Programming a board with custom connections

nRF5340 DK Hardware

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 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 nRF5340 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.

Figure 2. Debug output connector P20
Debug output connector P20 on nRF5340 DK

The following table describes the pinout of the P20 connector.

Table 1. Pinout of connector P20 for programming external targets
Pin number Signal Description
1 VDD_nRF Application nRF5340 SoC power domain
2 VDD_nRF´ See Function of pin 2 (VDD_nRF´)
3 SWD1_VTG Voltage supply from external target that is used as an enable signal to activate SWD1
4 SWD1_SWDIO Serial Wire Debug (SWD) Input/Output line
5 SWD1_SWDCLK SWD clock line
6 SWD1_SWO The Serial Wire Output (SWO) line is not used for programming and debugging over SWD
7 SWD1_RESET Reset line
8 N.C. Not used
9 VIN3-5V Voltage supply
10 VDD_nRF_HV nRF5340 DK VBAT power domain for current measurement
11 VDD_nRF_HV´ Main VBAT power domain
12 VIO_REF GPIO voltage reference input
13 BOARD_ID DK ID resistor

The function of pin 2 (VDD_nRF´) depends on the positions of switches SW9 and SW10 as described by the following table.

Table 2. Function of pin 2 (VDD_nRF´)
Position SW9 Position SW10 Description
VDD OFF Main nRF5340 DK power domain
VDD ON The pin is connected to the external power supply connector P21
Li-Po or USB OFF or ON The output voltage from the on-chip regulator of nRF5340

Supply power to an external board through the DK

If you do not have a separate power supply on the external board, the nRF5340 DK can supply power through pin 2 (VDD_nRF') of P20.
  1. Ensure that SW9 is in the VDD position.
  2. Ensure that SW10 is in the OFF position.
  3. Connect power to external board on pin 2 (VDD_nRF') of connector P20 as shown with a grey outline in Connecting an external board to P20.
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 the nRF5340 DK is connected to the external board and follow the instructions carefully.