Zephyr applications use the nrf52840_pca10056 board configuration to run on the nRF52840 Preview Development Kit (PCA10056) hardware. It provides support for the Nordic Semiconductor nRF52840 ARM Cortex-M4F CPU and the following devices:

  • ADC
  • GPIO
  • I2C
  • MPU
  • NVIC
  • PWM
  • RADIO (Bluetooth Low Energy and 802.15.4)
  • RTC
  • Segger RTT (RTT Console)
  • SPI
  • UART
  • USB
  • WDT
nRF52840 PCA10056 Preview DK

nRF52840 PCA10056 Preview DK (Credit: Nordic Semi)

More information about the board can be found at the nRF52840 PDK website [1]. The Nordic Semiconductor Documentation library [2] contains the processor’s information and the datasheet.


nRF52840 PDK has two external oscillators. The frequency of the slow clock is 32.768 kHz. The frequency of the main clock is 32 MHz.

Supported Features

The nrf52840_pca10056 board configuration supports the following hardware features:

Interface Controller Driver/Component
ADC on-chip adc
CLOCK on-chip clock_control
FLASH on-chip flash
GPIO on-chip gpio
I2C(M) on-chip i2c
MPU on-chip arch/arm
NVIC on-chip arch/arm
PWM on-chip pwm
RADIO on-chip Bluetooth, ieee802154
RTC on-chip system clock
RTT Segger console
SPI(M/S) on-chip spi
UART on-chip serial
USB on-chip usb
WDT on-chip watchdog

Other hardware features are not supported by the Zephyr kernel. See nRF52840 PDK website [1] and Nordic Semiconductor Documentation library [2] for a complete list of nRF52840 Development Kit board hardware features.

Connections and IOs


  • LED1 (green) = P0.13
  • LED2 (green) = P0.14
  • LED3 (green) = P0.15
  • LED4 (green) = P0.16

Push buttons

  • BUTTON1 = SW1 = P0.11
  • BUTTON2 = SW2 = P0.12
  • BUTTON3 = SW3 = P0.24
  • BUTTON4 = SW4 = P0.25
  • BOOT = SW5 = boot/reset

Programming and Debugging

Applications for the nrf52840_pca10056 board configuration can be built and flashed in the usual way (see Build an Application and Run an Application for more details); however, the standard debugging targets are not currently available.


Follow the instructions in the Nordic nRF5x Segger J-Link page to install and configure all the necessary software. Further information can be found in Flashing. Then build and flash applications as usual (see Build an Application and Run an Application for more details).

Here is an example for the Hello World application.

First, run your favorite terminal program to listen for output.

$ minicom -D <tty_device> -b 115200

Replace <tty_device> with the port where the board nRF52 DK can be found. For example, under Linux, /dev/ttyACM0.

Then build and flash the application in the usual way.

# On Linux/macOS
cd $ZEPHYR_BASE/samples/hello_world
mkdir build && cd build

# On Windows
cd %ZEPHYR_BASE%\samples\hello_world
mkdir build & cd build

# Use cmake to configure a Ninja-based build system:
cmake -GNinja -DBOARD=nrf52840_pca10056 ..

# Now run ninja on the generated build system:
ninja flash


Refer to the Nordic nRF5x Segger J-Link page to learn about debugging Nordic boards with a Segger IC.

Testing the LEDs and buttons in the nRF52840 PDK

There are 2 samples that allow you to test that the buttons (switches) and LEDs on the board are working properly with Zephyr:


You can build and flash the examples to make sure Zephyr is running correctly on your board. The button and LED definitions can be found in :file: boards/arm/nrf52840_pca10056/nrf52840_pca10056.dts.

Using UART1

The following approach can be used when an application needs to use more than one UART for connecting peripheral devices:

  1. Add device tree overlay file to the main directory of your application:

    $ cat nrf52840_pca10056.overlay
    &uart1 {
      compatible = "nordic,nrf-uarte";
      current-speed = <115200>;
      status = "ok";
      tx-pin = <14>;
      rx-pin = <16>;

    In the overlay file above, pin P0.16 is used for RX and P0.14 is used for TX

  2. Go to menuconfig and enable CONFIG_UART_1_NRF_UARTE:

    (top menu) -> Device Drivers -> Serial Drivers -> nRF UART nrfx drivers

  3. Use the UART1 as device_get_binding("UART_1")

Overlay file naming

The file has to be named <board>.overlay and placed in the app main directory to be picked up automatically by the device tree compiler.

Selecting the pins

To select the pin numbers for tx-pin and rx-pin:

tx-pin = <pin_no>

Open the nRF52840 Product Specification [3], chapter 7 ‘Hardware and Layout’. In the table 7.1.1 ‘aQFN73 ball assignments’ select the pins marked ‘General purpose I/O’. Note that pins marked as ‘low frequency I/O only’ can only be used in under-10KHz applications. They are not sutiable for 115200 speed of UART.

Translate ‘Pin’ into number for Device tree by using the following formula:

pin_no = b\*32 + a

where a and b are from the Pin value in the table (Pb.a). For example, for P0.1, pin_no = 1 and for P1.0, pin_no = 32.