Exporting Trend Data to USB on Siemens Unified Comfort Panel

1. Problem Statement

On a SIMATIC Unified Comfort Panel (MTP700 / MTP1000 / MTP1200 / MTP1500 / MTP1900 / MTP2200) configured with TIA Portal V18 and WinCC Unified V18, an engineer wires a trend control to logged tags, presses the trend control's "Export" toolbar button in Runtime, types a filename (for example, trendExport.csv), and confirms the dialog. The panel responds with "Done" or returns immediately with "Failed" when a full path such as /media/simatic/X64/trendExport.csv is pasted into the name field. The resulting CSV never appears on the USB stick, while a file with the supplied name shows up in an unrelated directory on the panel's internal flash.

This is a documented limitation of the trend control's built-in Export action when the panel runtime (not the WinCC Unified PC Runtime in a browser) is used. The export dialog only honors a file name, not an absolute path, and the panel writes the file to a fixed internal download directory regardless of what the operator types.

2. Root Cause Analysis

The trend control is a screen-context widget. Its Export button invokes an internal WinCC Unified scripting method bound to the screen's download location. On the PC Runtime, that location is the browser's configured download folder; on a Unified Comfort Panel, the same call resolves to the runtime's internal download directory (under /home/industrial/... on the panel filesystem). The Export dialog is not file-system aware and does not enumerate mounted USB partitions (/media/simatic/X64/ or /media/simatic/sd/).

Two failure modes are typically reported in the field:

• Symptom A — silent misroute: Operator sees "Done", finds no CSV on USB. The file is actually written to the panel's internal download path. Cause: dialog accepted the bare filename and dropped it into the default directory.
• Symptom B — explicit failure: Operator pastes /media/simatic/X64/trendExport.csv, panel responds "Failed". Cause: the dialog rejects absolute paths because the underlying export API only accepts a leaf filename on this control.

Both behaviors are consistent with the trend control being a "PC-style" widget that was retrofitted to the panel runtime. Unlike the older Comfort Panels (TP/Comfort), which used WinCC Flexible / TIA WinCC Comfort and had a separate Export button honoring user-defined paths, the Unified trend control exposes only the browser-equivalent download flow. The full path-write capability is delegated to either the Data Logger configuration or to a user-supplied JavaScript snippet bound to a custom button.

3. Unified Comfort Panel File-System Reference

Understanding the panel's mount layout is required to choose the right export sink. The Unified Comfort Panel runs a Linux-based runtime (Siemens Linux, not Windows IoT). The relevant paths in TIA V18 / WinCC Unified V18 firmware are:

4. Solution A — Remap the Data Logger to USB (Recommended for Continuous Logging)

If your goal is to produce a CSV for offline analysis on a regular schedule, do not use the trend control's Export button at all. Configure a Data Logger in the HMI tags with the storage path set to /media/simatic/X64/My_Archives/TagLogs. This is the documented archive path and is honored by the runtime regardless of trend control state.

1. In the TIA Portal project tree, open HMI Tags and select the tags you want logged.
2. Open Logs → right-click → Add new log. Choose TagLogging (segmented CSV or SQL variant).
3. Under Storage location, select File system (CSV).
4. Set the storage path to: /media/simatic/X64/My_Archives/TagLogs
5. Under Segment settings, define a segment size (e.g. 1 day) and enable Sequential numbering so segments do not overwrite each other.
6. Compile and download to the panel.
7. Insert the USB stick. Runtime will create the directory tree on first write. Verify the directory appears via the panel's service menu (Control Panel → Storage media).

5. Solution B — Use a JavaScript Snippet to Export to USB (Recommended for On-Demand Trend Export)

When the operator must trigger an export on demand and the file must land directly on the USB stick, replace the trend control's Export button with a custom button wired to a WinCC Unified JavaScript snippet. The snippet reads the trend buffer via the trend control's API, formats it as CSV, and writes it through the panel's FileSystem scripting interface to /media/simatic/X64/.

