3.5.3 Embedded Debugger (J-Link-OB) Interface
The SAMA7G54-EK includes a built-in SEGGER J-Link-On-Board (J-Link-OB) device. The functionality is implemented with an ATSAM3U4C microcontroller in an LFBGA100 package. The ATSAM3U4C provides the functions of the JTAG interface and a bridge from USB to the serial debug port (CDC, or Communication Device Class). The two-colored LED (D10) shows the status of the J-Link-OB device.
The J-Link-OB device is designed to provide an efficient, low-cost, on-board alternative to the standard J-Link or SAM-ICE.
Its own dedicated USB port acts as a power source for this block (which is separated from the rest of the system) and provides the communication link to program and debug the MPU.
| LED D10 | State | Description |
|---|---|---|
| Red and green | Off | J-Link (SAM3U device) is not programmed, or J25 and J26 are shorted. |
| Red | On | J-Link (SAM3U device) is programmed but J-Link is disabled (J26 shorted). |
| Green | Flashing | J-Link is operational but the USB port is not connected. |
| Green | On | J-Link-OB is connected and ready. |
The ATSAM3U microcontroller (U26) is powered only through the J-Link USB connector. The programmer IC is therefore separated from the rest of the system and the user can have a better reading of the power that the system is drawing when interrogating the on-board power measurement devices.
The MIC5528 (U28) has been selected to convert the 5V coming from the USB connector into the 3.3V rail required by the microcontroller. The MIC5528 is a simple low-power, low dropout regulator designed for optimal performance in a very small footprint. It is capable of sourcing up to 500 mA of output current while only drawing 38 μA of operating current. For more information about the MIC5528, refer to the product web page.