Electrical impedance detection system based on FPGA

Abstract

The invention belongs to the technical field of biological detection, and provides an electrical impedance detection system based on an FPGA (Field Programmable Gate Array), which comprises an FPGA main control board, an impedance measurement chip, a peripheral circuit of the impedance measurement chip, an RS232 serial port transmission module, a PC (Personal Computer) end upper computer and a power supply module, the power supply module supplies power to the FPGA main control board, the impedance measurement chip, the peripheral circuit of the impedance measurement chip and the PC end upper computer, the FPGA main control board is arranged between the PC end upper computer and the impedance measurement chip and the peripheral circuit of the impedance measurement chip, the impedance measurement chip is connected with the FPGA main control board through an I2C bus, and the FPGA main control board communicates with the PC end upper computer through the RS232 serial port transmission module. The electrical impedance detection system is higher in detection precision, better in stability and low in power consumption and cost, and has extremely high production and application value.

Description

Technical Field

[0001] The invention belongs to the technical field of detection and monitoring, and relates to bioelectrical impedance detection, in particular to an electrical impedance detection system based on FPGA. Background Art

[0002] With the continuous development of modern medical technology, people are paying more and more attention to their own health problems. Nowadays, various human health testing equipment has become popular, such as blood glucose meters, blood pressure monitors, etc. These devices can easily help people conduct health tests and obtain human health data, so as to better understand their own health status. However, most of the current health detection systems have certain limitations, and the test signal is single. This singleness limits the accuracy and applicability of the system, making it difficult to fully evaluate the health status of organisms. The bioimpedance detection system can reflect various status information of organisms by testing bioimpedance information.

[0003] The bioimpedance system mainly obtains bioelectric signals by measuring the resistance and conductivity of the human body to electric current. When electric current passes through the human body, the resistance and conductivity of different tissues will cause changes in the current. By measuring these changes, the system can calculate the bioelectrical impedance of the human body. The bioelectrical impedance detection system usually includes electrodes and measuring equipment. The electrodes are on the surface of the human body and are used to transmit current and voltage signals. The measuring equipment is used to control the generation of excitation signals, collect response signals and process and calculate. Using the bioimpedance system, the bioelectrical signals of the human body can be obtained at low cost and non-invasively. However, most of the existing bioimpedance systems have low acquisition efficiency and low accuracy of the measured impedance data. Summary of the invention

[0004] The purpose of the present invention is to provide an FPGA-based electrical impedance detection system that can quickly, stably and accurately collect the bioimpedance information of the human body.

[0005] The technical solution adopted by the present invention to achieve the above-mentioned purpose is: An electrical impedance detection system based on FPGA comprises an FPGA main control board, an impedance measurement chip and its peripheral circuits, an RS232 serial port transmission module, a PC-end host computer and a power module. The power module supplies power to the FPGA main control board, the impedance measurement chip and its peripheral circuits and the PC-end host computer. The FPGA main control board is arranged between the PC-end host computer and the impedance measurement chip and its peripheral circuits. The impedance measurement chip is connected to the FPGA main control board via an I2C bus, and the FPGA main control board communicates with the PC-end host computer via the RS232 serial port transmission module.

[0006] The impedance measurement chip adopts the AD5933 chip, which integrates a digital frequency synthesis signal generator, a digital-to-analog converter, an integrated amplifier circuit, a gain-amplifying low-pass filter, an analog-to-digital converter and a digital signal microprocessor; the digital frequency synthesis signal generator is connected to the epidermis to be measured through the digital-to-analog converter and the integrated amplifier circuit, and the epidermis to be measured is then connected to the digital signal microprocessor through the gain-amplifying low-pass filter and the analog-to-digital converter; the signal generated by the digital frequency synthesis signal generator is used as input to stimulate the epidermis to be measured through the digital-to-analog converter and the integrated amplifier circuit, and the response signal of the epidermis to be measured is then collected by the gain-amplifying low-pass filter and the analog-to-digital converter and transmitted to the digital signal microprocessor; the digital signal microprocessor performs discrete Fourier transform calculation on the collected digital signal to obtain impedance data.

[0007] The PC host computer is used to generate control signals, receive and display data, draw data curves, and store and clear data; RS232 serial port transmission module is used for data transmission over shorter distances; The FPGA main control board receives the control instructions from the PC host computer, controls the impedance measurement chip to perform frequency scanning, obtains impedance data and performs calculations, and transmits and displays data between the PC host computer through the RS232 serial port transmission module.

