The EFR32 Flex Gecko Wireless Starter Kit SLWSTK6061A contains a Wireless System-On-Chip from the EFR32FG family built on an ARM® Cortex®-M4F processor with excellent low power capabilities.


EFR32-SLWSTK6061A (image courtesy of Silicon Labs)


The SLWRB4250B radio board plugs into the Wireless Starter Kit Mainboard BRD4001A.

Wireless Starter Kit Mainboard:

  • Advanced Energy Monitoring provides real-time information about the energy consumption of an application or prototype design.
  • Ultra-low power 128x128 pixel memory LCD
  • 2 user buttons and 2 LEDs
  • Si7021 Humidity and Temperature Sensor
  • On-board Segger J-Link USB and Ethernet debugger

Radio Board:

  • EFR32FG1P133F256GM48 Flex Gecko SoC
  • 8Mbit SPI NOR Flash

For more information about the EFR32FG1 SoC and EFR32-SLWSTK6061A board, refer to these documents:

Supported Features

The efr32_slwstk6061a board configuration supports the following hardware features:

Interface Controller Driver/Component
NVIC on-chip nested vector interrupt controller
SYSTICK on-chip systick
FLASH on-chip flash memory
GPIO on-chip gpio
UART on-chip serial port-polling; serial port-interrupt

The default configuration can be found in the defconfig file:


Other hardware features are currently not supported by the port.

Connections and IOs

The EFR32FG1P SoC has five GPIO controllers (PORTA to PORTD and PORTF). All of them are enabled for the EFR32-SLWSTK6061A board.

In the following table, the column Name contains Pin names. For example, PA2 means Pin number 2 on PORTA, as used in the board’s datasheets and manuals.

Name Function Usage
PF6 GPIO Push Button PB0
PF7 GPIO Push Button PB1
PA5 GPIO Board Controller Enable EFM_BC_EN

System Clock

The EFR32FG1P SoC is configured to use the 38.4 MHz external oscillator on the board.

Serial Port

The EFR32FG1P SoC has two USARTs and one Low Energy UARTs (LEUART). USART0 is connected to the board controller and is used for the console.

Programming and Debugging


Before using the kit the first time, you should update the J-Link firmware from J-Link-Downloads


The EFR32-SLWSTK6061A includes an J-Link serial and debug adaptor built into the board. The adaptor provides:

  • A USB connection to the host computer, which exposes a debug interface and a USB Serial Port.
  • A physical UART connection which is relayed over interface USB Serial port.
  • An Ethernet connection to support remote debugging.

Flashing an application to EFR32-SLWstk6061A

The sample application Hello World is used for this example. Build the Zephyr kernel and application:

# On Linux/macOS
cd $ZEPHYR_BASE/samples/hello_world
mkdir build && cd build

# On Windows
cd %ZEPHYR_BASE%\samples\hello_world
mkdir build & cd build

# Use cmake to configure a Ninja-based build system:
cmake -GNinja -DBOARD=efr32_slwstk6061a ..

# Now run ninja on the generated build system:

Connect the EFR32-SLWSTK6061A to your host computer using the USB port and you should see a USB Serial Port. Use J-Link or Silicon Labs Simplicity Studio to flash the generated zephyr.bin.

OpenOCD included in the Zephyr SDK v0.9.3 is too old and does not support the EFR32FG1P chip, neither does the latest OpenOCD 0.10.0 release. You will need to compile the newest version of the source code and install the tool yourself. Modify the following command if you install OpenOCD to a location different than the default /usr/local/.

cmake -GNinja -DBOARD=efr32_slwstk6061a -DOPENOCD=/usr/local/bin/openocd -DOPENOCD_DEFAULT_PATH=/usr/local/share/openocd/scripts ..
ninja 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 be able to see on the corresponding Serial Port the following message:

Hello World! arm