USB-KW41Z - FSCI - BLE Notifications not propagated / No NotificationCallback

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USB-KW41Z - FSCI - BLE Notifications not propagated / No NotificationCallback

Contributor III


I'm using the "ble_fsci_blackbox" image with the USB-KW41Z and have a problem with receiving gatt notifications.

The device which the USB-KW41Z is connected to have 2 characteristics, one for data transmission towards the gatt-server (only write permissions) and one for receiving notifications from the gatt-server (only notify permissions).

Now the Problem is, the notification-only characteristics does not have a CCCD to write to / enable notifications as the client is authenticated before (by writing first to the write-only-characteristic) and therefore must be able to handle notifications (gatt server don't have to distinguish whether a client is able to process indications or not - it just sends one if authentication was successful).

While sniffing the BLE traffic I can see a "ATT Handle Value Notification" package on the air from the gatt-server towards the USB-KW41Z, but no NotificationCallback/Indication get triggered.

I registered the "GATTClient-RegisterNotificationCallback.Request" before any GATT operations and also (the GATT-Table is static and I actually know all the handles so first i tried directly writing to the handle) tried first discovering all services/characteristics (I thought, maybe internals need to know about all characteristics to be able to forward notifications on characteristic-handles) but with no success.

I'm expecting "GATTClient-Notification.Indication" but none is received although there is one "in the air".

I'm unable to change the behavior of the gatt-server / unable to implement a CCCD for the characteristic as it's given.

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Contributor III

So I hacked myself into the FSCI-Blackbox sample application by compiling it by myself and running on the device and when I register a Notification-Callback by myself (i.e not "enable" it via FSCI but register one directly in code) I do reach my breakpoint - so the Notification is received and handle by the BLE-Stack but is NOT FORWARDED BY FSCI EVEN AFTER REGISTERING/ENABLING NotificationCallbacks!

It seems to me that is a bug in the fsci-ble implementation ...

The FSCI-BLE functions are referenced by "lib_ble_4-2_host_fsci_cm0p.a"  - is there any code for this or is it only binary included within the SDK?

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Contributor III

My workaround for this issue is following:

I added inside BleApp_Init() of ble_fsci_blackbox sample my own notification callback handler notificationCallback(...) and inside that callback-function I send the expected Notification-Indication ...

Should be fixed in lib_ble_4-2_host_fsci_cm0p.a !

void BleApp_Init(void)
    /* Init serial manager */

    /* Init FSCI */

    /* Register BLE handlers in FSCI */

    /* Register my own Notification-Callback */

#if gHkb_d

void notificationCallback(
     deviceId_t  deviceId,                   /*!< Device ID identifying the active connection. */
     uint16_t    characteristicValueHandle,  /*!< Handle of the Characteristic Value attribute to be notified. */
     uint8_t*    aValue,                     /*!< The Characteristic value array. */
     uint16_t    valueLength                 /*!< Value array size. */
) {
 clientPacketStructured_t*   pClientPacket;
 uint8_t*                    pBuffer;

    /* Allocate the packet to be sent over UART */
    pClientPacket = fsciBleAllocFsciPacket(
      gFsciBleGattOpcodeGroup_c, // opCodeGroup
      gBleGattEvtClientNotificationOpCode_c, // opCode
   sizeof(deviceId_t) + 2 * sizeof(uint16_t) + valueLength // dataSize

    if(NULL == pClientPacket)

    pBuffer = &pClientPacket->payload[0];

    // deviceId
    *pBuffer = deviceId;

    // characteristicValueHandle
    pBuffer[0] = (uint8_t)((characteristicValueHandle) & 0xFF);
    pBuffer[1] = (uint8_t)(((characteristicValueHandle) >> 8) & 0xFF);
    pBuffer += 2;

    // valueLength
 pBuffer[0] = (uint8_t)((valueLength) & 0xFF);
 pBuffer[1] = (uint8_t)(((valueLength) >> 8) & 0xFF);
 pBuffer += 2;

 // value
 FLib_MemCpy(pBuffer, aValue, valueLength);
 pBuffer += valueLength;

 FSCI_transmitFormatedPacket(pClientPacket, 0);
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NXP TechSupport
NXP TechSupport

Hi Chilipp,

What is the version that you are working on? Are you using the FRDM or the USB Dongle?

DId you look at the App_GattClientNotificationCallback? AppMain.c



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Contributor III

Hi Mario,

as the title states I am using the USB-Dongle (USB-KW41Z) with SDK Version: KSDK 2.2.0 (2019-01-16).

I have not looked further at the App_GattClientNotificationCallback because to me it seems this is only for dispatching the notification from the Host-Thread to the Application-Thread.

The issue is already fixed by my approach and is working - so I think I will "not change my running system" :smileywink:

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