[0008] The AD5933 chip realizes its operation functions by reading and writing the registers on the AD5933 chip through the FPGA main control board.

[0009] The AD5933 chip also integrates a clock oscillator to provide an internal clock to drive the AD5933 chip and its peripheral circuits.

[0010] The beneficial effects of the present invention are: The hardware circuit uses the FPGA main control board as the control core. The FPGA main control board has rich hardware resources and powerful parallel computing capabilities, small internal delay, high integration, strong stability, and fast computing speed, and can complete the rapid acquisition and processing of target signals.

[0011] At the same time, impedance detection based on the high-precision impedance detection chip AD5933 has higher detection accuracy, better stability, low power consumption and low cost, which is conducive to large-scale production and use. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 is a system block diagram of the present invention; Figure 2 The impedance measurement chip and its peripheral circuit diagram in the present invention; Figure 3 is a graph of reactance values ​​displayed by the system of the present invention; Figure 4 is a flowchart of the impedance measurement process of the present invention; DETAILED DESCRIPTION

[0013] The present invention will be further described below in conjunction with the accompanying drawings: An electrical impedance detection system based on FPGA, such as Figure 1 As shown, it includes an FPGA main control board, an impedance measurement chip and its peripheral circuits, an RS232 serial port transmission module, a PC-side host computer and a power module. The power module supplies power to the FPGA main control board, the impedance measurement chip and its peripheral circuits and the PC-side host computer. The FPGA main control board is arranged between the PC-side host computer and the impedance measurement chip and its peripheral circuits. The impedance measurement chip is connected to the FPGA main control board through an I2C bus, and the FPGA main control board communicates with the PC-side host computer through the RS232 serial port transmission module.

[0014] Impedance measurement chip and its peripheral circuits, such as Figure 2 As shown, the impedance measurement chip adopts the AD5933 chip, which integrates a digital frequency synthesis signal generator, a digital-to-analog converter, an integrated amplifier circuit, a gain amplification low-pass filter, an analog-to-digital converter and a digital signal microprocessor; the digital frequency synthesis signal generator is connected to the epidermis to be measured through the digital-to-analog converter and the integrated amplifier circuit, and the epidermis to be measured is then connected to the digital signal microprocessor through the gain amplification low-pass filter and the analog-to-digital converter.

[0015] The signal generated by the digital frequency synthesis signal generator is used as input to stimulate the epidermal part to be tested through a digital-to-analog converter and an integrated amplifier circuit. The response signal of the epidermal part to be tested is then collected by a gain-amplifying low-pass filter and an analog-to-digital converter and transmitted to a digital signal microprocessor; the digital signal microprocessor performs discrete Fourier transform calculation on the collected digital signal to obtain impedance data.

[0016] The PC host computer uses the Qt cross-platform C++ graphical user interface application to implement the following functional operations of the system: Send control signals: Send commands to start and stop acquisition to control the operation of the system; Receive and display data: Receive impedance data transmitted by the system and display it in real time; Draw data curves: Draw real-time data curve waveforms based on the received data to facilitate the observation of real-time changes in data, such as Figure 3 As shown; Data storage and clearing: After completing a data transmission, you can choose to save or clear the received data for the next data collection.

[0017] The control program is written in Verilog HDL assembly language in QuartusⅡ software, designed using a top-down approach, and simulated and debugged using Modelsim software.

[0018] The RS232 serial port transmission module is used for data transmission over shorter distances. The RS232 serial port transmission module has good compatibility and scalability. Due to its lower transmission rate, the RS232 serial port transmission module performs well in data transmission over shorter distances. It not only supports data transmission, but also supports the transmission of multiple control signals, such as data flow control, handshake signals, etc., which can help the system achieve efficient control and management of data transmission. Moreover, the cost of the RS232 serial port transmission module is relatively low, and it is easy to purchase and apply.

[0019] The FPGA main control board is the EP4CE6F1722C8 model of Alter Company. It has more than 22320 logic units, 4 PLL resources, 608256 on-chip storage and 154 user-definable I / O ports, which can well meet the requirements of system design and implementation. In the detection system, the FPGA main control board receives the control instructions of the PC host computer, controls the impedance measurement chip to perform frequency scanning, obtains impedance data and calculates it, and transmits and displays data with the PC host computer through the RS232 serial port transmission module.

