Changing advertising maximum size with BLE extended advertisin

[Gabriel Pinto]

Hello! I'm currently using nRF52 SDK to create a BLE beacon in which I update the advertising data at runtime.

I'm using the provided ble beacon example as a base for my program, I found that if I configure the extended advertising in the advertising initialization, it actually support up 251 bytes in the advertising data, however I don't seem to be able to change the base size past 0x18. 

This is how my advertising_init() function looks like: 

static void advertising_init(void)
{
    uint32_t      err_code;
    
    uint8_t       flags = BLE_GAP_ADV_FLAG_BR_EDR_NOT_SUPPORTED;

    manuf_specific_data.company_identifier = APP_COMPANY_IDENTIFIER;

    manuf_specific_data.data.p_data = (uint8_t *) m_beacon_info;
    manuf_specific_data.data.size   = APP_BEACON_INFO_LENGTH;

    // Build and set advertising data.
    memset(&advdata, 0, sizeof(advdata));

    advdata.name_type             = BLE_ADVDATA_NO_NAME;
    advdata.flags                 = flags;
    advdata.p_manuf_specific_data = &manuf_specific_data;

    // Initialize advertising parameters (used when starting advertising).
    memset(&m_adv_params, 0, sizeof(m_adv_params));

    m_adv_params.properties.type = BLE_GAP_ADV_TYPE_EXTENDED_CONNECTABLE_NONSCANNABLE_UNDIRECTED;
    m_adv_params.p_peer_addr     = NULL;    // Undirected advertisement.
    m_adv_params.filter_policy   = BLE_GAP_ADV_FP_ANY;
    m_adv_params.interval        = NON_CONNECTABLE_ADV_INTERVAL;
    m_adv_params.duration        = 0;       // Never time out.
    m_adv_params.primary_phy        = BLE_GAP_PHY_AUTO;
    m_adv_params.secondary_phy      = BLE_GAP_PHY_AUTO;
    m_adv_params.set_id             = 4;
    m_adv_params.filter_policy      = BLE_GAP_ADV_FP_ANY;

    err_code = ble_advdata_encode(&advdata, m_adv_data.adv_data.p_data, &m_adv_data.adv_data.len);
    APP_ERROR_CHECK(err_code);

    err_code = sd_ble_gap_adv_set_configure(&m_adv_handle, &m_adv_data, &m_adv_params);
    APP_ERROR_CHECK(err_code);
}

 

The beacon doesn't let me change its max size however because the following setting doesn't go above 0x18 (24 bytes) or it will output an error:

#define APP_BEACON_INFO_LENGTH          0x17

What am I missing to be able to advertise the 251 bytes? 

Thank you and best regards. 

Gabriel

[Vidar Berg]

Hi Gabriel,

Please try the changes I mentioned in this post:  RE: Extended advertising fails configuration . And if still fails, check if the error is returned by ble_advdata_encode() or sd_ble_gap_adv_set_configure().

The beacon doesn't let me change its max size however because the following setting doesn't go above 0x18 (24 bytes) or it will output an error:

You are free to change the length here. APP_BEACON_INFO_LENGTH specifies the length of the nRF beacon format. 

Best regards,

Vidar

[Gabriel Pinto]

Hi Vidar, 

Thank you for your quick reply, I did as you said and it seems to work. I have just one more question: 

Even though I can increase the APP_BEACON_INFO_LENGTH up to 251, it seems to stop showing the data in the nRF Connect App after 243 (screenshot), is this just a visualization limitation or something more? Can I trust that the data is still being advertised with after 243? 

Best regards

[Vidar Berg]

Hi Gabriel,

Did you only change APP_BEACON_INFO_LENGTH, or did you also add more data to the manufacturer field? Note that sd_ble_gap_adv_set_configure() will return with an error if you exceeded the payload limit, and you will not be able to start advertising in that case.

You can click the "RAW" button to inspect the encoded payload data:

Best regards,

Vidar

[Gabriel Pinto]

Hi Vidar, I'm filling the manufacturer field wiith 0's up to the defined size. The moment I go above 0xF3 on APP_BEACON_INFO_LENGTH, the data disappears from the beacon. RAW also displays "empty". Here's what it looks like with 0xF3:  

[Vidar Berg]

Hi,

I was unable to reproduce this here. I tested with a Pixel 2 running Android 11 and nRF connect version 4.26.0. Please try with the attached hex file below and see if you get the same result.

ble_app_beacon_pca10056_with_s140.hex