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[STM32L4xx] How to increase BlueNRG-MS ATT_MTU

Question asked by Mick Avery on Jul 6, 2017
Latest reply on Feb 13, 2018 by Asela Leelaratne

The BlueNRG-MS library for BLE v4.1 sets ATT_MTU to 23 bytes. Is it possible to increase this limit as long as it's less than the 255 character value length limit?


I am working with the SensorTile eval board with an STM32L4xx MCU, and I working with a modified version of the BlueMicrosystem2 example.


I've done the following:

  1. Set ATT_MTU to 46 bytes (or any number that's less than 255).
  2. I pair with the SensorTile using the ST BlueMS iPhone app.
  3. Immediately after receiving a EVT_LE_CONN_COMPLETE event that tells me that connection was successful, I call aci_gatt_exchange_configuration() to exchange ATT_MTU configurations.
  4. I then get back a EVT_BLUE_ATT_EXCHANGE_MTU_RESP event telling me that exchanging configurations was successful. The event also comes with a data packet that tells me what the new server_rx_mtu is. However, this is still set to 23 bytes.

Am I missing anything? Or is it not possible to increase the ATT_MTU?