How to add more services with 128b UUID - ble_advdata_set() returns error 12 (exceed data limit)

[Martin]

Hi, I'm trying to add more user services to LBS demo. I generated 128b UUIDs for my services. Then I should add them to list returned by scan response in function advertising_init() - there are 2 structs: ble_advdata_t advdata, scanrsp; the secon one is filled by ble_uuid_t adv_uuids[]={ {LBS_UUID_SERVICE, BLE_UUID_TYPE_VENDOR_BEGIN}, {MY_UUID_SERVICE, BLE_UUID_TYPE_VENDOR_BEGIN} }; then the struct array is passed to err_code=ble_advdata_set(&advdata, &scanrsp); APP_ERROR_CHECK(err_code); and I got assert with error 12 - NRF_ERROR_DATA_SIZE What is maximum size of scanrsp? What should I do if my service doesn't fit in? Is it important to return scanrsp at all? In other examples (heartrate demo) I can see that 16b short UUIDs are used that fits but I have to use 128b UUIDs.

The second question is about how to dynamically change some manufacturer specific data in advertise packet that I want to transmitt to all clients that will only listen. I found that it is possible to add some data to ble_advdata_t advdata; sctructure into field advdata.p_manuf_specific_data=&adv_spec_data_s; - There's no much space but I need only few bytes. I filled ble_advdata_manuf_data_t adv_spec_data_s; and point an array with 2 bytes. It seems to work but I cannot see this data by any existing smartphone BLE app. I can use BLE sniffer to see that my user bytes are near the end of adv. packet. This will probably need some custom programming on smartphone to extract this data. I need to know to update this data by some call from main loop. Should I use ble_advdata_set() again or is there some specific function to do this? And the data array is passed as a pointer - are they buffered in the BLE stack or I must keep them as global or static variable?

[Martin]

I solved the second question by simply calling
err_code=ble_advdata_set(&advdata, NULL); again when data is changed. A colleague wrote simple android app to display this manuf. spec. data.

[Mihail]

You can add additional 31 bytes via second parameter of:

uint32_t ble_advdata_set (const ble_advdata_t *p_advdata, const ble_advdata_t *p_srdata)

So you can pass additional ble_advdata_t for scan response.

[Martin]

I know, but only one 128b UUID fits to 31B what if I have more services?

[Ole Morten]

As you've found out, you can change advertising data at any time by just calling ble_advdata_set() again. Beware that you are by spec required to use the first two bytes of the manufacturer specific data for your company identifier, but this should already be taken care of in the ble_advdata_manuf_data_t struct.

As for your other question, there is simply no easy way to advertise multiple 128-bit UUIDs. As you've found out, there isn't room for two 128-bit UUIDs in one advertisement packet, so if you need more, the only option is to have one in the advertisement packet and one in the scan response. More than 2 is simply not possible, as there isn't sufficient room in the packets.