General Info

BLE is built up of several protocols that are being used on different layers to transfer information between physical parts of the chip and the application level. The protocols supported by the ALPWISE BLE stack.

• GAP (General Access Profile)

• GATT (Generic Attribute Profile)

• L2CAP (Logical Link Control and Adaption Protocol)

• HCI (Host Controller Interface)

The BLE controller (EM9301) supports Bluetooth version 4.0 and can be run as a master or slave device.

Once the connection is established the BLE devices exchange data in a client-servercommunication consisting of two roles:

• a server hosting the BLE data services, typically a data sensor offering values like heart rate or accelerometer

• a client requesting information from the server, typically a data collector computing information (e.g. displaying it to a user)

  The BLE stack from ALPWISE provides all roles defined in the BLE specification but in most use cases, the XDK is usually employed as a peripheral device to advertise data for interested central devices.

The following operations to move data between the client and the server are supported in BLE:

• read

  requests can be executed by the client and the server responds with the requested data

• write

  commands are issued by the client to write values to the characteristics of the server

• notify

  needs to be actively enabled by the client at the server so the server sends notifications including the values periodically or whenever an update of data is available

• indicate

  works the same way notify does but it also requests acknowledgement by the client whenever the values have been received which makes the notify faster but less reliable