Periodic Advertising

Periodic channels are used for periodic broadcast between unconnected devices. A periodic channel is represented by a channel map and a set of hopping and timing parameters.

The set of channels is represented by the 37 data channels. A packet sent by an advertiser can also have a payload of up to 255 bytes and it can be sent on any LE PHY. Figure 1 and Figure 2.

Peripheral Setup

First set the extended advertising parameters using Gap_SetExtAdvertisingParameters. The extended advertising type must be set to non-connectable and non-scannable.
Set the periodic advertising parameters using the same handle as in the previous command.
```
bleResult_t **Gap\_SetPeriodicAdvParameters**
(
    gapPeriodicAdvParameters_t*    pAdvertisingParameters
);
```
Wait for a gPeriodicAdvParamSetupComplete_cevent in the generic callback.
Next, set the periodic advertising data by calling:
```
bleResult_t **Gap\_SetPeriodicAdvertisingData**
(
    uint8_t                      handle,
    gapAdvertisingData_t*  pAdvertisingData,
    bool_t bUpdateDID
);
```
pAdvertisingData cannot be NULL. If periodic advertising data must be empty, set cNumAdStructures to 0. Wait for a gPeriodicAdvDataSetupComplete_cevent in the generic callback.
Start extended advertising using Gap_StartExtAdvertising.
Last, enable Periodic Advertising. Periodic advertising starts only after extended advertising is started.
```
bleResult_t **Gap\_StartPeriodicAdvertising**
(
    uint8_t handle,
    bool_t  bIncludeADI
);
```
Wait for a gPeriodicAdvertisingStateChanged_cevent in the advertising callback.

Parent topic:Periodic Advertising

Central Setup

The application may decide to listen to periodic advertising by going through the following states:

[Optional] Add a known periodic advertiser to the periodic advertiser list held in the Controller by calling:

**bleResult\_t Gap\_UpdatePeriodicAdvList**
(
    gapPeriodicAdvListOperation_t operation,
    bleAddressType_t               addrType,
    uint8_t*                       pAddr,
    uint8_t                        SID
);

Wait for the gPeriodicAdvListUpdateComplete_c event in the Generic Callback.

Synchronize with a periodic advertiser by calling:
```
bleResult_t **Gap\_PeriodicAdvCreateSync**
(
    gapPeriodicAdvSyncReq_t*   pReq,
);
```
pReq parameter filterPolicycan be set to gUseCommandParameters_c to synchronize with the given peer, or to gUsePeriodicAdvList_c to start synchronizing with all the devices in the previously populated periodic advertiser list.

Wait for the gPeriodicAdvSyncEstablished_c event and check the status. If scanning is not enabled at the time this command is sent, synchronization occurs after scanning is started. Synchronization remains pending until gPeriodicAdvSyncEstablished_cevent is received. If synchronization was successful, the syncHandle is returned in this event.
Terminate the synchronization with the periodic advertiser by calling:
```
bleResult_t **Gap\_PeriodicAdvTerminateSync**
(
    uint16_t syncHandle
);
```
To cancel a pending synchronization, the application should call Gap_PeriodicAdvTerminateSync with syncHandle set to the reserved value gBlePeriodicAdvOngoingSyncCancelHandle and wait for gPeriodicAdvCreateSyncCancelled_c event.

Otherwise, to terminate an already established sync with an advertiser, use the syncHandle value from the gPeriodicAdvSyncEstablished_c event and wait for a gPeriodicAdvSyncTerminated_c event.

Parent topic:Periodic Advertising

Parent topic:Generic Access Profile (GAP) Layer