Creating Text Files on Siemens MP277 HMI Panels Using VBScript

Overview

The Siemens SIMATIC MP277 Multi Panel runs Windows CE 5.0 and supports VBScript for runtime automation. Writing text files from the panel — for datalogging, recipe export, alarm archiving, or audit trails — uses the bundled MSCEFile.dll COM library that exposes FileCtl.FileSystem and FileCtl.File automation objects. This reference covers the exact syntax, file open modes, path conventions, error handling, and verification steps required to write reliable text files from an MP277 panel project configured in WinCC flexible 2008 SP3 or TIA Portal V13 SP1+ WinCC Comfort/Advanced.

The MP277 differs from a desktop PC: only the Windows CE file system is accessible through MSCEFile.dll. The same VBScript code will not run on a WinCC Runtime Professional station running Windows 7/10/11, which instead uses the standard FileSystemObject.CreateTextFile model.

Prerequisites

• SIMATIC MP277 panel — 6AV6 643-0CD01-1AX1 (8" Touch), 6AV6 643-0DD01-1AX1 (10" Touch), or 6AV6 643-0BA01-1AX1 (8" Key). All ship with Windows CE 5.0.
• WinCC flexible 2008 SP3 (for legacy projects) or TIA Portal V13 SP1+ with WinCC Comfort/Advanced (for migrated projects).
• Storage media: built-in Flash (~6 MB free after image) or CF card inserted in slot 1. CF cards up to 2 GB formatted FAT16 are supported.
• VBScript familiarity at the WinCC flexible scripting level — runtime scripts support a subset of VBScript 5.x without Wscript.Shell or WScript.Network.
• Panel transfer cable or Ethernet connection for downloading the compiled HMI project.
• Remote-control channel (CEBC) or VNC server enabled on the panel for runtime verification.

Understanding the File System on MP277

The MP277's Windows CE image presents a hierarchical file system that differs from desktop Windows. Paths always start with a backslash; forward slashes are accepted interchangeably. The default mounted volumes are:

Network drives mapped through the control panel appear as \server\share once DNS and the Workgroup are configured; VBScript can read from but cannot always write to UNC paths depending on the user context. See the network-access section below for the supported mechanism.

MSCEFile.dll Architecture

MSCEFile.dll ships in the MP277 image under \Windows\MSCEFile.dll and registers itself as a COM automation server during boot. Two objects are exposed to VBScript:

• FILECTL.FileSystem — provides file-system queries such as FileExists, GetFile, GetFolder, CreateFolder, and DeleteFile.
• FILECTL.File — provides sequential text-file I/O including Open, LinePrint, LineInputString, EOF, Close, Kill, and Seek.

Both objects are created with the standard CreateObject syntax:

' Create FileSystem object for WinCE
Set filesys = CreateObject("FILECTL.FileSystem")

' Create File object for WinCE
Set logFile = CreateObject("FILECTL.File")

The FILECTL.File object is the equivalent of a Visual Basic 6 Scripting.TextStream, but its syntax is older and uses integer mode flags rather than the string constants ForReading/ForAppending used by the desktop FileSystemObject.

Step-by-Step: Creating and Writing a Text File

1. Add a script to your HMI project. In WinCC flexible, right-click the screen or scheduler that should trigger the write and select "Properties → Events → Click" (for buttons) or "Value change" (for tag events). Choose VBScript as the action type.
2. Declare the object variables. The runtime instance lifetime is per-call; declare inside the subroutine to avoid leaks.
3. Resolve the target path. Use FILECTL.FileSystem.FileExists to test before opening if you want conditional logic.
4. Open the file with the correct mode. See the mode table below; mode 8 (append) is the safest default for datalogging because it never destroys existing data.
5. Write the line using LinePrint. The method appends a CRLF automatically.
6. Close the file and clear the references. Failing to close will lock the file until the panel reboots.
7. Add an error handler. Wrap the body in On Error Resume Next and inspect Err.Number afterwards; surface the result to a tag so it can be alarm-logged.

Minimal working example for a button click on an MP277 8" Touch panel:

' VBScript - WinCC flexible / TIA Portal WinCC Comfort
' Trigger: Button "Log Event" - Click event

Dim sPath, sFile, sLine
Dim filesys, logFile

' --- Configuration ---
sPath  = "\Flash\My Documents\"   ' Writable location
sFile  = "TestLog.txt"

' --- Build a tab-separated line ---
sLine = Now & vbTab & _
        SmartTags("Machine.State") & vbTab & _
        SmartTags("Production.Counter")

On Error Resume Next
Set filesys = CreateObject("FILECTL.FileSystem")
Set logFile = CreateObject("FILECTL.File")

' Mode 8 = Open for appending (create if missing)
logFile.Open sPath & sFile, 8

If Err.Number = 0 Then
    logFile.LinePrint(sLine)
    logFile.Close
    SmartTags("Logging.LastStatus") = 1   ' OK
Else
    SmartTags("Logging.LastStatus") = Err.Number
    SmartTags("Logging.LastError")  = Err.Description
End If

