Apple

Responses inline ( [+Allan+]: )

From: Etan Kissling <email@hidden>
Date: Fri, 11 Jan 2013 10:54:52 -0800
To: Allan Morgan Young <email@hidden>
Cc: "email@hidden" <email@hidden>
Subject: Re: Core Bluetooth > Subscribed characteristic sometime not getting updated in Central

Allan,

I don't get your "configuration swap" description. As I understand, you have two

iPhones. If iPhone A is peripheral and iPhone B is central, it doesn't work. If

iPhone A is central and iPhone B is peripheral, it works. Are these assumptions

correct?

[+Allan+]: Correct. In my test app I have UI switches that allow the app to run as either or both Central and Peripheral. So, for the testing, I can run the app on a particular device as either a Central or Peripheral, to make the testing scenario more simple.

If yes, try building a minimal example and building two apps, one

peripheral only and one central only, so that you can rule out bugs in your

real application.

Another issue may be that you use an encrypted link between your iPhones. As

soon as you have a bond, characteristic and service information may be cached.

Try to read the characteristic properties on your central side to make sure that

notifications are not anymore available, but only indications are set.

If you want to completely reset iOS Bluetooth state, a "Reset All Settings" is required.

This also clears the UUID cache and UUIDs of all devices will appear again as

"nil" before the first connection.

[+Allan+]: By "Reset All Settings", are you referring to Settings > General > Reset > Reset All Settings? I performed this just now on the device that I had been running as a peripheral, and now the central is getting notified about the indication change. It would be nice if I could programmatically out my app's items from this cache when I launch…possible?

Also, do you wait until you receive the acknowledgment for the indication on the peripheral side

before you send another one? Bluetooth Low Energy supports only one indication at a time.

[+Allan+]: If you're referring to get a call to peripheralManagerIsReadyToUpdateSubscribers, interestingly that never gets called for me, in cases where the indication/notification is received and not received. Note, though, that my call to updateValue:forCharacteristic:onSubscribedCentrals: always returns YES, so maybe that's why I'm not getting this call?

Packet sniffer:

Yes, it's that packet sniffer that you linked with the physical device that you linked.

The software can be downloaded on the first page. Unfortunately, it's Windows only

and is not the most stable piece of software. Have not tried it under VMware or

Parallels. However, the software is free and you can try to run it in a virtual Windows

environment.

On iOS, as far as I know, you cannot specify which of the advertising channels to use

as a peripheral. Therefore, you will only succeed with this sniffer with a 33% probability,

as you have to listen on the same frequency as the connection occurs. As there are three

advertising channel and the iPhone most probably is using all of them, the 33% chance

is deduced. In my opinion, it's still a better option for your use case than the other sniffers

that have price tags that are up to three magnitudes higher.

[+Allan+]: Thanks for this good information.

Etan