Design Of Multi-Channel ECG Acqusition System

In modern society, more people are increasingly strong demanding for ECG monitoring equipment. Some patients with mild heart disease or in the recovery period need the equipment to monitor their situation of heart in daily lives; Some patients suffering from heart attacks may need a long period of observation to capture some special information. And there are a number of patients can't always go to the hospital for treatment. Based on the above situations, the design of a kind of portable ECG devices which can real-time detecting of the human heart, and analysing data, is of great significance for the early detection and treatment of heart disease.This paper introduces the multi-channel portable ECG equipment based on international standard12-lead ECG. the device from the analog board and digital board.Analog circuit board is composed of input buffer circuit, preamplifier circuit,50Hz notch circuit, high-pass filter circuit, low-pass filter circuit, main amplifier circuit, level uplift circuit, A/D conversion circuit of MSP430and the channel inspection circuit. The main function of these circuits is to amplicate and filter collected ECG signals, Suppress common-mode interference in the signals. Ultimately, sent the conditioned ECG signal to integrated A/D converter of MSP430for conversion of analog to digital. On the peripheral circuits of MSP430, by the use of external+3.3V supply for energy, and low frequency crystal oscillator of frequency of32768Hz as auxiliary clock for TimerA, so that can controlling the sampling frequency of ADC12. On the software of A/D conversion, it should to configurate the ADC12for sequence of channel single conversion mode, and the sampling frequency is controlled at500Hz. Finally, tranmissing the signal to ARM by the use of the serial port of baud rate of11520bps.The circuit of the digital board is mainly composed by the ARM (S3C2440) processor and associated peripheral circuits, wireless transmitter module circuit and wireless receiver module circuit, the master of wireless transmitter module is ARM processor, and wireless receiver module is AT90S8515. ARM processor is to complete the digital processing of ECG data, Flash,SD card as data memories, TFT touch screen display device to play the role of human-computer interaction. As ARM processor communication with PC terminal, the system uses wireless transmission to replace the traditional RS232serial or USB port, so that the use of ECG equipment not subject to the constraints of the short distance. Wireless transmitter module and receiver module controlled respectively by ARM and AT90S8515microcontroller, sending or receiving data by the use of nRF905chip to complete communication of wireless ECG data transmission. In the receiver module, AT90S8515transmiss the data to the PC terminal by the USB port that PC to complete the final data analysing and procession.