How to tell a peripheral to switch to central mode and connect to another specific peripheral?

[Andy]

Hello,

I'm not posting this as a problem, but rather to get some suggestions and ideas about this feature. I have a device based on the NRF52832. It is meant to work as a peripheral, but now I want to extend its features by connecting to other peripherals, for example, a BLE GPS receiver to get GPS data.

My device does not have a screen or any buttons, but I have a working app that connects to my peripheral. I would like to somehow choose in the app the peripheral I want my device to connect to.

I'm looking for suggestions on how to go about this. My initial idea is that the app should scan for devices, then the user would choose one and the app would tell the device to enable central mode and to start scanning for the chosen device. What would be a good way to identify the same device in both the app and the device?

Thanks in advance for your insights!

[awneil]

Andy said:

What would be a good way to identify the same device in both the app and the device?

MAC address?

[Andy]

Can I have access to that information without actually connecting to the device? Imagine a situation where I choose one device out of 50 in range. Can I determine the MAC address of a device just by scanning the advertisement packets?

[Andy]

Yeah I thought so too, but I can't guarantee that all devices will have different advertising names

[awneil]

Yeah - that's the catch.

Are they 3rd-party devices?

If they were your own devices, perhaps you could incorporate some "unique ID" into the advertising name?

Otherwise you're just going to have to ensure that only 1 of each type is "visible" at a time...

[Andy]

They're 3rd-party devices. But still, let's say that there are two devices advertising the name "GPS". Even if I filter out one of them, if I tell my device to go to central mode and connect to "GPS", there's no way to guarantee that the device will connect to the same "GPS" that was on the list. Right? 

[Andy]

Maybe I should just ask the user in the app to turn off conflicting devices and that's it.

[awneil]

Correct.

But, once your app has identified which device is which, it can tell your device the appropriate MAC address.

Or, back to the earlier suggestion, your device sends a list of MAC+Name pairs to the app...

Andy said:

Maybe I should just ask the user in the app to turn off conflicting devices

Well, if the devices can't be distinguished by their names (which seems common), then you're going to have to work out some plan for how to distinguish them - maybe by the app telling the user to switch only one on at a time...

[Andy]

But the problem is that I can't tell the MAC address in iOS

[awneil]

like I said, you'd have to get your device to send a list of MAC+Name pairs to the app...

[Andy]

Oh I get it. Sorry

[awneil]

Apple making life difficult again!

I know nothing about iOS development, but I've heard there may be "workarounds" to get BLE MAC addresses - so it might be worth searching around some iOS developer forums ...

[Andy]

There are some workarounds when dealing with other peripherals on the same device, but not across different devices. Apple has some sort of MAC address or UUID that's unique for each peripheral the phone is dealing with. But this UUID is different on every phone, and it has nothing to do with the actual MAC address of the device.