If you are upgrading from version 5.3.1 or older to version 5.4.0 please note the following changes: All BluetoothHelper class events now have BluetoothHelper as their 1st parameter. this is for better support of connection to multiple instance, for example, previously you would do: bluetoothHelper.OnConnected += () { //do something... } now you do : bluetoothHelper.OnConnected += (helper) { //do something... //inside this function, you now have a reference to the caller of that function! } the above is applicable for all events. another exampler: bluetoothHelper.OnCharacteristicChanged += OnCharacteristicChanged; void OnCharacteristicChanged (BluetoothHelper helper, byte[] value, BluetoothHelperCharacteristic characteristic) { //do somthing } previously it was : void OnCharacteristicChanged (byte[] value, BluetoothHelperCharacteristic characteristic) { //do somthing }