Bluetooth Low Energy Modules
Bluetooth Low Energy Overview
- Central (or Master) devices scans for advertising Peripheral devices, and initiates connection requests. The Central device is typically a smartphone, tablet, or computer, and can be connected to multiple Peripheral devices at the same time.
- Peripheral (or Slave) devices advertise and wait to accept incoming connection requests. A Peripheral is typically a small device like a fitness tracker or a smartwatch, and can only be connected to one Central device at a time.
- A device cannot be Central and Peripheral at the same time, but some devices can switch modes.
- The Central/Peripheral roles control how the BLE connection is managed.
- Client devices access remote resources over the BLE link using the GATT protocol. Usually, the Central is the client.
- Server devices have local data, access control methods, and provide resources to the remote client. Usually, the Peripheral is the server.
- A device can be a Client and Server at the same time.
- The Client/Server roles are dictated by the storage and flow of data.
- Use Read, Write, Notify, or Indicate operations to move data between the Client and the Server.
- Read and Write operations are requested by the Client and the Server responds (or acknowledges).
- Notify and Indicate operations are enabled by the Client but initiated by the Server, providing a way to push data to the Client.
- Notifications are unacknowledged, while Indications are acknowledged data transfers.
- A GATT Database implements one or more Profiles, where each profile is made up of one or more Services, and each service is made up of one or more Characteristics.