nRF52832 v3.x.x

Programming a board with custom connections

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
Connecting a custom board with custom connections 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.
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.
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
Debug output connector P20 on nRF52 DK
Table 1. Pinout of connector P20 for programming external targets
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