n8n-nodes-modbus-fccomplete

Description

n8n community node package for industrial automation with complete Modbus protocol support. Provides three nodes for reading, writing, and converting Modbus data with an intuitive interface.

Features

Nodes

1. Modbus Trigger - Triggers workflows based on Modbus events
2. Modbus - Read/write operations for function codes FC1-FC4
3. Modbus Data Converter - Quick and custom data conversion with scaling

Modbus Support

• Function codes: FC1 (Read Coils), FC2 (Read Discrete Inputs), FC3 (Read Holding Registers), FC4 (Read Input Registers)
• Data types: INT16, UINT16, INT32, UINT32, FLOAT32, Double, BCD, Bitfields
• Byte ordering: Big Endian and Little Endian
• Connection types: TCP/IP with configurable timeout and retry

Data Converter Features

Quick Convert Mode

• Single Value - Basic INT16 conversion with scaling
• Float (2 Registers) - IEEE 754 32-bit floating point
• Long Integer (2 Registers) - 32-bit signed/unsigned with value selection
• Double (4 Registers) - 64-bit double precision
• BCD - Binary Coded Decimal conversion
• Bitfield - Individual bit extraction for status flags
• All Common Types - Shows all possible conversions

Custom Mode

• Multiple conversion rules per execution
• Named output fields
• Full data type support
• Configurable scaling and offsets

Output Organization

• Configurable field names for clean output structure
• Optional metadata with conversion details
• Timestamp support for time-series data
• Scaling options with direct factor input

Installation

Follow the installation guide in the n8n community nodes documentation.

npm install n8n-nodes-modbus-fccomplete

Quick Start

Power Meter Example (replaces Node-RED function)

1. Modbus Node:

   • Function Code: FC3 (Read Holding Registers)
   • Memory Address: Power register address
   • Quantity: 2 (for 32-bit values)

2. Modbus Data Converter:

   • Conversion Mode: Quick Convert
   • Quick Convert Type: Long Integer (2 Registers)
   • Long Integer Value: Signed (for negative power)
   • Scale: ✅ Enabled
   • Scale Factor: 0.001 (divides by 1000)
   • Add Timestamp: ✅ Enabled

Output:

{
  "output": {
    "value": 1.234
  },
  "timestamp": "2024-01-01T12:00:00.000Z"
}

Access your power value with: {{ $json.output.value }}

Temperature Sensor Example

1. Modbus Node:

   • Function Code: FC3 (Read Holding Registers)
   • Memory Address: Temperature register
   • Quantity: 2

2. Modbus Data Converter:

   • Conversion Mode: Quick Convert
   • Quick Convert Type: Float (2 Registers)
   • Byte Order: Big Endian
   • Output Field Name: "temperature"

Output:

{
  "temperature": {
    "value": 23.5
  }
}

Configuration

Modbus Connection

Configure connection credentials in n8n:

• Host: Modbus server IP address
• Port: Default 502 for Modbus TCP
• Unit ID: Modbus slave/unit identifier
• Timeout: Connection timeout in milliseconds

Data Converter Scaling

Common scaling examples:

• Temperature sensors: Often need scaling (e.g., 0.1 for tenths of degrees)
• Power meters: Typically 0.001 for kW conversion
• Pressure sensors: Various factors depending on units

Troubleshooting

Common Issues

1. "No register data found"

   • Ensure Modbus node output contains data array
   • Check connection to Modbus device

2. Incorrect values

   • Verify byte order (Big Endian vs Little Endian)
   • Check data type selection (signed vs unsigned)
   • Confirm scaling factor

3. Connection timeouts

   • Increase timeout in credentials
   • Verify network connectivity
   • Check Modbus device configuration

Version History

• v0.10.0 - Initial release with simplified Quick Convert and Custom modes, improved UI with always-visible output options

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

License

MIT License