SLSTK3400A USB-enabled Happy Gecko


Platform Silicon Labs EFM32: Silicon Labs EFM32 Gecko 32-bit microcontroller (MCU) family includes devices that offer flash memory configurations up to 256 kB, 32 kB of RAM and CPU speeds up to 48 MHz. Based on the powerful ARM Cortex-M core, the Gecko family features innovative low energy techniques, short wake-up time from energy saving modes and a wide selection of peripherals, making it ideal for battery operated applications and other systems requiring high performance and low-energy consumption.

Microcontroller EFM32HG322F64
Frequency 25MHz
Flash 64KB
Vendor Silicon Labs


Please use efm32hg_stk3400 ID for board option in “platformio.ini” (Project Configuration File):

platform = siliconlabsefm32
board = efm32hg_stk3400

You can override default SLSTK3400A USB-enabled Happy Gecko settings per build environment using board_*** option, where *** is a JSON object path from board manifest efm32hg_stk3400.json. For example, board_build.mcu, board_build.f_cpu, etc.

platform = siliconlabsefm32
board = efm32hg_stk3400

; change microcontroller
board_build.mcu = efm32hg322f64

; change MCU frequency
board_build.f_cpu = 25000000L


SLSTK3400A USB-enabled Happy Gecko supports the next uploading protocols:

  • blackmagic
  • jlink
  • mbed

Default protocol is mbed

You can change upload protocol using upload_protocol option:

platform = siliconlabsefm32
board = efm32hg_stk3400

upload_protocol = mbed


PIO Unified Debugger - “1-click” solution for debugging with a zero configuration.


You will need to install debug tool drivers depending on your system. Please click on compatible debug tool below for the further instructions and configuration information.

You can switch between debugging Tools & Debug Probes using debug_tool option in “platformio.ini” (Project Configuration File).

SLSTK3400A USB-enabled Happy Gecko has on-board debug probe and IS READY for debugging. You don’t need to use/buy external debug probe.

Compatible Tools On-board Default
Black Magic Probe    
J-LINK Yes Yes


Name Description
mbed The mbed framework The mbed SDK has been designed to provide enough hardware abstraction to be intuitive and concise, yet powerful enough to build complex projects. It is built on the low-level ARM CMSIS APIs, allowing you to code down to the metal if needed. In addition to RTOS, USB and Networking libraries, a cookbook of hundreds of reusable peripheral and module libraries have been built on top of the SDK by the mbed Developer Community.