Using modbus tcp/ip to control vfd speed

Hi, I'm brand new to Modbus and fairly new to LabVIEW. I do not have any code constructed yet, so I'm posting to here so that hopefully I can get led in the right direction. I have downloaded the free modbus library because after explaining to NI what I needed, they told me that this would give me enough functionality. I am trying to read the vfd frequency and display it on my front panel, as well as be able to adjust the frequency of the vfd through the front panel. I'm sure that this is a fairly simple and straightforward solution, but since I am brand new to modbus, I really am not sure what values I need to get in order to make this happen. I'm assuming that I need to initialize a tcp master, but what values do I need to feed it so that it can read anything from my vfd? I have an ABB ACS355 VFD with a FENA-01 ethernet adapter. I have the manuals for both and I see lots of parameters and numbers but I don't know how to make sense of them. Are there any keywords I should be looking for in these manuals? Sorry for posting such a general question but I really don't know how to begin this properly. Thanks in advance for any help!

Hello,
A great place to get started will be the shipping examples in the example finder. In LabVIEW, if you go to Help>> Find Examples and the search "Modbus" you will see and example called Modbus Fundamentals.lvproj. This uses shared variables and can communicate with TCP/IP (or ethernet etc) and is set to connect to the localhost. This example also shows how to read and write using Modbus. There is a readme also included in the project if you need more information.
Additionally, there is a great getting started white paper that may be helpful for you. I've linked it below:
Introduction to Modbus: http://www.ni.com/white-paper/7675/en/
I hope this helps!
Best regards,
Anna L
Applications Engineer
National Instruments

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Hello,
My name is Francisco Loras. My team and I are looking forward to building a dynamometer in order to obtain test standards for motors. We're going to use a Load Drive in order to control the Load Motor. The Drives we have been looking at are either from ABB or from Yoskawa (a1000), both offer the option of connecting via Modbus TCP/IP or via Ethernet IP. I was wondering if someone has previously worked with them and could give me some feedback on either the drive or connection type. I would preferrably use Ethernet because the complete system we're building requires at least one more ethernet connection (for a Power Analyzer).
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1- Using an ethernet module (from NI that fits in the Chassis) to drive in both the Power Analyzer and the Load Drive.
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To conclude, I'm looking forward to se if someone has:
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2) Recommended any specific load drive
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PD. If something is unclear (which I sense it is) please ask me and I can develop more on it.

Florasga,
Which ethernet module are you looking at? And what kind of chassis are you planning on using?
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Hello,
I'm using LabVIEW 8.6 and want to communicate with a Beckhoff BK9000 Ethernet TCP/IP Bus Coupler via Modbus TCP. Instead of using the NI Modbus Library, I've tried the new LabVIEW 8.6 feature "DSC Shared Variables" as described at the bottom of this page: Latest NI LabVIEW DSC Module Features and Demos. Reading of analog input bus terminals works fine. However, I haven't figured out yet how to write on an anolog output bus terminal with these shared variables.
It's about a 16 bit analog output and I need to write to the registers 0x1121 and 0x0801. It works with the NI Modbus Library (just using function code 6 and choosing the registers), but on the other hand I don't know which shared variables I have to choose for these registers. I've tried several data items (e.g. 400001 upwards as well as 402049 for 0x0801) but none of them worked. I would be glad for a short explanation - thanks in advance for your support!
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utechle

The Beckhoff documentation says, that holding registers start with 0x0800. I've checked this by using the NI Modbus Library. I used the "MB Ethernet Master Query.vi" togehter with the function code 6 for "Write Single Registers", changed the settings of the starting address to hexadecimal view and entered 801 (since it starts with a control byte in 0x0800 and the data out word follows in 0x0801). Furthermore, I had to address register 0x1121 in the same way for resetting the watchdog. As I've mentioned in my first post, this method works fine. However, I haven't found out yet which shared variables i have to use for accessing these registers.
On the other hand, it's no problem to read data from analog input bus terminals using shared variables. They start with 0x0000 (status byte) and 0x0001 (data in word) and I can read data with the shared variable and data item 300001, respectively.
Message Edited by utechle on 01-27-2009 11:12 PM

