Debugging; On-Board Debugger; Virtual Com Port - Silicon Laboratories BGM220 Explorer Kit User Manual

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UG465: BGM220 Explorer Kit User's Guide

Debugging

4. Debugging

The BGM220 Explorer Kit contains an on-board SEGGER J-Link Debugger that interfaces to the target BGM220P using the Serial Wire

Debug (SWD) interface. The debugger allows the user to download code and debug applications running in the target BGM220P. Addi-

tionally, it also provides a virtual COM port (VCOM) to the host computer that is connected to the target device's serial port, for general

purpose communication between the running application and the host computer. The Packet Trace Interface (PTI) is also supported by

the on-board debugger, which offers invaluable debug information about transmitted and received packets in wireless links. The on-

board debugger is accessible through the USB Micro-B connector.

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 BGM220P.

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 which then powers the board. When the USB cable is removed, the on-board debugger goes into a very low

power shutoff mode (EM4S), consuming around 80 nA typically (EFM32GG12 data sheet number). This means that an application run-

ning off batteries 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.

The virtual COM port is a connection to a UART of the target BGM220P 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 inserted.

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. For more information on

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.

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