Can't Read Tags but can Write them

I have an issue with Reading tags from the PLC ( it’s a S7-1500 ).
I’ve configured manually some tags as the Manual says: [S7-1500]DB1001,X0.0 for a Bolean tag inisde the DB1001
The PLC is connected and it’s seen by Ignition.
If I enable the option “OPC Read After Write” inside the Scan Class, I’m able to write the tag from Ignition to the PLC but if I set the same tag from the PLC (TIA PORTAL V14), the tag will not change value inside Ignition.
If I disable the same option (OPC Read After Write) inside the Scan Class, I’m no longer able to even write the tag from Ignition.
I’m aware that the following considerations and configurations changes must be made when using the S7-1200 and S7-1500 drivers.

Only global DBs can be accessed
The optimized block access must be turned off
The access level must be “full” and the “connection mechanism” must allow GET/PUT
Reads and Writes can not be used in TM/CT areas

And it’s all set up correctly.

Any helps?

After the DB number should be a comma, not a full stop.
So for your example above it should be [S7-1500]DB1001,X0.0

Ups :sweat_smile:
I misswrote that part in the post.
Inside Igntion it’s correctly written.
Thanks anyway :slight_smile:

After everything you said, it should work.
And read after write should not make any difference.
How is the gateway connected to the PLC?
Have you looked at the logs on the gateway page? There should be some indications what’s going on…

I’m full of this Warning message

In my experience, in this case, the best you can do is:

  • delete all tags in designer Tag Browser
  • delete all scan classes
  • close everything (clients, designer)
  • delete the connection to PLC
  • stop gateway
  • restart PC/VM
  • do everything in reverse order (plc connection, scan classes, tags…)

I think, that Siemens driver gets somehow ‘confused’ if you make too many config mistakes when you are creating tags…
It happened to me 1-2 times and also some other people here on the forum…

Can you provide support with your logs and a tag export or some other list of tags you have created for this device?

There seems to be some internal error in the UA server happening, but there’s not enough information in the screenshot to know more.

“system_logs_26gen2018-16-11-42” <<— This file is too large for being uploaded here, i’m doing it with WeTransfer, here it is the link:
https://wetransfer.com/downloads/2231c779e8d8d8a510a2a24fc614d7cc20180126152350/efdaf72c64ec31ff498217a6622be2a720180126152350/b5927b
the other file is an export of all my tags
tags.xml (45.8 KB)

Looking at your tags.xml I see that you configured String tags with 256 bytes lenghts.
Ignition siemens driver supports ONLY 202 bytes.
Change your string tags and you’re good.
I had the same problem some years ago (you can search the forum for my post) and spend many hours until I found the problem.

1 Like

I found out what was the issue!
I had one tag, with this grammar " [S7-1500]DB201,ISTRING1024.256 " for a string tag.
The “I” before STRING was causing the issue! After I edit that grammar to “[S7-1500]DB201,STRING1024.256” everything went fine.
Thanks to all for the help! I really appreciated it!
Cheers, and many thanks again!

1 Like

There are more options then using Ignition’s S7-driver with your S7/1500.
First option, PLC firmware 2.0 and above has a built in OPC_UA server.
Second option, use Simatic Net from Siemens. It does the absolute to symbolic conversion for you.

This allows you to come in with ignition OPC_UA client and read the tags. I likes these options a little better than trying call the datablock address with all of its offset. Seams to make development and changes go a little faster.

Thank you for your suggestions Mike :wink:
I’ll try what you suggest :slight_smile:
Cheers,

A post was merged into an existing topic: Siemens Addressing