Lookout's Modbus Slave Address

Hi,
It appears that the Modbus Slave (Ethernet) Object in Lookout (6.0.1) doesn't work with an Address (or "Identifier") greater than 127.
I tried a simple test with the Modbus Object in one process with an address of 128. And a ModbusSlave Object in another process with its address as 128. There's no communication. However, when I make the addresses 127 (or lower), they yak like nobody's business!
I haven't tested the Serial version though.
Est-ce un bug?
-Khalid

Hi Khalid,
I think I was overlooking the Lookout 6.01 version that you mentioned earlier in your post ! I was able to recreate the issue that you are facing if I create a modbus slave object in Lookout 6.01 version. Thats a bug! And version 6.02 has a fix for it!
Have a great day!
Regards,
Prashanth

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CRIO and ni 9234 modules not working or communicating through fpga with accelerometers, fpga connected to real time application which is also connected to shared variables linked to modbus slave

Hi,
I have a compact rio which has a 4 way chassis attached to that chassis is three ni9234 modules they are linked using fpga to a real time application then using shared variables in the low speed loop that are linked to a modbus slave to communicate with dcs, the ni 9234's have accelerometers connected to them with iepe ac coupled option on the c modules, my problem is the real time application seems to be running okay even when power loss occurs it restarts with no problem and the fpga writes to the portable hard drive bin files fine but without a accelerometer connected I get low noise readings as soon as I connect a accelerometer to any one of the 10 outputs it just goes to a fixed number (0.03125) as soon as disconnect it again it reverts back to reading noise, I have run a scan on the modules and only get a spike when I connect or disconnect the accelerometer, I have tested the voltage at the pins of the module and I get 22 volts dc which makes it more likely that the hardware is not the problem but a software is maybe causing this to hang-up, I attach project and files for your perusal. I also carried out a new project which in scan mode directly linked the module input to shared variable and the same scenerio again. Help would be much appretiated.
Many thanks
Jason
Solved!
Go to Solution.
Attachments:
logger 2plusmodbus2.zip ‏679 KB

Whren using waveform acquisition with the 9234s we recommend the following FPGA and RT template.
http://sine.ni.com/nips/cds/view/p/lang/en/nid/209114
it can be extended as a data logger with:
http://zone.ni.com/devzone/cda/epd/p/id/6388
or using shared variables combined with scan engine
http://zone.ni.com/devzone/cda/tut/p/id/9851
The FPGA in all of these, as well as the RT framework have been used successfully by 1000s of users. I would recommend giving these a try.
Preston Johnson
Principal Sales Engineer
Condition Monitoring Systems
Vibration Analyst III - www.vibinst.org, www.mobiusinstitute.com
National Instruments
[email protected]
www.ni.com/mcm
www.ni.com/soundandvibration
www.ni.com/biganalogdata
512-683-5444

Problems writing to network published shared variable hosted on rt (set as modbus slave for crio)

Hello Ni Forums
This is my first post on this forum and I have been using labview for about 8 months now
I have a problem regarding writing data to modbus registers through an i/o server set as a modbus slave for my 9074 hardware.After I have completed building project and deploying the variables and following instructions from here , it yields no result but a line zeros. I have the Ni DSM open and modbus master setup to see whether the data is actually being read/written from the respective sides which both yield the same line of zeros as well. What I am actually trying to write to is an array of single precision floating data. The registers are structured from ranges F40000-F46534 for 10 elements or have them for range AF40001L1-AF46534L1 of item AF40001L10 where it is an array of length 10. (Referenced ranges here)
I know 1 thing for sure, the modbus connection works and is ready for data requests, I tested this through NI DSM and manually set data for and my master received them .
System and Project specifications
Windows 7 OS
Labview Full Development System 2011
No Labview DSC module but I am using the real time module as referenced by one of the documents
This project is a real time application with fpga mode (not scan interface mode)
The master and slave are the same subnet and network
Modbus Connection Type: TCP
9074 compact rio 8 slots
9234 module x3
9221 module x1
9472 module x1
Shared Variable Engine service running on windows os and rtos system
Used this guide to learn about the modbus protocol as I searched all over the internet to learn about modbus
I already having Modbus IO Server software installed on the crio through ni max version 1.8 for NI RIO 4.0
attached file(s)
Image of Crio software specifications
Image of the Data being written into variable in rt block diagram
Short Version of the problem: Why is the io variable not being written into with properly converted data?

