Can I connect single MFI accessory with two apps at a time

Question

I have two apps with same UISupportedExternalAccessoryProtocols. These are communicating with the MFI certified device. How I can know that the session is already created with other app on the same device. So I can alert to the user that you can't create multiple sessions with the same accessory at a time.

Please help to fix this. Thanks in advance.

Answer 1

I personally consider AyBayBay's answer invalid, since you tagged your question with the "iOS tag" and NSDistributedNotificationCenter is not supported on this platform. (There is a low level api to do this, but I think it's in a private framework)

If you are pretending to target your app to iOS8+, the simplest way to do it is using iOS8's AppExtensions feature. I made some tests creating a session within my app, and sending info to the device from another app using extensions the way below.

some app -> app extension -> my app connected with ext.device -> ext.device

so I'm pretty sure you can check if the session is opened or not and return this info to the caller app.

FYI: To pass info to another app you can also use URLSchemes or UIPasteboard too, but both behaviours in a different way than AppExtensions and I think it not fits on your case. Maybe it helps someone else...

Answer 2

Well when one app connects and establishes a session with your MFI device, you can post a notification to NSDistributedNotificationCenter. Your other app can subscribe and listen for this message, upon recieving it and processing it in its runLoop (when it comes back into the foreground) you can have code that blocks it off from creating a session at the same time. You will have to experiment with this a bit but it can be done.