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

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

awneil — Thu, 15 Nov 2018 15:41:18 GMT

See comment about having the nRF doing the scanning ...

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

Andy — Thu, 15 Nov 2018 15:31:36 GMT

Yeah, again, I thought about sending the MAC address from my device to the app, but then it is useless on iOS since the phone can't match it to anything. And it's not like showing the MAC address is either useful or user friendly anyway.

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

awneil — Thu, 15 Nov 2018 15:05:42 GMT

Note that an nRF52832 can have both a peripheral connection (to your app) and also be scanning at the same time - so it could all be done in your "peripheral", and just "directed" from the phone app...

Then you have no problems with iOS hiding MAC addresses from you, etc!

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

Vidar Berg — Thu, 15 Nov 2018 14:52:21 GMT

Hi,

1 and 2 will not be possible for a 3rd party device. The RSSI part should be easy to do in the app.

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

awneil — Thu, 15 Nov 2018 14:42:48 GMT

[quote userid="15909" url="~/f/nordic-q-a/40445/how-to-tell-a-peripheral-to-switch-to-central-mode-and-connect-to-another-specific-peripheral/157168"] it's not like the user will see 0x53af2043bd or whatever and then say yeah that's my device.[/quote]

If you're (very?) lucky, the MAC address might be printed on the unit or its packaging or documentation.

But, in general, you're probably right - it's not meaningful to the user.

But it is meaningful to the nRF - so you can use it to distinguish devices to the nRF. And the nRF can give it to the app.

So you'd probably still need some guided user interaction at the app for the user to identify which peripheral is which.

Yes, you still have troubles with the iOS restrictions.

But it's your project. I don't know the (full) details of what you're trying to achieve or why. I'm just throwing you some ideas - you need to think it all through.

PM me if you want to discuss private consultancy...

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

Andy — Thu, 15 Nov 2018 14:07:38 GMT

Hi Vidar,

I'm not sure if I will have control of these things in 3rd-party devices. I have thought about the RSSI to at least differentiate similar devices, but I think I will pass the issue to the user so that he's responsible for turning off conflicting devices.

I think in the end I'll just send the advertised name from the phone to my device and I'll use it in the device to scan and connect to a 3rd device with a matching name.

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

Vidar Berg — Thu, 15 Nov 2018 13:40:55 GMT

I have some general suggestions that you may consider. Some of these assumes you have control of the GPS receiver implementation, not sure if that's the case or not.

1. Include a unique service uuid in the advertisement packet for the GPS receiver so only relevant devices are displayed to user

2. Append a unique number to the device name. Part of the mac address for instance.

3. Include measured RSSI along with device name

4. Scan and select device to connect from the phone, then send a command to the peripheral telling it what device to connect to.

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

Andy — Wed, 14 Nov 2018 12:11:34 GMT

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.

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

awneil — Wed, 14 Nov 2018 12:06:06 GMT

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 ...

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

Andy — Wed, 14 Nov 2018 12:00:08 GMT

Oh I get it. Sorry

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

awneil — Wed, 14 Nov 2018 11:59:08 GMT

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

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

Andy — Wed, 14 Nov 2018 11:37:34 GMT

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

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

awneil — Wed, 14 Nov 2018 11:21:10 GMT

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...

[quote userid="15909" url="~/f/nordic-q-a/40445/how-to-tell-a-peripheral-to-switch-to-central-mode-and-connect-to-another-specific-peripheral/157264"]Maybe I should just ask the user in the app to turn off conflicting devices[/quote]

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...

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

Andy — Wed, 14 Nov 2018 11:15:01 GMT

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

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

Andy — Wed, 14 Nov 2018 11:14:21 GMT

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?

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

awneil — Tue, 13 Nov 2018 19:26:21 GMT

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...

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

Andy — Tue, 13 Nov 2018 19:07:29 GMT

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

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

awneil — Tue, 13 Nov 2018 17:16:13 GMT

[quote userid="15909" url="~/f/nordic-q-a/40445/how-to-tell-a-peripheral-to-switch-to-central-mode-and-connect-to-another-specific-peripheral"]My initial idea is that the app should scan for devices, then the user would choose one [/quote]

So how did you envisage that the user would distinguish devices in that scenario?

Were you assuming that they would have different advertising names?

In that case, have the app tell the nRF which advertising name to connect to ...

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

Andy — Tue, 13 Nov 2018 16:48:47 GMT

But I still don't understand how to use that MAC address on the phone. I mean, it's not like the user will see 0x53af2043bd or whatever and then say yeah that's my device. Since the iOS app does not have access to the MAC address, it wouldn't know how to match the addresses to the devices the iOS app is scanning for

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

awneil — Tue, 13 Nov 2018 16:40:18 GMT

sounds like a plan ...

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

Andy — Tue, 13 Nov 2018 16:25:12 GMT

So I could scan all devices with the nRF, pass the MAC addresses to the phone and let the user choose one?

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

awneil — Tue, 13 Nov 2018 16:21:06 GMT

Android gives it; iOS doesn't.

If you had your nRF do the scanning, it would see it - and could pass it on to the app ...

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

Andy — Tue, 13 Nov 2018 16:13:16 GMT

Moreover, do iOS and Android have access to this information? I believe iOS restricts access to the MAC address but I'm not 100% sure about this.

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

Andy — Tue, 13 Nov 2018 16:12:16 GMT

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?

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

awneil — Tue, 13 Nov 2018 16:03:05 GMT

[quote userid="15909" url="~/f/nordic-q-a/40445/how-to-tell-a-peripheral-to-switch-to-central-mode-and-connect-to-another-specific-peripheral"]What would be a good way to identify the same device in both the app and the device?[/quote]

MAC address?