DDEPoke - Sending a String to ControlLogix?

kdcui

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I used DDE to message down data to a bunch of PLCs, most of the time it is all numeric and this works fine.

However with this latest PLC I have a 20 character String tag on the ControlLogix which contains the ID of an device.

I'd like to update this string trough DDE but my DDEPoke command does not seem to work.

My code looks similar to this:

Channel = DDEInitiate("RSLINX", Topic)

''Reads and write work great until the following
''CM_pH[1].Cfg_ID is the tag (DDE Item) I am trying to write

DDEPoke Channel, "CM_pH[1].Cfg_ID", Range("B2").Value

DDETerminate

I noticed that the String tag on the CLX has the String Data and Length tags in the structure. Do I need to write to there instead or is there a way to write directly to the string value? If not, that would be a pain...

Thanks.
 
I just kicked myself in the head...

You pass the entire range down, for some reason I thought I was doing this until I saw the .Value in my code.

Removed that and I was good.
 
Thanks for the tip...not very intuitive, usually when trying to access the contents of a cell in Excel you would use the .Value. But doesn't work with this DDE stuff
 
kdcui said:
I used DDE to message down data to a bunch of PLCs, most of the time it is all numeric and this works fine.

However with this latest PLC I have a 20 character String tag on the ControlLogix which contains the ID of an device.

I'd like to update this string trough DDE but my DDEPoke command does not seem to work.

My code looks similar to this:

Channel = DDEInitiate("RSLINX", Topic)

''Reads and write work great until the following
''CM_pH[1].Cfg_ID is the tag (DDE Item) I am trying to write

DDEPoke Channel, "CM_pH[1].Cfg_ID", Range("B2").Value

DDETerminate

I noticed that the String tag on the CLX has the String Data and Length tags in the structure. Do I need to write to there instead or is there a way to write directly to the string value? If not, that would be a pain...

Thanks.
Click to expand...

@kdcui

Do you mind sharing the code for sending numeric values please ? Assuming it is different from what you posted above.
 
Passwordg,

Is indicated in my later post, when doing a DDEPoke to send data, numerical or string, you have to remove the ".Value" of the excel range (or cell).

This applies to both numerical and string.

For quick things DDE is fine but if you are thinking of a more complicated but faster and more robust solution, consider using the OPC object model to pass data.
 

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