Design Of Heart Sound Wireless Transmission System Based On Wi-Fi Technology

Cardiovascular disease has become a “Silent Killer” that resulted in the deaths of human beings. It has become the global health security problem because of its high incidence, and brings great challenges to the survival of human health. Heart sounds is a complex mixed signal which contains much cardiovascular physiological and pathological information, has closely contact with the heart, blood vessels and valves. Thus, heart sounds detection and analysis is an important means of noninvasive detection to evaluate cardiac function, and also provides a kind of important method for clinical auxiliary diagnosis of cardiovascular disease(CVD). Most traditional heart sounds detection methods that need a fixed heart sounds detection instrument and connected devices to acquit heart sounds signal from the human body. Obviously, the complexity of the wires connected the devices will bring extra psychological pressure and tension to patients, and it will have a certain deviation between the collected data and the real situation. On the basis of analysis of heart sound detection circuit and the network transmission protocol. In this paper, a kind of heart sounds wireless transmission system designed based on Wi-Fi technology.According to the systematic, modular thinking, this wireless transmission system can be contains four parts: heart sounds acquisition part, data processing part, data transmission part and power supply part. Heart sounds acquisition part, that is to say, the analog circuit part mainly includes: the heart sounds signal amplifying circuit, band-pass filter circuit, 50 Hz notch circuit, gain adjustment and level control circuits. Then the collected heart sounds signal goes into the MSP430F149 which has 12 conversion accuracy that could meet the requirements for A/D conversion. In this system, we need ± 5 V and + 3.3 V, so we need to design a suitable power supply module to provide power for the whole hardware circuit. Data transmission module includes Wi-Fi module and user control center software components, after A/D conversion, the data that stored in the disk and displayed on the screen at the same time. A wireless network sets up through Wi-Fi module and the digital signal transmitted to the remote server which implementations of the data receiving and display, filtering and storage operations.In this paper, the client and server part connected through Wi-Fi module, after setting the corresponding parameters and authentication codes the heart sounds datum can be rapidly transmitted. The server software mainly realized heart sounds datum receiving, waveform displaying and storage etc. In order to eliminate the interference of the heart sounds signal, this paper chooses five layer decomposition of ‘coif3’wavelet function to get heart sounds signal denoised to obtain a good effect. After wavelet denoising, we store the signals which could get parameter extraction and pathological analysis, so as to achieve the purpose of heart noninvasive detection. Function tests, heart sounds were collected through the terminal, there is no big difference of heart sounds waveforms between the oscilloscope and the end, it just burrs more mixed with noise in the process of transmission through Wi-Fi module. After the wavelet denoising, we get good effect of the signals. Thus, could make a good foundation for heart sound signal parameters extraction, heart sound recognition and pathological analysis. Finally, under the heart sounds acquisition circuit, the Wi-Fi module controlled by MCU and software platform work together, the system realized the heart sounds datum wireless transmission, and it can work stably.