String Display Issue (RSLogix5000 and PvP)

bradc1988

Member
Join Date
Dec 2011
Location
Sydney
Posts
3
Hi all,

I am having an issue with strings sent from my L32E to my PanelView Plus where the string displayed in RSLogix5000 is right but the message displayed is not right.

The goal is to have a list of messages in an array, and depending on the circumstances I grab one of those message and store it in another string to send it to the touchscreen. There are however possible situations where more than one of these circumstances maybe true so I have prioritized the messages by their position in the ladder. What this means is I need to delete what is currently in the string being sent to the HMI and then push the new string in.

I am using the two instructions delete, to clear the string being sent to the HMI (SYSTEM.STATUS_TS), and insert, to load the new message.

Below are two images, one of the string as seen in the PLC and one of the same string being displayed within FactoryTalk View Studio.

plcview.jpg

hmiview.jpg


As you can see the strings do not match! I am assuming it may be a memory issue? I should note there is another message called "RC01-RC04 are in fault" which the intended message seems to have concatenated with.

Any help or insight in a different way of doing what I want would be greatly appreciated!

I should note previous to this project I would have these messages hard coded in the HMI program, and simply send a number to the screen which calls upon the hard coded messages. This method means it's simpler to change messages as it can be done via the PLC instead of the HMI program.

Thanks!!!
 
The problem is likely in the way FTView is updating it's reading of the .LEN element of the String.

Try moving the SYSTEM.STATUS_TS string out of the UDT and into a standalone STRING datatype. Check carefully to be sure the .LEN value is what you think it ought to be.

I just did a quick test with FTView ME 6.10 and wasn't able to reproduce the problem, so it's more complicated than just "I changed the string and FTView is reading the old length".
 
Hi Ken, thanks for the quick reply!

I just tried moving SYSTEM.STATUS_TS out of the UDT and made it a stand alone string, however this unfortunately did not fix the problem. The remainder of the previous longer string is still being displayed at the end of the desired shorter string but not appearing in the PLC.

The value of the .LEN for SYSTEM.STATUS_TS is matching the contents of the string.

I am using ME 5.10 if that means anything.

Very confusing and frustrating!
 
I'm sitting in front of the tv right now, but I can test this tomorrow. I haven't used the delete string instruction before, I usually create an empty string "StringNull" that I copy in to clear a string and I've only used the insert when I'm piecing strings together. Try just copying the new string in.

Edit - you dont need to clear the first message, just copy the new string in - COP Source-oldmessage Destination-new message-length 1.
 
Last edited:
I want to ask in this forum, how to open the MMC in PLC card S7 300 memory 331?
I allready download the DBFEdit, but when I try to open using memory card, the MMC need the psw and/or format the card.

Please help me.

Thanks for advancing.

Felix
 
Brad, I have a vague recollection of encountering this issue in the past with PanelView Plus, and it might have been in version 5.10. I only have a v6 terminal to work with at this time.

I would try an experiment, and a workaround.

The experiment is to see if the issue is when the PV+ reads the .LEN element for the String Display object. It might be the first time the Display is opened, so try creating an On Top display with the String Object, then opening and closing it.

The workaround would be to fill the String's .DATA[x] field with spaces, instead of nulls. Simply using the File Fill (FLL) instruction with a source value of 16#20 (decimal 32) prior to moving the new String into that Tag should give you trailing spaces instead of the "leftover" characters.

If it's any consolation I just went through a similar issue with a Red Lion G3, so this sort of thing is common, but not necessarily brand-specific.
 
I suppose another work-around would be to have all the strings in the PLC right-padded with spaces so they are all the same length. You will not be using any more memory, space for the strings is allocated up to the maximum length anyway.

It may be a PITA when you come to add a new string, or modify an existing one, however, you could write a little piece of code to automatically do this for you if it finds that .LEN is not what it is supposed to be.

On the subject of string length, the pre-defined STRING data-type allows for up to 82 characters. If your HMI layout can only display strings up to say 24 characters, then you can create your own data-type (e.g. call it STRING24), and configure it for 24 characters. This will save memory in the controller, and the comms to the HMI will be optimised.

2013-01-25_215048.jpg
 
Strings are generally a PITA in a PLC especially with ladder logic. It might serve you well to start using a DINT for the error condition and create a list of string messages in the PV+ which are correlated via the "normal" tag.
 
Strings are generally a PITA in a PLC especially with ladder logic. It might serve you well to start using a DINT for the error condition and create a list of string messages in the PV+ which are correlated via the "normal" tag.

Agreed, but the OP is not trying to manipulate the strings in the PLC code.

I can understand his choice of where they are stored, in a PLC they are just data elements and can be changed at any time without halting the process.

In a HMI its a re-compile and download, which will take the HMI off-line.
 
Sorry about the long delay in replying to this, I was locked out of the worksite due to some building works and only got back recently.

In the mean time I had upgraded my Factory Talk View Studio from 5.10 to 6.10 because the actual panel had 6.00 and I couldn't download to it initially.

So now the issue is still happening in 6.00 on the panel but when I simulate it on my laptop in ME Station using 6.10 it works perfectly. For some reason I can't update the panel to 6.10 so I am stuck with 6.00.

I tried most of the suggestions in this thread (apart from moving the strings to the HMI program as that would defeat the purpose of what I am trying to acheive) to no avail. I did however make a workaround where I am now concatenating the string being displayed with a string of spaces. The display format looks a bit silly but it works...

The workaround would be to fill the String's .DATA[x] field with spaces, instead of nulls. Simply using the File Fill (FLL) instruction with a source value of 16#20 (decimal 32) prior to moving the new String into that Tag should give you trailing spaces instead of the "leftover" characters.

This may be better than what I am currently doing, I will give this a go next time I'm out on site.

Thanks for all the replies! It is very much appreciated!
 
This could be unrelated, but I know that the older Wonderware Ethernet I/O Server (ABTCP) for Allen Bradley had an issue with resolving string length when reading string data arrays. The workaround patch for this issue was to create a topic only for string data that was limited (by configured block size) to reading only one word per message.
 
Hi, can anyone tell me the solution for this problem.. All the string displays in my FactoryTalk View program are in "?". I'm pertaining to a project which I have imported. I have tried to re-install the program but it failed to resolve the problem. Your help will be very muuch appreciated. Thanks.
 

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