The Bluetooth low-energy application space is much wider than the Classic Bluetooth space, going beyond the most popular examples of health and fitness, short-range medical monitoring, and keeping track of children and pets with RF tags.
Inside the smart home of the future, Bluetooth low-energy is a strong contender for the personal area network (PAN) that will adjust thermostats, turn appliances on or off, and activate or deactivate home security systems.
Automotive applications are likely to focus on the ability to control accessories and basic operational features from outside the car (that is, from a mobile phone). Frequently mentioned applications are keyless entry, starting the car, and adjusting climate-control settings.
Remote control of home entertainment equipment – for decades the province of IR technology – is another opportunity largely because IR technology’s limited data bandwidth is insufficient for advanced remote control devices equipped with joysticks and LCD screens.
This broad application space brings with it some interesting challenges. Precise Bluetooth application profiles have to be developed and tested, for example, and it takes time to identify all the potential complications. Developers also have to optimize energy consumption. Some will have to learn how to handle dual-mode operation, which is an integral part of the communication system.
To accelerate the learning curve, the Bluetooth SIG recently initiated a program called ATLAS (Advanced Training Lab and Services). ATLAS gives members of the trade association access to an intensive one-week program. Participants get hands-on experience with 4.0 development boards – writing code and learning the nuts and bolts of how to build and to self-certify an LE product. Course details include Profile Tuning Suite (PTS), protocol analyzer and the Bluetooth SIG Device Library.
Development tools are always a key differentiator for wireless products in particular, and Hotenda offers more than 70 Classic Bluetooth products, such evaluation kits, boards, and software in its line card from companies such as CSR PLC , ConnectBlue and STMicroelectronics. So far, only two companies have fielded development kits for Bluetooth low-energy chips. One is the leader in Bluetooth technology, CSR PLC.
CSR Synergy is based on the company’s BCHS – the industry’s most widely used embedded Bluetooth software stack. Like BCHS, CSR Synergy has source code in ANSI C, is easily extendable and has a virtual OS for easy portability.
Texas Instruments is also early into the race with its CC2540DK-MINI development kit, which provides a reference design for software development of single-mode Bluetooth low-energy applications based on the company’s CC2540. Using the Windows application BTool and a USB dongle, the CC2540 Bluetooth low-energy stack can be tested and verified while developing custom applications. The image below shows the protocol stack.
Texas Instruments is early to the Bluetooth LE race with its CC2540DK-MINI development kit. Using the Windows application BTool and a USB dongle, the CC2540’s BLE stack (shown above) can be tested and verified while developing custom applications.
The PHY layer is a 1 Mbps adaptive frequency-hopping radio operating in the unlicensed 2.4-GHz ISM band. The LL essentially controls the device’s RF state with five possibilities: standby, advertising, scanning, initiating or connected.
Advertisers transmit data without being in a connection, and scanners listen for advertisers. Initiators respond to an advertiser with a connection request. If the advertiser accepts, the two connect. The device that initiated the connection becomes the master, and the device that accepted the request becomes the slave.
The HCI layer provides communication between the host and controller over a standardized interface. This layer can be implemented through an API or a hardware interface such as UART, SPI or USB. The L2CAP layer provides data encapsulation services to the upper layers, which permits end-to-end communication.
The SM layer defines the methods for pairing and key distribution, and provides functions for the other layers of the stack to securely connect and exchange data with another device.
The GAP layer directly interfaces with the application and/or profiles, and handles device discovery and connection-related services for the device. In addition, GAP handles the initiation of security features. The ATT protocol allows a device to expose certain pieces of data, known as “attributes”, to another device. In the context of ATT, the device exposing attributes is referred to as the “server”, and the peer device is referred to as the “client.”
The LL state (master or slave) of the device is independent of the ATT role of the device. A master can be either an ATT server or an ATT client, and so can a slave device.
The GATT layer is a service framework that specifies the structure of profiles and defines the sub-procedures for using ATT. In BLE, all data used by a profile or service are called “characteristics.” All data communications that occur between two devices in a BLE connection are handled through GATT sub-procedures.
By taking advantage of new development tools, designers can accelerate the delivery of both Classic Bluetooth and new LE applications to the market.
- Bluetooth Development Tools
- Bluetooth Modules
- Bluetooth Transceiver ICss
- Product Training