Transferring CSV Files from S7-1500 SIMATIC Memory Card to IOT2040

This reference covers the end-to-end path required to move a CSV data-log file written by a SIMATIC S7-1500 CPU onto its SIMATIC Memory Card, copy it to a SIMATIC IOT2040 gateway, package the file with a ZIP utility, push it to a remote FTP server, and then perform the reverse flow so that files coming back from the server are unzipped and written back to the S7-1500. The implementation uses the open web server of the S7-1500, the Node-RED runtime on the IOT2040, and standard Linux command-line tools (wget, curl, zip, unzip) available in the IOT2000 Yocto image.

1. Architecture Overview

The integration consists of three logical zones:

• OT zone — the S7-1500 CPU (for example 6ES7515-2AM02-0AB0 or 6ES7513-1AL02-0AB0) with a SIMATIC Memory Card (for example 6ES7954-8LE03-0AA0, 12 MB) hosting the active DataLog.
• Edge zone — the SIMATIC IOT2040 (6ES7647-0AA00-1YA2), running the IOT2000 SD card image with Node-RED pre-installed. It pulls the CSV, compresses it, and forwards it.
• IT zone — a remote FTP/HTTPS server that stores the archive and pushes new parameter or recipe CSVs back to the line.

The data path for outbound logs is:

S7-1500 DataLog (.csv) → /Memory Card/DATALOG/datalog.csv
        │
        │ (S7-1500 integrated Web Server, "User-defined Web pages")
        ▼
IOT2040 /home/root/datalog.csv  (pulled by Node-RED exec → wget)
        │
        │ (zip -j datalog.zip datalog.csv)
        ▼
IOT2040 /home/root/datalog.zip
        │
        │ (curl -T → FTP / SFTP / HTTPS)
        ▼
Remote server: /upload/<plant>/<timestamp>.zip

The inbound path is the mirror image, terminating in the S7-1500 via a user-defined web page PUT/POST or via an S7 PUT/GET trigger.

2. Prerequisites

3. S7-1500 DataLog Configuration in TIA Portal

The S7-1500 DataLog function block family writes comma-separated files onto the SIMATIC Memory Card under /<Card>/DataLog/<name>.csv. The required programming steps are:

1. In the CPU's Properties → Web server, enable Enable Web server on the CPU, set Permit access only via HTTPS if needed, and create a user with the Read files right.
2. Add a DataLogCreate instance (FB 1000) in your program and define the columns matching your process tags.
3. Call DataLogOpen (FB 1001) once at startup; call DataLogWrite (FB 1002) cyclically or on event; call DataLogClose (FB 1003) on controlled shutdown.
4. Optionally, configure DataLogNewFile (FB 1004) to roll the file on size or time.

Minimal ladder snippet for the open + header cycle:

// STL / SCL equivalent
IF "FirstScan" THEN
    DataLogCreate_Instance(MODE := 1,    // create new file
                           NAME := 'datalog',
                           HEADER := 'Timestamp;Pressure;Temp;Flow',
                           DATA   := 'MyData',
                           ID     := "LogID");
END_IF;

IF "StartLog" AND NOT "LogBusy" THEN
    DataLogOpen_Instance(MODE := 1, NAME := 'datalog', ID := "LogID");
END_IF;

// Write trigger every 1 s
IF "Tick1s" THEN
    DataLogWrite_Instance(ID := "LogID", DATA := "MyData");
END_IF;

After compiling and downloading, verify the file by going to the S7-1500 Web Server (browser: http://<plc-ip>/), logging in, and drilling into Files → DataLog → datalog.csv. A valid session token is required for any non-browser HTTP client.

4. SIMATIC IOT2040 Setup

On the IOT2040, confirm Node-RED and the Linux utilities are present:

root@iot2040:~# opkg list-installed | grep -E 'wget|curl|zip|node-red'
root@iot2040:~# node-red --version
Node-RED 0.20.x
root@iot2040:~# which wget curl zip unzip
/usr/bin/wget
/usr/bin/curl
/usr/bin/zip
/usr/bin/unzip

If a package is missing, install it with opkg update && opkg install <name>. Create a working directory with predictable permissions:

mkdir -p /home/root/iot/queue /home/root/iot/archive
chmod 755 /home/root/iot

5. Pulling the CSV from the S7-1500 Web Server

The S7-1500's web server presents the DataLog directory under a hashed URL once you are logged in. Capture the file with a Node-RED exec node that calls wget. The trick is two-step authentication: first POST credentials, then GET the file with the resulting cookie.

Step 1 — obtain a session cookie and write it to a file:

curl -c /home/root/iot/cookies.txt \
     -d 'Login=<user>&Password=<pass>' \
     http://<plc-ip>/FormLogin

Step 2 — fetch the CSV with the cookie. The exact path on the web server for a DataLog file looks like:

wget --load-cookies /home/root/iot/cookies.txt \
     -O /home/root/iot/datalog.csv \
     'http://<plc-ip>/DataLog/datalog.csv?Action=DownloadFile&FileName=datalog.csv'

A clean Node-RED flow using the exec node looks like this in JSON form (paste via Import → Clipboard):

