Research On Weak Eeg Extraction Method Using3-lead Electrode Based On STM32

With the advancement of society, humans are paying increasing attention to thebrain research, and many nations in this world regard the21stcentury as the age of brain,which show that man want to uncover brain’s mysreries eagerly. Recently, China hasproduced several kind of EEG acquisition equipments that represent the Chineseachievements in this field. However, their performance is greatly inferior to the foreignones, and the core components mainly rely on imports, which makes them moreexpensive and restricts the domestic study on EEG. Therefore, it is of great practicalsignificance and application value to develop EEG acquisition devices with independentintellectual property rights.EEG is a weak and low-frequency signal, whose amplitude is just microvolt andfrequency is less than150Hz. Besides, it is vulnerable to external signals and theinterference from human body. Taking a variety of factors into consideration, this paperdesigned a EEG acquisiton system based on STM32. In this system, EEG signals aresensed when biological electrodes have good contact with the skin, then they can beamplified and filtered in the preprocessing circuit. After that, EEG signals are conventedto be digitals using12bit ADC. Under the control of STM32, digitized EEG signals arenot only displayed on the LCD, but also transferred to the PC via Bluetooth module. Inorder to make EEG more pure, the baseline drift, frequency interference and ocularatrifacts are removed respectively by programming the MATLAB codes. In this paper,the control program for EEG acquisition system was developed in the C/OS-IIandC/GUIembedded operating platform, and then it was transplanted to STM32. Theupper computer was controlled by the E-language program with the function ofsampling signal, preservating data, displaying waveform and adjusting parameter, andthe interface is user-friendly, hard real-time and high accuracy.Finally, some relevant comparison experiments were designed to test the systemperformance, including the signal acquisition test, wireless transmission test and dataprocessing test. Results showed that the system can sample EEG accurately bycomparing with the foreign EEG acquisition equipment, and the reliable transmissiondistance for Bluetooth module is5meters in the environment with obstacles. In addition,the interferences were effectively removed, which indicates the actual processing results are consistent with the theoretical analysis. Therefore, this system achieves the expectedgoal. At the same time, it lays the foundation for further research on EEG.