3 Replies Latest reply on Sep 7, 2017 2:09 PM by e.pratt_1639216

    Attempting to add another custom characteristic to BLE101 project, need a little help.



      I started with the BLE101 (CapSenseLed) example project and that worked fine (using CY8CKIT-042-KIT  aka BLE Pioneer Kit). I wanted to track the time since reset so I put a timer component on the schematic and added an ISR to the TC (Terminal Count) of the timer. The Timer_ISR, which occurs every 5 seconds, toggles the green led and increments a variable "OnTime". And that all works fine.


      Then I tried to add a custom characteristic to track the time since reset. I think I did everything right in the BLE component in PSoC Creator 4.1. I used the CySmart1.2 to verify operation and it looks good. (capsenseled Project archive attached).


      Then I modified the BLE101 Android Studio project to accomidate the additional "OnTime" data. I did it just like the "capsense" data I think.

      However, when click the notify switch for my "OnTime" I get a null pointer exception at the line number 310 in PSoCCapSenseLedService.java. The offending instruction is mOnTimeCccd.setValue(byteVal);


      The Android Monitor shows:

      Shutting down VM

      09-06 13:54:40.786 5263-5263/com.cypress.academy.ble101 E/AndroidRuntime: FATAL EXCEPTION: main

                                                                                Process: com.cypress.academy.ble101, PID: 5263

                                                                                java.lang.NullPointerException: Attempt to invoke virtual method 'boolean android.bluetooth.BluetoothGattDescriptor.setValue(byte[])' on a null object reference

                                                                                    at com.cypress.academy.ble101.PSoCCapSenseLedService.writeOnTimeNotification(PSoCCapSenseLedService.java:310)

                                                                                    at com.cypress.academy.ble101.MainActivity$5.onCheckedChanged(MainActivity.java:186)

                                                                                    at android.widget.CompoundButton.setChecked(CompoundButton.java:165)

                                                                                    at android.widget.Switch.setChecked(Switch.java:1138)

                                                                                    at android.widget.Switch.toggle(Switch.java:1133)

                                                                                    at android.widget.CompoundButton.performClick(CompoundButton.java:123)

                                                                                    at android.view.View$PerformClick.run(View.java:22570)

                                                                                    at android.os.Handler.handleCallback(Handler.java:739)

                                                                                    at android.os.Handler.dispatchMessage(Handler.java:95)

                                                                                    at android.os.Looper.loop(Looper.java:158)

                                                                                    at android.app.ActivityThread.main(ActivityThread.java:7231)

                                                                                    at java.lang.reflect.Method.invoke(Native Method)

                                                                                    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230)

                                                                                    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120)


      I have no idea why that is a null pointer. Since this is only a slight variation from the example code I was wondering if someone could try out my code and see what I am doing wrong. Any help would be greatly appricated!


      Thank you,


        • 1. Re: Attempting to add another custom characteristic to BLE101 project, need a little help.

          The byteval is fine; you create and declare it in the function itself, so that is not the part failing. My guess is that the error is referring to the mOnTimeCccd object being null; This would be caused by your service discovery not having found the handle/service before you are trying to write a notification (using the writeOnTimeNotification function). Can you verify that you are receiving the service discovered event for the capsenseLedService? Maybe put a breakpoint in that function to see what values are being returned or stepping through it to make sure it is getting a service. Otherwise, the safe fix would be to add a check to make sure you received the UUID handles before trying to send the notification.

          (Not that I work with Java much at all )



          • 2. Re: Attempting to add another custom characteristic to BLE101 project, need a little help.

            Hello Epratt, Thank you for the suggestions! I agree that the problem must be mOnTimeCccd object being null. I'm new at this so still trying to get my head around everything. So as I understand it, onServicesDiscovered(BluetoothGatt gatt, int status) is called when a service discovery has completed. And gatt is the gatt data base, right? So I should be able to set a break point inside of onServicesDiscovered

            and view the gatt data base. I do that and look at it but not sure how to interpret it all. I expected one service with three characteristics. I don't see anything about characteristics.


            Still struggling...




            • 3. Re: Attempting to add another custom characteristic to BLE101 project, need a little help.

              Hello Mark,


              I'm not sure how the GATT data is stored, but for access and usage it uses temporary index offset values as "handles"; this means that when you get a handle to a specific service or characteristic it should just return a simple number between 0 and n (n is roughly the number of attributes/declarations in your BLE profile). The phone is most likely holding an "empty" GATT database object with nothing in it when it first connects; Next, it will proceed to "service discovery" this is where it requests all of the services and their offset index (handle) from the device. The device will then return each service as a "service discovered" event/data. Based on this being the method of operation for discovering services, my guess would be that the onServicesDiscovered() event is being called after the example code discovers the handle for the capsense service, but not necessarily after the onTime service handle has been discovered. Or, it could be that the onServicesDiscovered() function is being called upon each service response from the device, in which case you might need to break after the 2nd or 3rd hits rather than the first hit.

              This thread should have some useful information: GATT services discovery