The data can have zeros but not all of them will be zeros and I have another program (on local computer for database storage)that is recieving the same data through TCP and they are not zeros.
If a machine is running and is active then the data that will be collected should not be zero , it should infact be some analog value > 0.
I will look into the function you described
How do you view the errors in the IO server subfolders ?
Is it the modbus register called error status that returns an error code if so that value is currently 0
Regards mzamstl

DF Profi II Set Slave Address.

What is the content of the telegram the DF PROFI II board sends when it is a master and the Set Slave Address is Sent from the configurator II software? I am designing a slave with a settable address and can't get this function to work. All I get a is "fault" in the Status. I've tried numerous combinations and am now leaning towards the DF Profi II isn't sending the correct telegram to SAP 55. I don't have a bus analyzer so I was hoping someone here might know.
Any Help with this would be appreciated.
Regards
John

Hi Dirk
Thank you for your response.
The Set Slave address dialog is available in configurator II under the online menu selection. It is only available if the gsd has Set_Slave_Add_supp=1. I was hopoing someone has a bus analyzer and can tell me what the content of the telegram is that they see. It should be minimum of 4 bytes
byte 0 New Slave address
byte 1 Ident HI
byte 2 Ident Lo
byte 3 future change address not allowed.
If anyone has a bus analyzer and can tell me what they recieve on SAP 55 when they hit they try to set slave address it would help me out.
Regards.

How can I edit the database in Lookout OPC Modbus driver OPC sever with the address that has a write attribute?

When I use Lookout Modbus driver OPC to communicate with my instrumnets, I edited the database number such as 41202 that has a Write attribute in my instrumnet manual, the OPC explorer got bad data, and the OPC server gave the illegal address alarm, when I input the address such as 41203 that has R/W attribute, it worked very well. Is there a way to fix this problem. When I used other OPC server, there was no this kind of problem. Thanks!

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Error when running ethernet modbus slave demon in an executable - reoccurence

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Maybe the exe is struggling to locate the TCP functions.
Any help would be much appreciated.
Attachments:
MB Ethernet Example Slave.vi ‏47 KB

I have checked the path and double checked by dragging the VI into an empty path constant. I also created a version that uses the file dialog express VI so that I can select the slave demon VI when the program runs. I've also set the slave demon to be always included in the project build. The error message still appears.
By disabling sections of the slave demon vi I found that a VI called Internecine Avoider was linked to the appearance of the invoke node error message. By disabling this VI I could get the invoke node error message to disappear, although the slave demon then didn't work as intended. This VI is included in my project under the vi.lib so it should be found.

Modbus Slave Demon - Executable cannot find VI.

I have included in my application Modbus Ethernet Example Slave, which I've altered a bit ( only the inside of While Loop ). Everything is working fine until I've come to using an executable built from my project.
When I start it I got: Error 7 occurred at Open VI Reference in Modbus Init.vi->Main_v0.3.5.vi
Possible reason: LabVIEW: File not found. The file might have been moved or deleted, or the file path might be incorrectly formatted for the operating system.
In my project library I have Modbus Ethernet Example Slave in directory where the .lvproj file is, and the so the "Open VI Refference.vi" gets it from there (path is built using "Application Directrory Constant" + Name of VI).
I've also set "Always include" for MB Eth Example Slave in build properties but I still get the error of not founding the VI.
Do You have any idea why is it happening?

For your example, your exe has to reside in the same folder as the project as well.
Kudos and Accepted as Solution are welcome!

Has anyone tried to use LabVIEW as a modbus slave with a PLC master?

