CODESYS - the IEC 61131-3 automation software

Hi,

When monitoring large arrays of data i occasionally get "<Value of the expression cannot be retrieved>" in the Value columns for the data (See attached screenshot).

Why is this happening and how can I stop it? It seems pretty random as to when I am not able to monitor my data. Restarting CodeSys does not fix it. I should note that I am monitoring a large number of data items, and sometimes have 3 instances of Codesys running online talking to various bits of hardware.

Thanks
Laythe

With 2.3 this could also happen when too many variables were monitored. The most simple solution is to close all Editors except the one you would like to monitor.
With CoDeSys V3 I have not seen this yet. How do you now solve it?
What happens if you close all Windows?
Which device do you have?
Which CoDeSys version do you use?
What happens if you close one of the other CoDeSys IDE instances?

Hi Tim,

The IDE version is CodeSys 3.4 SP1. Two of the instances are talking over the network to windows xpe controller boxes running CodeSys SP RTE v3.4.1.0. The other instance is talking to a locally running CodeSys SP RTE v3.4.1.0.

In terms of a fix, I havn't really found an reliable soloution for this. I'm guessing this is a performance issue but the PC im running is reasonably fast.

I get the same result if I close the other instances of CodeSys or other windows within the instance. However, I found that sometimes closing and restarting the CodeSys instance which I want to monitor works, but again this is only sometimes.

Cheers
Laythe

In V2.3 you can have a similar problem when trying to retrieve data from a variable of type Var_in_out from with in the FB that the variable / pointer was defined in.

Example

In a program some where you defined tMyStruct :MY_STRUCT;

then create a FB Set_Data with the following

Var_in_out
tMyStructure : MY_STRUCT;
end_var

then in the program create an instance of Set_Data and pass tMyStruct to tMyStructure

Var
MyData :Set_Data;
end_var

When online if you selected the instance of the Set_data FB MyData and then looked at the variable tMyStructure the data values will all be ??? . In order to see the data in the structure you need to view the reference in the program.

Also I have had some problems viewing global data.

_________________
Thanks,
Steve Pfeifenroth

We have been having more and more difficulty monitoring variables online as our project gets bigger. We are using CoDeSys V3.4 SP1 (for STW ESX-3XL = TriCore). Our download is size is about 470K. Variables are being displayed with "???" or "<Value cannot be retrieved: Too many expressions. >". Previously we have closed all windows and restarted CoDeSys and the 3XL controller to see variables again. This is painful and and in any case is no longer as effective.

This problem is slowing down software development/testing and is very frustrating.

Can anyone explain what causes this and help us find a workaround. Is this a resouce issue (CPU power / RAM size / CAN bandwidth) on the controller or PC side? Any clues as to what to experiment with (e.g. slow down PLC scan rate, try a more powerful PC)?

Use the watch window with just the variables you're wanting to monitor.

I don't think the issue is the speed of the computer, but of the canbus and how fast it can pull the information. They probably limit the amount data pulled over the canbus as you still want the bus to be functional for other devices.