Hacking Apartment Wallpads: From RS485 Packet Sniffing to Ventilation (Fan) Reverse Engineering
Anchored by two USB dongles (RS485 & Zigbee) on a Home Assistant host, here is how I sniffed an apartment's closed serial bus and reverse-engineered an undocumented 8-byte ventilation protocol.
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Table of Contents
- Hacking Apartment Wallpads: From RS485 Packet Sniffing to Ventilation (Fan) Reverse Engineering
- 1. The Two Pillars of My Smart Home: Wired RS485 and Wireless Zigbee
- 2. Hardware Setup: Tapping into the Wallpad Wiring
- 1) Unmounting the Wallpad
- 2) Wiring the USB-to-RS485 Converter
- 3. Real-Time Packet Sniffing: Finding Patterns in Hexadecimal Noise
- wallpad_dump.py: Sniffing raw serial frames
- 4. Frame Dissection: Reverse-Engineering the Undocumented Ventilation Unit
- 1) Ventilation Control Command Structure (0x78 Header)
- 2) State Report and Acknowledgment Frames (0xF6 / 0xF8 Header)
- 5. Building the Bridge: From Node.js SerialPort to MQTT
- mqtt.yaml excerpt: Native fan entity configuration
- 6. Epilogue: The Joy of Unlocking Closed Systems
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