Crash in CBPeripheral writeValue: forDescriptor:

Question

After establishing a connection with a TI BLE Keyfob and retrieving the descriptors for a characteristic, I attempt the call

   [peripheral writeValue: nsData forDescriptor: descriptor];

The various objects look reasonable in the debugger. nsData has a single byte of 1, peripheral is a valid looking CBPeripheral object returned from iOS, and descriptor is a valid looking CBDescriptor returned by iOS.

My app crashes with the error

* Assertion failure in -[CBConcretePeripheral writeValue:forDescriptor:], /SourceCache/CoreBluetooth/CoreBluetooth-59.3/CBConcretePeripheral.m:358

Any thoughts on why this is happening or how to debug it?

Answer 1

Note from the documentation of writeValue:forDescriptor

Client characteristic configuration descriptors cannot be written using this method, and should instead use setNotifyValue:forCharacteristic:

So if you are trying to write the descriptor of the connected peripheral, then it will fail.

For writing the characteristic, use the - writeValue:forCharacteristic:type: method.