Design of exhibition hall personnel registration and entry system based on MSP430F149 microcontroller

    This article mainly describes the design of a personnel registration and entry system using video image analysis technology. Infrared signals of people entering and leaving the museum are collected and sent to the single-chip microcomputer MSP430F149. The single-chip microcomputer processes the signals to count the number of people entering and leaving the museum and displays them on the LCD12864 liquid crystal display. At the same time, photos of people entering and leaving the museum are taken and stored. The personnel registration and entry system can obtain accurate numbers of people and photos in the museum in a timely manner, which is conducive to more efficient organization of museums. It can be integrated with third-party software systems to provide data support for scientific decision-making.

    The population counting system can play different roles in different application scenarios. It can obtain information such as the number of people distributed in different time periods and the direction of crowd flow inside the mall for shopping malls or retail outlets, which is conducive to evaluating the attractiveness of goods to customers and evaluating whether the location of the mall is appropriate; for large buildings, managers can use the crowd counting system to understand the behavior of the crowd and evaluate whether the service facilities provided by the building are convenient and sufficient, such as seats, public telephones and sanitary facilities, etc., to improve the utilization rate of building facilities, guide the design of buildings and improve the efficiency of staff in certain occasions. In addition, the passenger flow in the building can be monitored to avoid safety hazards caused by crowd congestion.

1 Overall Design
    The personnel registration and entry system is designed for the exhibition hall. The system is mainly composed of five parts: single-chip microcomputer control, signal acquisition, camera, LCD display, and power supply . The hardware structure diagram is shown in Figure 1. When someone wants to enter the hall, the signal collected by the infrared device will be sent to the single-chip microcomputer, which processes the collected signal and controls the camera to take pictures of the people entering the hall, while recording the entry time, and then displays the number of people in the hall on the LCD screen. When someone leaves the hall, the working principle of this system is the same as when entering the hall.

　　The functions that this system can realize are:

　　1) Display the number of people in the museum;

　　2) Take photos of people entering and leaving the museum;

　　3) When the museum is full, there will be clear signs prohibiting entry;

　　4) Record the time people enter and leave the museum.

　　The MSP430 series microcontroller is used as the control chip, the signal acquisition circuit uses an infrared integrated tube as the main component, the camera is used for taking pictures, the display part uses an LCD12864 liquid crystal display, and the power supply part uses a homemade +5 V regulated power supply. Compared with the 51 series microcontroller, the MSP430 microcontroller has stronger processing power, convenient peripheral circuits, and a reset function. It is a new generation of microcontrollers with high speed/low power consumption/super strong anti-interference. Its interrupts, timing, and I/O outputs are far more than the 51 series, and the internal integrated comparison amplifier and multi-channel AD determine that it has strong scalability. Therefore, this system uses the MSP430F149 microcontroller as the control chip. Compared with the pressure sensor, the infrared sensor is a non-contact sensor. Its own loss is much smaller than that of the pressure sensor. It has the advantages of fast response speed, long service life, and easy maintenance and detection. So in this environment we choose to use infrared sensors.

　　2 Circuits of each hardware module

　　2.1 Single chip control module

　　MSP430 is a new type of single-chip microcomputer with FLASH and 16-bit bus developed by Texas Instruments. It adopts 16-bit bus, unified addressing of peripherals and memory, addressing range up to 64K, external memory expansion, unified interrupt management, and rich on-chip peripheral modules. There are precision hardware multipliers, two 16-bit timers, a 14-channel 12-bit analog-to-digital converter, a watchdog, 6-channel P ports, two USART communication ports, a comparator, an internal oscillator and two external clocks, supporting 8M clock. Because it is a FLASH type, the single-chip microcomputer can be debugged and downloaded online, and the JTAG port is directly connected to the FET, without the need for additional simulation tools, which is convenient and practical. Moreover, it can work in ultra-low power consumption mode, with low radiation to the environment and human body, so this system uses MSP430F149 single-chip microcomputer as the control chip.

　　The MSP430F149 microcontroller control circuit is shown in Figure 2.