Using modbus/TCP with USB ethernet adapters

I have a test stand where I have a handful of USB instruments and a single modbus/TCP slave. I'm considering adding a USB ethernet adapter to the stand so that there is a single USB cable connecting the computer to the hardware rather than both a USB and an ethernet connection. Does anybody out there have experience (good or bad) using USB ethernet adapters with modbus/TCP slaves?
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Adam G wrote:
Hello Mark,
I was wondering what NI hardware you are going to be using in your application? Also are you going to be using LabVIEW for the programming? Have a great day!
Best Regards,
Adam G
The test software is written in LabVIEW, and the test stand uses M-Series cards for data acquisition.
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Problems using Modbus TCP accessed by NI OPC Server

Hi there,
i'm using NI OPC-Server to access a measurement module. The buildup is quite easy, my system with NI OPC, a modbus gate and there the module connected with RS485.
There's a thermocouple to provide me some sample data.
But there's the point. I know, my data is in the Holding Registers and I can access them, but every data type I'm trying doesn't bring my my data out, just any other (sometimes Huge with e34, sometimes very small like e-13...) sorts, i can't understand.
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In Lookout the address used to be is 41000 in Labview it's just 999 and in the "target" OPC-Server I get some values at 401000 but not useful.
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Solved!
Go to Solution.

Thanks for your reply.
in LabVIEW I'm using the provided Modbus Libraries. If I unbundle the Holding registers, my value appears at Holding Register [0], I'm type casting it to single and get the sample temperature. (Address 999->unbundle->typecast->value)
In NI OPC, I'm reading ( [depends on zero based addressing] 300999/301000 equal to 400999/401000) an already typecasted Holding Register [1] compared to LabVIEW (and the value changes in the second or third digit behind the comma and they are changing at the same time). Data type in the tag is float.
Another disturbing thing is even if I change in the options "using zero-based addressing in registers" my value does not change.
If I'm reading two addresses close to each other (as you mentioned 401000-401001) I'm getting an unknown data type and no results. How do I read multiple addresses without such errors? And how do I specify a special register to read?
Scaling should not be the problem, I am having three ways to get my value (FTP-Server on the gate (just a *.dat file with correct type), software the the module manufacturer (while measuring and configuring the module) and LabVIEW(as can be seen above)) .
Sadly, I have not found any useable modbus documentation about the module (just it can use modbus, you have the registers, you could read/write and fine)
When I'm adding a second couple to the module, in LabVIEW Values in Holding Register [2] and Holding Register [3] appear and are changing.
Cateros

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Thanks
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arikb wrote:
Thanks A_Patel,
I thought of doing that but do I need to run this as a VI server in that case? How would I pass inputs and outputs of the subvi?
Appreciate the help,
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Take a look at my Nugget on dynamically creating occurences found here.
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Ben Rayner
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Though I am not familiar with the specific drives in question, I have used Modbus/TCP in LabVIEW a few times recently.
As the previous posters pointed out, there are a couple of VI libraries available. LabVIEW 2014 added Modbus VI's with the DSC and LabVIEW Real-Time. The others you would have to get and add in yourself.
Another option is to use LabVIEW I/O Servers; as long as you have DSC or Real-Time, you can create Modbus I/O Servers as library items and deploy to a target. You don't get as much direct control in this way (and may run into difficulties if you need them to be field-configurable and do not have DSC) and use bound network shared variables, but they are very fast and easy to setup and I have yet to have any issues with using them in my applications.
A tutorial on setting up a Modbus I/O Server: http://www.ni.com/tutorial/13911/en/
A tidbit on deciding between Modbus VI's and a Modbus I/O Server: http://zone.ni.com/reference/en-XX/help/370622M-01/lvmve/choose_modbus_ioserver_vi/
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Modbus/TCP Queries

