It makes use of a generic data protocol called the Attribute Protocol (ATT), which is used to store Services, Characteristics and related data in a simple lookup table using 16-bit IDs for each entry in the table. GATT is an acronym for the Generic Attribute Profile, and it defines the way that two Bluetooth Low Energy devices transfer data back and forth using concepts called Services and Characteristics. This is the approach use by Apple's iBeacon, for example, which inserts a custom payload in the main advertising packet, using the Manufacturer Specific Data field. This is known as Broadcasting in Bluetooth Low Energy. This is only possible using the advertising packet since data sent and received in connected mode can only be seen by those two connected devices.īy including a small amount of custom data in the 31 byte advertising or scan response payloads, you can use a low cost Bluetooth Low Energy peripheral to sent data one-way to any devices in listening range, as shown in the illustration below. The main use case here is where you want a peripheral to send data to more than one device at a time.
This guide will give you a quick overview of BLE, specifically how data is organized in Bluetooth Low Energy, and how devices advertise their presence so that you can connect to them and start passing data back and forth.īroadcast Network TopologyWhile most peripherals advertise themselves so that a connection can be established and GATT services and characteristics can be used (which allows for much more data to be exchanged and in both directions), there are situations where you only want to advertise data. There are plenty of wireless protocols out there for engineers and product designers, but what makes BLE so interesting is that it's almost certainly the easiest way to design something that can talk to any modern mobile platform out there (iOS, Android, Windows phones, etc.), and particularly in the case of Apple devices it's the only HW design option that doesn't require you to jump through endless hoops to be able to legally market your product for iOS devices. While there is some overlap with classic Bluetooth, BLE actually has a completely different lineage and was started by Nokia as an in-house project called 'Wibree' before being adopted by the Bluetooth SIG.
Bluetooth Low Energy (BLE), sometimes referred to as "Bluetooth Smart", is a light-weight subset of classic Bluetooth and was introduced as part of the Bluetooth 4.0 core specification.
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