Skip to content

Choose a Zigbee or Thread radio mode

The EFR32 is a separate processor from the RTL8196E Linux system. Flashing Linux does not automatically change the radio application, and changing the radio does not reinstall Linux.

Choose the radio mode from the service you want to run, not from the firmware name that sounds newest.

Short answer

  • Want a reliable Zigbee coordinator for Zigbee2MQTT or ZHA? Choose NCP.
  • Want to experiment with EmberZNet 8.2 on the host? Choose RCP.
  • Want a Thread Border Router? Choose OT-RCP.
  • Want this box to extend an existing Zigbee mesh, without acting as a coordinator? Choose Router.

NCP is the recommended default for new users.

Comparison

Mode Main use Where the protocol stack runs Client connection Knowledge level
NCP Zigbee2MQTT or ZHA coordinator EFR32, EmberZNet 7.5.1 / EZSP v13 Directly to gateway TCP:8888 Beginner
RCP Modern host-side Zigbee stack cpcd + zigbeed on a host, EmberZNet 8.2.2 / EZSP v18 Client connects to zigbeed, not directly to the RCP Advanced
OT-RCP Thread/Matter or Zigbee-on-Host OpenThread or Zigbee stack on gateway/external host Depends on selected host stack Intermediate to advanced
Router Extend an existing Zigbee mesh Entire router application on EFR32 No coordinator client Intermediate

Choose NCP if your goal is to pair and control Zigbee devices with Zigbee2MQTT or Home Assistant ZHA. It has the fewest moving parts: the Zigbee stack runs on the EFR32 and the Linux gateway transports EZSP frames over TCP.

Flash it with:

# Lidl
./flash_efr32.sh -y -g <gateway-ip> ncp

# Sengled Smart Hub G4
BOARD=sengled-e39-g8c ./flash_efr32.sh -y -g <gateway-ip> ncp

Zigbee2MQTT configuration:

serial:
  port: tcp://<gateway-ip>:8888
  adapter: ember

Home Assistant ZHA configuration:

Radio type: EmberZNet
Serial device path: socket://<gateway-ip>:8888

The default NCP baud is 115200. A TCP client does not set that baud; the gateway bridge reads it from /userdata/etc/radio.conf. Higher pre-built baud variants exist for the Lidl board, but the default is the best starting point.

Full reference: NCP-UART-HW.

RCP: EmberZNet 8.2 on the host

RCP moves the Zigbee stack off the Series-1 radio. The EFR32 handles only the 802.15.4 radio layer, while cpcd and zigbeed run on the Linux host. This allows the project to expose EmberZNet 8.2.2 / EZSP v18 even though recent Silabs SDKs no longer target the EFR32MG1B directly.

This path adds several components and a second network endpoint:

EFR32 RCP -> gateway TCP:8888 -> cpcd -> zigbeed -> EZSP endpoint -> Z2M/ZHA

Choose RCP only if you specifically need or want the host-side stack. Flashing the RCP is one step; deploying and maintaining cpcd and zigbeed is another.

./flash_efr32.sh -y -g <gateway-ip> rcp

For Sengled, prefix the command with BOARD=sengled-e39-g8c; its safe default baud is selected automatically.

Continue with the RCP guide and the EmberZNet 8.x guide.

OT-RCP: Thread or Zigbee-on-Host

OT-RCP exposes the OpenThread Spinel protocol. The same EFR32 image supports three arrangements:

  1. OTBR on the gateway — otbr-agent runs natively on the RTL8196E. This is the default configuration written by flash_efr32.sh.
  2. OTBR on another host — the UART bridge exposes the RCP to a more powerful machine running OTBR.
  3. Zigbee-on-Host — Zigbee2MQTT's zoh adapter runs the Zigbee stack on an external host.

For a Thread Border Router running on the gateway:

./flash_efr32.sh -y -g <gateway-ip> otrcp

The script writes MODE=otbr and the selected baud to radio.conf, so Linux starts otbr-agent instead of the TCP bridge. A Thread Border Router supplies Thread network connectivity; it is not by itself a Matter controller or Home Assistant installation.

Read the Thread and Matter primer before commissioning a production Thread network. Deployment details are in the OT-RCP guide.

Router: dedicated Zigbee mesh extender

Router firmware turns the EFR32 into a standalone Zigbee 3.0 router. It joins an existing coordinator's network and relays mesh traffic. It does not expose a coordinator to Zigbee2MQTT or ZHA.

./flash_efr32.sh -y -g <gateway-ip> router

After flashing, open permit-join on the existing Zigbee coordinator and follow the router joining procedure.

Board and baud selection

flash_efr32.sh chooses a pre-built file from the selected board and mode. The normal defaults are:

Board NCP RCP OT-RCP Router
Lidl 115200 460800 460800 115200
Sengled G4 115200 230400 230400 115200

The G4 has no RTS/CTS wiring and therefore uses board-specific flow control and safer high-speed defaults. Do not copy Lidl baud choices to it without reading the per-board validation notes.

To see every supported option without changing the gateway:

./flash_efr32.sh --help

Switching modes safely

  • Stop Zigbee2MQTT, ZHA, cpcd, or any other client before flashing. Only one client can hold TCP port 8888.
  • Let flash_efr32.sh update radio.conf; do not pre-edit the baud to the target value.
  • Keep the gateway powered until the script reports success and completes its reboot.
  • After flashing, verify the recorded state:
ssh root@<gateway-ip> cat /userdata/etc/radio.conf

If the new mode cannot communicate with the radio, use the radio troubleshooting path.