2.2 Infrared sensing and communication module
    Infrared light emitting diodes
    Infrared light emitting diodes are made of semiconductor materials such as gallium arsenide (GaAs) and gallium aluminum arsenide (GaAlAs). Their appearance is basically the same as that of ordinary light emitting diodes and they are encapsulated with transparent resin materials. Medium and high power infrared light emitting diodes use metal or ceramic materials as bases and glass or resin lenses as windows.
    Infrared receiving diodes
    The infrared receiving tube of the receiving circuit is a photosensitive diode. When used, a reverse bias voltage must be added to the infrared receiving diode so that it can work normally and obtain high sensitivity. Infrared receiving diodes are generally round and square. Since the infrared light emitting diode has a small transmission power, the infrared receiving diode receives a weak signal, so a high gain amplifier circuit must be added to the receiving end.
    Infrared remote control communication module
    Considering that this system may be installed in a higher place, ordinary wired buttons cannot meet the actual requirements. Therefore, we choose to use infrared remote control buttons to control this system. The infrared remote
    control key human-computer interaction module includes two parts: the hardware infrared receiving transistor receiving part and the single-chip microcomputer software decoding part.
    The transmitting part is a wave of fixed frequency modulated with the binary number (high and low level) to be sent and transmitted in the form of light through the infrared transmitting tube.
    The receiving part decodes the modulated signal into the binary number (high and low level) to be sent through the infrared receiving transistor, and then achieves multi-button remote control through the specific programming of the single-chip microcomputer.
2.3 Waveform generation module The
    555 integrated circuit was originally used as a timer, so it is called a 555 timer or a 555 time base circuit. It can also be used for various controls and measurement detection such as dimming, temperature adjustment, voltage adjustment, speed adjustment, etc., to form pulse oscillation, monostable, bistable and pulse modulation circuits, which are used for AC signal sources, power conversion, frequency conversion, pulse modulation, etc. It is reliable, easy to use, and low-cost, and is currently widely used in various electronic products. We use the 555 integrated circuit to generate a 38 kHz square wave.

    
    The 555 integrated circuit is an 8-pin package, dual in-line type, as shown in Figure 3, where pin 6 is called the threshold terminal (TH), which is the input of the upper comparator; pin 2 is called the trigger terminal (TR), which is the input of the lower comparator; pin 3 is the output terminal (Vo), which has two states, 0 and 1, determined by the level added to the input terminal; pin 7 is the discharge terminal (DIS), which is the output of the internal discharge tube, and has two states, floating and grounded, which is also determined by the state of the input terminal; pin 4 is the reset terminal (MR), which can make the output low when a low level is added; pin 5 is the control voltage terminal (Vc), which can be used to change the upper and lower trigger level values; pin 8 is the power supply terminal, and pin 1 is the ground terminal.
2.4 Photo module
    This system uses a high-definition video head, which can be connected to a PC, has a visual monitoring interface, and can control the video head through hardware. When taking pictures, the time can be automatically stored and printed.
2.5 Overview of
    LCD 12864
    LCD12864 with Chinese character library is a dot-matrix graphic LCD display module with multiple interface modes such as 4-bit/8-bit parallel, 2-wire or 3-wire serial, and internally contains the national standard first-level and second-level simplified Chinese character libraries; its display resolution is 128x64, with 8192 16*16-dot Chinese characters and 128 16*8-dot ASCII character sets built in. With the flexible interface mode and simple and convenient operation instructions of this module, a full Chinese human-computer interactive graphic interface can be constructed. It can display 8x4 lines of 16x16 dot Chinese characters, and can also complete graphic display. Low voltage and low power consumption are another significant feature. Compared with the same type of graphic dot-matrix LCD display module, the LCD display solution composed of this module is much simpler in terms of hardware circuit structure and display program, and the price of this module is also slightly lower than that of the graphic LCD module with the same dot matrix.
    Basic characteristics
    1) Low power supply voltage (VDD: +3.0～+5.5 V).
    2) Display resolution: 128x64 dots.
    3) Built-in Chinese character library, providing 8,192 16x16 dot matrix Chinese characters (Simplified and Traditional Chinese optional).
    4) Built-in 128 16x8 dot matrix characters.
    5) 2MHZ clock frequency.
    6) Display mode: STN, semi-transparent, positive display.
    7) Driving mode: 1/32DUTY, 1/SBIAS.
    8) Viewing angle direction: 6 dots.
    9) Backlight mode: side high-brightness white LED , power consumption is only 1/5-1/10 of ordinary LED.
    10) Communication mode: serial, parallel port optional.
    11) Built-in DC-DC conversion circuit, no external negative voltage required.
    12) No chip select signal required, simplifying software design.
    13) Working temperature: 0~+55℃, storage temperature: -20~+60℃.
    The LCD12864 liquid crystal display circuit in this system is shown in Figure 4.

3 Software Design
    The system program flow chart is shown in Figure 5.

4.1 Hardware
debugging
    The hardware debugging results are shown in Table 1.
4.2 Software debugging
    The software debugging results are shown in Table 2.

     5 Conclusion
    The paper mainly introduces the exhibition hall personnel registration and entry system based on MSP 430F149 single chip microcomputer , including hardware and software. The experiment shows that the system is sensitive in application, accurate in counting and has good effect. At the same time, the system has certain reference value for occasions where personnel registration information is required.