.. _openthread_rcp_arduino_shield:

OpenThread RCP over Arduino header ##################################

Overview

This (virtual) shield can be used to connect a board with an Arduino R3 compatible header to an external OpenThread RCP_ device. The RCP device would function as the Thread radio, while another board can function as the OpenThread host.

Requirements

An RCP radio device is needed for this shield to work. As an example, the reference from OpenThread using the :zephyr:board:nrf52840dk is chosen as a demonstration. Refer to the OpenThread on nRF52840 Example website_.

Both UART and SPI can be used as the transport, depending on the board connections.

The following was executed on Ubuntu 24.04 to build and flash the RCP firmware:

Preparation

.. code-block:: bash

git clone https://github.com/openthread/ot-nrf528xx.git --recurse-submodules cd ot-nrf528xx python3 -m venv .venv source .venv/bin/activate ./script/bootstrap

Building

.. tabs::

.. group-tab:: UART

  .. code-block:: bash

     # Set -DOT_PLATFORM_DEFINES="UART_HWFC_ENABLED=1" to enable flow control
     ./script/build nrf52840 UART_trans -DOT_PLATFORM_DEFINES="UART_HWFC_ENABLED=0"

.. group-tab:: SPI

  .. code-block:: bash

     ./script/build nrf52840 SPI_trans_NCP

Flashing

.. code-block:: bash

arm-none-eabi-objcopy -O ihex build/bin/ot-rcp build/bin/ot-rcp.hex nrfjprog -f nrf52 --chiperase --program build/bin/ot-rcp.hex --reset

Pins Assignments

The RCP firmware comes with default pins assigned, the following table lists both the Arduino header pins and the nRF52840DK pins.

.. tabs::

.. group-tab:: UART

  +-----------------------+-----------------------+-----------------------+
  | Arduino Header Pin    | Function (host)       | nRF52840 DK Pin       |
  +=======================+=======================+=======================+
  | D0                    | UART RX               | P0.06                 |
  +-----------------------+-----------------------+-----------------------+
  | D1                    | UART TX               | P0.08                 |
  +-----------------------+-----------------------+-----------------------+
  | Host specific         | UART CTS              | P0.05 (flow control)  |
  +-----------------------+-----------------------+-----------------------+
  | Host specific         | UART RTS              | P0.07 (flow control)  |
  +-----------------------+-----------------------+-----------------------+

.. group-tab:: SPI

  +-----------------------+-----------------------+-----------------------+
  | Arduino Header Pin    | Function              | nRF52840 DK Pin       |
  +=======================+=======================+=======================+
  | D8                    | RSTn                  | P0.18/RESET           |
  +-----------------------+-----------------------+-----------------------+
  | D9                    | INTn                  | P0.30                 |
  +-----------------------+-----------------------+-----------------------+
  | D10                   | SPI CSn               | P0.29                 |
  +-----------------------+-----------------------+-----------------------+
  | D11                   | SPI MOSI              | P0.04                 |
  +-----------------------+-----------------------+-----------------------+
  | D12                   | SPI MISO              | P0.28                 |
  +-----------------------+-----------------------+-----------------------+
  | D13                   | SPI SCK               | P0.03                 |
  +-----------------------+-----------------------+-----------------------+

Programming

Include --shield openthread_rcp_arduino_serial or --shield openthread_rcp_arduino_spi when you invoke west build for projects utilizing this shield. For example:

.. tabs::

.. group-tab:: UART

  .. zephyr-app-commands::
     :zephyr-app: samples/net/sockets/echo_client
     :board: stm32h573i_dk/stm32h573xx
     :shield: openthread_rcp_arduino_serial
     :conf: "prj.conf overlay-ot-rcp-host-uart.conf"
     :goals: build

.. group-tab:: SPI

  .. zephyr-app-commands::
     :zephyr-app: samples/net/sockets/echo_client
     :board: stm32h573i_dk/stm32h573xx
     :shield: openthread_rcp_aduino_spi
     :conf: "prj.conf overlay-ot-rcp-host-uart.conf"
     :goals: build

References

.. target-notes::

.. _OpenThread RCP: https://openthread.io/platforms/co-processor

.. _OpenThread on nRF52840 Example website: https://github.com/openthread/ot-nrf528xx/blob/main/src/nrf52840/README.md