The main part of the system is intelligent ECG monitoring and analysis, which assists the above computer storage and display software. According to the system requirements, the ECG monitor can not only collect ECG data and display ECG waveforms in real time, but also have the function of displaying heart rate and data analysis in real time. To achieve these functions, you need a powerful processor with rich peripheral interfaces and high-speed real-time ECG signal processing. Due to the friendly design concept of human-machine interface, multiple pictures will be displayed during the operation, which puts high requirements on the storage space of the processor. Based on the above considerations, the system selected the BF533 (7.1) development board of Yiqi Company as the design motherboard. It contains external ports such as touch screen, SPI, SPORT, UART and contains 128Mbytes of synchronous storage space, which meets the design requirements of this system.
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The intelligent ECG monitoring analysis is mainly divided into three parts: front-end analog signal acquisition, data processing and analysis, and data transmission. The design of the front-end circuit includes an amplifier circuit, a lead selection circuit, a filter circuit, an AD conversion circuit, and the like. The monitoring analyzer uses ADSP-BF533 as the processor, cyclically collects 8-lead ECG signals, calculates heart rate in real time, and can perform simple condition analysis, and finally gives ECG health index. The system can store the collected ECG signals in a systematic manner to facilitate the user to view historical data, and can also transfer the collected data from the serial port to the host computer program.
The upper computer software can store and display the received data, and can calculate the important ECG parameters such as heart rate and QRS interval, which is convenient for the doctor to further diagnose. The overall structure of the system is shown in Figure 1.
Functions and indicators
Intelligent ECG monitoring and analysis part
(1) Acquisition function: The front-end analog acquisition circuit can accurately collect 10-lead ECG signals: RA, RL, LA, LL, V1 to V6.
(2) Display function: After the user enters the lead selection interface, he can arbitrarily select one guide display in the 12-lead standard ECG signal, or select 12-channel all display.
(3) Historical data reading function: After entering the system, the user can choose to newly collect or read historical data.
Historical data has historical data collected by each family member last time.
(4) Real-time heart rate calculation function: When any one of the display ECG waveforms is selected, the real-time heart rate calculation result is displayed.
Heart rate measurement accuracy: ± 1 time / minute.
(5) Automatic analysis function: After collecting the ECG signal for a period of time, the detection analyzer will automatically perform data analysis, and give the disease analysis and ECG health index.
(6) Lead-off detection function: If a 50Hz sine wave and its harmonic waveform are displayed during the detection process, it indicates that the lead is off or not connected.
PC software part
(1) Communication function: Receive the ECG signal data collected by the analyzer through the serial port.
(2) Storage function: Save the data in the host computer and call it at any time.
(3) Display function: You can select any one of the ECG signals to be displayed in the window, and access the telemedicine expert consultation through the Internet to facilitate the doctor to observe the diagnosis.
(4) Parameter calculation function: Calculate and display important parameters such as heart rate and RR interval of ECG signal to assist doctors in diagnosis.
hardware design
The hardware acquisition part of the front end mainly performs functions such as ECG acquisition, amplification, filtering and AD conversion. The entire hardware block diagram is shown in Figure 2.
According to the design requirements of the standard 12-lead, it is necessary to collect 10-lead ECG signals at the front end of the circuit, which are the right arm electrode RA, the left arm electrode LA, the right leg electrode RL, the left leg electrode LL, and the chest six electrodes V1 to V6. The right leg drive is mainly used to eliminate common mode signals such as 50/60 Hz and displacement current. The LA, LL, V1~V6 eight-conductor signals are transmitted to the AD8221 amplifying circuit through the input buffer stage amplifying circuit as an input terminal; the RA is sent to the AD8221 as a reference end signal through the same parameter buffer stage amplifying circuit. After amplification by AD8221, eight signals LA-RA, LL-RA, V1-RA to V6-RA are obtained. The eight-way signal is separately sent to the input end of the lead selector, according to the output of the address selection signal, and then transmitted to the BF533 SPORT via a 50 Hz notch circuit, a high-pass, a low-pass filter circuit, a level-up circuit, and an AD conversion circuit. Port for subsequent digital signal processing.
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