[0020] The function of the AD5933 chip is realized by reading and writing the registers on the AD5933 chip through the FPGA main control board. The program flow is as follows: Figure 4 As shown; The registers related to the measurement frequency parameters include the start frequency, frequency increment and frequency point registers. The start frequency, frequency increment and frequency point registers jointly control the output frequency of the AD5933 chip when scanning.

[0021] The time cycle number register is used to set the number of initialization cycles of the analog-to-digital converter outputting the excitation signal to the impedance to be measured before starting sampling measurement.

[0022] The control register is used to set the mode of the AD5933 chip so that it can perform different functions.

[0023] The status register is used to mark the measurement status. The program can determine whether the measurement conversion is completed by reading the data in the status register. After the display is completed, the real and imaginary register data can be read through the I2C interface and transmitted to the FPGA main control board for calculation and processing, and the final data is transmitted to the PC host computer.

[0024] The AD5933 chip also integrates a clock oscillator, which can provide an internal clock with a typical frequency of 16.776MHz. After the system clock is divided inside the chip, it drives each module inside the chip. The user can also choose whether to connect an external clock. The internal clock of the AD5933 chip is used in this system design.

[0025] The detection system uses the FPGA main control board to control the AD5933 chip to collect and measure impedance data. First, the PC host computer sends a command to start collecting, and outputs current signals to the detection target area through a pair of detection electrodes. At the same time, the impedance data is detected and calculated, and finally the calculated impedance value is transmitted to the PC host computer for real-time display and storage; the hardware circuit uses the FPGA main control board as the control core, which has stronger computing power and can efficiently complete the rapid collection and processing of target signals; impedance detection is based on the high-precision impedance detection chip AD5933, with higher detection accuracy, better stability, and low power consumption cost, which is conducive to large-scale production and application of the detection system.

Claims

1. An electrical impedance detection system based on FPGA, characterized in that: The invention comprises an FPGA main control board, an impedance measurement chip and its peripheral circuits, an RS232 serial port transmission module, a PC-end host computer and a power supply module; the power supply module supplies power to the FPGA main control board, the impedance measurement chip and its peripheral circuits, and the PC-end host computer; the FPGA main control board is arranged between the PC-end host computer and the impedance measurement chip and its peripheral circuits; the impedance measurement chip is connected to the FPGA main control board through an I2C bus; and the FPGA main control board communicates with the PC-end host computer through the RS232 serial port transmission module.

2. The FPGA-based electrical impedance detection system according to claim 1, characterized in that: The impedance measurement chip adopts an AD5933 chip, and the AD5933 chip integrates a digital frequency synthesis signal generator, a digital-to-analog converter, an integrated amplifier circuit, a gain-amplifying low-pass filter, an analog-to-digital converter and a digital signal microprocessor; the digital frequency synthesis signal generator is connected to the epidermis to be measured through the digital-to-analog converter and the integrated amplifier circuit, and the epidermis to be measured is then connected to the digital signal microprocessor through the gain-amplifying low-pass filter and the analog-to-digital converter; the signal generated by the digital frequency synthesis signal generator is used as input to stimulate the epidermis to be measured through the digital-to-analog converter and the integrated amplifier circuit, and the response signal of the epidermis to be measured is then collected by the gain-amplifying low-pass filter and the analog-to-digital converter and transmitted to the digital signal microprocessor; the digital signal microprocessor performs discrete Fourier transform calculation processing on the collected digital signal to obtain impedance data.

3. The FPGA-based electrical impedance detection system according to claim 1, characterized in that: The PC host computer is used to send control signals, receive and display data, draw data curves, and store and clear data.

4. The FPGA-based electrical impedance detection system according to claim 1, characterized in that: The RS232 serial port transmission module is used for data transmission between the FPGA main control board and the PC host computer.

5. The FPGA-based electrical impedance detection system according to claim 1, characterized in that: The FPGA main control board receives control instructions from the PC host computer, controls the impedance measurement chip to perform frequency scanning, obtains impedance data and performs calculations, and transmits and displays data with the PC host computer through the transmission module.

6. The FPGA-based electrical impedance detection system according to claim 2, characterized in that: The AD5933 chip realizes the operation function by reading and writing the registers on the AD5933 chip through the FPGA main control board.

7. The FPGA-based electrical impedance detection system according to claim 2, characterized in that: The AD5933 chip also has an integrated clock oscillator inside to provide an internal clock to drive the AD5933 chip and its peripheral circuits.

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