An Embedded EEG Analyzing System Based On μC/os-Ⅱ

The 21st century is recognized by the world scientific community as the age of biological science and brain science.Advances in technology,humanity has a deep knowledge of the external world,but human awareness of its own brain is very superficial.In the promotion of global research projects,the research of human brain cognitive progress has become one of the mainstreams of contemporary scientific research.The brain cognitive function is a very complicated brain function process.EEG analyzing plays a very important part in the current research of the cognitive function.At present,the analyzing system used for brain cognitive research is too expensive to popularize. Therefore,a new high-performance and low-cost EEG analyzing system based on embedded system is very necessary.An EEG analyzing system based on Advanced RISC Machines(ARM)andμC/os-Ⅱreal time operating system is discussed in this paper.This system consists of two parts:EEG measurement and PC(personal computer).EEG measurement is connected with the PC by USB interface.The design of EEG measurement is the focus of this paper.The design of hardware and software of EEG measurement are completed.The data acquisition experiment is done using the EEG acquisition and analysis software SDUND which is developed by the laboratory independently.The experiment shows that the capabilities of this equipment are satisfied.The following works are completed in this paper.1)The design of high-performance EEG pretreatment circuit including amplification,filtering and A/D converter are described.The performance of EEG pretreatment circuit depends on preamplifier primarily.In this paper the high-precision instrumentation difference Operational Amplifier AD620 is selected to build amplifier circuit. 2)The hardware design of embedded subsystem is completed.An ARM microprocessor S3C44BOX is used as the core of the embedded system.The design of power supply,JTAG interface,reset,crystal,the memory and USB interface circuit are discussed.The BootLoader program of S3C44BOX is also discussed.3)TheμC/os-Ⅱreal-time embedded system is transplanted in S3C44BOX successfully.In this paper software design is based onⅡC/os-Ⅱ.Introduction of an operation system can manage programs more easily and make the structure of software clear.More importantly,its software can upgrade conveniently for further development.The design of communication software is completed.The driver of USB is developed in the base ofμC/os-Ⅱ.The system function is divided into five modules,signal acquisition,data preprocessing,parameter setting,order implementing,ordinary transmission and synchronous data transmission.4)A simple experiment of evoked EEG acquisition is done using the EEG acquisition and analysis software SDUND.This system uses hardware interfaces to deal with the synchronization of events.It uses 8 channels signal 0V/5V to distinguish eight different stimulations because brain cognitive research has to deal with ERP under different stimulations.Synchronization signals of different stimulations are acquired while recording EEG signals,then these signals are processed together.The system can accurately measure the EEG signals and synchronize the ERP signals and the stimulating signals.Therefore,this system can provide us with the event flag in the offline analysis of ERP.So it is a considerably useful experimental tool in brain cognitive research.It also supports us with a reliable experimental tool and analyzing platform for the Brain-Computer Inteface.