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Bluetooth: Direction Finding Periodic Advertising Beacon

Overview

A simple application demonstrating the BLE Direction Finding CTE Broadcaster functionality by sending Constant Tone Extension with periodic advertising PDUs.

Requirements

Nordic nRF SoC based board with Direction Finding support (example boards: nRF52833 DK, nRF5340 DK)
Antenna matrix for AoD (optional)

Check your SoC’s product specification for Direction Finding support if you are unsure.

Building and Running

By default the application supports Angle of Arrival (AoA) and Angle of Departure (AoD) mode.

To use Angle of Arrival mode only, build this application as follows, changing nrf52833dk_nrf52833 as needed for your board:

west build -b nrf52833dk_nrf52833 samples/bluetooth/direction_finding_connectionless_tx -- -DOVERLAY_CONFIG=overlay-aoa.conf
west flash

To run the application on nRF5340DK, a Bluetooth controller application must also run on the network core. The samples/bluetooth/hci_rpmsg sample application may be used. To build this sample with direction finding support enabled:

Copy samples/bluetooth/direction_finding_connectionless_tx/boards/nrf52833dk_nrf52833.overlay to a new file, samples/bluetooth/hci_rpmsg/boards/nrf5340dk_nrf5340_cpunet.overlay.
Make sure the same GPIO pins are assigned to Direction Finding Extension in file samples/bluetooth/direction_finding_connectionless_tx/boards/nrf5340dk_nrf5340_cpuapp.overlay. as those in the created file samples/bluetooth/hci_rpmsg/boards/nrf5340dk_nrf5340_cpunet.overlay.
Copy samples/bluetooth/direction_finding_connectionless_tx/boards/nrf52833dk_nrf52833.conf to a new file, samples/bluetooth/hci_rpmsg/boards/nrf5340dk_nrf5340_cpunet.conf. Add the line CONFIG_BT_EXT_ADV=y to enable extended size of CONFIG_BT_BUF_CMD_TX_SIZE to support the LE Set Extended Advertising Data command.

Antenna matrix configuration

To use this sample with Angle of Departure enabled on Nordic SoCs, additional configuration must be provided via devicetree to enable control of the antenna array, as well as via the ant_patterns array in the source code.

An example devicetree overlay is in samples/bluetooth/direction_finding_connectionless_tx/boards/nrf52833dk_nrf52833.overlay. You can customize this overlay when building for the same board, or create your own board-specific overlay in the same directory for a different board. See nordic,nrf-radio for documentation on the properties used in this overlay. See Set devicetree overlays for information on setting up and using overlays.

Note that antenna matrix configuration for the nRF5340 SoC is part of the network core application. When Bluetooth: HCI RPMsg is used as network core application, the antenna matrix configuration should be stored in the file samples/bluetooth/hci_rpmsg/boards/nrf5340dk_nrf5340_cpunet.overlay instead.

In addition to the devicetree configuration, to successfully use the Direction Finding locator when the AoA mode is enabled, also update the antenna patterns in the ant_patterns array in samples/bluetooth/direction_finding_connectionless_tx/src/main.c.