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Low Power Bluetooth Connects Devices

Bluetooth Smart – A Revolution for Low Power Connectivity

Small devices must minimize power yet communicate. Bluetooth Smart enables the smallest devices to communicate with larger, Classic Bluetooth devices, which can form bridges to the Web, making possible a huge sphere of connected applications, devices and users.

BY VISHAL GOYAL, STMICROELECTRONICS

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Bluetooth Smart, or Bluetooth Low Energy (BLE), is a wireless personal area network that enables low-power devices and sensors to connect to smartphones and tablets. It uses radio transmission at the 2.4 GHz band. BLE is promoted by Bluetooth SIG and aimed at innovative applications such as healthcare, fitness, security, wearable and home automation. Innovators can build new products that work seamlessly with the smartphone and benefit from the rich user interface and connectivity it provides, while supporting compact hardware accessories with incredible battery life.

Classic Bluetooth is a wireless technology standard for exchanging data or voice over short distance. It is widely used for data, audio and video transmission between smartphones, laptop, PC peripherals, earpiece, etc. But Classic Bluetooth consumes high current, making it unsuitable for battery powered applications, which are expected to run for a long period without the need of battery replacement or charging.

Bluetooth Low Energy (BLE) technology operates in the same spectrum as Classic Bluetooth technology, but uses a different set of channels. Instead of Bluetooth technology’s 79 1 MHz wide channels, Bluetooth Low Energy technology has 40 2 MHz wide channels. Bluetooth Low Energy technology uses frequency hopping to counteract narrowband interference problems. BLE enables ultra-low power connectivity and basic data transfer for applications previously limited by the power consumption. A comparison of Classic Bluetooth and Bluetooth Low Energy technologies is given in Table 1.

Table 1
Comparison of Bluetooth technologies.

In addition, there are two flavors of Bluetooth Low Energy. Bluetooth Smart, another name for Bluetooth Low Energy, has ultra-low power consumption as it is a pure low energy implementation. Bluetooth Smart devices can run for months to years on a standard coin cell battery. These are accessory devices that send information to another Bluetooth Smart device or to Bluetooth Smart Ready-enabled smartphones, tablets or laptops. Bluetooth Smart Ready is Classic Bluetooth + Bluetooth Low Energy on a single chip. These are hub devices that can receive data from both Classic Bluetooth and Bluetooth Smart devices and convert them into useful information. Table 2 shows the interoperability of Bluetooth devices

Table 2
Interoperability of Bluetooth devices.

Bluetooth ICs

For use in its target application, a Bluetooth Smart IC should have certain key attributes, especially low current consumption. Most of the applications of Bluetooth Smart run on battery, so current consumption directly affects the battery life and is a crucial feature in 90% of target applications. In a competitive BLE IC, power modes such as ultra-low-power sleep modes and very short transition times between operating modes allow very low average current consumption, resulting in longer battery life. ST’s BlueNRG is a very low-power Bluetooth Low Energy (BLE) single-mode network processor, compliant with Bluetooth specification v4.0. The BlueNRG allows applications to meet the tight advisable peak current requirements imposed with the use of standard coin cell batteries.

If the Bluetooth SIG changes the stack, the compliancy is mandatory, so the Bluetooth Smart device should have the ability to update the stack. The entire Bluetooth Low Energy stack of ST’s BlueNRG IC runs on the embedded Cortex M0 core. The non-volatile Flash memory allows in-field stack upgrading.

To enable RF communication a BLE IC also needs Balun matching and a filter network. Often it may act as a bottleneck because it is required to be perfect and to not consume critical PCB space. ST has introduced a silicon-based reliable Balun IC that is an integrated solution, thus saving PCB size, cost and making it easier to integrate.

System Partitioning

There are mainly two ways of partitioning a BLE system: System on Chip (SoC) and network processor. An SoC integrates BLE transceiver and microcontroller. An SoC not only contains the BLE stack but also profiles and applications. The advantage of the SoC is better integration and suitability to relatively simple systems. But an SoC does not offer flexibility for the user to select the right microcontroller according to peripherals of a system, or to handle complex tasks such as managing multiple sensors.

A network processor uses an external microcontroller for running profiles and applications. The network processor may or may not contain the stack. If the stack is not present within the network processor, then it is required to be present inside an attached microcontroller. ST’s BlueNRG is a network processor with built-in stack and easy SPI interface with a microcontroller. This system partitioning offers flexibility to select the right microcontroller according to peripherals and complexity of the system. It allows better management of the system’s power requirements (Figure 1).

