OpenThread RCP Firmware for Lidl Silvercrest Gateway¶

OpenThread Radio Co-Processor (RCP) firmware for the EFR32MG1B232F256GM48 chip found in the Lidl Silvercrest Smart Home Gateway.

This firmware transforms the EFR32 into a raw 802.15.4 radio using the Spinel/HDLC protocol. It is the single firmware shared by all 3 use cases described below.

1. Firmware¶

Hardware¶

Component	Specification
Zigbee SoC	EFR32MG1B232F256GM48
Flash	256 KB (firmware uses ~100 KB)
RAM	32 KB (firmware uses ~16 KB)
Radio	2.4 GHz IEEE 802.15.4
UART	PA0 (TX), PA1 (RX), PA4 (RTS), PA5 (CTS) @ 115200 baud

Flash Pre-built Firmware (recommended)¶

From the repository root:

./flash_efr32.sh <GATEWAY_IP>
# Select [4] OT-RCP

The script handles serialgateway restart, flash, and reboot.

Build from Source¶

For users who want to customize the firmware or use a different SDK version.

# Install Silicon Labs tools (once)
cd 1-Build-Environment/12-silabs-toolchain && ./install_silabs.sh

# Build
cd 2-Zigbee-Radio-Silabs-EFR32/26-OT-RCP
./build_ot_rcp.sh

Output: firmware/ot-rcp.gbl (UART flash) and firmware/ot-rcp.s37 (J-Link/SWD).

Technical Notes¶

UART driver: Uses uartdrv_usart (low-level, DMA, async), not iostream_usart which would corrupt the binary Spinel stream with LF→CRLF conversion.
RTL8196E boot delay: 1-second delay at startup for host UART initialization.
Hardware flow control: RTS/CTS enabled, required for reliable operation over TCP.
Hardware radio acceleration: All 802.15.4 MAC operations in hardware.
Baud rate: 115200 recommended. Only 115200 and 230400 are reliable on this gateway (460800+ causes UART overruns — see 25-RCP-UART-HW). All pre-built firmware uses 115200 to match the Gecko Bootloader. If you recompile at 230400, flash_efr32.sh will automatically detect it, send a Spinel reset-to-bootloader command, and reflash via the Gecko Bootloader — no J-Link/SWD needed.

2. Use Cases¶

All 3 use cases run the same OT-RCP firmware on the EFR32. They differ in what runs on the gateway's RTL8196E main CPU and on the Docker host.

#	Use case	Protocol	Gateway runs	Host runs (Docker)
1	ZoH	Zigbee	serialgateway	Zigbee2MQTT + Mosquitto
2	OTBR on host	Thread/Matter	serialgateway	OTBR + Matter Server + HA
3	OTBR on gateway	Thread/Matter	otbr-agent (native)	Matter Server + HA

Use case 1: ZoH (Zigbee on Host)¶

The Zigbee stack (zigbee-on-host by @Nerivec) runs on the host via Zigbee2MQTT's zoh adapter. The gateway only bridges UART to TCP.

Zigbee Devices                        Docker Host
       │  802.15.4                  ┌──────────────────────────┐
       ▼                            │  Zigbee2MQTT (zoh)       │
┌─────────────┐  UART   ┌────────┐  │  + zigbee-on-host stack  │
│  EFR32 RCP  │◄──────► │ serial │◄─┤  Web UI :8080            │
│  Spinel/    │ 115200  │ gateway│  └──────────────────────────┘
│  HDLC       │         │ :8888  │
└─────────────┘         └────────┘
     Gateway (Zigbee mode)

Gateway setup: flash userdata in Zigbee mode. Quick start: see docker/README.md — Use Case 1.

zigbee-on-host is open-source, integrated in Zigbee2MQTT 2.x, and under active development. See the GitHub repo.

Use case 2: OTBR on Host¶

OTBR runs in a Docker container on the host PC. It connects to the gateway's serialgateway over TCP to reach the EFR32 radio.

Matter Devices                        Docker Host
       │  Thread 802.15.4           ┌──────────────────────────┐
       ▼                            │  OTBR (Docker container) │
┌─────────────┐  UART   ┌────────┐  │  REST API :8081          │
│  EFR32 RCP  │◄──────► │ serial │◄─┤  Matter Server :5580     │
│  Spinel/    │ 115200  │ gateway│  │  Home Assistant :8123    │
│  HDLC       │         │ :8888  │  │  ← Companion App (BLE)   │
└─────────────┘         └────────┘  └──────────────────────────┘
     Gateway (Zigbee mode)

Gateway setup: flash userdata in Zigbee mode (serialgateway bridges the radio to TCP; OTBR runs on the host). Quick start: see docker/README.md — Use Case 2.

