The Debug in connector (P18) makes it possible to connect external debuggers when the interface MCU USB cable is not connected, or the Development Kit (DK) is in nRF only mode.
Figure 1. Debug input and trace connectors
For trace, a footprint for a 20-pin connector is available (P25). If trace functionality is required, it is possible to mount a 2x10 pin 1.27 mm pitch surface-mount pin header. To use trace, you must disable flow control on UART_0, by switching Flow Control (SW7) for serial port 0 to off.
| GPIO | Trace | Default use |
|---|---|---|
| P0.12 | TRACECLK | |
| P0.11 | TRACEDATA[0] | UART_0 RTS |
| P0.10 | TRACEDATA[1] | UART_0 CTS |
| P0.09 | TRACEDATA[2] | BUTTON 4 |
| P0.08 | TRACEDATA[3] | BUTTON 3 |
By default, the reference voltage for the debug input and trace is connected to VDD_nRF'. This can be connected to the VDD by cutting SB60 and soldering SB59.