CN101278834A - ECG wireless remote monitoring system based on GPRS - Google Patents

Abstract

The invention is a GPRS-based ECG wireless remote monitoring system, which belongs to the field of human physiological parameter detection and electronic medical instruments. The invention includes electrocardiographic electrodes, electrocardiographic amplifiers, a core processor, a serial port connected with the core processor, a liquid crystal display circuit, a GPRS module and the like. The detection end of the ECG electrode is connected with the human body, the output end of the ECG electrode is connected with the core processor through the ECG amplifier, and the ECG electrode transmits the collected ECG signal to the core processor. If the ECG signal is abnormal, the core processor sends an alarm message through the GPRS module, and at the same time transmits the ECG signal to the receiving end where the doctor is located through the GPRS module. If abnormal ECG occurs, the present invention will automatically send an alarm message through GPRS to reduce the risk of the patient's attack, and at the same time, the electrocardiogram at the time of the attack can be transmitted to the receiving end where the doctor is through GPRS for diagnosis and analysis by the doctor.

Description

ECG wireless remote monitoring system based on GPRS

technical field

The invention is a GPRS-based ECG wireless remote monitoring system, which belongs to the field of human body physiological parameter detection and electronic medical instruments.

Background technique

With the development of sensor technology, wireless communication technology and information technology, telemedicine and family health monitoring have gained a broader development space. The most commonly used in family health monitoring is ECG monitoring. At present, the health problems of the elderly have attracted more and more attention from the society. At the same time, according to the statistics of the Chinese Medical Association, nearly 60% of heart disease deaths occur within the family and community. Therefore, if the ECG abnormality can be detected in the early stage and the family members can be notified in time, the patient can gain valuable treatment time and improve the chance of survival. Medical practice shows that if heart diseases can be detected in time and treated appropriately, the survival rate of patients will be 70% to 80%. Therefore, the portable design of the ECG monitor has become an inevitable trend in the development of modern medical instruments. Most of the current ECG monitors are costly, complicated to operate, and use wired communication, which limits the scope of use of patients and fails to achieve the purpose of dynamic monitoring.

Contents of the invention

The purpose of the present invention is to provide a GPRS-based ECG wireless remote monitoring system. This system can achieve real-time ECG monitoring for patients, and can automatically analyze and diagnose patients' ECG, and can display three-channel ECG waveforms in real time on the LCD screen. If an abnormal ECG occurs, the system will automatically send an alarm message through GPRS.

In order to achieve the above object, the present invention adopts the following technical solutions. The system includes ECG electrodes, ECG amplifiers, core processors, serial ports, USB ports, JTAG ports, network ports, storage modules, liquid crystal display circuits, touch screen circuits and power management circuits; the detection terminals of ECG electrodes are connected to the human body, The output end of the ECG electrode is connected to the core processor through the ECG amplifier. The ECG electrode collects the ECG signal from the human body, amplifies and filters the collected signal and sends it to the S3C2410A for processing. The system also includes a GPRS module connected to the core processor. If the ECG signal is abnormal, the core processor sends an alarm message through the GPRS module, and at the same time transmits the ECG signal to the receiving end where the doctor is located through the GPRS module.

The system also includes a lead-off alarm circuit. The lead-off alarm circuit can light an alarm when the ECG electrode is separated from the human body, indicating that the lead is off.

The core processor selected is 32-bit processor S3C2410A.

The instrument uses a low-power 32-bit single-chip microcomputer as the core processor, and uses Linux as the operating system, which can achieve real-time ECG monitoring for patients, and can automatically analyze and diagnose the patient's ECG, and can display real-time on the LCD screen. Displays three-channel ECG waveforms. In case of abnormal ECG, the system will automatically send an alarm message through GPRS to reduce the risk of the patient's attack. At the same time, the ECG at the time of the attack can be transmitted to the receiving end where the doctor is through GPRS for diagnosis and analysis by the doctor.

