The Debug in connector (P18) makes it possible to connect external debuggers for debugging when the interface MCU Universal Serial Bus (USB) cable is not connected or the Development Kit (DK) is in nRF only mode.
For trace, a footprint for a 20-pin connector is available (P25). If trace functionality is required, it is possible to mount a 2×10 pin 1.27 mm pitch surface mount pin header.
Some of the trace pins are by default used for other functionality on the DK. By sliding the TRACE switch (SW7) from Def. to Alt., the functionality is transferred to other General-Purpose Input/Output (GPIO)s. See the following table for the list of GPIOs that have multiple functionalities.
| GPIO | Trace | Default use | Optional GPIO |
|---|---|---|---|
| P0.07 | TRACECLK | UART CTS | P0.04 |
| P1.00 | TRACEDATA[0] | ||
| P0.11 | TRACEDATA[1] | Button 1 | P1.07 |
| P0.12 | TRACEDATA[2] | Button 2 | P1.08 |
| P1.09 | TRACEDATA[3] |
The reference voltage for the debug input and trace is by default connected to VDD_nRF'. This can be connected to the VDD by cutting SB60 and soldering SB59.