.. zephyr:code-sample:: bluetooth_hci_spi
:name: HCI SPI
:relevant-api: hci_raw bluetooth spi_interface
Expose a Bluetooth controller to another device or CPU over SPI.
Overview
********
Expose Bluetooth Controller support over SPI to another device/CPU using
the Zephyr SPI HCI transport protocol (similar to BlueNRG).
Requirements
************
A board with SPI slave, GPIO and Bluetooth Low Energy support.
Building and Running
********************
You then need to ensure that your :ref:`devicetree <dt-guide>` defines a node
for the HCI SPI slave device with compatible
:dtcompatible:`zephyr,bt-hci-spi-slave`. This node sets an interrupt line to
the host and associates the application with a SPI bus to use.
See :zephyr_file:`boards/nrf51dk_nrf51422.overlay
<samples/bluetooth/hci_spi/boards/nrf51dk_nrf51422.overlay>` in this sample
directory for an example overlay for the :ref:`nrf51dk_nrf51422` board.
You can then build this application and flash it onto your board in
the usual way; see :ref:`boards` for board-specific building and
flashing information.
You will also need a separate chip acting as BT HCI SPI master. This
application is compatible with the HCI SPI master driver provided by
Zephyr's Bluetooth HCI driver core; see the help associated with the
:kconfig:option:`CONFIG_BT_SPI` configuration option for more information.
Refer to :zephyr:code-sample-category:`bluetooth` for general Bluetooth information, and
to :ref:`96b_carbon_nrf51_bluetooth` for instructions specific to the
96Boards Carbon board.
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