Modbus TCP/IP Device Data-logging to SQLite Database using Python

Modbus TCP/IP to SQLite Datalogger

This project logs Modbus TCP/IP device data into an SQLite database for historical storage and analysis. It uses pymodbus for Modbus communication and Python’s built-in sqlite3 for database operations.

Library Version Details

Features

• Reads Modbus holding registers (default; other types supported)
• Per-address reading for flexibility (supports non-consecutive addresses)
• Logs only when values change
• Each register/address is logged with timestamp, type, address, and value
• Configurable update interval
• Easy configuration via src/config.py

Project Structure

modbus-sqlite-datalogger-02092025
├── src
│   ├── main.py               # Main application logic
│   ├── modbus_client.py      # Modbus TCP client wrapper
│   ├── sqlite_logger.py      # SQLite logger for Modbus data
│   ├── modbus_data.db        # SQLite database file (created at runtime)
│   └── config.py             # User configuration for Modbus/database/interval
├── requirements.txt          # Python dependencies
├── README.md                 # Project documentation

Installation

1. Clone the repository:

   git clone <repository-url>
   cd modbus-sqlite-datalogger-02092025
   

1. Install dependencies:
   powershell or CMD
pip install -r requirements.txt

Configuration

Edit src/config.py to set:

• Modbus server IP and port
• Modbus slave ID (unit)
• SQLite database filename
• Register types and addresses to read (currently only holding registers enabled)
• Update interval (in seconds)

Example (src/config.py):

SQLITE_DB_NAME = 'modbus_data.db'
MODBUS_SERVER = '127.0.0.1'
MODBUS_PORT = 502
MODBUS_SLAVE_ID = 1
MODBUS_READ_CONFIG = {
    "holding_registers": {
        "addresses": [0, 1, 2, 5, 6, 7]
    }
    # "coils": {"addresses": [0, 1, 2]},
    # "discrete_inputs": {"addresses": [0, 1, 2]},
    # "input_registers": {"addresses": [0, 1, 2]},
}
UPDATE_INTERVAL = 5  # seconds

To enable other data types (coils, discrete inputs, input registers), uncomment and configure them in MODBUS_READ_CONFIG.

Usage

Start the datalogger:
powershell or CMD
python src/main.py

• The app reads configured Modbus addresses at the set interval.
• Only changed values are logged to the SQLite database.
• Each value is stored with timestamp, type, address, and value.

Testing & Validation

• Ensure your Modbus server is running and accessible.
• Use any SQLite client or tool to inspect the modbus_data.db database.
• Change Modbus register values to see new rows logged in the database.

Advanced

• Supports all Modbus data types (add to MODBUS_READ_CONFIG as needed).
• Easily extend for batch reads, custom logging, or data export.