STM32WB Bluetooth^® LE Additional Advertising

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1. STM32WB - additional advertising

This section gives a description on how to use Additional advertising feature available with STM32CubeWB MCU Package ^[1]

Additional advertising (beacon ) may broadcast:

An identifying code that allows apps to retrieve information from app servers. These can be used for indoor location, identification of physical objects, and to interact with apps. It is up to the developer to decide.
A URL of at most 18 characters that redirects to a website that is secured using SSL. This beacon is the underpinning of the Physical Web.

It is a solution to get additional advertising set on top of the standard advertising including:

one additional advertising: undirected non connectable
random address (or public address if not currently used by the standard advertising)
handled at GAP level
dedicated Tx power level for the beacon advertising
no whitelist and privacy unused

Additional advertising - what for?

2. Technical description

The additional adversting is managed at GAP level thanks to three commands:

ACI_GAP_ADDITIONAL_BEACON_START

Parameters	Description
Adv_Interval_Min	Minimum advertising interval. Time = N * 0.625 ms
Adv_Interval_Max	Maximum advertising interval. Time = N * 0.625 ms
Adv_Channel_Map	Advertising channel map. Default: 00000111b (all channels enabled).
Own_Address_Type	Own address type: public or static random.
Own_Address	Public Device Address or Random Device Address.
PA_Level	Power amplifier output level. Output power is indicative and depends on the PCB layout and associated components.

ACI_GAP_ADDITIONAL_BEACON_SET_DATA

Header text	Header text
Adv_Data_Length	Length of Adv_Data in octets
Adv_Data	Advertising data used by the device while advertising.

ACI_GAP_ADDITIONAL_BEACON_STOP

For more information refer to STM32WB Bluetooth^® Low Energy (BLE) wireless interface application note

2.1. Standard advertising first, additional beacon second

This is an example on how to implement both sets of advertising with standard advertising first

A1 = standard advertising Interval: Minimum = 125 ms maximum = 125 ms
A2 = additional advertising interval: minimum = 240 ms maximum = 256 ms

Standard Adverting first

:

2.2. Additional beacon first, standard advertising second

This is an example on how to implement both sets of advertising with additional advertising first.

A1 = additional advertising Interval: minimum = 62.5 ms maximum = 62.5 ms
A2 = standard advertising Interval: minimum = 240 ms maximum = 256 ms

Additional Advertising First

The minimum interval to support both advertising sets is 30 ms

3. STM32WB - P2P server application and additional advertising implementation

Based on the official P2P server application, below is a description on how to implement an additional beacon with the following characteristics:

advertising interval between 30 ms and 40 ms
advertising data element contains Eddystone-URL: www.st.com

Since the requested advertising interval is less than the advertising Interval of P2P application (80/100 ms), it is recommended first to initiate the additional non-connectable advertising.

#define CFG_ADD_ADV_INTERVAL_MIN          (0x30)   /**< 30ms */
#define CFG_ADD_ADV_INTERVAL_MAX          (0x40)  /**< 40ms */
 tBleStatus ret = BLE_STATUS_INVALID_PARAMS;

**
 * Advertising Data Additional Beacon - Eddystone URL
 */
uint8_t add_beacon_data[17] =
  {
    16 ,                                                /*< Length. */
    AD_TYPE_SERVICE_DATA,                               /*< Service Data data type value. */
    0xAA, 0xFE,                                         /*< 16-bit Eddystone UUID. */
    0x10,                                               /*< URL frame type. */
    0x00,                                               /*< Tx Power - Ranging data. */
    0x02,                                               /*< URL Scheme Prefix is http://www. */
    0x77,0x77,0x77,0x2E,0x73,0x74,0x2E,0x63,0x6F,0x6D,  /*< www.st.com */
   };

ret = aci_gap_additional_beacon_start (
        CFG_ADD_ADV_INTERVAL_MIN,
        CFG_ADD_ADV_INTERVAL_MAX,
        0x07,
        CFG_BLE_ADDRESS_TYPE,
        bd_addr,
        CFG_TX_POWER);
    if (ret == BLE_STATUS_SUCCESS)
    {
      APP_DBG_MSG("CMD ==> Successfull ACI_GAP_ADDITIONNAL_BEACON_START\n" );
    }
    else
    {
       APP_DBG_MSG("CMD ==> Failed ACI_GAP_ADDITIONNAL_BEACON_START , result: %d \n", ret);
    }
        
    ret = aci_gap_additional_beacon_set_data(
          sizeof(add_beacon_data),
          (uint8_t*) add_beacon_data);
    if (ret == BLE_STATUS_SUCCESS)
    {
       APP_DBG_MSG("CMD ==> Successfully ACI_GAP_ADDITIONNAL_BEACON_SET_DATA \n" );
    }
    else
    {
       APP_DBG_MSG("CMD ==> Failed ACI_GAP_ADDITIONNAL_BEACON_SET_DATA, result: %d \n", ret);
    }