TapHome to Modbus RTU / ASCII / TCP#

Supported Communication Layers#

The system accommodates three distinct protocols:

  • Modbus RTU via RS485 (accessible through BUS 1, BUS 2, or BUS 3 terminals)
  • Modbus ASCII via RS485 (accessible through BUS 1, BUS 2, or BUS 3 terminals)
  • Modbus TCP (via ethernet, connecting to local IP address or VPN)

Setup Process#

Configuration involves three primary steps:

  1. Navigate to Settings → Expose devices and select Add Interface. Choose Modbus RTU, Modbus ASCII, or Modbus TCP.

  2. Define communication properties:

    • For Modbus RTU or ASCII: Configure Terminal (BUS 1, BUS 2 or BUS 3), Baud rate, Parity, Data bits, Stop bits
    • For Modbus TCP: Set TCP Port (IP Address is configured individually per device)

  3. Add devices for exposure:

    • Each device displays a brief overview of how third-party systems can access them

Example: Switch Configuration

Switch device configuration example

Using Modbus TCP for System Integration#

Simply Modbus provides comprehensive protocol documentation. Multiple open-source libraries enable TapHome integration with external systems:

  • NModbus4 - C# Modbus protocol implementation GitHub
  • libmodbus - Cross-platform library for Linux, Mac OS X, FreeBSD, QNX, Windows GitHub
  • pymodbus - Complete Python-based Modbus protocol GitHub
  • digitalpetri/modbus - High-performance Java implementation GitHub
  • goburrow/modbus - Go language fault-tolerant implementation GitHub
  • node-modbus-tcp - NodeJS Modbus TCP/IP

Debugging Modbus RTU Connections#

RS485 physical layer utilization enables parallel monitoring. Consider connecting a “standard USB to RS485 converter” to your PC for communication visibility during integration efforts.

Recommended tools: