NCP-UART-HW Firmware¶

Network Co-Processor (NCP) firmware for the EFR32 radio: EFR32MG1B232F256GM48 on the Lidl Silvercrest Smart Home Gateway (BOARD=lidl, the default), EFR32MG13P732F512IM32 on the Sengled Smart Hub G4 (BOARD=sengled-e39-g8c). Both ship prebuilt.

This firmware enables communication with Zigbee coordinators like Zigbee2MQTT and Home Assistant ZHA via EZSP (EmberZNet Serial Protocol).

Multi-board: this firmware also builds for other RTL8196E hubs via BOARD= (default lidl); e.g. BOARD=sengled-e39-g8c for the Sengled Smart Hub G4, whose prebuilt is committed and validated end-to-end on real hardware (#130) — see ../boards/README.md.

Features¶

EZSP v13 - EmberZNet 7.5.1 serial protocol
Zigbee PRO R22 - Full Zigbee 3.0 support
Green Power - Support for battery-free devices
Source routing - 100-entry route table for large networks
Up to 32 children - Sleepy end-devices supported
Hardware flow control - RTS/CTS for reliable TCP operation

Hardware¶

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

Option 1: Flash Pre-built Firmware (Recommended)¶

Pre-built firmware is available in the firmware/ directory. From the repository root:

# Lidl Silvercrest (default board)
./flash_efr32.sh -y ncp                 # default baud 115200, gateway from gateway.env
./flash_efr32.sh -y ncp 460800          # 460800 baud (faster, max-tested 892857)
./flash_efr32.sh -y -g 10.0.0.5 ncp     # custom gateway IP

# Sengled Smart Hub G4: validated NCP image, default baud 115200
./flash_efr32.sh -y --board sengled-e39-g8c -g 10.0.0.6 ncp

./flash_efr32.sh --help                 # full CLI reference

The script handles everything: pulse nRST for a clean chip state, switch the in-kernel UART bridge to flash mode, run the Xmodem upload, write the matching FIRMWARE_BAUD=<baud> to /userdata/etc/radio.conf so the bridge arms at the right speed on next boot, then reboot.

Supported NCP bauds (pre-built GBLs): 115200, 230400, 460800, 691200, 892857. For a custom baud, see Option 2 below.

Legacy env-var interface (deprecated, kept for v3.0.x compat): FW_CHOICE=2 BAUD_CHOICE=460800 CONFIRM=y ./flash_efr32.sh still works with a deprecation warning. Prefer the flag form above.

Need other formats (.s37, .hex, .bin)? Build from source (Option 2), they will be in build/debug/.

Gateway state after flash¶

flash_efr32.sh writes the matching baud to /userdata/etc/radio.conf so the gateway-side init scripts arm the bridge correctly on next boot. For NCP at baud <B>:

FIRMWARE=ncp           # what's in the EFR32 application slot
FIRMWARE_VERSION=7.5.1 # EmberZNet version embedded in the GBL
FIRMWARE_BAUD=<B>      # chip-side UART baud — S50uart_bridge reads this and
                       # arms TCP:8888 at <B> (no MODE= line; otbr-agent off)

FIRMWARE_BAUD is the single source of truth (chip-side baud = host-side baud, since both ends of the UART link must agree); the FIRMWARE* companion keys are informational. See 3-Main-SoC-Realtek-RTL8196E/34-Userdata/README.md for the full key reference.

The init script S50uart_bridge reads this on boot. Z2M/ZHA then connect to tcp://<gw>:8888 — no baud setting needed on the client side, the bridge handles it.

Option 2: Build from Source¶

For users who want to customize network parameters or use a different EmberZNet version.

Prerequisites¶

Install Silicon Labs tools (see 1-Build-Environment/12-silabs-toolchain/):

cd 1-Build-Environment/12-silabs-toolchain
./install_silabs.sh

Or use Docker (see 1-Build-Environment/ for setup):

docker run --rm -v $(pwd):/workspace rtl8196e-gateway-builder \
    /workspace/2-Zigbee-Radio-Silabs-EFR32/24-NCP-UART-HW/build_ncp.sh

Build¶

cd 2-Zigbee-Radio-Silabs-EFR32/24-NCP-UART-HW
./build_ncp.sh                  # default baud 115200
./build_ncp.sh 460800           # custom baud (any value; warns if outside tested set)
./build_ncp.sh --help           # show baud options + defaults

Output¶

The output filename embeds the EmberZNet version and the chosen baud:

firmware/
├── ncp-uart-hw-7.5.1-115200-hw.gbl   # default (-hw = RTS/CTS flow, #145)
├── ncp-uart-hw-7.5.1-230400-hw.gbl   # if you ran ./build_ncp.sh 230400
├── ncp-uart-hw-7.5.1-460800-hw.gbl
├── ncp-uart-hw-7.5.1-691200-hw.gbl
└── ncp-uart-hw-7.5.1-892857-hw.gbl

flash_efr32.sh resolves the right file via a glob — no need to keep filenames in sync manually.

Other formats (.s37, .hex, .bin) are available in build/debug/ after compilation. Use these for J-Link/SWD flashing or debugging.

Clean¶

./build_ncp.sh clean

Flash¶

Via network (same as Option 1):

./flash_efr32.sh -y ncp 460800     # baud must match what you built above

Via J-Link/SWD (if you have physical access to the SWD pads):

commander flash firmware/ncp-uart-hw-7.5.1-460800-hw.gbl \
    --device EFR32MG1B232F256GM48

Usage¶

Architecture¶

+-------------------+    UART     +-------------------+   Ethernet   +---------------------+
|  EFR32MG1B (NCP)  |   115200    |  RTL8196E         |    TCP/IP    |  Host (x86/ARM)     |
|                   |    baud     |  (Gateway SoC)    |              |                     |
|  EmberZNet Stack  |<----------->|  in-kernel        |<------------>|  Zigbee2MQTT        |
|  + EZSP Protocol  |   ttyS1     |  UART<->TCP bridge|   port 8888  |       or            |
|                   |             |  (rtl8196e-uart-  |              |  Home Assistant ZHA |
|  HW Flow Control  |             |   bridge)         |              |                     |
+-------------------+             +-------------------+              +---------------------+

The RTL8196E kernel bridges the EFR32's UART to TCP:8888 via the in-kernel rtl8196e-uart-bridge driver (replaces the former serialgateway daemon). See 34-Userdata for gateway setup.

Zigbee2MQTT Configuration¶

Edit configuration.yaml:

serial:
  port: tcp://192.168.1.88:8888
  adapter: ember

Home Assistant ZHA Configuration¶

Add integration with: - Serial port path: socket://192.168.1.88:8888

Note: Baudrate and flow control are handled by the in-kernel UART bridge on the gateway side, not by the client application. Change the rate via echo <baud> > /sys/module/rtl8196e_uart_bridge/parameters/baud.

Customization¶

Changing Baudrate¶

Default is 115200. With the in-kernel UART bridge on kernel 6.18, rates up to 892857 are supported (115200, 230400, 460800, 691200, 892857 tested). See 25-RCP-UART-HW for the math behind 892857.

# 1. Build the GBL at the desired baud
cd 2-Zigbee-Radio-Silabs-EFR32/24-NCP-UART-HW && ./build_ncp.sh 460800

# 2. Flash — radio.conf FIRMWARE_BAUD is updated automatically
./flash_efr32.sh -y ncp 460800

NCP/EZSP doesn't have cpcd's POSIX baud restriction, so all 5 tested values work end-to-end (Z2M ember adapter, ZHA).

Network parameters¶

The build process applies patches to optimize the firmware for these gateways. See patches/README.md for details.

Network Parameters¶

Edit patches/apply_config.sh to modify. For a complete guide, see the Zigbee Network Sizing Guide.

