How to use the JLink CDC UART Port on EFM32/EFM8 STK?


EFM32 or EFM8 STK board provides a virtual COM port which is implemented by the Board Controller (BC) via the USB Mini-B connector on the Starter kit.


The JLink CDC UART Port TX/RX pins can be connected to the on-board EFM32 or EFM8 MCU UART pins depending on the EFM_BC_EN signal which is controlled by the target MCU. 



The BC enable signal connects the EFM32/8 MCU to the board controller:
• 0: EFM32/8 UART pins are isolated from the Board Controller.
• 1: EFM832/8 UART pins are connected to the Board Controller (default upon reset).


Please refer to target starter kit User Manual for more information on the pins connection.


Note: If need to use the MCU UART to connect to other serial port device instead of the JLink CDC port, ensure the BC enable signal is set to proper value.


Therefore, user can use the target MCU UART interface to communicate directly with USB host through the CDC UART Port. The default serial port setting is 115200 baud rate and 8-N-1.


Here is the device viewing from Windows Device Manager when connecting the STK board to PC using a USB cable.



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