| In recent years,with the rapid development and increasing perfection of intelligent and wearable technology,more and more intelligent wearable products appear in our lives.The areas covered by these intelligent wearable products are also broadened from the field of entertainment information to the areas of sports life and health care.The emergence of intelligent wearable products makes people’s lives become more and more intelligent.Combined with the background of intelligent wearable technology,taking the fact that in recent years children are often forgotten in the car be in danger into account,this paper will be designed to prevent such accidents occur in children wearing a heart rate monitoring and anti-lost system.The difference between this system and other children’s anti-lost systems that have emerged on the market is that most of the children’s anti-lost products on the market are designed solely for the purpose of preventing the loss of children.Some simple anti-lost device is only through the distance set to achieve a simple anti-lost function,this anti-lost products generally not have an accuracy.And some high-end children’s anti-lost products have added the GPS positioning,GSM location query and GPRS communication technology to track the location of children’s information.Such products are powerful,but costly and useful for preventing children from being forgotten in the car.So this article is based on the NRF51822 wearable heart rate monitoring and anti-lost system.As the name suggests,in function,the system in addition to have lost the reminder function,but also added a heart rate monitoring function.As long as in the communication range,even leave the child in the car deliberately,parents can also see the state of the child through the heart rate monitor to avoid accidents.The system is based on a Bluetooth 4.0BLE chip NRF51822,combined with heart rate sensor,heart rate algorithm and RSSI ranging technology,the use of BLE wireless communication technology and Andrews smart phone to communicate with a wearable heart rate monitoring and anti-lost system.The system as a whole is divided into two parts.One is the intelligent wearable products that can wear in the children,this part is defined as a slave,which is part of this paper will focus on the study.Second,the parents carry smart Andrews mobile phone,this part is defined as the host.And the communication between the slave and the host will through Bluetooth 4.0BLE technology to complete the master and slave data interaction.The system is expected to achieve the overall function,when the slave and host through the BLE technology connection,the host can be from the machine wearer heart rate monitoring,when the wearer’s heart rate exceeds the host’s preset heart rate range,the host on Will be prompted to alert the police,so as to achieve the purpose of monitoring the child’s heart rate.Another function is based on the principle of RSSI distance measurement,when the distance from the host and the host beyond the default range of the host,the host will send an alarm signal to remind the host carrier,the slave has been lost,so as to achieve the purpose of forgetting.The communication between the slave and the host is one of the important aspects of the system design,so the Bluetooth 4.0BLE technology will be introduced in Chapter 2 of this paper,including the development of Bluetooth,Bluetooth 4.0BLE technical characteristics,protocol stack Characteristics and characteristics of network topology.In addition,as the system of two important functional modules,heart rate monitoring module and anti-lost module.The techniques involved will be introduced in Chapter 2 too,such as the heart rate acquisition technique used by the heart rate monitoring module and the ranging technique involved in the anti-lost module.In the hardware design of the slave,this article will use the modular design,that is,the slave in the hardware structure is subdivided into the various modules for design.This part will be divided into three modules from the overall module,namely,the controller module,heart rate acquisition module and power supply module.The design of the controller module is based on the master chip NRF51822 for a series of peripheral configuration circuit design,such as: clock circuit design,reset circuit design antenna matching circuit design.Heart rate acquisition module is mainly through the sensor to complete the heart rate signal acquisition and processing.In the design of the power module,this paper not only to the power supply module design,will also increase the charging module and battery power detection module hardware circuit design.In this paper,the software design of the slave is mainly for the master chip NRF51822 programming.The communication link,the realization of heart rate monitoring function,the realization of RSSI anti-lost function and the realization of battery power detection function will be designed in this paper.In this part,we will also introduce the heart rate algorithm and RSSI distance principle in detail.Finally,the system functions will be tested in two ways.Firstly,by capturing the Bluetooth broadcast channel and data channel data packets,the data analysis to determine the system function to achieve the situation.Secondly,through the corresponding APP on the system to verify the function. |
