Classic Bluetooth is used for short-distance (a few metres at most) wireless transfer of data from one device to another, and is common in consumer products such as for streaming audio data from a smartphone to a headset or speaker, or transferring a file from a smart camera to a PC. Bluetooth is useful in industrial / commercial / medical applications such as barcode scanners, sensors and controls, measurement and monitoring systems, asset tracking and wireless diagnostic equipment. It operates in the unlicensed Industrial, Scientific and Medical (ISM) 2.4GHz band.
Bluetooth Low Energy / Bluetooth Smart was developed to use considerably less power and have a shorter start-up latency than Classic while maintaining a similar range (but at a cost of slower data throughput). It is not backwards compatible with Bluetooth Classic but does operate at the same radio frequency, allowing devices to implement either or both (termed “Smart Ready”) of the protocols and use the same antenna. Data rates are in the order of several Mbit/s.
As the Internet of Things (IoT) progresses, Bluetooth is increasingly being incorporated into products to such as lighting, thermostats, window sensors, door locks etc to communicate locally around interconnected smart homes. Bluetooth can also be an appropriate technology to meet the growing demand for wireless data collection in consumer and professional healthcare and fitness applications, such as wirelessly sending measurements from a pulse oximeter or blood pressure monitor to the user’s (or healthcare practitioner’s) smartphone / tablet / laptop.
Future developments in Bluetooth include longer range, faster speed communications and mesh networking (i.e. the ability to ‘hop’ data from one device to another around a network without going via a central hub) which will all add to its attractiveness in future IoT applications.
A straightforward low-risk approach to add Bluetooth functionality to embedded systems designs is to use a qualified module which handles the hardware and software stack and connects to a separate host microcontroller typically via a standard UART interface. Alternatively a Bluetooth software stack can be implemented and integrated into the main embedded processor code, with due consideration of resource limitations. Using a third-party module considerably simplifies and shortens the design cycle and is often the best approach unless the anticipated production volumes are large enough to warrant spending the extra design time and effort on developing a more tailored in-house solution.
The Bluetooth protocol includes specifications for top-level applications; Bluetooth Profiles have been developed to ensure compatibility between different devices and applications designed and produced by different manufacturers. The Profiles are predefined sets of characteristics with detailed requirements for how specific applications should behave. For example, a blood pressure monitor which uses Bluetooth to wirelessly upload its data should conform to the Bluetooth Blood Pressure Profile, which defines how the monitor should identify itself, how the receiving device should collect and process the blood pressure measurements, and also the protocol for interpreting specific auxiliary information e.g. which bits of the data-stream indicate cuff fit and body movement detection information. The profiles also specify more generic behaviour such as what to do if connection is terminated / idle, and security considerations (different profiles can set different security modes and levels).
Bluetooth is a trademark owned by Bluetooth SIG.