The nRF52840 DK supports programming and debugging external boards with an nRF51 Series, nRF52 Series, nRF53 Series, or nRF54 Series System on Chip (SoC) or an nRF91 Series System in Package (SiP).
The interface MCU on the nRF52840 DK runs SEGGER J-Link Onboard (OB) interface firmware. It is used to program and debug the application firmware of the nRF52840 SoC by default.
To program or debug an external board, connect to the Debug out connector P19 using a 10-pin cable or use P20 for custom connection.
Note: 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.
Figure 1. Debug output connectors
