Bluetooth: Direction Finding Periodic Advertising Locator


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


  • nRF5340DK board

  • nRF52833DK board with nRF52833 SOC

  • nRF52833DK board with nRF52820 SOC

  • antenna matrix for AoA (optional)

Building and Running

This sample can be found under samples/bluetooth/direction_finding_connectionless_rx in the Zephyr tree.

By default the application supports Angle of Arrival and Angle of Departure mode.

To use Angle of Departure mode only, build this application as follows:

west build -b nrf52833dk_nrf52833 samples/bluetooth/direction_finding_connectionless_rx -- -DOVERLAY_CONFIG=overlay-aod.conf
west flash

To run the application on nRF5340DK there must be provided a child image aimed to run on network core. samples/bluetooth/hci_rpmsg sample application may be used for that purpose.

To build samples/bluetooth/hci_rpmsg sample with direction finding support enabled:

See bluetooth samples section for common information about bluetooth samples.

Antenna matrix configuration

To use this sample when Angle of Arrival mode is enabled, additional GPIOS configuration is required to control the antenna array. Example of such configuration is provided in devicetree overlay samples/bluetooth/direction_finding_connectionless_rx/boards/nrf52833dk_nrf52833.overlay.

The overlay file provides the information about which GPIOs should be used by the Radio peripheral to switch between antenna patches during the CTE transmission in the AoD mode. At least two GPIOs must be provided to enable antenna switching.

The GPIOs are used by the Radio peripheral in order given by the dfegpio#-gpios properties. The order is important because it affects mapping of the antenna switching patterns to GPIOs (see Antenna patterns).

To successfully use the Direction Finding locator when the AoA mode is enabled, provide the following data related to antenna matrix design:

Antenna matrix configuration for nRF5340DK SOC is part of child image that is run on network core. When samples/bluetooth/hci_rpmsg is used as network core application, the antenna matrix configuration is stored in the samples/ bluetooth/hci_rpmsg/boards/nrf5340dk_nrf5340_cpunet.overlay.

Antenna patterns

The antenna switching pattern is a binary number where each bit is applied to a particular antenna GPIO pin. For example, the pattern 0x3 means that antenna GPIOs at index 0,1 will be set, while the following are left unset.

This also means that, for example, when using four GPIOs, the pattern count cannot be greater than 16 and maximum allowed value is 15.

If the number of switch-sample periods is greater than the number of stored switching patterns, then the radio loops back to the first pattern.