Design of Cardiopulmonary Auscultation Skill Training System Based on Single Chip Microcomputer

With the development of society, the reform of the medical system, the publicity of the media, and the legal awareness of the people have been greatly strengthened. The introduction of a series of medical regulations has further clarified the rights and interests of patients. The patient, the subject of traditional medical teaching in the past, has more choices to refuse to cooperate with the teaching work.

In recent years, the increase in medical disputes and the tension between doctors and patients, due to their own interests, the teaching performance of hospitals continues to weaken. The regular mode of medical colleges in clinical medical education is: theoretical teaching + single skill training - trainee - clinical internship. However, due to various reasons, the internship cannot be effectively carried out, which leads to the formation of the teaching mode of “theory teaching + individual skill training”. Based on the above reality, the embarrassing situation of teaching in medical colleges urgently needs to change. Introduce “simulation teaching” into the teaching process in the school, and form a new clinical medical teaching mode of “theoretical teaching + single skill training – simulation teaching – clinical practice”. The system is simple in structure and reproduces the clinical medical work scene by means of a model person, providing learners with a condition and environment for risk-free learning of clinical knowledge and skills.

1 system structure

From a structural point of view, the system can be divided into two parts: the model person and the remote controller. The model person mainly has internal wireless receiving devices and control devices as well as special devices for the human body surface. There are LCD screens, keyboards and related instructions on the remote control. The assessor can conveniently send a command signal to the wireless receiving device inside the model person, and the wireless receiving device uses the received command to determine what type of disease is, thereby controlling what sounds should be emitted at each position on the model person, when the stethoscope is touched. When the model person has the corresponding position point, the corresponding device will give the control unit a position signal, and then the control unit will control the signal through the multi-channel analog switch to control the corresponding speaker to emit the cardiopulmonary auscultation sound at the point where the examinee passes the stethoscope. This sound is transmitted to the human ear, which completely simulates a real auscultation process. The examinee palpates the different postures of the model person through the probe of the stethoscope, and auscultates various pathological features at different positions through the stethoscope, thereby judging whether it is a certain disease, thereby achieving the purpose of teaching and training.

2 system's functional composition

From the functional point of view, the system can be divided into six parts: voice playback unit, multi-channel analog switch, position recognition switch, wireless communication unit and power supply and low-power design unit. The internal system block diagram of the model person is shown in Figure 1.

Figure 1 Internal structure of the model person

The system block diagram of the remote control is shown in Figure 2.

Figure 2 Remote control system block diagram

2. 1 selection of the main controller chip

The main controller is the core part of the whole system. The choice of the main controller chip is related to the realization of the whole system function. The system needs to realize functions such as voice playback, wireless transceiver, multi-channel analog switch, low power consumption of power supply, teaching of upper computer, etc., so the chip is required to have higher computing speed, larger RAM and FLA SH space, and can be expanded. The IO port (such as I2C, SPI, etc.) is compatible with some external chips (such as FLASH memory with SPI or some other chip), and has low power consumption and convenient debugging. Based on the above factors, the main control chip uses the MSP430 produced by Texas Instruments (USA). Because the system is a portable cardiopulmonary auscultation system, it is battery-powered, so it must be ultra-low power consumption, so as to meet the medical teaching. Requirements, and the biggest feature of the chip is low power consumption, the voltage preparation mode is 3.3 V, and the current is in the milliamperes during normal operation, which fully meets the system requirements. The chip has the following properties:

Low voltage range: 1. 8~ 3. 6 V;

Ultra-low power consumption: standard mode 1. 3 mA, RAM is 0. 1 mA when it is turned off;

Low current: 7 mA at 32 kHz, 2. 2 V, 250 mA at 1 MHz, 2. 2 V;

5 node modes and wake up from wait mode within 6 ms;

16-bit RISC instruction structure and 125 ns instruction cycle;

12-bit A/D conversion and internal reference voltage, sample-and-hold, auto-scan feature;

16-bit timer with 7-channel capture and compare registers of the map register, timer B;

16-bit timer with 3 capture/compare registers, timer A;

On-chip comparator

Serial online programming, no external programming voltage, safety fuse protection program code;

Contains 60 KB of flash memory, 2 KB of random access memory.

2. 2 voice playback

Voice playback is one of the important components of this system. There are two problems to solve here, one is the storage of voice data, and the other is the encoding and decoding of voice. Since the WAV waveform data takes up a lot of space, it is necessary to compress and encode the original data first. Therefore, the system uses the PM50 intelligent voice chip developed by Zhongqing Century Technology Co., Ltd. It is both a voice playback circuit and a smart single-chip microcomputer. Its sound quality and price are slightly better than the well-known ISD circuit, and it also has a high-fidelity sound quality of 21 kHz. The chip consists of a dedicated voice MCU and FLA SH RAM memory set. It has 13-100 s multi-segment voice playback function, and also has programmable logic features. The chip has the following features:

Sound length can be stored: 13~ 100 s;

Wide range of operating voltage: DC 3~ 6 V;

Operating current 50 mA, quiescent current 1 A;

Directly drive 8 0. 5 W speakers with PWM and DAC audio output modes;

Wide range sampling frequency: 4. 8~ 21 kHz;

The recorded voice can be divided into parallel 1~8 segments and serial 128 segments;

With 8 input ports and 9 output ports, the functions can be customized by the user;

FLASH RAM structure, can be erased and written continuously, with a life of more than 10,000 times;

Two package types: COB28 and COB16;

The computer software for development is a super-intelligent fool graphic design, which can also be used by laymen;

With the programming software, parallel, serial, intelligent and other control modes can be developed;

The peripheral circuit of the minimum system only needs one oscillation resistor and one power supply filter capacitor;

Available in 13 s / 20 s / 50 s / 100 s multiple time grades;

After the development and trial production are completed, the mask is directly put into production with the source file, and the sound quality and function performance are unchanged.

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