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.
Figure 1. Connecting an external board to P20
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 3V.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 it is inconvenient to have a separate power
supply on the external board, the nRF52 DK can supply power through pin 2
(VDD) of P20. The connection is shown with a grey outline in
Connecting an external board to P20. If
the interface MCU detects boards connected to both P19 and P20, it
programs or debugs the target connected to P19 by default.
CAUTION:
To avoid overloading the power supply and damaging the DK, use
VDD and keep the supply below 100 mA. Do not use a Lithium-polymer (Li-Poly)
source.
CAUTION:
To avoid damaging your board, do not connect a
separate power supply to the external board when VDD of nRF52 DK is
connected to the external board.
The following section includes an illustration of the P20 connector pinout
with a description table.
Figure 2. Debug output connector P20
| 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 |