bw-sbu-bridge

The Ultimate ESP32-C6 IoT Gateway & USB-C SBU Breakout

Status License

bw-sbu-bridge is a next-generation IoT Gateway architecture designed by BUSWARE. It bridges up to 4 external RF sticks (CUL, Zigbee, Z-Wave, EnOcean) to Ethernet/WiFi/Matter, utilizing the ESP32-C6 as the host processor.

Unlike traditional USB hosts, this project introduces the "SBU-Native" standard, leveraging the USB-C Sideband Use pins for raw UART communication. This eliminates USB protocol overhead on the ESP32 side while maintaining full USB compatibility for PC maintenance.

• Dual-Path Architecture:
  • Operation Path: Raw UART via SBU pins -> SPI Bridge -> ESP32-C6 (Zero Latency).
  • Maintenance Path: Standard USB D+/D- -> USB Hub -> PC (Access to all Sticks AND the Host C6).
• Triple-Radio Host:
  • Matter / Thread: Native 802.15.4 support via ESP32-C6.
  • Zigbee 3.0: Can act as Coordinator or Router.
  • WiFi 6 (802.11ax): Low-power, high-efficiency wireless uplink.
• Professional Connectivity:
  • Dedicated WIZnet W5500 Ethernet Controller.
  • Power over Ethernet (PoE) support (802.3af) for single-cable installation.
• High-Performance I/O: WK2124 SPI-to-Quad-UART bridge for reliable serial streams.

The system is built around a split-bus topology with 5 USB downstream ports (4x Sticks + 1x Host MCU) and a dedicated wireless frontend:

graph TD
 subgraph External [External Connections]
 PC["Computer USB-C"]
 RJ45["LAN Switch / PoE"]
 HomeNet[("Matter Fabric / WiFi / Zigbee Mesh")]
 end
 subgraph PCB [bw-sbu-bridge PCB]
 Hub["USB Hub 5-Port"]
 MCU["ESP32-C6"]
 Eth["W5500 Ethernet"]
 UART_Bridge["WK2124 SPI-UART"]
 PoE_Power["PoE Power Extraction"]
 Antenna(("2.4GHz Antenna"))
 
 subgraph Ports [Stick Ports]
 Slot1["Stick Slot 1"]
 Slot2["Stick Slot 2"]
 Slot3["Stick Slot 3"]
 Slot4["Stick Slot 4"]
 end
 
 PC == "USB 2.0 Uplink" ==> Hub
 Hub -. "D+/D- (Port 5)" .-> MCU
 Hub -. "D+/D- (Port 1)" .-> Slot1
 Hub -. "D+/D- (Port 2)" .-> Slot2
 Hub -. "D+/D- (Port 3)" .-> Slot3
 Hub -. "D+/D- (Port 4)" .-> Slot4
 RJ45 == "Data & Power" ==> PoE_Power
 PoE_Power -- "5V DC" --> Hub
 PoE_Power -- "5V DC" --> MCU
 PoE_Power -- "Magnetics" --> Eth
 MCU == "SPI" ==> Eth
 MCU == "SPI" ==> UART_Bridge
 
 MCU -. "802.15.4 / WiFi 6" .- Antenna
 Antenna -. "Matter / Zigbee / Thread" .-> HomeNet
 
 UART_Bridge == "UART/SBU" ==> Slot1
 UART_Bridge == "UART/SBU" ==> Slot2
 UART_Bridge == "UART/SBU" ==> Slot3
 UART_Bridge == "UART/SBU" ==> Slot4
 end

This project defines a custom usage of the USB-C Sideband pins to enable dual-mode operation.

Note: The 1kΩ resistors on SBU lines are mandatory to protect the MCU if the stick is inserted into a non-compliant USB-C audio adapter.

• ESP-IDF: Native support for C6, W5500, and WK2124 drivers available.
• Tasmota: Potential for a custom build supporting the WK2124 driver for easy scripting.
• ESPHome: Custom component required for quad-UART bridging over SPI.

MIT License - Copyright (c) 2026 BUSWARE