.. zephyr:code-sample:: ble_central
   :name: Central
   :relevant-api: bluetooth

   Implement basic Bluetooth LE Central role functionality
   (scanning and connecting).

Overview

This application demonstrates basic Bluetooth LE Central role functionality by scanning for other Bluetooth LE devices and establishing a connection to the first one with a strong enough signal.

Core features

Scanning for devices

The application initiates a passive scan to detect nearby Bluetooth LE devices. It specifically looks for devices that have a signal strength greater than -50dBm. This threshold helps the app filter out weaker signals, ensuring it only interacts with devices that are within a reasonable RSSI range for communication.

Connection handling

1. The Central scans for Peripheral devices and if it finds a Peripheral which has a signal strength higher than -50dBm, an attempt to establish LE connection is made.
2. If the connection is successful, the Central initiates disconnect to the Peripheral and then restarts the scan.
3. If there are no connections, the Central keeps scanning continuously.

The sample is used to demonstrate the Central mode capabilities of Bluetooth LE and hence a disconnect is issued right immediately after establishing a connection with a Peripheral, allowing the Central to resume scanning for other devices.

Requirements

• BlueZ running on the host, or
• A board with Bluetooth LE support

Building and running

Build and flash the sample as follows, replacing board_name with your target board:

.. zephyr-app-commands::
   :zephyr-app: samples/bluetooth/central
   :board: board_name
   :goals: build flash
   :compact:

To test Central's scanning functionality, either flash the :zephyr:code-sample:`ble_peripheral` sample on a second compatible board or use an off-the-shelf Bluetooth LE enabled device that can act as a Peripheral (eg. smartphone, smartwatch, etc.).