Figure 1
Bluetooth Smart IC Specification: Layered Architecture of BlueNRG – Bluetooth Smart IC from STMicroelectronics.

Applications for Bluetooth Smart

As devices get smaller and take lower power, the possible applications for Bluetooth Smart are rapidly proliferating. Wearable and mobile devices for fitness are becoming increasingly popular. Connected Smart watches, activity monitors and pedometers enable users to monitor their fitness activity through their smartphones. It allows capturing biometrical data such as heart rate, speed/pace, distance, cadence, total steps and burned calories. BLE send this data to the app running on a smartphone or tablet, and allows it to be shared with social communities. It allows optimizing sports performance, goal monitoring, weight control, direction data and location sharing.

The same is true for healthcare and wellness. Heart rate monitors, glucose monitors and pulse oximeters can now be connected to smartphones through BLE. BLE not only allows these gadgets to connect to smartphones wirelessly, but also to get connected to the Internet through smartphones. It allows tracking your activity and recording biometrical data all day long without necessarily needing 24-hour care. It will enable information to be stored on the Cloud and shared with doctors and family members. BLE has also enabled these gadgets to be worn on strategic locations such as on shoes or on the wrist. BLE supports many healthcare-related profiles such as glucose meters, heart rate monitoring, thermometers and blood pressure meters.

For the smart home, BLE offers a painless path to control lights, home appliances, door locks, garage doors, the security system, air conditioning and heater. These devices, when fitted with Bluetooth Smart, can communicate with Bluetooth Smart-ready phones or tablets. Innovative apps can be developed to control the various elements of smartphones according to the person’s own requirements. BLE also provides secure wireless communication that ensures accurate metering and control of electricity consumption at home.

BLE supports assisted living, which allows elderly people to be remotely monitored by their children. A pillbox with an accelerometer and BLE can alert the user if the pills are not taken on time or the pill box is not opened. Using an accelerometer and BLE on home appliances, toilet seats and doors, the activity level of elderly people can be recorded on a smartphone. Their children can then be assured of the activity level of their parents and can reach help in case of an emergency without any manual intervention.

Today, infrared is the most popular media of wireless communication in a remote control. Infrared suffers limitations from its line of sight requirement and one way communication. BLE-compatible remotes do not need to be in line of sight and can also be used to make gesture-based remotes by integrating MEMS sensors. BLE-compatible remotes can even receive input from the main media such as turning on a remote LED light or finding the lost remote in a room. BLE has also made it possible to use Bluetooth Smart Ready smartphones as remote controllers. One just needs to add BLE in the main media and avoid the separate remote controller.

Industrial equipment can now send key performance and safety information without the need for long cables directly to a Bluetooth Smart Ready phone, tablet or computer. It allows for higher flexibility for machinery installation and easy integration into the network.

A small BLE proximity and anti-theft accessory, when tagged to pets and kids, can alert the smartphone if they sneak out of reach or are abducted by aliens. BLE-enabled car keys can be found easily with the help of a connected smartphone. Wallets and luggage tagged with BLE can alert the smartphone if someone trys to steal them. BLE supports proximity and “find me” profiles, which can seamlessly enable these applications.

BLE allows displaying many features such as bike mileage, trip, key parameters, etc. on a smartphone. ST’s BlueNRG also has integrated key identification, so 1 million unique codes can be implemented without an encoder/decoder circuit. This feature makes it possible to pair a bike or car with the right remote or smartphone. Thus BLE can also be used to implement “find me” lamps, which can help search for a bike in a parking lot.

Bluetooth Smart Certification

A Bluetooth Smart product needs to be certified by the Bluetooth SIG before it can be listed as a certified Bluetooth Smart product. A successful certification needs a qualified design listing, RF-PHY testing, qualification of stack and Bluetooth GATT-based profiles. ST offers a certified stack in both master and slave role, so additional stack qualification is not needed.

BLE is a bridge between hub devices such as smartphones to peripherals and accessories. It has revolutionized the innovation of IoT and wearable devices, and reduced human intervention in decision making. BLE is now supported by major new smartphones along with key operating systems, such as iOS, Windows and Android. And we are already seeing that BLE is becoming a standard feature. This presence of millions of Bluetooth Smart Ready smartphones, laptops and tablets has provided a platform for Bluetooth Smart accessories. BLE offers ultra-low peak power, the ability to run for years on coin cell battery and low cost, so it has become a preferred choice for connectivity. At STMicroelectronics, we are investing heavily in this technology and offer several sensors and analog products to complete the hardware offering.

STMicroelectronics
Santa Clara, CA.
(408) 919-8400.
www.st.com