The nRF21540 DK supports programming and debugging external boards with nRF51 Series, nRF52 Series, and nRF53 Series System on Chip (SoC)s or the nRF91 Series System in Package (SiP)s.
The interface MCU on the nRF21540 DK runs SEGGER J-Link OB interface firmware and is used to program and debug the firmware of the nRF52840 SoC by default.
To program or debug an external board, connect it to the P19 Debug out header with 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 headers