Description of drawings

Figure 1: System Structure Diagram

Figure 2: Software flow chart of the sending end of the system

Figure 3: Software flow chart of the receiving end of the system

Figure 4: ECG signal amplification filter circuit Figure 1

Figure 5: ECG signal amplification filter circuit Figure 2

Figure 6: Schematic diagram of the system power supply

Figure 7: Schematic diagram of the LCD part of the system

Figure 8: Schematic diagram of other interfaces of the system

Figure 9: Overall connection diagram of the system

Detailed ways

The present invention is based on GPRS ECG wireless remote monitoring, and the system block diagram is shown in Fig. 1 . The system includes ECG electrodes, ECG amplifier, core processor, serial port, USB port, JTAG port, network port, liquid crystal display circuit, touch screen circuit, GPRS module and power management circuit. The ECG electrodes are connected to the human body and the ECG amplifier respectively. The ECG electrodes are used to collect analog signals and transmit the collected signals to the ECG amplifier. The ECG amplifier amplifies and filters the signals and sends them to the core processor. to process. The system can transmit data through the USB port and the serial port, and can also program the startup code through the JTAG port. At the same time, the system can be connected to the Internet through the network port. The ECG electrodes can directly collect three-channel ECG signals from the human body surface, and can detect the leads of the ECG electrodes. If looseness is detected, lights of different colors will light up to warn that the corresponding leads are off. The system uses a 32-bit single-chip microcomputer as the core controller, which can display the signal on the LCD screen. The LCD screen has the function of a touch screen. The system can also send the ECG signal to the receiving end through the GPRS module. The system is powered by batteries, and the input voltage is converted to the working voltage required by the system through the power conversion chip.

This embodiment adopts S3C2410A as the core processor, and S3C2410A adopts ARM920T core, CMOS standard macro unit and memory unit of 0.18um process, and its operating speed can reach up to 266MHz. S3C2410A has 8-channel 10-bit ADC and touch screen interface, so no additional ADC chip is needed, and it also has 3-channel UART, 2-channel USB host controller/1-channel USB device controller and 117 general-purpose I/Os, making the interface circuit The design is simpler, the integration is higher, the volume of the instrument is greatly reduced, and the portability of the monitor is enhanced.

The ECG amplification and filtering circuit of the system is shown in Figure 4 and Figure 5. It consists of a preamplifier circuit, a main amplifier circuit, a low-pass filter, a level boost circuit and a lead-off alarm circuit. The circuit uses 3 pieces of 8-pin IC chips AD620, 7 pieces of 14-pin IC chips LM342 and 2 pieces of 14-pin IC chips 74LS08, which have high gain, high input impedance, high common mode rejection ratio, low noise, low drift, and dynamic range. Large size, stable performance, and safe use. The ECG signal collected from the human body surface is extremely weak, the peak value of the general ECG signal is about 1mV, the frequency of the body surface ECG signal is mainly concentrated in 0.05-100Hz, and the center frequency is 17Hz, which is a weak low frequency bipolar signal. It is submerged in many strong interferences and noises, mainly from the influence of 50Hz power frequency interference. Therefore, in order to accurately measure the ECG signal, an amplifier and filter circuit with excellent performance must be designed, and the amplification factor must be at least 1000 times. In practical applications, the gain of the first-stage amplifier circuit usually does not exceed 100 times, and the higher the amplification factor will cause the circuit to oscillate, so we divide the amplifier circuit into two stages of amplification. We use AD620 as the first stage of amplification. AD620 is a low-power, high-precision instrumentation amplifier. It can adjust the magnification of 1-1000 times with an external resistor. Although AD620 is developed from the traditional three-op amplifier, some main performances are better than those made by Instrumentation amplifier composed of three operational amplifiers. According to the calculation formula of AD620 magnification $A_{}$${}_1=\frac{49.4\mathrm{K\Ω}}{R}+1$ The magnification of the first stage can be calculated. Among them, R is the resistance value between AD620 pins 1 and 8, here is the sum of the resistance values of R103 and R104, here we choose R103=750Ω, R104=750Ω. Calculated according to the formula, the magnification of the first stage is about 34 times. We use a signal generator to input a 20Hz sinusoidal signal with a peak-to-peak value of 20mV at the first-stage input terminal, and a 20Hz, peak-to-peak sinusoidal signal with a peak-to-peak value of 0.72V can be detected at the first-stage output terminal, which is amplified by about 35.5 times and basically conforms to Estimated magnification. The second stage amplifier circuit is realized by LM324. We input a 20Hz sinusoidal signal with a peak-to-peak value of 20mV at the input of the second-stage amplifying circuit, and measured a 20Hz sinusoidal signal with a peak-to-peak value of 892mV at the output of the second stage, which is about 45 times amplified. So far, the entire amplification circuit has been amplified by about 1530 times. Since the center frequency of the ECG signal is 17Hz, we only need to collect signals within 40Hz to describe the characteristics of the ECG signal and judge its abnormality. And through the low-pass filter of 40Hz, it can also filter out the influence of 50Hz power frequency interference and high-frequency signal. Since the internal A/D module of the S3C2410A single-chip microcomputer can only convert the signal of 0-3.3V, it is necessary to perform level conversion on the ECG signal so that its waveform is in the positive range. The voltage of the electrical signal. The portable ECG monitor is an instrument carried by the patient, and the lead wire is easy to fall off, which will introduce a lot of interference, resulting in distortion of the ECG waveform, making it difficult for the ECG monitor to output the actual waveform, resulting in distortion of the ECG signal. Misjudgment can affect the diagnosis result. Therefore, we designed the lead-off circuit, using one 14-pin IC chip 74LS08 and three 14-pin IC chips LM324 in the circuit, in order to achieve the alarm function when the lead is off. The ECG signal amplified by the ECG amplifier is simultaneously sent to the lead-off circuit for detection to determine whether the voltage is within the range of the lead-off, and if it exceeds the normal range, an alarm will be issued for the lead-off. We choose a three-color indicator light (red, yellow, green) to indicate that the lead is off, and each lead has a color indicator connected to it. When the lead is off, the corresponding indicator light will be on to indicate that the lead is off.

