Ticket Created
over 4 years ago

WERETECH-8478

messages from BTLE GATT server truncated at 20 bytes

All messages from a BTLE GATT server are truncated at 20 bytes.

The server can be tested against a different client and the full payload is visible (in my case 150 bytes).

This issue is reported by other users as well (see https://forums.garmin.com/developer/connect-iq/f/q-a/196823/bluetooth-low-energy-mtu-size-for-characteristics)

As 20 bytes is the default MTU size, I guess this bug might be MTU size related.

5458292
  • over 3 years ago

    Also running into this issue while trying to connect to a continuous blood glucose monitor.
    I should get 363 bytes, but all i get is 3x 20 bytes. I assume these three messages would originally be 121 bytes each and are truncated...

  • over 3 years ago

    This makes no sense as there are products on the market with messages well over 20 bytes!! And I own developed firmware for NRF52, using own Nordic SDK, that supports well over 20 bytes!!

  • over 4 years ago

    I've been recently working on application using BLE on Edge 530, and I'm seeing the same issue. Only 20 bytes of raw data is delivered in scan results.

    I took a screenshot from raw data in nRF Connect application, of advertisement package of Polar H10 sensor. Green data is visible in Edge 530, which makes exactly 20 bytes. But the red part, 0x9 Complete Local Name, is cut off.

  • over 4 years ago in reply to Michael

    I have word back from my team and they are hoping to get a little more info:

    "Can we confirm the specific format and type of message being sent? Can we capture the desired behaviour using nRF Connect app on Android and send us some annotated logs?"

    Wondering if either of those are something you might be able to grab?

    Thanks,

    Coleman

  • over 4 years ago

    I've got a ticket to track this and I've reached out to our BT team for guidance. Thank you.