STR-3221-R1 Stair LEDs Module

Overview

The STR-3221-R1 is a configurable smart LED and I/O controller designed for multi-channel lighting control and digital input monitoring in building automation, architectural lighting, stair illumination, and general control systems. It offers 4 opto-isolated digital inputs, 32 MOSFET-switched outputs, 4 user buttons with LEDs, and 4 configurable status LEDs. All I/O channels are individually configurable, allowing flexible logic such as toggle, pulse, manual override, and pattern sequencing.

It connects via RS-485 (Modbus RTU) to a MicroPLC, MiniPLC, or any compatible controller, and can also integrate with Home Assistant (ESPHome) or SCADA/PLC systems. Configuration and diagnostics are performed through a driverless Web Serial interface via USB-C, using the browser-based WebConfig Tool. The module supports both master-controlled and standalone local logic modes.

Getting Started

Quick Setup Process

1. Mount & Wire – Install on 35mm DIN rail, connect 24V DC power, sensors, and relay loads.

2. Configure – Plug in USB-C, open the WebConfig tool in Chrome/Edge, set Modbus address and I/O mapping.

3. Integrate – Connect to your controller via RS-485 and start automation.

What You Need

• STR-3221-R1 module

• 24V DC SELV power supply

• RS-485 cable (twisted pair)

• USB-C cable for configuration

• Chromium-based browser (Chrome/Edge)

Web Configuration Steps

1. Connect USB-C to module and PC

2. Open https://www.home-master.eu/configtool-str-3221-r1

3. Click "Connect" and select serial port

4. Set Modbus address (default: 3) and baud rate (default: 19200 8N1)

5. Configure input actions, mapping, LED modes, and button functions

6. Settings save automatically to flash

Tech Specs

Documentation

The ESTR-3221-R1 is open-source hardware! You can build your own board using the following files:

Hardware Design Files

• Field Board Schematic: SRT-3221-R1-FieldBoard.pdf

• MCU Board Schematic: SRT-3221-R1-MCUBoard.pdf

• System Block Diagram: STR_SystemBlockDiagram_New.png

• Field Board Layout: FieldBoard_Diagram.png

• MCU Board Layout: MCUBoard_Diagram.png

All design files and documentation are available in the HomeMaster GitHub repository.

Input and Output

Digital Inputs:

• 4× isolated 24V DC inputs (ISO1212)

• 9–30V operating range, 8V typical ON threshold

• PTC fuse and TVS diode protection per channel

• Configurable as normally open, normally closed, or toggle

LED Outputs:

• 32× low-side MOSFET outputs 

• Grouped in 4 banks of 8 channels

• 12–24V DC operation, 1A max per channel

• Constant-current drive via TLC59208F controllers

Auxiliary:

• 2× fused sensor rails (SENS.A, SENS.B)

• 200 mA total current limit

Communication Interfaces

• Protocol: Modbus RTU

• Role: Slave device

• Default Settings: Address 3, 19200 baud, 8 data bits, No parity, 1 stop bit

• Supported Functions: Read Coils (0x01), Read Discrete Inputs (0x02), Read Holding Registers (0x03), Read Input Registers (0x04), Write Single Coil (0x05), Write Single Register (0x06)

Home Assistant & ESPHome Integration Guide

Overview

The STR-3221-R1 integrates seamlessly with Home Assistant via ESPHome using the Modbus RTU protocol. This guide covers both quick integration using our pre-built package and manual configuration for advanced users.

Prerequisites

Before starting, ensure you have:

1. ESPHome device (HomeMaster MiniPLC/MicroPLC or any ESP32/ESP8266 with RS-485)

2. RS-485 connection between ESP device and STR-3221-R1

3. 24V power to STR-3221-R1 module

4. Home Assistant with ESPHome add-on installed

RS‑485 Configuration

uart:
  id: uart_modbus
  tx_pin: GPIO17
  rx_pin: GPIO16
  baud_rate: 19200
  parity: NONE
  stop_bits: 1

modbus:
  id: modbus_bus
  uart_id: uart_modbus

Import STR-3221-R1 Package:

packages:
  str_3221_r1:
    url: https://github.com/isystemsautomation/HOMEMASTER
    ref: main
    files:
      - path: STR-3221-R1/Firmware/default_str_3221_r1_plc/default_str_3221_r1_plc.yaml
    vars:
      str_prefix: "Main"  # Custom name for your entities
      str_id: main_module       # Unique internal ID
      str_address: 3            # Must match WebConfig Modbus address
      refresh: 1d

Customize Variables:

• str_prefix: Appears in entity names (e.g., "Main Panel Voltage L1")

• str_id: Internal identifier for the module

• str_address: Modbus address (must match WebConfig setting)

Example with Multiple STRs:

packages:
  str_main:
    url: https://github.com/isystemsautomation/HOMEMASTER
    ref: main
    files:
      - path: STR-3221-R1/Firmware/default_str_3221_r1_plc/default_str_3221_r1_plc.yaml
    vars:
      str_prefix: "Main"
      str_id: str_main
      str_address: 3
      refresh: 1d

  str_second:
    url: https://github.com/isystemsautomation/HOMEMASTER
    ref: main
    files:
      - path: STR-3221-R1/Firmware/default_str_3221_r1_plc/default_str_3221_r1_plc.yaml
    vars:
      str_prefix: "Second"
      str_id: str_second
      str_address: 4
      refresh: 1d

Programming

Supported Development Environments

• Arduino IDE with RP2350 support

• PlatformIO with RP2350 toolchain

• MicroPython (community builds available)

Firmware Flashing

1. Connect USB-C to PC

2. Hold Buttons 3 + 4 to enter BOOT mode

3. Hold Buttons 1 + 2 to RESET the module

4. Upload via:

   • UF2 drag-and-drop to mounted drive, OR

   • PlatformIO/Arduino IDE upload

Pin Mapping (Default Firmware)

MCU Board GPIO Mapping

LED Driver Configuration