RGB+CCT LED Controller With ESPHome and Home Assistant

In this project, we demonstrate a fully working smart-home lighting setup built around the HOMEMASTER RGB-621-R1 RGB+CCT LED Driver, integrated with the MicroPLC (ESP32-based) controller and fully managed from Home Assistant via Modbus RTU (RS-485).

This build shows how a professional DIN-rail LED system can be deployed in a home environment—providing smooth RGBWW control, real-time automation, and rock-solid communication.

Project Overview

This setup integrates:

• MicroPLC — ESP32-based controller with RS-485, running ESPHome
• RGB-621-R1 — 5-channel PWM RGB+CCT LED driver
• 24 VDC RGB+CCT LED strip
• 24 V power supply
• Home Assistant
• Modbus RTU (RS-485) communication

The modules are mounted neatly inside a DIN-rail control enclosure:

The RGB-621-R1 drives all high-current LED outputs, while the MicroPLC handles Modbus logic, automation, and Home Assistant integration.

Lighting Capabilities

The RGB-621-R1 exposes five independent PWM channels:

• Red
• Green
• Blue
• Warm White
• Cold White

Together, this enables full RGBWW lighting (RGB + tunable white temperature).

The driver outputs smooth, flicker-free PWM, even at very low brightness levels—perfect for ambient and architectural lighting.

Hardware Communication: MicroPLC ↔ RGB-621-R1

Communication uses Modbus RTU over RS-485.

RS-485 Wiring

MicroPLC UART pins:

• TX → GPIO17
• RX → GPIO16

Connections:
A → A  
B → B  
GND → GND (optional)

ESPHome Modbus Setup

Every HOMEMASTER module can be enabled by adding a single external ESPHome package—no manual register mapping required.

uart:
  tx_pin: 17
  rx_pin: 16
  baud_rate: 19200
  id: uart_modbus

modbus:
  id: modbus_bus
  uart_id: uart_modbus

packages:
  rgb1:
    url: https://github.com/isystemsautomation/HOMEMASTER
    ref: main
    files:
      - path: RGB-621-R1/Firmware/default_rgb_621_r1_plc/default_rgb_621_r1_plc.yaml
        vars:
          rgb_prefix: "RGB#1"
          rgb_id: rgb_1
          rgb_address: 3

The MicroPLC acts as the Modbus master, and the RGB-621-R1 is slave address 3

What’s Inside the External RGB Package

The included package (default_rgb_621_r1_plc.yaml) contains everything required for control:

1. Modbus Controller:

modbus_controller:
  - id: ${rgb_id}
    address: ${rgb_address}
    modbus_id: modbus_bus
    update_interval: 1s

2. Digital Input + Relay Pulses

One input and two pulse-based coil commands are available.

binary_sensor:
  - platform: modbus_controller
    name: "${rgb_prefix} DI1"
    register_type: discrete_input
    address: 1

Relay pulses:

switch:
  - platform: modbus_controller
    address: 200   # Relay ON
  - platform: modbus_controller
    address: 210   # Relay OFF

3. PWM Channels as Number Entities:

All channels are mapped directly to Modbus registers:

• The Red channel is controlled through Modbus register 400 with a value range from 0 to 255.
• The Green channel uses register 401 with a value range from 0 to 255.
• The Blue channel uses register 402 with a value range from 0 to 255.
• The Warm White channel maps to register 403 with a value range from 0 to 255.
• The Cold White channel maps to register 404 with a value range from 0 to 255.

number:
  - name: "RGB621 Red"
    address: 400
    value_type: U_WORD

4. Full RGB+CCT Light Object for Home Assistant

Each PWM output is mapped to a Modbus controller template:

output:
  - platform: modbus_controller
    id: rgb621_out_r
    address: 400
    multiply: 255.0

The combined RGBWW light:

light:
  - platform: rgbww
    id: rgb_1_light
    red: rgb621_out_r
    green: rgb621_out_g
    blue: rgb621_out_b
    warm_white: rgb621_out_ww
    cold_white: rgb621_out_cw

In Home Assistant, this provides:

• Full color wheel
• Separate warm/cold white sliders
• Brightness + temperature control
• Scenes and presets
• Real-time Modbus updates
• Per-channel control

Configuring the RGB-621-R1

The WebConfig tool (included in the repo) allows configuration directly from your browser using Web Serial.

You can adjust:

• Modbus address + baud rate
• Input behavior (DI1/DI2)
• Relay output logic
• Button actions
• Status LEDs
• Live RGB + WW + CW PWM testing

Summary

This project demonstrates how the RGB-621-R1, paired with the ESP32-based MicroPLC, creates a powerful and user-friendly DIN-rail LED lighting system. With Modbus RTU, ESPHome integration, and native Home Assistant support, the whole system offers:

• Zero manual register configuration
• Real-time, reliable RS-485 communication
• Full RGB+CCT lighting control
• Extensible modular architecture
• Professional-grade installation quality

Resources & Downloads

Product Page:https://www.home-master.eu/shop/rgb-621-r1-rgbcct-module-57

GitHub Repository (Firmware, ESPHome Packages, Schematics, WebConfig):https://github.com/isystemsautomation/HOMEMASTER/tree/main

This repository includes everything required to integrate all HOMEMASTER modules (RGB, DIO, DIM, WLD, ENM, ALM, and more) into a unified automation ecosystem.