Problems with Beckhoff plc and .Net app

Hi!
I'm building an HMI i .NET and for some reason i can't write or read the string from my PLC! Why is that?

this is how my code looks like right now:


PLC:
HMI_AktParIns: STRING;

global in .NET app:
Public HMIaktparaminst = ".HMI_AktParIns"

Read from plc:
VarParamInst = TcClientSync.ReadVar(HMIaktparaminst)
txtAktParamInst.Text = CStr(VarParamInst)
System.Diagnostics.Debug.Write("ReadVar:" & VarParamInst)

Write to plc:
varAktparamInst = CStr(System.IO.Path.GetFileNameWithoutExtension(openFileDialog1.FileName))
System.Diagnostics.Debug.Write("WriteVar:" & varAktparamInst)
Call TcClientSync.WriteVar(HMIaktparaminst, varAktparamInst)

Hi there Joel.

I think that you need to be a bit more specific about what you are planning to do… I assume that your are not communication thru a OPC, are you sending TCP/IP telegram?

Do you get any exception thrown back at you from your runtime?

I´ve seen that you have been asking some questions about this in a computer developing forum (pellesoft)
but I´m sure that someone here can help you (don’t think many people there are well familiar with plc´s and communication between PLC-PC)

Best Regards.

//e

Hi Edda! well.. I'm storing values in xml documents and when I open any of them in my app I also want to store the xml filename in the plc. save string to plc and get string from plc. Thats the problem.
And i'm sure the script works because I do the same thing when I get numeric values, it's just when I try to get a string.

No, it doesn't return anything at all.



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Hi again!

Are you sure that TwinCat ADS-Script-DLL (that is what you are using right?) supports reading/writing strings? I have just quickly looked at this document and I can’t find anything about it, just Bool, Int8-32, Real32-64...

http://www.beckhoff.de/Download/Document/Software/TwinCAT/1033/TcScriptDll.pdf

Regards

/e

you're right! It doesn't seem to support string at all. hm.. Now the problem is to find what I should use instead.

There is a .Net dll called TwinCAT ADS.NET.

If you look in the reference manual and the method called TcAdsClient.ReadAny, It says...

Reads data synchronously from an ADS device and writes it to an object. If the Type of the object to be read is a string type,
the first element of the parameter args specifies the number of characters of the string.
If the Type of the object to be read is an array type, the number of elements for each dimension has to be specified in the parameter args.
At the moment only 1 dimensional Arrays are supported.

public object ReadAny(int,Type,int[]);

Maby this can help you... Check out the beckhoff site

There is a guy called Archie Jacobs (username: Archie) here that works alot with Beckhoff(I think ), maby he knows and can help you...

Regards.