Array of UDT

[arcimus]

Hello, I'm attempting to list and read tags in ControlLogix software written by an equipment manufacturer. I am able to list tags and UDTs using your sample code, but I'm not sure how to enumerate arrays of UDTs.

Here's an example set of tags retrieved using a 3rd party tool:

Using libplctag.NET, I can determine that "B0501_COM262_Node2:I.Slot" is a UDT, and can retrieve the UDT definition that contains ".Fault" and ".Data" DINTs. However, I'm not sure how to determine that "B0501_COM262_Node2:I.Slot" is an array of UDTs.

B0501_COM262_Node2:I.Slot:
Type: 44080
Offset: 4
Metadata: 7
NumFields: 2
Size: 60

The 7 value for Metadata sticks out, but after searching around, I'm not sure what Metadata is used for.

[timyhac]

There is some information about the meaning of the UDT info structure in the source code here - you are onto something!

[arcimus]

Hello and thanks for your reply. In the source code you mentioned, I see:

     * N x field info entries
     *     uint16_t field_metadata - array element count or bit field number
     *     uint16_t field_type
     *     uint32_t field_offset

So, the 7 returned in the libplctag.NET Metadata field could be an array element count or bit field number. How can I use libplctag.NET to determine if it's the former or the latter?

[timyhac]

I believe that it refers to a bit field number when it is a BOOL type.

[arcimus]

Hi and thanks. The print_element_type function here helped me identify tag types.