Understanding Low Power Bluetooth Applications

The Bluetooth Special Interest Group (SIG) introduced the Bluetooth 4.0 specification in 2010, which included low energy Bluetooth that meets the demand for low-power wireless connections in small battery-powered devices, leading to widespread adoption. This article will take you deep into the applications of low energy Bluetooth.

Introduction to Low Energy Bluetooth

In 2010, the Bluetooth SIG renamed low-power wireless technology to “Bluetooth Low Energy” (Bluetooth LE) and launched the Bluetooth 4.0 specification. Bluetooth Low Energy (BLE) technology, also known as Bluetooth® Smart, has been part of the core specification since Bluetooth V4.0, specifically designed for functionalities and applications built for Internet of Things (IoT) devices, with the main feature of reducing costs and power consumption. It meets the requirements for low-power wireless connections in small battery-powered devices, significantly extending battery life, with some devices operating for years on a button cell battery. Currently, Bluetooth Low Energy technology is widely used in applications including: location tags, asset tracking, sports and fitness sensors, medical sensors, smartwatches, remote controls, toys, etc.

Guangzhou Zhiyuan Electronics Co., Ltd. has launched multiple series of low energy Bluetooth modules for different application scenarios, including the ZLG52810 series slave Bluetooth module, ZM52820 series master-slave Bluetooth module, and ZM8258 series master-slave Bluetooth module. The products meet the needs of low-power wireless communication for small battery-powered devices and support two low-power modes, with the lowest power consumption reaching nA level. Users can configure the appropriate power mode for their devices based on usage scenarios using AT commands.

• Normal sleep mode: The serial port stops working, and the module’s power consumption reaches uA level, while the protocol stack operates normally, waking up through the wake-up pin or when the module receives BLE data.

• Deep sleep mode: Most peripherals are turned off, the protocol stack stops operating, entering deep sleep mode, with the lowest power consumption reaching nA level. To wake the Bluetooth module, the wake-up pin can be used.

How Low Energy Bluetooth Achieves Low Power Consumption

1. Shorter Advertising Time

BLE has 40 channels, of which 37, 38, and 39 are advertising channels, also known as primary advertising channels. The primary advertising channel can advertise a maximum of 31 bytes, while the remaining 37 are data channels, also known as secondary advertising channels. When large data packets need to be broadcasted, they must be sent through secondary advertising channels with lengths ranging from 0-255 bytes. To achieve low power consumption, Bluetooth typically broadcasts once on each of the three primary advertising channels, with the radio frequency on time reduced from the traditional 22.5ms to 0.6-1.2ms.

2. Lower Standby Power Consumption

Low energy Bluetooth replaces the idle state of traditional Bluetooth with a deep sleep state. In the deep sleep state, the host remains in an ultra-low load cycle state for a long time, and many interfaces are turned off during sleep, activated only when needed by the controller, saving the most energy and achieving deep sleep.

3. Software Layer Optimization

• Efficient encoding methods can send the same amount of data in less time, thereby reducing power consumption;
• Compared to traditional Bluetooth, low energy Bluetooth supports ultra-short packets, which requires less time to send, while faster startup times shorten the waiting time for transmission and reception;
• Low energy Bluetooth uses only one protocol to achieve server discovery, name discovery, and information reading and writing, requiring less overhead than classic Bluetooth that uses multiple protocols, thus reducing power consumption;

• The low energy Bluetooth protocol adopts a client-server architecture, reasonably distributing tasks between the client and server to reduce communication overhead in the system.

Common Low Energy Application Scenarios

1. Smart Door Locks

In the application scenario of smart door locks, by installing a Bluetooth module inside the lock, users can read the Bluetooth information of the smart lock in real-time through an app, pair it, and send an unlock request to the server. The server then sends the unlock command to the phone, which receives the unlock information and sends the command to the smart lock via the Bluetooth module, making unlocking convenient, fast, and secure.

Figure 1 Smart Door Lock Application

2. Smart Healthcare

Currently, health monitoring devices are typically wearable products that can receive and analyze health data via Bluetooth modules, serving real-time monitoring purposes. Typical products include: bracelets, watches, smart scales, blood glucose meters, blood pressure monitors, pulse oximeters, heart rate bands, activity sensors, etc.

Figure 2 Healthcare Products

3. Smart Lighting

Low energy Bluetooth smart MESH lights utilize low energy Bluetooth technology and MESH networking technology. By simply installing an app on a smartphone, users can achieve smart networking control of lighting, which is more convenient and flexible, while also supporting remote control devices.

Figure 3 Smart Lighting System

4. HID Device Applications

Using low energy Bluetooth technology, compared to traditional Bluetooth keyboards and mice, it features lower power consumption and faster, more convenient pairing connections. Existing mice and keyboards can be upgraded quickly by adding BLE.

Figure 4 HID Device

5. Smart Home Appliances

In traditional home appliances, such as soymilk machines and rice cookers, low energy Bluetooth control can upgrade them to smarter devices. Users can control home appliances through smartphones for switching, scheduling, and other functions, as well as conduct self-diagnosis and firmware upgrades.

Figure 5 Smart Home Appliance Products

6. iBeacon Applications

iBeacon broadcasts information to phones based on low energy Bluetooth, helping businesses optimize their operational strategies by providing services based on users’ geographic locations. Utilizing low energy Bluetooth offers more stable and reliable performance with lower power consumption, allowing devices to maintain longer operational times.

Figure 6 iBeacon Application Scenario

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