The communication mode of this embodiment adopts the GPRS wireless module, and the GPRS network covers a wide area, thus greatly expanding the range of activities of the user and improving the quality of life of the user. The GPRS module of the system adopts the GSM/GPRS dual-frequency module SIM100-E produced by SIMCOM. SIM100-E mainly provides wireless interfaces for voice transmission, short message and data services. SIM100-E integrates a complete radio frequency circuit and GSM baseband processor, suitable for developing some GSM/GPRS wireless application products, such as mobile phones, handheld devices, wireless POS machines and wireless data transmission services, with a wide range of applications. The SIM100-E module provides users with a fully functional system interface. The 60Pin system connector is the connection interface between the SIM100-E module and the application system, mainly providing external power supply, RS-232 serial port, SIM card interface and audio interface. SIM100-E has built-in AT command set and TCP/IP protocol. Under the control of the single-chip microcomputer, the existing GPRS network is used for signal processing and transmission, so as to realize the purpose of remote wireless monitoring. The SIM100-E module can quickly and reliably realize wireless communication functions such as data and voice transmission, short message and fax services. The system can send ECG signal data through GPRS, and the software flow of the system sending end is shown in Figure 2. After the system starts running, collect and display ECG data, and process the collected ECG signals to determine whether they are abnormal. Once abnormal ECG is found, the GPRS module is triggered to send an alarm message to the fixed mobile phone, and Send the abnormal ECG to the receiving end. The software process of the receiving end of the system is shown in Figure 3. The receiving end of the system is a PC connected to the Internet with a public IP. Then the PC runs the receiving end software, constantly monitors the connection request from the designated port, stores the data into the buffer when receiving data, converts the byte array into int data, analyzes the three-channel data and displays the ECG waveform on the screen.

