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Overview

boards/nordic/nrf21540dk/doc/index.rst

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.. zephyr:board:: nrf21540dk

Overview

The nRF21540 DK (PCA10112) shows possibility of the Nordic Semiconductor nRF21540 Front End Module connected with nRF52840 ARM Cortex-M4F CPU.

More information about the board can be found at the nRF21540 website. nRF21540 Product Specification contains the processor's and front end module's information and the datasheet.

Hardware

The nRF52840 on the nRF21540 DK 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

.. zephyr:board-supported-hw::

See nRF52840 Product Specification_ and nRF21540 DK Hardware guide_ for a complete list of nRF21540 Development Kit board hardware features.

Connections and IOs

LED

  • 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

Front End Module

  • MOSI = P1.13
  • MISO = P1.14
  • CLOCK = P1.15
  • CHIP SELECT = P0.21
  • PDN = P0.23
  • MODE = P0.17
  • RXEN = P0.19
  • ANTSEL = P0.20
  • TXEN = P0.22

Programming and Debugging

.. zephyr:board-supported-runners::

Applications for the nrf21540dk/nrf52840 board configuration can be built, flashed, and debugged in the usual way. See :ref:build_an_application and :ref:application_run for more details on building and running.

Flashing

Follow the instructions in the :ref:nordic_segger page to install and configure all the necessary software. Further information can be found in :ref:nordic_segger_flashing. Then build and flash applications as usual (see :ref:build_an_application and :ref:application_run for more details).

Here is an example for the :zephyr:code-sample:hello_world application.

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

.. code-block:: console

$ minicom -D <tty_device> -b 115200

Replace :code:<tty_device> with the port where the board nRF21540 DK can be found. For example, under Linux, :code:/dev/ttyACM0.

Then build and flash the application in the usual way.

.. zephyr-app-commands:: :zephyr-app: samples/hello_world :board: nrf21540dk/nrf52840 :goals: build flash

Debugging

Refer to the :ref:nordic_segger page to learn about debugging Nordic boards with a Segger IC.

Testing the LEDs and buttons in the nRF21540 DK

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

.. code-block:: console

samples/basic/blinky samples/basic/button

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 :zephyr_file:boards/nordic/nrf21540dk/nrf21540dk_nrf52840.dts.

Changing UART1 pins

The following approach can be used when an application needs to use another set of pins for UART1:

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

    .. code-block:: devicetree

    &pinctrl { uart1_default_alt: uart1_default_alt { group1 { psels = <NRF_PSEL(UART_TX, 0, 14)>, <NRF_PSEL(UART_RX, 0, 16)>; }; }; /* required if CONFIG_PM_DEVICE=y */ uart1_sleep_alt: uart1_sleep_alt { group1 { psels = <NRF_PSEL(UART_TX, 0, 14)>, <NRF_PSEL(UART_RX, 0, 16)>; low-power-enable; }; }; };

    &uart1 { pinctrl-0 = <&uart1_default_alt>; /* if sleep state is not used, use /delete-property/ pinctrl-1; and * skip the "sleep" entry. */ pinctrl-1 = <&uart1_sleep_alt>; pinctrl-names = "default", "sleep"; };

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

See :ref:set-devicetree-overlays for further details.

Selecting the pins

Pins can be configured in the board pinctrl file. To see the available mappings, open the nRF52840 Product Specification_, 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 suitable for 115200 speed of UART.

References

.. target-notes::

.. _nRF21540 DK Hardware guide: https://docs.nordicsemi.com/bundle/ug_nrf21540_dk/page/UG/nrf21540_DK/intro.html .. _J-Link Software and documentation pack: https://www.segger.com/jlink-software.html .. _nRF21540 website: https://www.nordicsemi.com/Products/Low-power-short-range-wireless/nRF21540 .. _nRF52840 Product Specification: https://docs.nordicsemi.com/bundle/ps_nrf52840/page/keyfeatures_html5.html .. _nRF21540 Product Specification: https://docs.nordicsemi.com/bundle/ps_nrf21540/page/keyfeatures_html5.html