Android Question BLE SetNotify crashes program.

[fjb]

I am trying to use the setnotify service on a connected arduino. I am able to make a connection, send and receive data but when I try to use setNotify I get the below error and the program crashes. I have the characteristic set up with notify enabled I am using the correct service and characteristic UUIDs. Any help is appreciated.

BLECharacteristic firstChar(MY_UUID("0001"), BLERead | BLEWrite, 40 | BLENotify);

Sub Manager_Connected (services As List)
    Log("Connected")
    connected = True
    'ConnectedServices = services
    Sleep(1000)
   169 -  manager.SetNotify(strBcSvcUUID,strBcChrUUID,True)
    StateChanged

End Sub

connecting
Discovering services.
Discovering services.
Connected
Connected
Error occurred on line: 169 (B4XLoadingIndicator)
java.lang.NullPointerException: Attempt to invoke virtual method 'boolean android.bluetooth.BluetoothGattDescriptor.setValue(byte[])' on a null object reference
    at anywheresoftware.b4a.objects.BleManager2.setNotify(BleManager2.java:343)
    at anywheresoftware.b4a.objects.BleManager2.SetNotify(BleManager2.java:332)
    at java.lang.reflect.Method.invoke(Native Method)
    at anywheresoftware.b4a.shell.Shell.runVoidMethod(Shell.java:777)
    at anywheresoftware.b4a.shell.Shell.raiseEventImpl(Shell.java:354)
    at anywheresoftware.b4a.shell.Shell.raiseEvent(Shell.java:255)
    at java.lang.reflect.Method.invoke(Native Method)
    at anywheresoftware.b4a.ShellBA.raiseEvent2(ShellBA.java:146)
    at anywheresoftware.b4a.BA.raiseEvent(BA.java:193)
    at anywheresoftware.b4a.shell.DebugResumableSub$RemoteResumableSub.resume(DebugResumableSub.java:22)
    at anywheresoftware.b4a.keywords.Common$13.run(Common.java:1716)
    at android.os.Handler.handleCallback(Handler.java:938)
    at android.os.Handler.dispatchMessage(Handler.java:99)
    at android.os.Looper.loopOnce(Looper.java:226)
    at android.os.Looper.loop(Looper.java:313)
    at android.app.ActivityThread.main(ActivityThread.java:8751)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:571)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1135)

 

[fjb]

Figured this one out but created more problems for myself.
You have to use BLEByteCharacteristic not BLECharacteristic with the arduino arduinoBle library for the notify to be available. I was counting on using BLECharacteristic because you can send up to 512 bytes at a time. So know it back to the drawing board.

 

[fjb]

I discovered with the help from the Arduino forum that I was not setting the BLECharacteristic parameters correctly.
I can indeed read and write large arrays of bytes with one characteristic.

incorrect
BLECharacteristic fourthChar(MY_UUID("0004"), BLERead | BLEWrite, 40 | BLENotify);

correct
BLECharacteristic fourthChar(MY_UUID("0004"), BLERead | BLEWrite | BLENotify, 40);

 

[fjb]

Got it mostly working well. Now that the data is moving like it should I can see that I can send bytes and receive bytes no magical data conversion going on. It is great I can send 50 bytes from the arduino to the phone in one characteristic. I can also send 5 bytes that are set to notify in another. At first glance I thought I was going to have to setup 50 characteristics.
Now I just have to figure out how to reference a field (view) from a form (layout) that is loaded in a scrollview in another layout that has it's own module with the data first received from the arduino. I do have something working but I don't understand why.... I just know it is going to breakdown soon. Some things are much easier to accomplish in C#. You can go down a lot of rabbit holes searching for b4x stuff.

 

[emexes]

Sounds like the BLE device is more than just a wireless light or motor switch. Global variables, here we come!