Use case 3: OTBR on Gateway (v2.0+)¶

OTBR runs natively on the gateway (otbr-agent on the RTL8196E CPU). No serialgateway, no TCP bridge between OTBR and the radio. The host only runs Matter Server + Home Assistant.

Matter Devices                                       Docker Host
       │  Thread 802.15.4                          ┌──────────────────┐
       ▼                                           │  Matter Server   │
┌─────────────┐  UART   ┌──────────────────┐  REST │  :5580           │
│  EFR32 RCP  │◄──────► │  otbr-agent      │◄──────┤  Home Assistant  │
│  Spinel/    │ 115200  │  (native on CPU) │ :8081 │  :8123           │
│  HDLC       │         │  REST API :8081  │       │  ← Companion App │
└─────────────┘         └──────────────────┘       └──────────────────┘
     Gateway (Thread mode)

Gateway setup: flash userdata in Thread mode.

Advantages over use case 2: - Lower latency — OTBR talks directly to the EFR32 via UART - Simpler — no OTBR Docker container to manage - Self-contained — Thread mesh stays up even without the host

This is the recommended setup for Thread/Matter since v2.0. Quick start: see docker/README.md — Use Case 3.

3. Docker Stacks¶

Pre-configured Docker Compose files are in docker/:

#	Use case	Compose file	Command
1	ZoH	`docker-compose-zoh.yml`	`docker compose -f docker-compose-zoh.yml up -d`
2	OTBR on host	`docker-compose-otbr-host.yml`	`docker compose -f docker-compose-otbr-host.yml up -d`
3	OTBR on gateway	`docker-compose-otbr-gateway.yml`	`docker compose -f docker-compose-otbr-gateway.yml up -d`

See docker/README.md for full setup instructions: IPv6 forwarding, HA integrations, Companion App commissioning, chip-tool alternative, and troubleshooting.

4. Tested Devices¶

Device	Protocol	Use case	Status
Xiaomi LYWSD03MMC	Zigbee	1 (ZoH)	OK
IKEA TIMMERFLOTTE temp/hmd sensor	Matter/Thread	2 (OTBR host)	OK
IKEA TIMMERFLOTTE temp/hmd sensor	Matter/Thread	3 (OTBR gateway)	OK
IKEA BILRESA dual button	Matter/Thread	3 (OTBR gateway)	OK
IKEA MYGGSPRAY wrlss mtn sensor	Matter/Thread	3 (OTBR gateway)	OK

Troubleshooting¶

No response from RCP¶

Verify TCP connection: nc -zv <gateway-ip> 8888
Check baud rate matches (115200) on firmware and serialgateway
Verify hardware flow control is enabled

HDLC Parsing Errors¶

Ensure baud rate is 115200 (not higher)
Check for device flooding (remove battery from problematic devices)
Verify hardware flow control is enabled

Files¶

26-OT-RCP/
├── build_ot_rcp.sh              # Build script
├── README.md                    # This file
├── THREAD-MATTER-PRIMER.md      # Educational guide: Thread vs Zigbee vs Matter
├── patches/
│   ├── ot-rcp.slcp              # Project config (based on SDK sample)
│   ├── main.c                   # Entry point (RTL8196E boot delay)
│   ├── app.c / app.h            # OT instance init + hardware watchdog
│   ├── sl_uartdrv_usart_vcom_config.h  # UART: 115200, HW flow control
│   └── sl_rail_util_pti_config.h       # PTI disabled (suppresses SDK warning)
├── docker/                      # Docker Compose stacks
│   ├── README.md                # Full setup guide (3 use cases)
│   ├── docker-compose-zoh.yml           # Use case 1: ZoH
│   ├── docker-compose-otbr-host.yml     # Use case 2: OTBR on host
│   ├── docker-compose-otbr-gateway.yml  # Use case 3: OTBR on gateway
│   ├── z2m/configuration.yaml   # Zigbee2MQTT config
│   └── mosquitto/mosquitto.conf # MQTT broker config
└── firmware/                    # Pre-built binaries
    ├── ot-rcp.gbl               # For UART flashing
    └── ot-rcp.s37               # For SWD flashing

24-NCP-UART-HW/ — NCP firmware (EZSP protocol)
25-RCP-UART-HW/ — RCP firmware (CPC protocol, for cpcd + zigbeed)
27-Router/ — Autonomous Zigbee router (no host needed)
3-Main-SoC.../34-Userdata/ — Gateway firmware with native OTBR (v2.0+)

References¶

zigbee-on-host — Open-source Zigbee stack by Nerivec
Zigbee2MQTT
OpenThread RCP
bnutzer/docker-otbr-tcp — OTBR Docker image for TCP-based RCPs
Home Assistant Matter integration
Discussion #47 — Thread/Matter on the Lidl gateway

License¶

Educational and personal use. Silicon Labs SDK components under their respective licenses.