Bonded device scanning

[ble_bmt]

Hi all,

My project involves a ble-central initialising peripherals and creating a bond. When this is complete the peripheral should go into sleep mode and only wake up when data is ready. I want the central to be constantly scanning for the bonded peripherals and immediately connect to extract information when one is found. 

For this functionality i'll need to scan for only previously bonded devices so I can either; A) create a list of all the "awake" peripherals or B) automatically connect as they are discovered.

The amount of possible peripherals will be in the 20 - 30 range.

Does anyone know how this could be achieved? Any possible examples would be a big help.

Thanks,

[Hung Bui]

Hi ble_bmt, 

Have you used our peer manager library ? 

You can have a look at ble_app_hrs_c example, in the example we do use whitelist when scanning and connecting. So that the device only scan for bonded peripherals. To disable whitelist to add a new device, you need to press BTN_ID_WHITELIST_OFF (button 2 on the nRF52 DK)

However, the whitelist only support up to 8 addresses.  If you want to do a whitelisting for up to 20-30 devices, you would need to do it manually. Take a look at is_connect_per_addr inside scan_init() in the same example. 

[ble_bmt]

Hi Hung Bui,

Thanks for the reply. That's the example I am currently working off, I have managed getting it work to the point that it will scan for white listed peripherals and connect to the first one it sees. However, if there are more than one peripherals appearing on the scan only the first connect correctly. I suspect this is because I am trying to send a connect command to a second peripheral before the first has fully connected?

I am trying to connect after receiving a "Peripheral Found" event from the scan, is there a better way I can go about this?

Thanks,

[Hung Bui]

The ble_app_hrs_c example only support 1 peripheral at a time. If you want an example with multiple peripheral, please check the ble_app_multiplink_central. 
You need to start scanning again after a connection is established. 

[ble_bmt]

OK thanks i'll have a look.

[ble_bmt]

Thanks the example, my firmware is now working well as long as peer manager contains 8 or less bonded devices.My next step is to extend this to the full range of peripherals (>8). Are there any events I can use to tell me when to update the whitelist for the next peripherals(something like a "not found" event)?

[Hung Bui]

It's not possible to extend it for more than 8 peripherals (due to radio hardware limitation). You can rotate the list as you plan but there isn't any "Not Found" event, unless you set a timeout for the scanner. Then you will have a timeout event and then can rotate the list to new devices. 

But for large number of devices (30 ? ), I would suggest to just use the address list instead of whitelist. This meant you scan for any device, and then when you receive the advertising packet, you check if the address is in the list, then you can do connection to that address. This can be done in the application.