Siemens LOGO! Access Tool: Reading Historical Data from SD Card

Overview

The Siemens LOGO! 6ED1052-1MD08-0BA0 is a logic module that supports analog value monitoring, digital status capture, and time-stamping. A frequent field request is to read the last 50–60 recorded samples (or older values) directly from the LOGO! without launching LOGO! Soft Comfort (LSC). The LOGO! Access Tool (LAT) is the standard PC-side utility for live variable monitoring, but it does not give the operator direct access to the SD-card-resident data archive. This reference clarifies what the Access Tool can and cannot read, documents the Live-Data / History-Data feature, and presents the workarounds used in field installations to export historical data to Excel, CSV, or an external HMI/SCADA system.

LOGO! 6ED1052-1MD08-0BA0 Hardware Overview

The 6ED1052-1MD08-0BA0 is a LOGO! 8 logic module with integrated display. The relevant hardware boundary conditions for data acquisition are:

Two analog inputs, one digital byte, and the internal real-time clock are the typical data sources the operator wants to log. These map directly to VM addresses; for example, an analog value at AI1 is mirrored in the VM mapping that the Access Tool polls on a fixed interval (default 1 s, configurable 100 ms – 60 s).

Data Log Function Block Inside the LOGO! Program

Inside the LSC circuit diagram the user can drop a Data Log function block. Each block writes one record line (up to 32 bytes) to the SD card whenever its trigger condition is true.

The CSV that the Data Log block writes looks similar to the sample below. The header line is written once at file creation.

Date;Time;AI1_mA;AI2_mA;DI_Byte;Status
2025-01-14;08:00:01;4.02;12.45;0x0A;OK
2025-01-14;08:00:11;4.03;12.46;0x0A;OK
2025-01-14;08:00:21;4.05;12.44;0x0B;OK
...

Once the file is on the SD card, the Access Tool cannot read it. The only ways to retrieve the file are: (a) power down the LOGO!, remove the SD card, and open the file in Excel/Notepad, (b) use LSC's Tools → Transfer → Data Log menu, or (c) write a script that pulls the file from the SD card via FTP/SFTP – which the LOGO! base unit does not support.

LOGO! Access Tool: Capabilities and Limits

The LOGO! Access Tool is a free Siemens Windows application (part of the LOGO! Soft Comfort installation package, available in the Siemens Industry Online Support portal). It runs on Windows 10/11 and connects to the LOGO! over TCP/IP port 10005 (LOGO! protocol, fixed). It is designed for the use case "PC displays what the LOGO! currently sees" – not for archive retrieval.

History Data Number: What It Really Means

The History Data Number scroll bar that the user sees in the Access Tool main window is described in the official LOGO! Access Tool Help (en-US):

"In the scroll bar of History Data Number, you can drag the scroll box from up to down to select one number for the history data."

The number is a pointer to a sample already in the Access Tool's local RAM buffer. The buffer grows as the Access Tool polls the LOGO!. It is not an SD-card index and is not persistent across restarts. The maximum length of the buffer is determined by the configured Number of Records in the LAT project (default 100, max 1 000 in current builds). Once the buffer is full, the oldest sample is overwritten (FIFO).

Reading Live Data with the Access Tool – Step by Step

1. Install LOGO! Soft Comfort V8.3 or higher on the engineering PC. The Access Tool installer is included in the same package.
2. Connect the PC to the LOGO! Ethernet port. Use a static IP on the PC side (e.g. 192.168.0.100/24) and confirm ping 192.168.0.10 (default LOGO! IP) returns reply.
3. Start LOGO! Access Tool and create a new project.
4. Enter the LOGO! IP address, the port (default 10005), and the VM mapping table (imported from the LSC project file .lsc via File → Import → Variable Table).
5. Set the Cycle Time (100 ms – 60 000 ms). For 2 analog values, 1 s is a common default and produces a manageable CSV size.
6. Set the Number of Records (history buffer length) to the desired window. 60 is sufficient for the 50–60 sample target.
7. Click Start. The right-hand panel begins updating with the polled values. The History Data graph populates in real time.
8. Drag the History Data Number scroll box to inspect any past sample in the buffer.

Configuring CSV Data Logging in the Access Tool

To get a permanent file, the Access Tool can write the live data stream to a CSV on the PC disk.

