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CC2650STK: Characteristic write over 20 byte

asdafaq
Prodigy 170 points

Part Number: CC2650STK
Other Parts Discussed in Thread: CC2650, CC2640, BLE-STACK

Hy!

I read many forum thread, but I dont get an answer. I use a CC2650 sensortag hardware with modified ProjectZero with BLE SDK 2.2 . I create a custom service/characteristic in Bluetooth Developer Studio and generate a code, with TI plugin. Everything works fine, really. In my Android phone (Vernee Thor Android 6.0) with BLE Scanner android app. I see my service characteristic, the problem not in here.

When I write my characteristic with more than 20 byte (in BLE Scanner write in text mode) , I received all of my data, but seperate ChangeHandler. 

I write an example, if this unclear:

i write to the characteristic "012345678901234567890123456789" (3x10 byte) I received in two packet wih "01234567890123456789" (1x20) and an other "0123456789" (1x10). If I write with 50 byte I receive 2x20 and 1x10 packet, etc etc

The real question is, what way to determinate how many "packet" are left, or which packet received.

Realterm screenshot with awesome paint skill:

So the question is what way to determinate how many "packet" are left, or which packet received. Or I must "hack" wih a special character at the string end, or any other method.

Thank for answer!

Best reagrds,

Richard

  • 0
    TI__Guru** 105180 points

    Hello Richard,

    The behaviour is determined by the Bluetooth specification for ATT Read. See the CC2640 FAQ post pinned at the top of the BLE forum on where to find details for GATT/ATT in the specification.

    Question: Did you initiate a GATT MTU Exchange procedure from your GATT Client (i.e, you phone)? If you have configured larger MAX_PDU_SIZE in your BLE-Stack SDK and this procedure is performed, then the number of PDU transfers should be less due to a higher ATT_MTU size.

    Best wishes

  • 0 in reply to JXS
    Prodigy 170 points

    Srry for late answer.

    I change MAX_PDU_size and I try to another android applicaton and yes, the "packet" arrived in one piece. Thank for answer and clarification.

    Best regard, 

    Richard