Byte swap in modbus addressing

Hi,

In my setup i have pc (192.168.0.2) running ignition 8.0.0 (also tried with ignition 8.0.2) configured for Modbus TCP device (192.168.0.222).

The device connection is ok, but when i try reading the data i am getting bad quality in the designer, whereas with modbus utility i am able to read the holding registers.

I have configured both modbus TCP (ignition) and the modbus utility to read 2729 address . The wireshark frames I have captured indicate that ignition is trying to read 1328 address instead of 2729. I have tried enabling and disabling “reverse word order” but the addressing doesn’t seem to change.

attached are some screen shots.




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Did you subscribe to these tags in Ignition by dragging them from the OPC browser to the Tag browser in the Designer?

Creating the mapping by itself just makes them show up in the OPC browser. Ignition won’t read anything until you subscribe by creating tags.

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I also noticed your Modbus utility is using unit id 1 and you’ve configured your mapping for unit id 0.

I think we’re seeing some different request in the Ignition Wireshark capture though, because that was is for unit id 1 as well.

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@Kevin.Herron
Thanks for pointing that out, the device address should be 1.

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Yes, I had added the tag in designer. shouldn’t the address be correct even if the unit I’d is incorrect?

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What’s the OPC Item Path of the tag you added in the designer?

Have you dragged those mapped tags in from the OPC browser yet?

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Kevin, figured the issue I was also trying to access 1328 from the designer.

The issue is resolved. Thanks for the help.

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