Set logFile = Nothing
Set filesys = Nothing
On Error Goto 0

File Open Mode Reference

The integer passed as the second argument to File.Open selects the access mode. The following values are documented in MSCEFile.dll:

Path Conventions and Storage Options

Always prefer \Storage Card\Logs\ over \Flash\ when the log will exceed ~1 MB, because the internal flash has limited write endurance. Create a dedicated subfolder with FILECTL.FileSystem.CreateFolder on first run:

If Not filesys.FileExists("\Storage Card\Logs\") Then
    filesys.CreateFolder "\Storage Card\Logs\"
End If

Use dated filenames to bound file size and simplify operator-side housekeeping:

sFile = "Batch_" & FormatDateTime(Now, vbShortDate) & ".csv"
sFile = Replace(sFile, "/", "-")

Cap each file to 1 MB with a size check before opening; FILECTL.FileSystem exposes GetFile(path).Size for this purpose.

Advanced: PLC-Triggered Datalogging with Timestamps

The most common production use case is logging every time a PLC tag toggles — for example, an "Operation Complete" bit. Combine a WinCC flexible scheduler (1 s polling) or a tag-event trigger with the VBScript above:

' Scheduler "DatalogTick" - runs every 1000 ms
Dim fso, f
Set fso = CreateObject("FILECTL.FileSystem")
Set f   = CreateObject("FILECTL.File")

If SmartTags("PLC.NewBatch") = 1 Then
    SmartTags("PLC.NewBatch") = 0   ' acknowledge
    f.Open "\Storage Card\Logs\Batches.csv", 8
    f.LinePrint FormatDateTime(Now, vbShortTime) & "," & _
                SmartTags("PLC.BatchID") & "," & _
                SmartTags("PLC.ResultCode")
    f.Close
End If

Set f = Nothing
Set fso = Nothing

For high-frequency events (>5 Hz), switch the logging to the PLC side using a S7 data block and transfer the block image at end-of-shift via an FTP push; the MP277 VBScript runtime is single-threaded and a 200 ms file write blocks HMI update cycles.

Accessing PC Shared Folders from the Panel

The MP277 cannot browse a Windows network neighborhood by default, but it can access a UNC share if the panel's hostname is registered on the DNS server (often the engineering PC) and the PC's hosts file contains the panel name. Siemens documents this in Siemens Support Entry 13336639 under "How do you access the network drive of a PC from an HMI panel?".

1. Configure the PC's network adapter to share the folder with read/write permission for the panel service account.
2. Add the panel's hostname-to-IP mapping to C:\Windows\System32\drivers\etc\hosts on the PC (e.g. 192.168.0.10 MP277).
3. On the panel, open Control Panel → Network and configure the DNS server to point at the PC acting as the WINS resolver.
4. In VBScript, use the UNC path: f.Open "\\PC-NAME\SharedLogs\Line01.csv", 8. Computer name, not IP address, is required.

Error Handling and Diagnostics

Failures fall into three categories on the MP277:

Surface Err.Number and Err.Description to HMI tags so they can be archived in the alarm log; this provides an audit trail of logging failures.

Verification

1. Compile and download the project to the panel.
2. Connect via CEBC: start ProSave, select Ethernet, point at the panel IP, and click "File Browser".
3. Navigate to \Flash\My Documents\ or \Storage Card\Logs\ and confirm the new file exists.
4. Transfer the file via ProSave's "Receive" button and inspect with Notepad — line endings must be CRLF and the timestamp must match the panel clock.
5. Repeat for the error path: remove the CF card, trigger the script, confirm Logging.LastStatus shows a non-zero value and the alarm is raised.
6. Power-cycle the panel and confirm the file persisted. If it disappeared, you wrote to \Hard Disk instead of \Storage Card.

Limitations and Best Practices

• Single threading. The WinCC flexible / WinCC Comfort runtime uses one scripting thread; long writes block tag polling. Keep individual writes under 50 ms or batch them.
• No Unicode in CE 5.0. MSCEFile.dll writes ANSI; for non-ASCII characters (e.g. Cyrillic) use a UNICODE-aware library or escape them as \uXXXX.
• No transactional safety. A power loss during LinePrint corrupts the file. For audit-grade logs, write to a temporary file and rename atomically using FILECTL.FileSystem.
• CF card format. FAT16 only, max 2 GB. Format with Windows format X: /FS:FAT /Q; FAT32 cards over 4 GB are not recognized.
• Wear leveling. Internal flash supports roughly 100,000 write cycles per sector. For high-frequency logging, rotate files hourly and always use CF.
• Security. Files are world-readable from CEBC. If the data is sensitive, encrypt with a PLC-side AES routine and write the ciphertext only.
• Migration. Projects moved to TIA Portal V16+ WinCC Unified use JavaScript and the Node.js fs module; the MSCEFile.dll approach applies only to Comfort/Advanced panels on Windows CE.

FAQ