The Design Of ECG Signal Processing System Based On ARM Processor

1. IntroductionHeart disease is the main threaten to the human's life. With the aggravatingof aging population in our country, the number of people who were dead becauseof heart disease is increasing for years. How to prevent and treat heart disease hasbecame to a main problem of medical circle.The electrocardiogram is the basis ofdiagnosing heart disease. The display of electrocardiogram is displayed byelectrocardiogram signal which has been processed. The electrocardiogram signalis one of the first bioelectricity signal which has been studied and applied tomedical clinic. Comparable to another bioelectricity signal, electrocardiogramsignal is apt to detection and has a visualized regularity. Since 1993 theelectrocardiogram has been lead to medical clinic, no matter in the aspect ofbiomedicine, or in the field of engineering, it has been greatly developed in thetechnology of electrocardiogram signal record,processing and diagnosing, and wehas accumulated much important material. At present, the processing ofelectrocardiogram signal is one of most important object in the field ofbiomedicine engineering.The electrocardiogram signal processing system is the key component ofelectrocardiogram signal process, it can through high noisy environment anddetect weak electrocardiogram signal by poles, and then via amplifying and A/Dtransforming to process by computer. The use of computer makes the system moreadvantaged than other traditional electrocardiographs in the aspect of signalanalysis,memory and printing. But the communication interface between theprocessing system and computer communication interface has much problem,such as trouble with plug in and pull out, lack of safety, low speed of transmissionand processing. Therefore, in this thesis, the artical realize a electrocardiogramsignal processing system based on 32bit ARM processor and USBcommunication.2. Research ContentThe purpose of the thesis is to realize digital and portable electrocardiogramsignal data processing system. The electrocardiogram signal is transmitted tocollection case by sensor, then becomes digital signal though amplifying andfiltering. The core of the digital transmission and processing is the 32bit ARMprocessor S3C44B0X, which transmits digital signal to computer by USBinterface, then processed and shown by the computer.The construction of this paper has six parts:(1) Introduction of electrocardiogram and Electro Cardio Gram systeThe electrocardiogram is the electricity excited curve of the processed weakheart electrical signal generated by human heart. It plays an important part inclinic diagnoses. The choice of the lead is also very import to the assisteddiagnoses.This part first introduces the function of electrocardiogram and the conceptof Electro cardiogram, describes the significance of electrocardiogram in theclinical medicine.(2) The design of the analog circuitBecause of the weak character of the electrocardiogram signal (0.05~50mV)and the big background noise, emitter follower is designed to enhance the inputimpedance. In this way, the CMRR (Common Mode Rejection Ratio)of the signalis enhanced The anterior stage uses low cost and high accuracy amplifier chipAD620.to enhance the CMRR. Active band-elimination filters are adopted toreduce the 50Hz disturbance behind the amplificatory stage. The latter stageadopts LM358 to make the signal scope suitable for the A/D conversionThis part also introduced the A/D conversion circuit and program controlamplifier circuit. We used a high accuracy, high conversion speed chip MAX187as the A/D converter and two pieces of multichannel strobes to realize the choiceof channel and program control plus.(3) The design of the digital circuitA high speed and real-time processing is the system demand to the digitalpart.The core processor of the digital circuit is a 32bit ARM processor S3C44B0X,which has powerful control function and many enhanced peripherals. Thisprocessor has many advantages ,such as low power,low cost and good capability.The embedded software uses Real-time Operating System μC/OS-II to dispatchand distribute resources, which makes the system has good reusability andinhibition. The system software is preserved in FLASH ROM, when systemoperates, the program and data will be copied in high speed SDRAM to run andprocess.(4) The design of USB protocol transmissionIt concludes three parts design :hardware circuit,firmware program and PCdrive. The part of hardware uses PDIUSBD12 chip which is supported USB1.1protocol. Based on USB1.1, it introduces the structure and the realization processabout the USB1.1 protocol and PDIUSBD12 firmware program. The system USBtransmission utilizes asynchronous mode and three end points, one control endpoint used in transmission demand and other two data end points used inelectrocardiogram signal data. End point 1 is used to transmit the systemparameter and end point 2 is used to transmit the electrocardiogram data.(5) The study of the algorithm of electrocardiogram signal preprocessingIt includes the insulation of the 50Hz work frequency interference andcorrection of baseline drift. It includes the cancelling of the 50Hz in the signal andcorrect the base line The experimental result indicated that the pretreatmentalgorithm has obtained a good effect.(6) The design of electrocardiogram signal workstationIt includes the realization of USB driver program and user interface shown.Based on WDM(Windows Driver Model) structure, it describes the developmentof USB host driver program used Driver Studio. It introduces and displays thefunction of electrocardiogram signal workstation and the user interface ofobserving electrocardiogram signal waveform. The paper finally introduced themain interface and the main function module of the workstation based on thedatabase.3. ConclusionThe paper realizes amplifying, multi-collection and real-time transmission ofthe electrocardiogram signal in hardware, and the process,display and memory ofthe electrocardiogram signal data in software. It realizes the digitization andinformatization of the electrocardiogram signal processing system.The result shows, the gathering and processing of the system has improvedthe precision and stability of ECG signal. The system reachs the anticipatedtechnical indicator, has offer the foundation for the new ECG signal processinginstrument. The system has broad application prospect and practical value.