Suddenly I'm seeing spontaneous disconnects in my iOS 7 app from my nRF51822 peripheral

[Don]

Suddenly my app, running on iOS 7, is reporting lots of spontaneous disconnects by the peripheral device, an nRF51822, indicating a timeout:

didDisconnectPeripheral: Peripheral with UUID = 2F82C038-59AF-FA33-1963-644155D9CD09 disconnected, error = Error Domain=CBErrorDomain Code=6 "The connection has timed out unexpectedly." UserInfo=0x176d88c0 {NSLocalizedDescription=The connection has timed out unexpectedly.}

Also seeing lots of cases of service discovery reporting unknown error: didDiscoverServices: Error code was Error Domain=CBErrorDomain Code=0 "Unknown error." UserInfo=0x16d48850 {NSLocalizedDescription=Unknown error.},

This is a recent phenomenon, and I'm looking for some way of finding out what caused Core Bluetooth to report these. In the case of the timeout, what timed out? I assume this is coming from the interaction going on between CB and the peripheral, and CB possibly didn't get a response it was expecting? In the case of the service discovery error, it would help to know more about what CB is reporting with the unknown error code. Is there any way to get some additional feedback from CB? This is more a question for Apple and has been posted on the CB forum there, but maybe someone here has some insights.

[Rich]

We are seeing some kind of iO7 issue as well. An app that worked perfectly well in iOS with regard to core bluetooth is now unable to maintain connection. Unfortunately, I am working from the BTLE firmware side and don't know what the app is indicating. I would be interested in hearing about any resolutions you find. Rich

[Ole Morten]

This error is just a general connection timeout error, which can be caused by a lot of factors. First of all, I'd recommend you to make sure that app_error_handler does not contain a reset, since this will easily mask errors that could be returned by the softdevice.

Secondly, it would be interesting to know if there is anything in particular that is happening when you see this kind of problems. Is it close to some specific time (5 s, 10 s, 30 s or similar) after connection, or is it just random?

Third, this can happen if your clock source is not precise enough. What kind of low-frequency clock do you use?

The only change I've noticed from iOS 6 to 7 affecting applications is that iOS no longer seems to downgrade a write to a write without response, but instead just fails to transmit the data. This can be a problem if you have a characteristic that have the Write Without Response property, but your app tries to do a normal Write. In this case, it seems to me that iOS 6 will "downgrade" the Write to a Write Without Response, while iOS 7 will just not transfer the data. This should however not cause a disconnection.

[John]

Hi Ole,

I am working on the embedded FW portion of the project Don is asking about. I can answer questions 1 & 3 for you.

Currently the app_error_handler is doing a reset. I will modify the code to assert and lock up so we can catch it in the debugger easily.

Our low frequency oscillator is +/- 20 PPM for its accuracy at 25C. When I call BLE_STACK_HANDLER_INIT, I pass it NRF_CLOCK_LFCLKSRC_XTAL_20_PPM.

Regards, John

[Don]

Hi Ole. John has answered questions 1 & 3, I'll answer # 2. The disconnect happens at random locations/times. Earlier today I had a disconnect occur in the midst of the connection attempt (Core Bluetooth told to connect, started that process but then disconnected). Here are the lines from our log file: 2013-10-21 09:32:34.604 HOBOmobile[164:4703] MXBLEDevice.m:(1182) connectPeripheral: Tell the Central Manager to connect to the target peripheral 2013-10-21 09:32:34.645 HOBOmobile[164:1f6f] MXBLEDevice.m:(1841) didConnectPeripheral: Connection to peripheral with UUID = D93F9E39-89AA-BC5F-B0FA-30745532D7EA successful 2013-10-21 09:32:34.647 HOBOmobile[164:1f6f] MXBLEDevice.m:(1844) didConnectPeripheral: Active peripheral is now = <CBPeripheral: 0x175c5800 identifier = D93F9E39-89AA-BC5F-B0FA-30745532D7EA, Name = "MX1101", state = connected> 2013-10-21 09:32:34.648 HOBOmobile[164:1f6f] MXBLEDevice.m:(1854) PID = 9218, is a supported Onset device, created MXLoggerMX1101 logger object 2013-10-21 09:32:35.068 HOBOmobile[164:1f6f] MXBLEDevice.m:(1880) didDisconnectPeripheral: Peripheral with UUID = D93F9E39-89AA-BC5F-B0FA-30745532D7EA disconnected, error = Error Domain=CBErrorDomain Code=6 "The connection has timed out unexpectedly." UserInfo=0x175dcf00 {NSLocalizedDescription=The connection has timed out unexpectedly.} 2013-10-21 09:32:35.073 HOBOmobile[164:1f6f] MXBLEDevice.m:(1887) didDisconnectPeripheral: Unexpected disconnection detected - cleaning up

In another test I encountered another disconnect that happened spontaneously after the connection was fully established and there had been some other communication with the peripheral. Suddenly, from the app's point of view, a spontaneous disconnect occurred. The last communication with the device happened at 11:14:36.839, then there was some idle time, then the disconnect. Here are the log lines for that one - the didDisconnectPeripheral method is the callback from Core Bluetooth:

2013-10-21 11:14:51.881 HOBOmobile[188:1f0b] MXBLEDevice.m:(1880) didDisconnectPeripheral: Peripheral with UUID = D93F9E39-89AA-BC5F-B0FA-30745532D7EA disconnected, error = Error Domain=CBErrorDomain Code=0 "Unknown error." UserInfo=0x16d9c820 {NSLocalizedDescription=Unknown error.} 2013-10-21 11:14:51.884 HOBOmobile[188:1f0b] MXBLEDevice.m:(1887) didDisconnectPeripheral: Unexpected disconnection detected - cleaning up

[Bastiaan]

I have a sniffer log file from a ComProbe sniffer that shows a termination happening, initiated by the peripheral. I could provide that, or a printout of a section of the trace, or a screenshot. Is there a way to upload files associated with this thread? (the editing tools plug in URL's but this file isn't available via URL)