined

memory map for all the points collected over its MODBUS RS-485 link, but

it sends the data individually for each device considering that the

MODBUS device address will be used then to distinguish between these

data.

 

 

 

An example is:

 

RTU1 MODBUS address = 50 >> TI0001 on address 30001 and TI0002 on

address 30002

 

RTU2 MODBUS address = 60 >> TI0003 on address 30001 and TI0004 on

address 30002

 

.

 

.

 

etc.

 

 

 

As we see here, we shall then configure different device for each RTU to

include that different addresses and have the ability to use the similar

register allocation.

 

 

 

The problem then will be is that I still have one computer which is

assigned one IP address, and if I try to configure another device in the

system (same IP with different MODBUS address), the system gives the

error (duplicate connection) and disables the actions for "ENABLE

COMMUNICATION".

 

 

 

In my understanding, such a configuration can be connected to DCS via

only MODBUS Serial link not MODBUS Ethernet link (making use only of

MODBUS devices addresses and not TCP/IP).

 

 

 

The vendor has one MODBUS Scanner software (3rd party application), and

he used it to connect to his computer (in the place of my FBM) and then

it communicates very fine and was able to read the data from all his

devices directly with no problem.

 

 

 

Please advice

 

 

 

Ahmed Khaled

 

 

 

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This message may contain TASNEE's confidential information 
and is 
intended only for the individual named. If you are not the named 
addressee you should not disseminate, distribute or copy this e-
mail.
Please notify the sender immediately by e-mail if you have 
received this e-mail by mistake and delete this e-mail from your 
system.The information transmitted in electronic mail does not 
necessarily represent the views of TASNEE.
E-mail transmission cannot be guaranteed to be secured or error-
free as information could be intercepted, corrupted, lost, 
destroyed, received late or incomplete,or could contain viruses.
The sender therefore does not accept liability for any error or 
omission in the contents of this message, which arises as a 
result of e-mail transmission.
No representation is made that this email or any attachments are 
free of viruses. Virus scanning is recommended and is the 
responsibility of the recipient ...
 
 
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