Hello. I use modbus extensively with PLCs as slaves. I am finding that it might be benificial to make the PLCs be the master in my next application. I have tried this with the MB Ethernet Example Slave.vi without any luck. Can anyone help?
I am running LabVIEW 8.6 on Windows XP with AutomationDirect PLCs using ethernet communication.
Thank you in advance for your help.
Ron Deavers, CLD

Hi
There are two options to connect to a Modbus device. Either the Modbus IO Servers (found in the NI LabVIEW Datalogging and Supervisory Control Module) or the free Modbus Library.
FLAsh
National Instruments
Applications Engineer

Modbus Slave

Hi all,
I have to write a modbus client in LabView. My pc is a slave and has to
communicate with a SPS-station via RS232. Is there a vi available with a
smart interface for read/write ?
Thanks

Rene,
sorry, no.
but you might use a few of the VIs to write your own slave and then send me a
copy ;-)
Urs
Mareike schrieb:
> Hi urs.
>
> Great, the Modbus master works fine.
> But I'm looking for a slave-implementation. Do you have a solution?
>
> Rene
>
> "urs" wrote in message news:[email protected]..
> > Mareike schrieb:
> >
> > > Hi all,
> > >
> > > I have to write a modbus client in LabView. My pc is a slave and has to
> > > communicate with a SPS-station via RS232. Is there a vi available with a
> > > smart interface for read/write ?
> > >
> > > Thanks
> >
> > Mareike,
> >
> > try the dutch companie AIR's free modbus library - I think it's a modBus
> > Master only, but might be a good base to start with.
> >
> > http://www.air.nl/home.htm
> >
> > Best Regards
> > Urs
> >
> >

Modbus Communications address offset

Is there an option available in the Modicon Object to enable an address shift during communication with Modicon Devices. When communicating with a Modicon Quantum PLC 400010 will return the value from the device in reg 400010 but when communication with a Modicon M340, Premium and others 400010 will return the value in 400009.

Nothing a little data member export and import cant fix...
On the standard Koyo (automationdirect) PLCs we have to convert from Octal to decimal, then add 1.
For example:
PLC: V1200
Decimal: 640
MODBUS: 40641
Forshock - Consult.Develop.Solve.

Getting wrong values from modbus slave

Hi,
I'm trying to get data out of a lumel na5 digital meter. The device is connected via its RS485, through a RS232->RS485 converter to the RS232 port of the PC.
I've donwloaded the NI modbug library, and was able after some work to communicate with the device.
The problem is that the data I get out of it is wrong. I monitored the request and response data that the VI send, and it looks ok but the data is not correct.
Anybody has some similar experience?
Thanks in advance,
Eyal.

Hi,
I do not have any experience with your device but, if you get data (even if it is wrong) from your device with a ModBus protocol you have your communication working !!
The wrong ModBus data is often caused by simply using the wrong register number(s). Start at 0 or 1, hexa and decimal mixup, invalid register numbers in the range, things like that.

Could VBAI be use as Slave in ModBus communication ?

hello,
I'm working with VBAI 2010, in ModBus comunication I need to use VBAI as Slave.
I saw on help file that it is not possible but in menu "Tools\Communication device\" I can see "Vision Builder AI ModBus Adress :"
What does it mean ?
Is there any solution to use VBAI as slave in ModBus communication ?
Fabrice