The system collects ECG data from the human body surface, amplifies and filters them through the analog amplifier circuit, and then sends them to S3C2410A for processing. The AD module inside the single-chip microcomputer performs A/D conversion on the analog signal, and transmits the collected ECG waveform to until it is displayed on the LCD. The system can also be connected to a PC through a serial port and a USB port, or to the Internet through a network port. Since the system is a portable ECG monitor, it needs to be powered by batteries. The system uses 3 dry batteries for power supply, which is about 4.5V. The core operating voltage of S3C2410A is 1.8V, the operating voltage of the memory and external I/O is 3.3V, the LCD screen needs +5V, +15V, -10V to provide the bias voltage for normal display, and the +25V backlight voltage for driving the backlight LED and a backlight current of around 15mA. These requirements are difficult to achieve with a single power conversion, so multiple chips are required to achieve these voltages. The power circuit is shown in Figure 6. The system mainly uses three power chips LTC3441, LTC1911-1.8 and MAX1578ETG. The LTC3441 is a 95% efficient, fixed frequency buck-boost DC/DC converter that operates efficiently from input voltages above, below or equal to the output voltage. The design topology adopted by this chip can provide a continuous conversion through all operating modes. In the burst mode operating state, the quiescent current is only 25μA, which is in line with the low power consumption design of this system, so that its output voltage is at the battery voltage Ideal for single-cell Li-ion battery applications or multi-cell battery applications in the range. Burst Mode operation is under user control and can be enabled by driving the MODE/SYNC pin high. Fixed frequency switching is enabled if the MODE/SYNC pin is driven low or has a clock. The LTC1911-1.8 is a step-down charge pump DC/DC converter with an input voltage from 2.7V to 5.5V, an output voltage of 1.8V, and an output current of up to 250mA. Its main feature is high conversion efficiency, which is 25% (typical) higher than that of general linear regulators; the fixed 1.5MHz oscillator frequency not only provides low-noise regulated output, but its input noise is also higher than that of general regulated output. The pump is low, which reduces the capacity of the output filter capacitor; the power consumption is small, the quiescent current is 180μA, and it is 10μA when it is off; it has a soft start function; it has short-circuit and overheat protection; only 4 external capacitors (2 1μF capacitors and 2 10μF capacitor) can constitute a working circuit. PWREN on the CPU is an enable signal. When the system is powered off, PWREN will become low level, then VDD1.8 will stop supplying power, but it will not affect VDD1.8alive, and VDD1.8alive will supply power normally. VDD1.8alive powers the RTC and RESET of the CPU, so it keeps it in a powered state, which is conducive to the system's wake-up again. The MAX1578ETG provides four regulated outputs to meet all the voltage requirements of small active-matrix TFT-LCD displays used in handheld devices, where minimal external components and high efficiency are essential. Each device includes three advanced charge pumps for LCD bias supplies and a boost converter that can drive up to eight white LEDs in series for backlighting from an input voltage range of 2.7V to 5.5V. The charge pump provides fixed +5V, +15V, and -10V voltages for the LCD bias circuit without external diodes. A high-efficiency, fractional (1.5x/2x) charge pump followed by a low-dropout linear regulator provides the +5V for the source drivers. Automatic mode switching achieves the highest conversion efficiency. Two multistage, high-voltage charge pumps generate +15V and -10V to provide V _ON and V _OFF . Utilizing a clocking scheme and internal drivers, these charge pumps eliminate parasitic charging current pulse interference and reduce the maximum input current, thereby ensuring very low electromagnetic emissions. Sequential output is achieved at startup and shutdown. A high-efficiency inductive boost converter drives up to eight series-connected white LEDs for backlighting at a constant current. The series connection makes the current of each LED the same so as to unify the lighting brightness and minimize the connection of LEDs. The MAX1578ETG regulates a constant LED current over temperature. The MAX1578ETG is available in a space-saving 24-pin 4mmx4mm thin QFN package. Its efficiency is also relatively good, 83% for the charge pump and 84% for the boost converter. Therefore, the MAX1578ETG is very suitable for this system.

The digital circuit part of the system integrates LCD display module, serial port communication module, USB module, JTAG module, storage module and network card module, which can complete the functions of ECG signal collection, display, analysis and alarm.

The LCD display is the most important output device in the system. The LCD controller in S3C2410A can support both STN and TFT LCDs. The system uses Sharp's 3.5-inch transflective TFT-LCD: LQ035Q7DH02, and the LCD circuit is shown in Figure 7. Since LQ035Q7DH02 does not contain a controller, it needs to be used with a control circuit. The function of the LCD controller in the S3C2410A chip is to move the LCD image data from the display buffer in the system main memory to the external LCD driver. It can support up to 4K color STN display and 256K color TFT display, and support up to 1024×768 resolution Various LCD screens under the high rate, with LCD-specific DMA. The LCD controller inside the S3C2410A chip is used to control the transmission of image data, and its interface signals mainly include 24 data lines and 9 control signal lines. Since the LCD controller of S3C2410A and the display LQ35Q7DH02 cannot match in data format and display timing, it is necessary to select a timing control IC to map different data and timing. The timing control IC of the system chooses LZ9FC22 of Sharp Company. This chip is specially used for timing control of LCD with TFT QVGA screen (screen resolution is 320×240). This is an 18bit (R6G6B6) controller. Since the system uses the RGB565 16bit working mode, the two pins R0 and B0 actually do not input valid signals. In order to give full play to the data processing capability of S3C2410A, the system adopts two SDRAMs with 16-bit data width to be connected in parallel to form a 32-bit SDRAM memory system, which improves the communication efficiency with the CPU.

The system realizes the serial communication with the PC through the RS-232 serial port. Since the high and low level signals defined by the RS-232 standard are completely different from the high and low level signals defined by the LVTTL circuit of S3C2410A, the communication between the two must be converted through the signal level. Here we use MAX3232 to achieve. USB is an emerging computer peripheral serial communication interface standard. It overcomes the defects of traditional computer serial/parallel ports. It has the advantages of hot swap, plug and play, reliable data transmission, convenient expansion, and low cost. It has become the current computer One of the necessary interfaces is also widely used in the design of embedded systems. USB uses four cables, two of which are serial channels used to transmit data, and the other two provide power for downstream devices. It supports two data transmission rates. For high-speed and high-bandwidth peripherals, USB transmits data at a full speed of 12Mbps; for low-speed peripherals, it transmits data at a transmission rate of 1.5Mbps. The USB bus automatically switches between the two modes depending on the peripherals.