1. In LAT, open Settings → Data Logging.
2. Enable Log to CSV file.
3. Specify the output path (e.g. D:\LOGO_Hist\LineA_) and a file-name pattern that includes a timestamp token (e.g. yyyyMMdd_HHmmss).
4. Set the delimiter to ; or , to match the Excel locale (German Excel expects ;).
5. Select the Append mode checkbox if the file should grow continuously; otherwise LAT creates a new file on every Start/Stop cycle.
6. Click OK and then Start in the main window. The CSV grows row by row at the configured cycle time.

Resulting CSV (extract):

Timestamp;AI1_mA;AI2_mA;DI_Byte;Status
2025-01-14 08:00:01;4.02;12.45;10;OK
2025-01-14 08:00:02;4.03;12.46;10;OK
2025-01-14 08:00:03;4.03;12.46;10;OK
...

Reading the SD Card Directly (Without Soft Comfort)

The LOGO! stores Data Log files on the microSD card. The path layout on the card is fixed:

\LOGO\DATALOG\<DATA_LOG_BLOCK_NAME>_001.CSV
\LOGO\DATALOG\<DATA_LOG_BLOCK_NAME>_002.CSV
\LOGO\PROGRAM\<PROJECT_NAME>.LSC
\LOGO\PROJECT.LSC

To read the SD card without Soft Comfort:

1. Switch the LOGO! into STOP mode (or power off – the SD card is hot-swappable on 0BA8 onward, but stopping the program prevents a partial write).
2. Press the SD-card slot cover and remove the card.
3. Insert the card into a Windows PC microSD reader.
4. Open \LOGO\DATALOG\ in Explorer. The CSV files open directly in Excel without conversion.
5. Re-insert the card into the LOGO! and switch back to RUN.

This is the only method that gives access to records older than the LAT session buffer. It is the recommended approach for audit trails and reports.

Excel Add-In for Continuous Logging

The LOGO! Access Tool Excel Add-In (a separate component installed with LSC) exposes the polled variables as named cells inside Excel. The Add-In uses the same TCP/IP socket (port 10005) and can be combined with a VBA macro that appends new rows to a worksheet at a fixed interval. The advantage over plain LAT is that the user can build their own trending, formulas, and alarms inside Excel itself.

Minimal VBA pattern (place in ThisWorkbook):

Sub PollOnce()
    Dim ts As String
    ts = Format(Now, "yyyy-mm-dd hh:nn:ss")
    Sheets("Data").Cells(nextRow, 1).Value = ts
    Sheets("Data").Cells(nextRow, 2).Value = Range("AI1_mA").Value
    Sheets("Data").Cells(nextRow, 3).Value = Range("AI2_mA").Value
    Sheets("Data").Cells(nextRow, 4).Value = Range("DI_Byte").Value
    nextRow = nextRow + 1
    Application.OnTime Now + TimeValue("00:00:01"), "PollOnce"
End Sub

Call PollOnce from a Workbook_Open macro to start streaming. The worksheet then becomes the historical record for as long as the PC stays up.

Web Server as a Scriptable Workaround

The LOGO! 8 web server (default port 80) returns a plain-text variable snapshot:

GET http://192.168.0.10/<PASSWORD>/LOGO?.V123

A Python or PowerShell script can be written to issue this request on a schedule and append the response to a local CSV. The script runs on the PC, leaves the SD card untouched, and does not require the Access Tool to be open. Example PowerShell skeleton:

$ip = "192.168.0.10"
$pw = "LOGO"
while ($true) {
    $resp = Invoke-WebRequest -Uri "http://$ip/$pw/LOGO?.V123" -UseBasicParsing
    $ts = Get-Date -Format "yyyy-MM-dd HH:mm:ss"
    Add-Content -Path "D:\LOGO_Hist\web.csv" -Value "$ts;$resp.Content"
    Start-Sleep -Seconds 1
}

Limitations Summary

Alternative Architectures

If the project requires unattended, time-stamped, ring-buffered data retention, the LOGO! 6ED1052-1MD08-0BA0 is at the limit of what it can deliver. The following alternatives are field-proven upgrades.

Troubleshooting Matrix

Verification Checklist

After implementing any of the methods above, confirm the historical data path with the following checks:

• CSV file size grows monotonically (e.g. Get-Item D:\LOGO_Hist\*.csv | % Length every 60 s).
• Time stamps are in the expected timezone and advance by exactly the configured cycle (no gaps larger than 2 × cycle).
• The last N values in the CSV match the current value shown on the LOGO! display or the LAT main panel.
• For SD-card method: file modification time on the SD card is newer than the previous poll.
• For web-server method: HTTP response returns 200 OK within 50 ms on a quiet network.