User Manual

nRF51 Development Kit User Guide v1.0
Page 16
5.5 Buttons and LEDs
The four buttons and four LEDs on nRF51 DK board are connected to dedicated I/Os on the nRF51422 chip.
The connections are shown in Table 3.
Table 3 Button and LED connection
If GPIO P0.21 - P0.24 are needed elsewhere, the LEDs can be disconnected by cutting the short on SB5-SB8,
see Figure 12.
Figure 12 Disconnecting the LEDs
The buttons are active low meaning the input will be connected to ground when the button is activated.
The buttons have no external pull-up resistor, so to use the buttons the P0.17 - P0.20 pins must be
configured as an input with internal pull-up resistor.
The LEDs are active low, meaning that writing a logical zero ('0') to the output pin will illuminate the LED.
Figure 13 Button and LED configuration
Part GPIO Short
Button 1 P0.17 -
Button 2 P0.18 -
Button 3 P0.19 -
Button 4 P0.20 -
LED 1 P0.21 SB5
LED 2 P0.22 SB6
LED 3 P0.23 SB7
LED 4 P0.24 SB8
SB5
SB6
SB7
SB8
SW2
PB SW
SW1
PB SW
SW3
PB SW
SW4
PB SW
P0.18 P0.17 P0.20 P0.19
BUTTON1 BUTTON2 BUTTON3 BUTTON4
LED 2
L0805G
R2
220R
R1
220R
LED 1
L0805G
SB6
VIO
LED 3
L0805G
LED 4
L0805G
P0.21
P0.22
P0.24
P0.23
R3
220R
SB7
R4
220R
SB8
SB5