Yes, Vision Builder AI can actually only be used as a Modbus slave for now (users can implement the master functionality using a Run LabVIEW step).
To configure Vision Builder AI as a Modbus Slave device, select Tools>>Communication Device Manager.
Click New Device, to create the Modbus Master Device you want Vision Builder AI to communicate with.
Give it a name, then select either the Modbus Serial or Modbus TCP as the communication protocol depending on the physical layer used to connect to your device. For serial, you will need to specify the port and Modbus Mode (the most widely implemented is RTU).
Click OK.
Click the Start Server button, next to the Modbus Server, to start the background task that will listen for incoming Modbus messages. Note that the Modbus registers will be updated asynchronously from your inspection, whenever a Modbus frame is received.
The Vision Builder AI Modbus Slave Address is only used to identify the device, when the protocol is Serial, and you use the RS-485 protocol to connect together more than 2 Modbus devices in a multi-device configuration. Ignore this control if you are using Modbus TCP.
We know this dialog is a little confusing and are working towards improving it in future releases.
Once the server is running, use the Modbus Slave step to read and write the Modbus registers (that are located on the machine running VBAI, since you configured VBAI as a slave device).
Make sure that you specify the correct address in your Modbus Master device configuration software for the register you want to access in Vision Builder AI. In most Modbus device configuration software, you must enter a name for the register you want to use. Per Modbus convention, the register address of the slave device is calculated by subtracting 1 from the register name that you specify in the master device configuration software. Vision Builder AI expects register addresses, not register names, so you may have to subtract 1 from the address you defined in the Modbus device configuration software. For example, a register name defined as 2 in your Modbus configuration device translates to register address 1 in the Vision Builder AI Holding Registers table.
Modbus Device
Holding Register Name = 2
Vision Builder AI
Holding Register Address = 1
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0x10000 for the Discrete Inputs
0x30000 for the Input Registers
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Modbus Device
Holding Register Name = 0x40000
Vision Builder AI
Holding Register Address = 0
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Holding Register Name = 0x40008
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Best regards,
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How to implement Modbus Ethernet communication in Lookout, if we want to simulate the PC as PLC ?

Problem Description :
Dear Sir,
We are doing a project where we are using Lookout with
Front end Modicon PLC. The communication is by
Ethernet, using Modbus.
Since the installation is at a distant place, we wanted
to use another PC (running Lookout) to simulate the
PLC. For this, we tried to communicate
a: the server Lookout PC running Modbus Ethernet mode of
Modbus object as Master
b: with another PC (for simulating the PLC) running
Modbus Slave
We did not get any communication. (we have given the
details of what we have done, at the end of this email)
We also tried connecting the above 2 PC's as
a: the server Lookout PC running Modbus Serial mode of
Modbus object as Master
b: with another PC (for simulating the PLC) running
Modbus Slave object
Again we did not get any communication.
If instead of PC (b) we connect the Modbus simulator to
PC (a), there is no problem in communicating
Please let us know how to go about establishing the
communication between 2 PC's using Modbus serial,
and Modbus Ethernet. A detailed step by step procedure
would help us a lot.
Thanking you
Warm Regards
Raja Mahbubani
Procedure of our trial with ethernet.
This is what we have done in detail.
On PC A:
We created an object (Pot) and connected it to
the modbus data member of the modbus object say 40001. In the
properties of the modbus object we selected modbus ethernet mode
of communication and in the IP address field we wrote the IP
address of the machine B to which we are trying to communicate
i.e. 152.63.50.2.
On PC B: we tried the following two methods
Trial 1 : We created a modbus slave object and
inserted an expression for the same data memeber to which the
object was connected hoping to get the value of the pot of machine
A on machine B.
Trial 2 : We created a modbus object on machine B and we wrote
the IP address of machine A and inserted an expression for the
same datamemeber to which the object was connected hoping to get
the value of the pot of machine A on machine B.
NI Software : Lookout
Version : 4.0.1 or 4.5
OS : Windows 98
NI Hardware : N/A
Drivers : N/A
Other Hardware/Instruments : N/A
CPU : Pentium
RAM : 64
Vendor : S-Tech
Customer Information :
Raja Mahbubani
Theta Controls
IN
[email protected]
Ph: (+91) 20 4222556/7

The ModbusSlave which comes with Lookout currently supports only Serial communication. So, you cannot use Ethernet between your two PCs. At least not with Modbus Master-Slave setup (if you must speak Ethernet between the two PCs, IPASCII object lets you do that, but then you'll need to implement your own protocol).
Since all you want to do is simulate a Modbus PLC on a PC, you can use the Serial mode of communication for now. And later on just modify the Object in your Server Lookout to use the Ethernet mode.
For setting up a Serial Modbus Slave, use a null-modem cable between the two PCs (lines 2 and 3 are swapped). On your PC 'B,' create the Modbus Slave object with the right COM port for that PC. And on your PC 'A' create the regular Modbus Object as if you w
ere connecting to the Modbus Simulator box. The only difference here is the cable. The simulator box uses a straight-through cable whereas the Slave needs a null-modem cable.
Hope this helps.
Rgds,
Khalid