Parameter	Default	Range	RAM/Entry
`EMBER_MAX_END_DEVICE_CHILDREN`	32	0-64	~40 bytes
`EMBER_PACKET_BUFFER_COUNT`	255	20-255	~36 bytes
`EMBER_SOURCE_ROUTE_TABLE_SIZE`	100	2-255	~12 bytes
`EMBER_BINDING_TABLE_SIZE`	32	1-127	~20 bytes
`EMBER_ADDRESS_TABLE_SIZE`	12	1-256	~16 bytes
`EMBER_NEIGHBOR_TABLE_SIZE`	26	16/26	~32 bytes
`EMBER_KEY_TABLE_SIZE`	12	1-127	~32 bytes

Network Size Presets¶

Preset	Devices	Children	Buffers	Routes	Bindings
Small	<20	10	75	20	10
Medium	20-50	20	150	50	20
Large (default)	50-100	32	255	100	32
Very Large	100-150	48	255	150	48

Warning: The EFR32MG1B has only 32KB RAM. Current configuration uses ~27KB. Increasing parameters beyond presets may cause instability.

Technical Details¶

Memory Usage¶

Resource	Used	Available
Flash	~200 KB (78%)	256 KB
RAM	~24 KB (75%)	32 KB
NVM3	36 KB	Network data storage

Optimizations Applied¶

To fit in 256KB flash, the following were removed:

Component	Savings	Reason
Debug print	~12 KB	No debug output needed
ZLL / touchlink	~4 KB	Not used
Virtual UART	~1 KB	Not needed
PTI (Packet Trace)	~2 KB	No debug probe

Features¶

RTL8196E Boot Delay: 1-second delay for host UART initialization
Hardware Flow Control: RTS/CTS required for reliable TCP operation
NVM3 Storage: 36KB for network credentials and tokens

Troubleshooting¶

No response from NCP¶

Verify TCP connection: nc -zv <gateway-ip> 8888
Check baud rate matches (115200) on firmware side and on the gateway (cat /sys/module/rtl8196e_uart_bridge/parameters/baud)
Verify hardware flow control is on: cat /sys/module/rtl8196e_uart_bridge/parameters/flow_control → 1

EZSP communication errors¶

Ensure Z2M/ZHA is configured for ember adapter
Check for EZSP version mismatch (this firmware is EZSP v13)
Re-enable hardware flow control if left off by a failed flash: echo 1 > /sys/module/rtl8196e_uart_bridge/parameters/flow_control

Device won't pair¶

Enable permit join in Z2M/ZHA
Factory reset the device
Move device closer to coordinator for initial pairing

Files¶

24-NCP-UART-HW/
├── build_ncp.sh                 # Build script
├── README.md                    # This file
├── firmware/                    # Pre-built firmware files
│   ├── ncp-uart-hw-7.5.1.gbl
└── patches/
    ├── README.md                # Patch documentation
    ├── apply_config.sh          # Configuration script
    ├── ncp-uart-hw.slcp         # Project config
    ├── main.c                   # Entry point (1s delay)
    └── sl_*.h                   # Configuration headers

25-RCP-UART-HW/ - RCP firmware (CPC protocol, for cpcd + zigbeed)
26-OT-RCP/ - OpenThread RCP (for zigbee-on-host)
27-Router/ - Autonomous Zigbee router (no host needed)

References¶

License¶

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

NCP-UART-HW Firmware¶

Features¶

Hardware¶

Option 1: Flash Pre-built Firmware (Recommended)¶

Gateway state after flash¶

Option 2: Build from Source¶

Prerequisites¶

Build¶

Output¶

Clean¶

Flash¶

Usage¶

Architecture¶

Zigbee2MQTT Configuration¶

Home Assistant ZHA Configuration¶

Customization¶

Changing Baudrate¶

Network parameters¶

Network Parameters¶

Network Size Presets¶

Technical Details¶

Memory Usage¶

Optimizations Applied¶

Features¶

Troubleshooting¶

No response from NCP¶

EZSP communication errors¶

Device won't pair¶

Files¶

Related Projects¶

References¶

License¶