Steps:

1. In the WinCC Unified screen, add a Button to the same screen as the trend control.
2. In the button's Events → Click, add a Run script action.
3. Create a new JavaScript file (e.g. ExportTrendToUSB.js) under HMI → Scripts.
4. Implement the script using the HMIRuntime and FileSystem namespaces:

// ExportTrendToUSB.js
// Triggered by a button on the trend screen
// Writes a CSV of the configured trend tags to /media/simatic/X64/
(function () {
    var fs = HMIRuntime.FileSystem;
    var destDir = "/media/simatic/X64/TrendExports";
    var fileName = "Trend_" + HMIRuntime.DateTime.Now.ToString("yyyyMMdd_HHmmss") + ".csv";
    var fullPath = destDir + "/" + fileName;

    // Build CSV header
    var lines = [];
    lines.push("Timestamp;Tag1;Tag2;Tag3");

    // Pull current trend snapshot via the trend control's data interface
    var trend = Screen.Items("TrendControl1");
    var rows = trend.GetTrendData();   // returns array of {t, v1, v2, v3}

    for (var i = 0; i < rows.length; i++) {
        lines.push(rows[i].t + ";" + rows[i].v1 + ";" + rows[i].v2 + ";" + rows[i].v3);
    }

    var csv = lines.join("\n");

    try {
        // Ensure target directory exists
        if (!fs.DirectoryExists(destDir)) {
            fs.CreateDirectory(destDir);
        }
        fs.WriteFile(fullPath, csv, "utf-8");
        HMIRuntime.Trace("Trend exported: " + fullPath);
    } catch (e) {
        HMIRuntime.Trace("Export failed: " + e.message);
    }
})();

5. Compile the HMI project, download to the panel, and run Runtime.
6. Press the new button. The trend data is written as Trend_yyyyMMdd_HHmmss.csv into the USB stick at the configured mount point.

6. Solution C — Pre-Mount a Network Share on the Panel

If USB availability is intermittent or the customer prefers central collection, the panel runtime can mount a Windows SMB share as /media/simatic/net/<name>/ through the panel's Control Panel → Network drives. Once mounted, the same FileSystem.WriteFile call can target the share path. This is the only path that lets the on-demand trend export use the same code as Solution B while writing to a network location, including direct deposit onto an engineering PC.

Caveats:

• SMB v1 is disabled on current firmware; use SMB v2 / v3 only.
• The panel authenticates with a configured Windows account; permissions on the share must include Modify for the service user.
• Disconnect before logout, or the next mount fails with error 190200 in the diagnostic buffer.

7. Verifying the Export

After applying either Solution A or Solution B, run this verification sequence on the panel:

1. Insert the USB stick and wait for the panel's "Storage media" status icon to settle on green.
2. Open Control Panel → Storage media on the panel and confirm X64 shows Ready and the filesystem type (typically vfat or exfat).
3. Trigger the export (logger tick or button press).
4. Open the panel's Diagnostics viewer. Filter for Trend / TagLogging events. A successful write produces info event 190000; a failed write produces warning 190100 with reason text.
5. Use the panel's File browser (in Control Panel) to navigate to /media/simatic/X64/. The CSV must be present and timestamped within seconds of the export trigger.
6. Remove the USB stick via Control Panel → "Safely remove". Copy the file to a PC and confirm a header row, expected column count, and a non-zero row count.

8. Firmware / Software Version Compatibility

9. Error Code Reference

10. Troubleshooting Matrix

11. Best Practices

• For continuous process logging, prefer the Data Logger (Solution A) — it survives a power loss because segments are flushed atomically.
• For ad-hoc trend dumps at shift handover, use the JavaScript snippet (Solution B) bound to a clearly labeled button with a confirmation popup.
• Always use a timestamped filename pattern (yyyyMMdd_HHmmss) to prevent overwrites on hot-plug retries.
• Mirror critical logs to both internal SD and a rotating USB stick to avoid data loss when one medium fails.
• Document the export path in the HMI screen's help text so operators know where to retrieve the CSV without engineering intervention.