snap7-db-sync 0.1.1

A high-performance bridge for syncing Siemens S7 DBs to Shared Memory

Snap7 DB Sync

A high-performance bridge to synchronize Siemens S7 PLC Data Blocks (DB) into Python Shared Memory (SHM).

🚀 Key Features

Zero-Config Parser: Automatically calculates offsets and word-alignment from TIA Portal text exports (SCL or Table-copy).

Shared Memory IPC: Stores PLC data as a JSON string in a shared memory segment for fast access by other processes.

Lifecycle Managed: Shared memory is only allocated when connect() is called and is cleaned up properly on exit.

Thread-Safe: Uses internal locking to prevent crashes during simultaneous PLC read/write operations.

🛠 Usage

1. Get your Blueprint

Copy your Data Block structure from TIA Portal (Right-click > "Copy as text" or "Select All" > "Copy") and save it as db_blueprint.txt.

Run the Sync

Python

from snap7_db_sync import Snap7DBSync

Initialize metadata

sync = Snap7DBSync(
    ip_addr="192.168.0.1",
    db_num=10,
    db_bluprint_txt="db_blueprint.txt"
    )

Connect (Allocates Shared Memory and connects to PLC)

if sync.connect():
    # Start background logging at 50ms intervals
    sync.start_logging(cycle_time_ms=50)
    
    # Write values back to PLC safely
    sync.write_to_plc({"MySensorValue": 123.4})
    
    # Clean up when done
    sync.close_connection()

📄 License

This project is licensed under the MIT License - see the LICENSE file for details.