On-Board Debugger (OBD)

Note

The on-board debugger is available on ARDEP board revision 2.0 and later.

Overview

The On board debugger is connected to the ARDEP’s main µC as illustrated below. The Debug RX/TX Line are connected via 1kOhm resistors to the existing UART-A interface of the PCB with the resistors ensuring that an external device connected to the same UART Interface always has Priority and TX state interference will not cause a short circuit.

../../../../../_images/debugger_schematic_v2_0_0.png

The Debugger circuit is supplied via the same 3.3V net as the ARDEP’s main µC. As the debugger µC consumes ~30mA of idle current, which doubles the ARDEP board’s standby power consumption, it was decided to use a power rail supervisor to keep the debugger in reset state when no USB host is connected to the debug USB port. Measurement results have shown that this implementation can reduce the debugger’s idle current from ~30mA to ~4mA.

Host Interface

The ARDEP mainboard integrates a Black Magic Probe, exposing the following features:

  • Second USB-C connector labeled DEBUG for host connectivity

  • Two USB CDC ACM interfaces provided to the host system

    • uart-a bridge for a bidirectional serial console at /dev/ttyBmpTarg

    • Integrated GDB server for firmware debugging at /dev/ttyBmpGdb