Exporting S7 Connections from TIA Portal: CAx, Openness, AML

Overview

S7 Connection resources configured under Devices & Networks > Networks view > S7 connections are not written into the AutomationML (.aml) file produced by the TIA Portal CAx export wizard. The CAx exporter serializes topology, module parameters, and a subset of software objects, but the cross-PLC S7 connection objects are filtered out by design. As a result, a CAx round-trip (export → modify → import) on a TIA V17 project rebuilds the hardware and PLC software skeleton but leaves every S7 connection empty and rewrites every drive parameter to its default value.

This article documents the practical methods available to preserve S7 Connection configuration across project exchanges:

1. TIA Portal Openness API — programmatic export and re-import of S7 connection objects.
2. SIMATIC S7 Connector V2.1.0 XML workflow — structured tag-level export that complements Openness.
3. Direct PLC tag and connection XML export via the TIA Portal GUI — the lowest-effort manual path.
4. Workarounds for the drive-parameter default-on-import behavior seen during CAx round-trip.

Verification steps, a troubleshooting matrix for the most common failure modes, and an FAQ close the document.

Why S7 Connections Are Missing from CAx .aml Export

The TIA Portal CAx data exporter targets the AutomationML (AML) role-class Communication only for a narrow set of object types: subnets, IO controllers, IO devices, PN/PN coupler link tables, and a small subset of HMI tags. S7 connection objects are represented inside the project by the type S7Connection under Subnet.Connections, and these are deliberately omitted from the AML CAx profile.

The architectural reasons are documented across the Siemens support database:

• S7 connection semantics depend on protected CPU-to-CPU configuration objects (connection resources, TSAPs, local/partner IDs) that the AML CAx schema does not model.
• The S7 connection lifecycle (active/passive endpoints, one-way/two-way, PUT/GET vs. ISO-on-TCP) does not map cleanly to the AML Communication role.
• Drive parameters live in the GSD/GSDML importer pipeline; CAx import regenerates the device description from scratch, which resets parameters to GSD defaults unless a separate parameter file is re-applied.

Until Siemens extends the CAx exporter, the only reliable way to round-trip S7 connection objects is through TIA Portal Openness or manual XML handling.

Prerequisites

CAx Export Scope: What Is and Is Not Included

The following table summarizes the canonical CAx (.aml) coverage against a V17 project. Use it to predict what survives a round-trip before committing to a particular workflow.

Method 1: TIA Openness API for S7 Connection Export

TIA Portal Openness exposes the full S7 connection graph through Siemens.Engineering.HW.Features.ConnectionService and Siemens.Engineering.HW.S7Connection. A C# console application can enumerate every connection in the project, serialize it to XML, and later re-import it on the target station.

Step-by-Step Procedure

1. Create a new Console App (.NET Framework 4.7.2) project in Visual Studio.
2. Add references to Siemens.Engineering.dll and Siemens.Engineering.Hmi.dll from the TIA Portal installation directory (default C:\Program Files\Siemens\Automation\Portal V17\PublicAPI\V17).
3. Reference the assembly with Embed Interop Types = False; the types are not COM but they must not be embedded.
4. Compile the project to S7ConnectionExporter.exe.
5. Close the TIA Portal UI.
6. Run S7ConnectionExporter.exe "C:\Projects\Plant.ap17" "C:\Export\S7Connections.xml".
7. Open S7Connections.xml and validate against the schema in Verification Steps.

Reference Code: Export Side

using System;
using System.IO;
using System.Xml;
using Siemens.Engineering;
using Siemens.Engineering.HW;
using Siemens.Engineering.HW.Features;

namespace S7ConnectionExporter
{
    internal static class Program
    {
        private const string Ns = "urn:siemens:tia:s7conn:1.0";

        static int Main(string[] args)
        {
            if (args.Length != 2)
            {
                Console.Error.WriteLine("Usage: S7ConnectionExporter <project.ap17> <output.xml>");
                return 2;
            }

            var projectFile = new FileInfo(args[0]);
            if (!projectFile.Exists) { Console.Error.WriteLine("Project not found."); return 3; }

            using var tia = new TiaPortal(TiaPortalMode.WithoutUserInterface);
            using Project project = tia.Projects.Open(projectFile);

            var settings = new XmlWriterSettings { Indent = true, IndentChars = "  ", Encoding = System.Text.Encoding.UTF8 };
            using var w = XmlWriter.Create(args[1], settings);
            w.WriteStartDocument();
            w.WriteStartElement("S7Connections", Ns);

            int total = 0;
            foreach (Device device in project.Devices)
            {
                total += WalkDevice(device, w);
            }

            w.WriteEndElement();
            w.WriteEndDocument();
            Console.WriteLine($"Exported {total} S7 connection(s) to {args[1]}");
            return 0;
        }

        private static int WalkDevice(Device device, XmlWriter w)
        {
            int count = 0;
            foreach (DeviceItem item in device.DeviceItems)
            {
                // S7 connections live on DeviceItems that participate in a Subnet
                Subnet subnet = item.Subnet;
                if (subnet == null) continue;

                foreach (object connObj in subnet.Connections)
                {
                    if (connObj is S7Connection s7)
                    {
                        WriteConnection(w, s7, device, item);
                        count++;
                    }
                }
            }
            return count;
        }

        private static void WriteConnection(XmlWriter w, S7Connection s7, Device owner, DeviceItem item)
        {
            w.WriteStartElement("Connection");
            w.WriteAttributeString("name", s7.Name);
            w.WriteAttributeString("ownerDevice", owner.Name);
            w.WriteAttributeString("ownerItem", item.Name);
            w.WriteElementString("Type", s7.Type.ToString());         // IsoOnTcp / S7Communication / PutGet
            w.WriteElementString("Active", s7.Active ? "true" : "false");
            w.WriteElementString("LocalTsap", s7.LocalTsap?.IdString ?? "");
            w.WriteElementString("PartnerTsap", s7.PartnerTsap?.IdString ?? "");
            w.WriteElementString("LocalAddress", s7.LocalAddress?.ToString() ?? "");
            w.WriteElementString("PartnerAddress", s7.PartnerAddress?.ToString() ?? "");
            w.WriteElementString("LocalId", s7.LocalId.ToString());
            w.WriteElementString("PartnerId", s7.PartnerId.ToString());
            w.WriteEndElement();
        }
    }
}