The Ethernet port is used to connect to the Internet. Our ECG monitoring system needs to implement the function of an embedded web server, so that the outside can access the device terminal and view the ECG waveform through the Internet. Here we use AX88796 as the network card to realize its function, and use the standard RJ45 interface to connect to the network. Ax88796 is a NE2000 compatible Fast Ethernet controller launched by Taiwan Asix Company. It integrates 10/100Mb/s adaptive physical layer transceiver and 8K×16-bit SRAM inside, and supports various CPU bus types such as MCS-51 series, 80186 series and MC68K series. Ax88796 implements 10Mb/s and 100Mb/s Ethernet control functions based on IEEE802.3/IEEE802.3u local area network standards, and provides IEEE802.3u compatible media independent interface MII (Media Independent Interface) to support other media on the application. In addition, Ax88796 also provides an optional standard printing interface, which can be used to connect printing equipment or as a general I/O connection. The circuit of each interface part of the system is shown in Figure 8. The final system needs to combine various modules and be as small as possible in size. Since the package of S3C2410A is a BGA272 spherical package, it is difficult to extract many signals from it. At the same time, considering that there are many high-speed signals in the circuit board, in order to eliminate crosstalk and electromagnetic interference between signals and make the system work stably, we adopt a six-layer board design. The overall connection diagram of the system is shown in Figure 9.

Using this monitoring system, we carry out the following steps of testing. First open the HyperTerminal. After the system is powered on, a command prompt will appear on the HyperTerminal, indicating that the system has started. When a penguin icon appears on the upper left corner of the LCD screen, it means that the system startup is complete. If you run ./button on the HyperTerminal, the system will start to detect ECG, and then the system will perform ECG detection and analysis, and the screen will display the detected ECG signals of the three channels of I, II and III and heart rate. When the system detects abnormal ECG, it will touch the GPRS module to send alarm information to the mobile phone, and send the abnormal ECG data to the receiving end. The system can detect a variety of abnormal ECG signals (tachycardia, bradycardia, arrhythmia, arrest, missing beat).

In order to further verify the effectiveness and accuracy of the system, we compared the detection results with the actual parameters of the ECG waveform generated by the ECG signal generator, and the results are shown in Table 1. It can be seen that the heart rate parameters of the detection results are basically consistent with the actual ECG signal parameters, which reflects the accuracy of the system. At the same time, in order to verify the accuracy of the data received by the GPRS receiving end, we compare the ECG signals of the sending end and the receiving end. The heart rate sent by the sending end is 140 beats per minute. About 10 ECG cycles. The receiving end can correctly receive and analyze the ECG signal. The receiving end shows that it has received 10 ECG cycles. We choose one of the channels to analyze the ECG data. Here we choose the ECG signal of the third channel. According to the electrical signal analysis, his average heart rate was 139 beats per minute.

The test results show that the ECG monitor is easy to operate, works stably, and can monitor and alarm ECG signals in real time.

Table 1 Comparison of test results

serial number 1 2 3 4 5 6 7 8 9 10 Actual heart rate (times/minute) 30 40 45 60 80 90 100 110 120 140 Measure heart rate (times/minute) 30 42 47 60 80 90 101 110 121 141

Claims (3)

1,, includes electrocardioelectrode, ecg amplifier, core processor, serial ports, USB mouth, JTAG mouth, network interface, memory module, liquid crystal display circuit, touch screen circuitry and electric power management circuit based on the electro cardiscope wireless remote monitoring system of GPRS; The end of probe of electrocardioelectrode links to each other with human body, and the outfan of electrocardioelectrode links to each other with core processor by ecg amplifier, and electrocardioelectrode sends the electrocardiosignal that collects to core processor; It is characterized in that: also include the GPRS module that links to each other with core processor, if electrocardiosignal is unusual, core processor sends warning message by the GPRS module, also electrocardiosignal is transferred to the receiving terminal at doctor place simultaneously by the GPRS module.

2, the electro cardiscope wireless remote monitoring system based on GPRS according to claim 1 is characterized in that: also include the warning circuit that comes off that leads.

3, according to claim 1 or the described electro cardiscope wireless remote monitoring system based on GPRS of claim 2, it is characterized in that: that described core processor is selected for use is 32 bit processor S3C2410A.

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