nRF21540 DK v1.0.0

Buttons and LEDs

The four buttons and four LEDs on the nRF21540 DK are connected to dedicated General-Purpose Input/Output (GPIO)s on the nRF52840 System on Chip (SoC).

Table 1. Button and LED connection
Part GPIO GPIO alternative Solder bridge
Button 1 P0.11 P1.07 -
Button 2 P0.12 P1.08 -
Button 3 P0.24   -
Button 4 P0.25   -
LED 1 P0.13   SB5
LED 2 P0.14   SB6
LED 3 P0.15   SB7
LED 4 P0.16   SB8

If P0.13P0.16 are needed for other functions, the LEDs can be disconnected by cutting the short on SB5SB8 (see Disconnecting the LEDs). Since P0.11 and P0.12 are used as a part of the trace functionality, Button 1 and Button 2 can be moved to alternative GPIOs (see Debug input and trace) .

Figure 1. Disconnecting the LEDs
Disconnecting the LEDs by shorting SB5-SB8 on nRF21540 DK

The buttons are active low, meaning that the input is connected to ground when the button is activated. The buttons have no external pull-up resistor. To use the buttons, P0.11, P0.12, P0.24, P0.25 pins must be configured as an input with an internal pull-up resistor.

The LEDs are active low, meaning that writing a logical zero (0) to the output pin illuminates the LED.

Figure 2. Button and LED configuration
Button and LED configuration on nRF21540 DK