nRF52 Preview DK v1.1.x

I/O expander for buttons and LEDs

The nRF52 PDK has an I/O expander to avoid conflicts with boards that follow the Arduino standard, the on-board GPIOs for the buttons and LEDs would otherwise possibly conflict with such boards.

Table 1. GPIO connection
GPIO Part Arduino signal
P0.13 Button 1 2
P0.14 Button 2 3
P0.15 Button 3 4
P0.16 Button 4 5
P0.17 LED 1 6
P0.18 LED 2 7
P0.19 LED 3 8
P0.20 LED 4 9

The I/O expander will release these GPIOs for general use when the nRF52 PDK is used together with boards that follows the Arduino standard. The I/O expander can be permanently enabled by shorting solder bridge SB18 or permanently disabled by cutting the shorting track on SB19. You must also short SB18 when cutting SB19 for full compatibility with the Arduino standard.

The I/O extender can be temporarily enabled by connecting SHIELD DETECT to ground.

Figure 1. Enable or disable I/Os for Arduino standard
Enable or disable I/Os for Arduino standard

In addition to the buttons and LEDs, the following GPIOs are used for the I/O expander:

Table 2. I/O expander connection
I/O expander signal GPIO
/INT P0.17
SDA P0.26
SCL P0.27
Figure 2. I/O expander schematic
nRF52 PDK I/O expander schematic
Important: SW debouncing should not be needed when using the I/O expander. Each button on the nRF52 PDK is equipped with a debouncing filter.