For boards with custom pin connections for programming and debugging, use debug output on connector P20.
Connect the boards as shown in the following figure.
It is recommended to power the external board separately from the DK. The voltage on the external board must match that of the DK. When the DK is powered through the USB connector, the voltage is 3 V.
When the interface MCU detects the voltage of the external board on pin 3 (SWD1_VTG) of P20, it programs or debugs the target chip on the external board instead of the onboard nRF52832 System on Chip (SoC). If the interface MCU detects boards connected to both P19 and P20, it programs or debugs the target connected to P19 by default.
The following figure shows the pinout of the P20 connector.
The following table describes the pinout of the P20 connector.
| Pin number | Signal | Description |
|---|---|---|
| 1 | VDD_nRF | nRF52832 SoC power domain |
| 2 | VDD | Main nRF52 DK power domain |
| 3 | SWD1_VTG | Voltage supply from the external target. Used as an enable signal for activating SWD1 |
| 4 | SWD1_SWDIO | Serial Wire Debug (SWD) data line |
| 5 | SWD1_SWDCLK | SWD clock line |
| 6 | SWD1_SWO | The Serial Wire Output (SWO) line is not needed for programming and debugging over SWD |
| 7 | SWD1_RESET | Reset line |
| 8 | N.C. | Not used |