4.1 On-board Debugger
The on-board debugger is a SEGGER J-Link debugger running on an EFM32 Giant Gecko. The debugger is directly connected to the
debug and VCOM pins of the target EFR32FG23.
When the debug USB cable is inserted, the on-board debugger is automatically active, and takes control of the debug and VCOM inter-
faces. This means that debug and communication will
not
work with an external debugger connected at the same time. The on-board
LDO is also activated, providing power to the board.
When the USB cable is removed, the board might still be running on battery power, as described in section
. In this
case, the on-board debugger goes into a very low power shutoff mode (EM4S), consuming about 80 nA. This means that battery life-
time will not be affected too much by the on-board debugger power consumption. Since the I/O voltage rail of the debugger remains
powered in the battery operated mode, the pins connected to the debug and VCOM interfaces maintain proper isolation and prevent
leakage currents.
4.2 External Debugger
A Wireless Starter Kit (Wireless STK) mainboard with a debug adapter board from Silicon Labs can be connected to the Mini Simplicity
Connector and used for debugging instead of the on-board debugger. For instruction on how this can be done see "AN958: Debugging
and Programming Interfaces for Custom Designs". Debugging with an external Wireless STK mainboard gives access to the following
debugging features:
• Debugging of the target device through SWD
• Communication using the VCOM port
• Packet Trace Interface (for wireless devices only)
• Advanced Energy Monitor
Note that the Mini Simplicity Connector
cannot
be used at the same time as the on-board debugger is active (USB cable is plugged in).
For information on how to correctly connect to the kit, see
Figure 4.1 EFR32FG23 Dev Kit Debugging Possibilities on page 14
Powering the board when using the Mini Simplicity Connector with a Wireless STK mainboard and adapter board can be done using the
AEM voltage supply of the Wireless STK mainboard. When doing this, remove both the USB cable and the coin cell battery from the
EFR32FG23 Dev Kit before connecting the Wireless STK mainboard to the Mini Simplicity Connector. The power switch on the Wire-
less STK mainboard should be set in "AEM". Power-cycling of the board, if necessary, can easily be done by flipping the power switch
on the Wireless STK to "BAT" and back to "AEM" assuming a battery is not inserted in the Wireless STK mainboard.
It is possible to have the EFR32FG23 Dev Kit powered by a battery, and still use the Mini Simplicity Connector with a Wireless STK
mainboard for debugging and communication. In this case the power switch on the Wireless STK mainboard must be set to the "BAT"
position and the coin cell battery on the Wireless STK mainboard must be removed. In this case level shifters on the Wireless STK itself
take care of interfacing to different voltage levels on the EFR32FG23 Dev Kit. Connecting the board to an external debugger in other
ways than those described above might create power conflicts, compromise the ability to monitor power consumption and might haz-
ardously feed power back to the on-board battery.
Important:
Always remove the battery if you are not sure whether the external debugger is sourcing voltage to EFR32FG23 Dev Kit.
4.3 Virtual COM Port
The virtual COM port (VCOM) is a connection to a UART on the EFR32FG23, and allows serial data to be sent and received from the
device. The on-board debugger presents this as a virtual COM port on the host computer that shows up when the USB cable is inser-
ted.
Data is transferred between the host computer and the debugger through the USB connection, which emulates a serial port using the
USB Communication Device Class (CDC). From the debugger, the data is passed on to the target device through a physical UART
connection.
The serial format is 115200 bps, 8 bits, no parity, and 1 stop bit by default.
Note:
Changing the baud rate for the COM port on the PC side does not influence the UART baud rate between the debugger and the
target device. However, it is possible to change the VCOM baud rate through the kits Admin Console available through Simplicity Stu-
dio.
Alternatively, the VCOM port can also be used through the Mini Simplicity Connector with an external Wireless STK. Using the VCOM
port through the Mini Simplicity Connector with an external Wireless STK works in a similar way, but requires that the USB cable to the
on-board debugger is unplugged. The board controller on the Wireless STK then makes the data available over USB (CDC) or an IP
socket. Flow control is not available over the Mini Simplicity Connector.
UG508: EFR32FG23 Dev Kit User's Guide
Debugging
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