Read/Write a bit in a Modbus Address

Greetings,
I'm working on a project for a customer of mine. I'm working off of his I/O mapping list. We are using MODBUS to communicate to a Motorola MOSCAD FIU. According to the I/O Map, I need to read a bit from address 307682:01 which normal I would translate into 307682.1 but Lookout is not excepting this address as a valid Data Member. So I did some troubleshooting of my own and found that Modbus Data member (307682) is only used as "a 6-digit addresses of 16 bit input registers encoded as unsigned binary integers ranging from 0 - 65535." I guess an analog value.
Is my thought process correct on this? Does my customer need to change his I/O mapping. Am I overlooking something?
Attached is a copy of the I/
O map.
Oliver Scheurer
Aegis Solutions, Inc.
2660-T Yonkers Road
Raleigh, NC 27604
Phone: (919) 861-0103 Ext. 231
Fax: (919) 861-0104
www.aegis-solutions.com
Attachments:
IO_Map_for_lookout.xls ‏69 KB

WOW!!.. I get to answer my own question. You all are slow... J/K...
Anyway, the fine people at NI Tech Support Helped me out with this one. Seems that it is a problem related to Lookout and Modbus. After discussing this problem with a few engineers, I decided to call the customer and let him know of his mistake. Well, he proceeded to tell me that "Wonderware can do it with out a problem". So I called NI Support again, and they told me that further research showed that it is something that was not put into Lookout. The Support engineer started a "CARD?". But he also gave me a work around.
1. create an expression
2, enter getbit(3,1)
This expression will return a ON status since the number 3 in binary is 1 1 and looking at the first bit is 1.
So for my
application I would use
getbit(modbus1.307682,1)
I hope this makes sense.
Oliver Scheurer
Aegis Solutions, Inc.
2660-T Yonkers Road
Raleigh, NC 27604
Phone: (919) 861-0103 Ext. 231
Fax: (919) 861-0104
www.aegis-solutions.com

Modbus (DSC Module) - Illegal Data Address

Hi
I need to implement a Modbus Slave in an application on a cRIO system. I set up a "I/O server" (DSC Module) and created shared variables for all the registers I need. The Slave has been tested and works fine, I'm using about 20 holding registers and I'm able to both read from and write to them.
The issue is that when the Modbus Master reads a holding register that I have not implemented the slave replies with the value "0x00 0x00" (LabVIEW default for integer) and not with exception response code 02 (a holding register inquiry for a nonexistent address should reply with function 0x83 and code 0x02 - Illegal Data Address).
Is it possible to change a setting or something, in order to force the DSC Module to send an exception response code, in stead of simply a default value, for registers that are not specifically configured?
Hope someone can help me - I would really like not to write all the necessary code for a modbus slave myself.

Hi Lenvno
Thanks for your reply.
I think you misunderstood me.
I have an application running on a cRIO. On this cRIO I need to implement a Modbus Slave in which specific holding registers should be used. Through a serial connection a different device, acting as a Modbus Master, obtains information from this slave.
On the cRIO, in my LabVIEW application, I have created an I/O server - Modbus Slave. Using shared variables I write values to specific holding registers on the Modbus Slave.
The Modbus Master obtains the values from these registers using function code 0x03, read holding register - this works correctly. However, when the Modbus master query registers that I have not defined, the I/O server on the cRIO replies with a register value of 0, instead of Illegal Data Address. It seems like when using this I/O server, all possible Modbus registers is filled with the LabVIEW default value and the slave therefore always will reply with a value even if the register is not used.
My question is therefore, how can i change this? If the Master query a register that I am not writing to (and is therefore unused), I would like the slave to reply with "Exception Response" code 0x02 - "Illegal Data Address", and not just the value of 0.
/Simon

Lookout's Modbus Slave Address

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