Bluetooth Low Energy: The Developer's Handbook by Robin Heydon

Author:Robin Heydon
Language: eng
Format: mobi, epub
Tags: Software Development, Networking, Data in the Enterprise, Telecommunications & Sensors, Wireless Networks, APIs & Operating Environments, Programming, Testing & Engineering, Engineering & Transportation, Software Design, Engineering, Software Design & Engineering, Computer Science, Palm OS, Protocols & APIs, Computers & Technology, Networks
ISBN: 9780132888363
Publisher: Prentice Hall
Published: 2012-11-06T14:00:00+00:00

wait <until end of working day>

connect to lights:

send "off" to control point

disconnect

It is this combination of multiple services in the client that is one of the most powerful concepts in Bluetooth low energy. Each individual service can be kept very simple; it is the combination of services that provides the complexity and richness of the system. For this to be true, services must be atomic. Atomic in this context means that the services perform only one set of actions. By making services atomic, they can be reused by multiple clients, all doing different things.

This allows the first problem identified with classic profiles to be solved—it is almost impossible to define a classic profile that has explicit state. By defining the services as separate specifications, it is possible to keep them atomic so that the quantity of behavior in each service is very small. The small quantity of behavior means it is very much easier to define explicitly what a service does, and, therefore, it is also easier to test this by using standard unit testing methodologies. This means that atomic services have explicit state, and that this state can be relied upon by clients.

This approach also solves the second problem identified with classic profiles—it is almost impossible to use a classic profile in a way that was not envisioned. By splitting the use cases into services that are atomic with known behavior, it is possible to define clients that can use these services. Clients can use these either in isolation or in combination with other services. Because the services have explicit behavior, the complexity of combining services is minimized. Also, because each service is atomic, there is no “bleeding” of behavior from one service to another. Each service is separate, and its behavior is not dependent upon the state of another service. This means that services can be combined in any order that is conceivable.

This also means that clients can use services on a device in novel ways. There is no actual need for profiles; it is the services that define how devices interoperate, profiles just define the standard ways that this can be done for a given use case. Therefore, a device can determine that it can combine not only the temperature service and time service but also the solar panel’s power generation service to determine the current weather. This is probably not a profile or use case that would be defined by the Bluetooth SIG, but it could be something that a manufacturer might wish to do. By splitting the behavior of the server into services, it is possible to combine this behavior in interesting, novel, and useful ways in any client.

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