Design Of Smart Wristband Based On Bluetooth Low Energy

Bluetooth Low Energy transmission based smart wristband belongs to wearable devices. In recent years, with the rapid adoption of smart phones and tablets, people wish to have more diverse ways to interact with the smart devices, which makes the demand of wearable device; Bluetooth SIG released the Bluetooth low energy protocol standards in 2010, which provided the technical foundation of low-power wireless transmission for wearable devices.The main work of this paper is to design a smart wristband, using BLE wireless technology. Smart wristband contains two main functions: data encryption and motion recognition. Motion recognition function uses an accelerometer chip to recognize walk-pace, wrist-turn and tap. The data encryption function uses an encryption chip to encrypt the raw data and transfer it back to the smart phone through BLE connection. The system also contains LED time display, and Over the Air Download function. LED time display function uses 12 dual-color LEDs in a circle, to imitate a watch to display the time; the Over the Air Download function make the device update its firmware within BLE connection.On hardware design, according to the requirement of function and design goals to decide the hardware structure and components selection, and then design schematic of the main MCU module, the accelerometer module, extension IO chip module, LED, keys and battery detection module.In this paper, the software design contains the design of software process and its implementation based on OSAL, OSAL based application task design, BLE GATT customized profiles design, motion recognition and calculating algorithm design and the implementation of OAD function. The software process design realizes the basic user function; the smart wristband works as GATT server in a BLE connection, so it contains several GATT services. The paper design two costumized BLE GATT profiles to provide the two main function, data encryption profile and personal exercise information profile; the motion recognition and calculating algorithm details the pace detection, tap detection, and wrist-turning detection; The OAD design part expounds its working principle and implementation method.After all, we test prototypes of the smart wristband about the performance and function, including RF carrier test, BLE communication test, BLE GATT services verification, power consumption test. The testing and verification result show that the design meets the expected requirement.