Reference Code: Import Side

The reverse pass opens the target project and rebuilds the connections by matching ownerDevice + ownerItem against the live project graph.

using Siemens.Engineering;
using Siemens.Engineering.HW;
using Siemens.Engineering.HW.Features;

using var tia = new TiaPortal(TiaPortalMode.WithoutUserInterface);
using Project project = tia.Projects.Open(new FileInfo(args[0]));

var doc = new System.Xml.XmlDocument();
doc.Load(args[1]);

foreach (System.Xml.XmlNode node in doc.SelectNodes("//*[local-name()='Connection']"))
{
    string ownerDevice = node.Attributes["ownerDevice"].Value;
    string ownerItem   = node.Attributes["ownerItem"].Value;

    Device device = FindDevice(project, ownerDevice);
    DeviceItem item = FindDeviceItem(device, ownerItem);
    if (device == null || item == null) { Console.WriteLine($"Skip {ownerDevice}/{ownerItem}"); continue; }

    var connSvc = item.GetService<ConnectionService>();
    if (connSvc == null) continue;

    // Use the appropriate factory based on Type
    // Example for ISO-on-TCP:
    //   var c = connSvc.CreateIsoOnTcpConnection(...);
    //   c.LocalTsap  = ... ; c.PartnerTsap = ... ;
    //   c.LocalAddress = ... ; c.PartnerAddress = ... ;
    //   c.Name = node["@name"].Value;
}

Method 2: SIMATIC S7 Connector V2.1.0 XML Workflow

The SIMATIC S7 Connector V2.1.0 is an Industrial Edge application whose primary purpose is to forward PLC tag values to the IE runtime. As a side-effect of its configuration workflow, it forces a structured XML export of PLC tags that can be reused for partial project reproduction.

XML Export Procedure

1. Compile the TIA Portal project.
2. Navigate to the target PLC → PLC tags → Show all tags.
3. Right-click the tag table and select Export file.
4. Choose XML as the format and save to a known location.
5. Import the resulting XML into the S7 Connector configurator as described in the XML file export documentation.

The output schema is stable across V17/V18 of TIA Portal. Tags are addressable by fully qualified name and grouped by data block. The connector reads the file at deploy time and binds each tag to the IE runtime variable tree.

Method 3: Direct PLC Tag and Connection XML Export

For small projects where Openness is overkill, the TIA Portal GUI itself can export per-PLC tag tables and per-subnet connection tables. The procedure does not capture cross-references between devices but it is sufficient when the receiving project uses the same hardware catalog.

Tag Export

1. In the project tree, expand the target PLC → PLC tags.
2. Select Default tag table or a user-defined table.
3. Right-click → Export → Export to Excel or Export to XML.
4. Save the file as <plcname>_tags.xml.

Connection Export (Manual Snapshot)

Because the GUI does not expose a connection-only exporter, capture the connection properties via a screenshot or by copy-pasting the Properties → General tab of each S7 connection into a side document. Useful fields:

• Connection name
• Local interface / Local IP / Local TSAP
• Partner IP / Partner TSAP
• Connection type (ISO-on-TCP, S7 communication, PUT/GET)
• Active / Passive role
• Connection resource ID (hex, e.g., 10, 11)

For a 30-CPU plant this is tedious but viable when Openness is not available on the engineering station.

Drive Parameter Export Limitation and Workarounds

CAx import always rewrites drive parameters to the values defined by the GSD/GSDML file because the AML role for drives does not carry parameter payloads. The original values must be re-applied by one of the following methods:

If the drives are managed by Startdrive inside the same TIA project, parameter sets can be exported via Drive → Commissioning → Save to memory card. The card image is then loaded back after the CAx import completes.

Verification Steps After Import

1. Open the target TIA Portal project.
2. Navigate to Devices & Networks.
3. Open the Connections table (right-click the network → Show connections).
4. Confirm that every S7 connection from the source XML appears with the correct Type, Active, Local TSAP, and Partner TSAP.
5. Right-click each CPU → Compile → Software (rebuild all).
6. Check the Info → Compile tab for warnings of the form "S7 connection X references unknown partner Y". Resolve any by re-binding the partner.
7. Download the project to each CPU and force an Establish connection from the online diagnostics view.
8. For drives, compare the Online → Parameter assignment tab against the source project. Diff at parameter-set level.

Troubleshooting Matrix

Cross-Platform Notes

The TIA Portal V17 Openness API surface is consistent across Windows 10 LTSC 2019, Windows 10 21H2, and Windows 11 22H2. There is no native Linux or macOS support. Industrial Edge runtime targets Linux but the configuration is performed on a Windows engineering station.

For STEP 7 V5.x projects (pre-V15), the equivalent of CAx export is the Source code export via SIMATIC Manager → Options → Manage multilingual texts → Export. Net connections defined in NetPro are not preserved across that path either; only the S7 program blocks are. To migrate S7 connections from V5.x to TIA Portal, use Migration → Migrate project in the TIA Portal UI, which preserves connection objects at the project level.

Safety Considerations