Search a specific BLE peripheral device

RE: Search a specific BLE peripheral device

endnode — Wed, 16 Nov 2016 10:20:09 GMT

Well is Device Name present as AD element in ADV or SCAN_RSP data? Actually even if so it doesn't guarantee anything on today's crappy phones... welcome to real life;)

RE: Search a specific BLE peripheral device

NG — Wed, 16 Nov 2016 09:58:20 GMT

Hi, that's exactly what we are trying to do. A button pushed on the device will change the "device name" in the advertising string. However, while I do:

    err_code = sd_ble_gap_device_name_set(&sec_mode,(const uint8_t*)DEVICE_NAME_1,strlen(DEVICE_NAME_1));
    APP_ERROR_CHECK(err_code);

    err_code = ble_advdata_set(&advdata, NULL);
    APP_ERROR_CHECK(err_code);

I can't see the device name change (using BLE scanners: LightBlue, as well as Nordic's nfrConnect), until I actually connect to the device - which defeats the whole purpose. I want to see the advertising string change after a button press.

RE: Search a specific BLE peripheral device

Stian Røed Hafskjold — Tue, 29 Sep 2015 08:00:02 GMT

Sound like you are on the right path here. You push a button to set a flag in order to know which one to connect to, and then put the MAC in whitelist.

RE: Search a specific BLE peripheral device

Frederic — Tue, 05 May 2015 15:04:45 GMT

thats what we do, after we have find "our" device we use the MAC address in the smartphone APP to connect to this device.

RE: Search a specific BLE peripheral device

endnode — Tue, 05 May 2015 14:28:57 GMT

Well once you have mechanisms how to find "your" devices among all possible BLE peripherals then MAC address should be base for any further classification/logging/db. But maybe just my view;)

RE: Search a specific BLE peripheral device

Frederic — Tue, 05 May 2015 14:24:23 GMT

ok, with your solutions i can find my device from several differnt BLE devices. But if i have ten equal BLE devices with equal name and equal 128-bit UUID in ADV_IND and now I want to, for example, indentify the third device, we use the manufacturer specific data AD in ADV_IND to set a flag to indentify the device.

RE: Search a specific BLE peripheral device

endnode — Tue, 05 May 2015 09:07:42 GMT

My bad, I missed that you are interested into that initial phase of recognition of your devices from other BLE peripherals. There are 3 standard ways how to do it:

By specific name AD in ADV_IND or SCAN_RSP (this is the way if you must rely on 3rd party central apps or generic OS capabilities).
By advertising your specific 128-bit UUID in ADV_IND or SCAN_RSP (which you anyway must do if you are having such service and want to follow BLE specifications).
By putting manufacturer specific data AD in ADV_IND or SCAN_RSP and put some special string there (or consider joining BT SIG and reserving your specific code, then you might put just that).

Cheers Jan

RE: Search a specific BLE peripheral device

Frederic — Tue, 05 May 2015 08:31:42 GMT

Let's say we have ten equal BLE devices and all of them are in adevertising mode, how should it now possibl to identify the third BLE device if we don't know the MAC Address and don't transmit a serial number during advertising. It's Ok that sevaral smartphones can connect to one device.

RE: Search a specific BLE peripheral device

endnode — Tue, 05 May 2015 07:58:19 GMT

And how this scale with more than one phone? What you do when you see advertisement with flag set but that was done after connection with another phone? I'm either missing something from your high-level use case or it's rather "why to do it simple if we can make it complicated" story:)

RE: Search a specific BLE peripheral device

Frederic — Tue, 05 May 2015 07:19:33 GMT

Hey Jan,

thanks, for your answer. We have several BLE devices which are in advertsing mode, in the APP we find all devices and to identify one of these devices we push a button and set a flag in the advertising message. So, we known to which device we want to connect.

RE: Search a specific BLE peripheral device

endnode — Mon, 04 May 2015 21:30:39 GMT

Hello Frederic,

Why so complicated when you have "unique" MAC (Advertising) address of the peripheral device from the beginning (advertising, active scanning, target of connection)? Even BLE stack on handset side is using it for "db" of known devices (e.g. when you disable "Service Changed" characteristic on peripheral side then phones will use short service discovery just based on 6-byte MAC address and GATT handles from BLE peripheral stack will be "cached").

If you are worried about "uniqueness" of the MAC across your device base then you can either check it during manufacturing process (because then I assume your solution is based on that value and thus you read/log it at some point) or you can easily assign your unique 43-bit number, write it to the flash (e.g. to UICR region) and use as Adv. Address during every boot of the device. But even Nordic does guarantee neither 100% uniqueness nor randomness of the 8-byte Device Address (which I personally completely understand) I'd bet you will never see two equal MAC addresses in the field.

Cheers Jan