OBJ-C how-to: App using BLE connection and iBeacon in same device

Question

I have a use case where my objective-c application needs to immediately use iBeacon after it's been terminated in order to wake the application up from a terminated state, connect to BLE and send a command to the device. I have a larger longer running post found here that you can check out for my code if need be.

The Problem

The problem so far, happens when I run the application, search for previously paired devices and/or scan for peripherals, find my BLE device and connect. Once connected the user pairs the BLE connection so that they can send encrypted characteristic data over BLE connection. Without pairing (aka auth/bond in the device's naming conventions) the user cannot send the data to the device at all. It never makes it there. As soon as you pair you can send the command...

When I terminate the app, in the applicationWillTerminate method, I run through this code...

- (void)applicationWillTerminate:(UIApplication *)application {
    NSLog(@"*** Application Will Terminate.");

    NSUserDefaults *userDefaults = [NSUserDefaults standardUserDefaults];
    NSNumber *mode = [userDefaults objectForKey:@"deviceConnectedMode"];

    if([mode intValue] == CONNECTED_MODE_INDICATOR) {
        [self.bluetoothManager sendCodeToBTDevice:@"magiccommand1"
                                   characteristic:self.bluetoothManager.wipeCharacteristic];

//I have been turning this command on and off in testing to see if I can get it to work better while disconnecting in the device rather than in the app...
//The command magiccommand2 wipes the auth/bond inside of the device           
//        [self.bluetoothManager sendCodeToBTDevice:@"magiccommand2"
//                                   characteristic:self.bluetoothManager.disconnectCharacteristic];

        //Place where I attempt to stop being connected to BT
        [self.bluetoothManager disconnectDevice];
        [self.beaconManager startMonitoring];

        NSLog(@"*** Application terminated from connected mode!");

    } else {
        NSLog(@"*** DriveCare terminated without violation!");
    }
}

What I am trying to accomplish

The magiccommand1 and magiccommand2 commands are just silly test strings (for now, 128 bit tokens later) that the device is listening for over the serial port. Once they receive the commands they react by attempting to wipe the auth/bond on the device and also disconnecting from BLE in the device.

So the only way I can seem to get the app to wake up from a terminated state is with iBeacon. So I am having to do a bunch of seemingly dirty stuff here just to get this round peg in a square hole. In the app's lifecycle it connects and pairs and when I terminate I want it to completely be removed as a connected device from BLE. My hope is that iBeacon will wake up the app, connect back to BLE, shut off iBeacon monitoring and then send a command to the BLE device from a terminated state. This turning on/off or connecting/disconnecting from iBeacon to BLE and back would most likely cause the user to have to re-pair and I don't want this.

More Problems

When I call [self.centralManager cancelPeripheralConnection:self.thePeripheral]; the iOS system level BT manager seems to auto reconnect almost instantly (because of the pairing) so there is no time for the connection to be severed and iBeacon to be picked up again. If I attempt to disconnect from my centralManager instance before sending the disconnect command to my box (as seen above in code commented out) they obviously wont send either. If I just use only that CBCentralManager disconnect method it isn't enough for iBeacon to begin being detected as the iOS system is still paired with the device. Lastly, if I then go into my iOS system BT manager and choose "Forget this device", the iBeacon gets picked up again and my didEnterRegion method fires!

This is a lot of back and forth between iBeacon and BLE and I just wish I didn't even need iBeacon to wake up the app. I have all info.plist background BLE and iBeacon services turned on. If I don't connect to BLE at all and never pair once and connect my device, the local app notifications slide in without problem letting me know that the iBeacon didEnterRegion and didExitRegion methods are being fired without trouble.

What am I doing wrong here?

Answer 1

I figured out this answer! I was sort of on the right path... It's not a great idea to try and disconnect from BT pairing in order to try to get iBeacon delegate methods to fire. It causes a lot of weird dirty code, tightly coupled things that shouldn't be and worse... the dreaded spaghetti code.

Instead my solution was to build a board with 2 Bluetooth chips in it. One as a dedicated iBeacon chip and the other as a permanent connected/paired/auth and bonded chip. This way there does not need to be any timed connection and disconnection events to be monitored (or worse... resolved race conditions). Waiting for a device to disconnect in iOS is not a true disconnect, it is instead when the iOS system thinks it's disconnected (in the phone's side of things). The things going on inside of the peripheral system paint a very different picture...

This 2 chip approach made life so much easier on the development side because now anytime you need the application to wake up to handle something, you can power cycle the iBeacon device and receive the appropriate event.

Side note: When using iBeacon the didEnterRegion method fires almost instantly where as the didExitRegion can take 30 or more seconds sometimes to fire. Therefore if you need immediate beacon detection resolution you should try to make sure the iBeacon is being powered on and not off for this... if even possible.