EFR32 BRD4255A (SLWRB4255A)


The EFR32FG13P Flex Gecko 2.4 GHz and 915 MHz Radio Board is delivered as a standalone Proprietary Wireless radio board. It contains a EFR32FG13P Wireless SoC built on an ARM Cortex®-M4F processor with excellent low power capabilities.

SLWRB4255A Flex Gecko 2.4 GHz and 915 MHz Radio Board

SLWRB4255A (image courtesy of Silicon Labs)

The BRD4255A a.k.a. SLWRB4255A radio board plugs into the Wireless Starter Kit Mainboard BRD4001A and is supported as one of EFR32 Radio Boards.


  • EFR32FG13P233F512GM48 Flex Gecko SoC

  • CPU core: ARM Cortex®-M4 with FPU

  • Flash memory: 512 kB

  • RAM: 64 kB

  • Transmit power: up to 19 dBm

  • Operation frequency: 2.4 GHz, 915 MHz

  • Crystals for LFXO (32.768 kHz) and HFXO (38.4 MHz).

For more information about the EFR32FG13 SoC and BRD4255A board, refer to these documents:

Supported Features

Please refer to EFR32 Radio Board Supported Features for details of the configuration and common features supported by the efr32_radio_brd4255a board.

The default configuration can be found in the defconfig file:


System Clock

The EFR32FG13P SoC is configured to use the 38.4 MHz external oscillator on the board.

Serial Port

The EFR32FG13P SoC has three USARTs and one Low Energy UARTs (LEUART). USART0 is connected to the board controller and is used for the console.

Programming and Debugging

Please refer to Programming and Debugging EFR32 Radio Board for details on the supported debug interfaces.


Connect the BRD4001A board with a mounted BRD4255A radio module to your host computer using the USB port.

Here is an example for the Hello World application.

# From the root of the zephyr repository
west build -b efr32_radio_brd4255a samples/hello_world
west flash

Open a serial terminal (minicom, putty, etc.) with the following settings:

  • Speed: 115200

  • Data: 8 bits

  • Parity: None

  • Stop bits: 1

Reset the board and you should see the following message in the terminal:

Hello World! efr32_radio_brd4255a