How to get manufacturer's data from a received advertising message?

RE: How to get manufacturer's data from a received advertising message?

Igor — Mon, 28 Jan 2019 16:08:55 GMT

In NRF SDK 15.2 there is a method

uint8_t * ble_advdata_parse(uint8_t  * p_encoded_data, uint16_t data_len, uint8_t ad_type);

It returns pointer to the specified ad_type.

Example:

static void ble_evt_handler(ble_evt_t const *p_ble_evt, void *p_context) {
    if (p_ble_evt->header.evt_id != BLE_GAP_EVT_ADV_REPORT) // is this GAP advertisement?
        return;
    const ble_gap_evt_adv_report_t *p_adv_report = &p_ble_evt->evt.gap_evt.params.adv_report;
    const ble_data_t *data = &p_adv_report->data;
    uint8_t *mfd_data = ble_advdata_parse(data->p_data, data->len, BLE_GAP_AD_TYPE_MANUFACTURER_SPECIFIC_DATA);
    // *mfd_data is a pointer to BLE_GAP_AD_TYPE_MANUFACTURER_SPECIFIC_DATA data
}

RE: How to get manufacturer's data from a received advertising message?

Nildo — Fri, 04 Dec 2015 18:07:40 GMT

Thank you, very much. I was going to implement a parser for the advertising myself but this was really handy for me.

RE: How to get manufacturer's data from a received advertising message?

Nildo — Fri, 04 Dec 2015 18:06:12 GMT

Thank you for the explanation. All I really wanted to know was if I was really going to implement it that way.

RE: How to get manufacturer's data from a received advertising message?

Anders Strand — Fri, 04 Dec 2015 14:32:02 GMT

See the scanning part of the BLE central tutorial

Use this function:

static uint32_t adv_report_parse(uint8_t type, data_t * p_advdata, data_t * p_typedata)

{
    uint32_t index = 0;
    uint8_t * p_data;

    p_data = p_advdata->p_data;

    while (index < p_advdata->data_len)
    {
        uint8_t field_length = p_data[index];
        uint8_t field_type = p_data[index+1];

        if (field_type == type)
        {
            p_typedata->p_data = &p_data[index+2];
            p_typedata->data_len = field_length-1;
            return NRF_SUCCESS;
        }
        index += field_length+1;
    }
    return NRF_ERROR_NOT_FOUND;
}

Call it with type = BLE_GAP_AD_TYPE_MANUFACTURER_SPECIFIC_DATA (0xFF)

RE: How to get manufacturer's data from a received advertising message?

RK — Thu, 03 Dec 2015 23:15:25 GMT

ble_advdata_set() is only for encoding data and setting it for outgoing advertising, the scan response in that API isn't a response you got from a scan to be decoded, it's the data you want to set as advertising data into the scan response you're going to send out when you advertise yourself. So that's not going to help you, ble_advdata_set() is only used to set advertising data.

The advertising data is in a very simple format however. It's .. where length is 1 byte and is the length of the + , the type is the type, there's a list here and in the spec, manufacturer is 0xFF, then it's data, if there's another field it's directly afterwards.

So all you have to do is start at the beginning, figure out the type of the field which is the second byte, if it's not advertising you use the length to skip to the next field and do it again until you find your manufacturer data and/or consume the whole buffer. You don't even need to decode the other fields if you don't need them, since you have the length, you can skip right over them. If you wrote a function to find data of a specific type and return the address and length, or NULL if it's not there, it would probably be 3 lines of code.