Bluetooth: periodic_adv_conn

Overview

A simple application demonstrating the initiator side of the Bluetooth LE Periodic Advertising Connection Procedure. This sample implements the Periodic Advertising with Responses (PAwR) advertiser functionality and can establish connections to synchronized devices.

For more details, refer to zephyr/samples/bluetooth/periodic_adv_conn/README.rst.

The Periodic Advertising Connection Procedure is an advanced Bluetooth LE 5.4+ feature that allows devices to:

  • Advertise periodically with structured subevents and response slots

  • Receive responses from synchronized devices during specific time slots

  • Initiate connections to responding devices using connection procedure

  • Coordinate multiple devices through subevent and response slot assignment

This sample demonstrates the initiator/advertiser role by:

  1. Starting periodic advertising with multiple subevents and response slots

  2. Listening for responses from synchronized devices in designated slots

  3. Parsing device addresses from response data

  4. Initiating connections to responding devices using the synced connection procedure

  5. Managing connections and allowing reconnection after disconnect

The sample works in conjunction with the periodic-sync-conn-sample which implements the responder/synchronizer side of the procedure.

Key Features

Periodic Advertising with Responses (PAwR)

  • Configurable number of subevents (5 by default)

  • Multiple response slots per subevent (5 by default)

  • Structured timing for coordinated communication

  • Continuous data transmission with response collection

Connection Management

  • Automatic connection initiation to responding devices

  • Single active connection support (connects to one device at a time)

  • Automatic reconnection capability after disconnect

  • Connection parameter optimization for PAwR timing

Advanced BLE Features

  • Extended advertising support for larger payloads

  • Privacy and security (SMP) support

  • Periodic advertising sync transfer capability

  • Configurable subevent and response slot parameters

Requirements

Atmosic EVK <board | serial>

Controller Requirements:

  • Bluetooth LE 5.4+ support

  • Periodic Advertising with Responses (PAwR) - Advertiser feature

  • Extended advertising support

  • Central role capability

Building and Running

This sample is built from openair/samples/bluetooth/periodic_adv_conn. The source code can be found under zephyr/samples/bluetooth/periodic_adv_conn.

Build command:

west build -p always -b <board> openair/samples/bluetooth/periodic_adv_conn --sysbuild -T samples.bluetooth.periodic_adv_conn.atm

Flash command:

west flash --skip-rebuild --device <serial> --jlink --fast_load [--erase_flash]

Sample Output

The sample will start periodic advertising and display connection events:

Starting Periodic Advertising Demo
Start Periodic Advertising
Connecting to 12:34:56:78:9A:BC (random) in subevent 2
Connected (err 0x00)
Disconnected, reason 0x16 Connection Terminated by Local Host
Connecting to AA:BB:CC:DD:EE:FF (random) in subevent 1
Connected (err 0x00)
Disconnected, reason 0x13 Remote User Terminated Connection

Configuration Parameters

The sample uses several key configuration parameters that can be modified:

Subevent Configuration

#define NUM_SUBEVENTS     5      /* Number of subevents per periodic interval */
#define SUBEVENT_INTERVAL 0x30   /* Time between subevents (48 * 1.25ms = 60ms) */

Response Slot Configuration

#define NUM_RSP_SLOTS     5      /* Number of response slots per subevent */
#define RESPONSE_SLOT_DELAY   0x5    /* Delay before first response slot */
#define RESPONSE_SLOT_SPACING 0x50   /* Spacing between response slots */

Periodic Advertising Parameters

static const struct bt_le_per_adv_param per_adv_params = {
    .interval_min = 0xFF,        /* Minimum periodic advertising interval */
    .interval_max = 0xFF,        /* Maximum periodic advertising interval */
    .num_subevents = NUM_SUBEVENTS,
    .subevent_interval = SUBEVENT_INTERVAL,
    .response_slot_delay = 0x5,
    .response_slot_spacing = 0x50,
    .num_response_slots = NUM_RSP_SLOTS,
};

Protocol Flow

  1. Initialization Phase

    • Initialize Bluetooth subsystem

    • Create extended advertising set (non-connectable)

    • Configure periodic advertising parameters

    • Start periodic advertising with PAwR support

  2. Advertising Phase

    • Send periodic advertising packets with subevent data

    • Listen for responses in designated response slots

    • Parse received response data for device addresses

    • Maintain continuous periodic advertising

  3. Connection Phase

    • Detect valid device address in response data

    • Initiate connection using synced connection procedure

    • Establish connection with responding device

    • Handle connection events and disconnections

  4. Reconnection Phase

    • After disconnect, return to listening for responses

    • Allow connections to different devices

    • Maintain single active connection at a time

Testing

To test this sample you need two Atmosic EVKs:

Device 1 (Advertiser/Initiator):

  1. Build and flash this periodic_adv_conn sample

  2. The device will start periodic advertising with PAwR

  3. Monitor console for connection attempts and status

Device 2 (Synchronizer/Responder):

  1. Build and flash the periodic_sync_conn sample

  2. The device will synchronize to the periodic advertising

  3. It will respond with its address in designated response slots

  4. Connection will be established automatically

Expected Behavior:

  • Device 1 starts periodic advertising

  • Device 2 synchronizes and responds with its address

  • Device 1 detects the response and initiates connection

  • Connection is established between the devices

  • After disconnect, the process can repeat

Console Output Analysis

Successful Connection:

Connecting to 12:34:56:78:9A:BC (random) in subevent 2
Connected (err 0x00)

Connection Failure:

Failed to initiate connection (err -22)

Disconnection Events:

Disconnected, reason 0x16 Connection Terminated by Local Host
Disconnected, reason 0x13 Remote User Terminated Connection
Disconnected, reason 0x08 Connection Timeout

Troubleshooting

No responses received:

  • Verify that a periodic_sync_conn device is running nearby

  • Check that both devices support PAwR features

  • Ensure proper timing configuration matches between devices

  • Verify Bluetooth LE 5.4+ controller support

Connection failures:

  • Check connection parameter compatibility

  • Verify privacy and security settings match

  • Ensure sufficient connection resources available

  • Check for timing conflicts with periodic advertising

Build errors:

  • Verify controller supports CONFIG_BT_PER_ADV_RSP=y

  • Check that CONFIG_BT_CENTRAL=y is supported

  • Ensure extended advertising support is available

  • Verify Bluetooth LE 5.4+ feature support

Performance issues:

  • Adjust subevent interval for timing requirements

  • Optimize response slot spacing for multiple devices

  • Consider connection interval alignment with PAwR timing

  • Monitor for scheduling conflicts

Advanced Configuration

Multiple Device Support:

To support multiple responding devices, modify the response handling:

/* Increase response slots for more devices */
#define NUM_RSP_SLOTS 10

/* Adjust spacing for more response opportunities */
#define RESPONSE_SLOT_SPACING 0x30

Custom Connection Parameters:

/* Align connection interval with PAwR timing */
conn_param.interval_min = SUBEVENT_INTERVAL;
conn_param.interval_max = SUBEVENT_INTERVAL;
conn_param.latency = 0;
conn_param.timeout = 400;

Security Configuration:

Enable additional security features in prj.conf:

CONFIG_BT_SMP=y
CONFIG_BT_PRIVACY=y
CONFIG_BT_KEYS_OVERWRITE_OLDEST=y