TapHome

TapHome to Modbus RTU / ASCII / TCP

TapHome supports three Modbus communication protocols (RTU via RS485, ASCII via RS485, and TCP via ethernet) for system integration. Configure communication properties and add devices through Settings → Expose devices.

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

When the control unit is updated to 2026.1, existing Modbus slave interfaces are converted automatically, keeping the register addresses and Slave ID. The Stop register of a KNX blind, of a Packet parser blind and Awning device, and of a virtual Awning device is not converted; a master that used it gets exception 0x02 at its address (release notes 2026.1).

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: