nRF52840 Preview DK v0.9.x

IF Boot/Reset button

The nRF52840 Preview DK board is equipped with an IF Boot/Reset button (SW5).

This button is connected to the interface MCU on the board and has two functions: During normal operation the button will function as a reset button for the nRF52840 SoC. For this to work, pin reset on P0.18 needs to be enabled in the SoC.

The button is also used to enter the bootloader mode of the interface MCU. To enter the bootloader mode, keep the reset button pressed while powering up the board until LED (LED5) starts to blink. You can power up the board either by disconnecting and reconnecting the USB cable, or toggling the power switch (SW8).

Important: Pin reset can be enabled by defining the CONFIG_GPIO_AS_PINRESET variable in the project settings. This can be done, for example, by defining the preprocessor symbol in Keil, go to: Project > Options for Target > C/C++ > Preprocessor Symbols > Define. Here you can add the CONFIG_GPIO_AS_PINRESET variable after NRF52840_XXAA.

This functionality can be removed by using nrfjprog.exe with command --recover -f NRF52.