Hi,
I am trying to use Modbus TCP to set the time / date on my cFP-2120
running Labview Real-Time 5.0.1. For this purpose I have set up four holding
registers that hold two single precision floats, one for the time (format:
hhmmss) and one for the date (mmddyy). The idea is that each time the Modbus Master writes to the holding
registers, the time / date of the cFP2120 gets set.
In my application, I have implemented Modbus communication
similar to the MB Ethernet Example Slave.vi, which came with the NI Modbus library
for Labview 8.2. This is also similar to the Modbus tutorial here. Essentially,
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Manager.vi (also part of the Modbus library) and use their values to set the
controller.
The problem arising is that I set the controller time even
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have been written to by the Master, so that I can react on it as soon as this happens?
Thanks,
Volker

Devin,
thanks for the response.
Your suggestion are a possibility, especially the first one.
However, as these registers are holding registers (read/write), I was hoping to also post to them the current time by the slave to be read by the master.
In case the time needs to be synched, the master posts the correct time to the same registers upon which the slave will update its time and again start posting its current time to these registers.
I realize that the easiest way to accomplish this would be to just use different registers for posting the time by the slave and have the holding registers reserved to be written to by the Master. In a previous implementation in C ( ... please forgive me) I used to listen to the traffic and parsed each message coming in in order to determine whether (a) my device was queried and (b) which function code was used for which registers. Based upon the info I decided whether to just send back the current time of the slave to teh master or take the incoming time value and set the time of the slave.
How would I implement something like this in Labview? Or am I better off just having different registers for reading from and writing to the slave?
Volker

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Hello:
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Hello:
Thanks for answering Pedro. I've read the document you told me to, but it refers to problems with VI Server, the application is not using VI server, so I guess the problem comes from somewhere else. I still haven't figured out why this is happening.
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Thanks in advance.
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MODBUS/TCP very slow execution

Dear all
We are new user to Labview and to LabVIEW forum.
We are designing a LabVIEW application that interacts with PLCs.
We are trying to exchange information between a PC/labview and a PLC. Both support the MODBUS/TCP protocole. We have designed the 2 programs easily, the PC/LabVIEW one being easily made with VI Library.
We first the PC/LabVIEW as a cleint and the PLC as server and it works perfect. It is quite fast as it takes less than 1 second.
We test the reverse configuration ie PLC as client and PC/LabVIEW as server. Of course we use different programs there and monitor the MODBUS/TCP frames with WireShark.
It works also but the execution on the PC/LabVIEW is very long (in the debug mode) : it takes 5 secondes to execute the Write Multiple Register function ( 2 data to write) to prepare the response frame and to send it back. It is very nice to see the animation on the diagram but why is it so long ? This long time frame is a very big problem for our application.
We re not sure to know where to dig in !
Thank you in advance for your help.
Regards
Thierry

It sounds like you need to learn more about the LabVIEW development environment if you were confused about the slow speed of highlight execution.
I would recommend looking at the online LabVIEW tutorials
LabVIEW Introduction Course - Three Hours
LabVIEW Introduction Course - Six Hours

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Introduction to Dual Ethernet Architectures
http://zone.ni.com/devzone/cda/tut/p/id/7103
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I'm new at researching the LabVIEW Software.
I'm having a thesis in University.
My project is, use LabVIEW draw in PC a model of automation system. Then, use two Schneider Premium PLCs in mode Redundancy to control and supervisory this model through Modbus TCP.
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To run OHS at port 80 using solaris role based access control

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ias-instance id=asinst_1
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
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Just to add my two cents here.
The commando used on Solaris to assign the right privilege to bind TCP ports < 1024 is:
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Regards.
Edited by: Tuelho on Oct 9, 2012 6:05 AM

Using modbus tcp/ip to control vfd speed

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