3.4.2 Embedded Debugger (J-Link-OB) Interface

The baseboard includes a built-in SEGGER J-Link-On-Board device. The functionality is implemented with an ATSAM3U4C microcontroller in an LQFP100 package. The ATSAM3U4C provides JTAG functions and a bridge USB/Serial debug port (CDC). One dual LED D4 mounted on the baseboard shows the status of the J-Link-On-Board device.

J-Link-OB-ATSAM3U4C was designed in order to provide an efficient, low-cost, on-board alternative to the standard J-Link.

The internal J-Link-OB connects to the target only after it receives a first command; otherwise, it remains disabled.

The USB J-Link-OB port is used as a secondary power source and as a communication link for the baseboard, and derives power from the PC over the USB cable. This port is limited in most cases to 500 mA. A single PC USB port is sufficient to power the baseboard.