Matter-to-MAX! Bridge (cul32-c6)

The Matter-to-MAX! Bridge is an ESP-IDF based firmware that bridges legacy eQ-3 MAX! radiator thermostats, window contacts, and eco buttons to the Matter ecosystem over Wi-Fi. It allows you to control your existing 868MHz heating hardware using modern smart home platforms like Apple Home, Google Home, and Home Assistant without requiring the original MAX! Cube or FHEM.

Features

• Native Matter Integration: Directly discoverable as a Matter bridge via Bluetooth LE. No additional plugins or "hacks" required.
• High Capacity: Supports up to 61 MAX! peripheral devices per bridge.
• Auto-Discovery: Easily clone your existing MAX! devices via a virtual switch in your Smart Home app.
• Duty Cycle Management: Implements a strict ETSI-compliant 1% Duty Cycle limit using a Token-Bucket algorithm to ensure regulatory compliance and prevent 868MHz band spam.
• Hardware Optimized: Built for the ESP32-C6, utilizing its modern architecture for Wi-Fi connectivity and SPI communication with the CC1101.

Screenshots (Home Assistant Integration)

Here is how the bridged legacy 868MHz devices natively appear in Home Assistant via Matter – fully local and without any cloud dependency:

 

Hardware Requirements

• Microcontroller: ESP32-C6 (e.g., cul32-c6).
• Radio Module: TI CC1101 (868MHz MATCHED).
• SPI Pinout: GDO2=GPIO1, GDO0=GPIO2, CS=GPIO23, SCK=GPIO18, MISO=GPIO17, MOSI=GPIO16.

Installation & Commissioning

1. Flashing the Firmware

You don't need to compile the firmware yourself. A pre-compiled factory binary is available in the binaries/ folder.

esptool.py --chip esp32c6 -b 460800 --before default_reset --after hard_reset write_flash --flash_mode dio --flash_freq 80m --flash_size 4MB 0x0 binaries/max_matter_bridge_factory.bin

2. Pairing via Bluetooth LE

The firmware uses the standard Matter SDK test credentials for commissioning.

1. Power on the ESP32-C6.
2. Open your Smart Home App (e.g., Home Assistant, Apple Home, Google Home).
3. Add a new Matter device without a QR code and enter the standard Setup PIN:
   • Setup PIN: 34970112332
4. The device will appear in your Bluetooth list as MAX-XXXX (where XXXX is derived from its MAC address).
5. The App will securely transmit your Wi-Fi credentials to the Bridge over the air.

For detailed Home Assistant instructions, please refer to the HASS_HowTo.md file.

Duty Cycle Explanation

The 868MHz frequency band is subject to the ETSI EN 300 220 regulation, which limits transmission time to 1% (36 seconds per hour).

• This bridge implements a Token-Bucket mechanism.
• Every transmission consumes "airtime tokens" (especially the 1-second Wake-On-Radio preamble).
• If the bucket is empty, further commands are blocked until the bucket refills.
• This prevents the bridge from being blocked by regulatory authorities and ensures fair frequency usage.