[{"id":"f1","type":"inject","name":"Hourly tick","topic":"","payload":"","payloadType":"date","repeat":"3600","crontab":"","once":false,"onceDelay":0.1,"x":140,"y":140,"wires":[["f2"]]},
 {"id":"f2","type":"exec","name":"wget datalog.csv","command":"wget --load-cookies /home/root/iot/cookies.txt -O /home/root/iot/datalog.csv 'http://<plc-ip>/DataLog/datalog.csv?Action=DownloadFile&FileName=datalog.csv'","addpay":false,"append":"","useSpawn":"false","timer":"","oldrc":false,"x":360,"y":140,"wires":[["f3"],[],[]]},
 {"id":"f3","type":"exec","name":"zip archive","command":"cd /home/root/iot && zip -j /home/root/iot/datalog.zip datalog.csv","x":580,"y":140,"wires":[["f4"],[],[]]},
 {"id":"f4","type":"exec","name":"curl -T to FTP","command":"curl -T /home/root/iot/datalog.zip ftp://user:pass@server/plant1/ --ftp-create-dirs","x":800,"y":140,"wires":[[],[],[]]}]

Key flags in the above flow:

• --load-cookies reuses the session that the PLC returned in step 1; without it the CSV responds with HTTP 401.
• -O writes to a known local path; never use -P here because the IOT2040's home partition is small.
• zip -j strips the directory prefix so the archive contains only datalog.csv.
• curl -T performs an FTP upload, creating remote directories with --ftp-create-dirs.

6. Compression and FTP Upload

Although ZIP is convenient, tar.gz is smaller and avoids licensing noise. A typical production script does the following each cycle:

1. Rotate the previous local archive into /home/root/iot/archive/<timestamp>.zip.
2. Refresh datalog.csv from the PLC.
3. Compress and upload with a unique remote name.
4. Remove the local copy after a 200/226 server response.

Bash equivalent run from a exec node:

#!/bin/sh
STAMP=$(date -u +%Y%m%dT%H%M%SZ)
LOG=/home/root/iot/datalog.csv
OUT=/home/root/iot/datalog_${STAMP}.zip

# 1. refresh session
curl -s -c /home/root/iot/cookies.txt \
     -d 'Login=plcuser&Password=plcpass' \
     http://10.0.0.10/FormLogin > /dev/null

# 2. download latest csv
wget -q --load-cookies /home/root/iot/cookies.txt \
     -O $LOG \
     'http://10.0.0.10/DataLog/datalog.csv?Action=DownloadFile&FileName=datalog.csv'

# 3. zip
zip -j -q $OUT $LOG

# 4. upload
curl -s -T $OUT ftp://ftpuser:ftppass@ftpsrv/plant1/$STAMP/ --ftp-create-dirs
RC=$?

# 5. archive locally if upload ok
[ $RC -eq 0 ] && mv $OUT /home/root/iot/archive/ || echo "FTP fail rc=$RC" >> /home/root/iot/log.txt

For SFTP instead of FTP, swap the last step for:

sftp -o StrictHostKeyChecking=no ftpuser@ftpsrv <<EOF
put $OUT /plant1/$STAMP/${STAMP}.zip
bye
EOF

For HTTPS REST endpoints use curl -F "file=@$OUT" https://api.example.com/upload with a bearer token in -H "Authorization: Bearer ...".

7. Receiving Files from the FTP Server (Inbound Path)

The reverse path is symmetrical. A second Node-RED flow polls the FTP server, downloads new ZIP files into /home/root/iot/inbox/, unzips them, and writes the resulting CSV back to the S7-1500. The trickiest part is writing the file back to the PLC because the S7-1500's web server does not support generic PUT on DataLog files. Use one of two supported mechanisms:

7.1 Method A — S7 PUT/GET

Enable Permit access with PUT/GET communication from remote partner in the CPU's Properties → Communication. The IOT2040 can use the open-source snap7 library or a Node-RED node-red-contrib-s7 node to write the CSV contents to a data block on the S7-1500. The PLC then re-creates the file with DataLogNewFile on the next scan.

7.2 Method B — User-defined web page with file upload

From TIA Portal, create a user-defined web page (Web server → User-defined pages) with a small HTML form that posts a file. Then call it with curl -F:

curl -F "file=@/home/root/iot/inbox/recipe.csv" \
     -b /home/root/iot/cookies.txt \
     http://<plc-ip>/<UserDefinedPage>/upload.html

The S7-1500 web page invokes a custom WWW instruction in the user program to copy the file into a configured DataLog directory or to a recipe DB.

8. End-to-End Flow Summary

9. Verification and Diagnostics

Use this checklist before going into production:

1. File size sanity — confirm ls -l /home/root/iot/datalog.csv shows a non-zero file that grows after each tick.
2. CSV header check — head -1 /home/root/iot/datalog.csv should match the HEADER string from DataLogCreate.
3. Cookie validity — the S7-1500 default session is 30 minutes. If the cycle is longer, re-authenticate each iteration.
4. FTP return code — curl -v on the first run; expect 226 Transfer complete.
5. Round trip — download a file you uploaded, unzip, diff the CSV against the local source with diff -q local.csv remote.csv.

Common Failure Matrix

10. Performance and Timing Notes

Typical timings on an IOT2040 (single-core 600 MHz ARM, 1 GB RAM):

• FormLogin round trip: 50–120 ms on the same VLAN.
• 100 kB CSV download: 200–400 ms.
• zip -j of 100 kB: < 30 ms.
• curl -T of 100 kB: 300–800 ms depending on WAN RTT.

For larger files (multiple MB) raise the exec node timeout to 60 s and avoid concurrent transfers — the IOT2040 has a single NIC and limited CPU.

11. Field-Proven Caveats

• The S7-1500 file system path for DataLog is case-sensitive on newer firmware; use lowercase datalog.csv consistently.
• When the PLC is in STOP, the web server still serves files but the DataLog is not updated; your script will keep reading the same file.
• Avoid rm on the SIMATIC Memory Card from the IOT2040; the PLC manages its own retention.
• Node-RED flows persist at /home/root/.node-red/flows_<host>.json; back this up before firmware updates.