LCD Display Inverter

“In view of the problems of various target setting, time-consuming and labor-intensive Display, and potential safety hazards during the current field training of our army’s reconnaissance detachment and shooting command detachment, this paper proposes to design a target indicator based on the MSP430F149 single-chip microcomputer to meet the needs of the troops to quickly set targets during field training. And it can flexibly Display targets according to different tactical needs and display explosion points according to different shooting rules, which better solves the urgent need for field training of troops.

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In view of the problems of various target setting, time-consuming and labor-intensive display, and potential safety hazards during the current field training of our army’s reconnaissance detachment and shooting command detachment, this paper proposes to design a target indicator based on the MSP430F149 single-chip microcomputer to meet the needs of the troops to quickly set targets during field training. And it can flexibly display targets according to different tactical needs and display explosion points according to different shooting rules, which better solves the urgent need for field training of troops.

The function of the target indicator

Target indicators show targets or blast points with lights, pyrotechnics, etc., as needed. Each indicator can simulate and display n types of targets such as machine gun fire points, tank fire points, and artillery positions, and has m explosion point displays. The target indicator mainly completes the data collection of the GPS module, and performs tasks such as light display and fireworks display.

Target Indicator Hardware Design

hardware design

The design of the target indicator is a display and control device with the single chip as the core, which integrates the functions of light display, pyrotechnic display and target position display. The key points of the design include: 1. To ensure that the designed device can adapt to the requirements of the environment; 2. To reduce the power consumption of the single-chip system as much as possible, so that the system can run normally for a long time; 3. The designed software and hardware must be able to achieve powerful functions, Stable and reliable operation, accurate execution of control commands and communication functions; ④ The device must be operable and maintainable; ⑤ On this basis, the economic cost of realizing the device must be considered.

The target indicator is mainly used to realize the target display function, and its display forms include lights, pyrotechnics or popping sounds. composition, as shown in Figure 1.

Figure 1 The hardware composition diagram of the target indicator

The core of the target indicator is a MSP430F149 microprocessor, which uses the rich peripheral modules and a small number of external chips of the processor to realize various functions. It receives the control instructions transmitted from the main control station through the wireless transmission module, and controls The circuit is converted into the corresponding control signal. The light display module implements various modes of light display by the control signal from the main control station (including equal time interval display, alternate display of lights of different colors, etc.), and the pyrotechnic display module is ignited or exploded by high and low level signals to display, GPS The positioning module provides the geographic coordinates and elevations of each target to the master control station in real time. The power module provides the voltage required by the target indicator.

Introduction to Microprocessors

The control core of the hardware part of the target indicator uses the 16-bit high-performance MSP430F149 microcontroller of TI Company, which is used to control the work of each part of the indicator. MSP430F149 is an ultra-low-power Flash-type 16-bit microcontroller, especially suitable for battery-powered occasions or handheld devices. It has the following characteristics:

①Low power consumption: when the 2.2V clock frequency is 1MHz, the active mode is 200µA; the shutdown mode is only 0.1µA, and there are 5 energy-saving working modes;
②High-efficiency 16-bit RISC-CPU: When there are 27 instructions and a clock frequency of 8MHz, the instruction cycle time is 125ns, and most of the instructions are completed in one clock cycle; when the clock frequency is 32kHz, the execution speed of the 16-bit MSP430 microcontroller is higher than the typical 8 The execution speed of the MCU at 20MHz clock frequency;
③Low voltage power supply, wide working voltage range: 1.8V～3.6V;
④Flexible clock system: two external clocks and one internal clock;
⑤Low clock frequency can realize high-speed communication;
⑥ With serial online programming ability;
⑦ Powerful interrupt function;
⑧ Short wake-up time, only 6µs to wake up from low-power mode;
⑨ESD protection, strong anti-interference ability;
⑩The operating ambient temperature range is -40℃～+85℃, which is suitable for industrial environment.

Target Indicator Circuit Design

Power circuit design

(1) Technical requirements

• MSP430F149 MCU power supply voltage range: 3.3V;
• The power supply voltage range of GPS positioning module: 1.8V;
• LED driver chip MC1413 power supply voltage: 12V;
• The power supply voltage range of the wireless data transmission module: 9V.

(2) Design points

①Easy to carry and power supply. The indicator is to meet the use of troops in combat and training in field conditions, and must be easy to carry, so it is powered by a single-cell lithium battery with a voltage of 12V.

②At the same time supply power to the main chip and peripheral devices. The main chip power supply voltage is 3.3V, the GPS power supply is 1.8V, and the transmitter power supply is 9V, so the power supply circuit should be able to output 3.3V, 1.8V, and 9V at the same time.

③Meet the needs of low power consumption. The indicator is powered by batteries and is used in field conditions. It must be able to meet the time requirements of use, so the power consumption of the indicator is very low.

(3) Circuit Design

According to the power requirements of the indicator, the MSP430F149 microcontroller adopts the AS1117-3.3 three-terminal voltage regulator module of Alpha Company, and the GPS adopts the AS1117-1.8 three-terminal voltage regulator module. AS1117 series chips are commonly used voltage conversion chips, which are characterized by: small size, low price; strong current driving capability, the maximum output current of AS1117 is 800mA, which can meet the indicator requirements. The transmitter uses a 7809 three-terminal voltage regulator module, and the power supply circuit is shown in Figure 2.

Figure 2 Power circuit diagram

Reset circuit design

The design of the indicator reset circuit must enable the indicator to be fully reset and work stably and reliably in various complex situations. MSP430F149 has a RST reset pin, which is multiplexed with the non-maskable interrupt function pin, and its function can be selected by software. It is a reset function under normal circumstances. The indicator adopts the method of external chip reset, and the reset chip STM811 is connected to the reset pin. The specific circuit is shown in the STM811 circuit in the core circuit of the target indicator in Figure 5. The MSP430F149 microcontroller requires a reset voltage of 1.1V to 1.5V on the reset pin (the system power supply voltage is 3.3V), and the duration of the reset voltage is at least 2µs. When the voltage on the pin RST/NMI reaches Vmin (1.1V), the system enters the reset state. When the voltage rises to VPOR (1.5V), the system exits the reset state.

Crystal oscillator circuit design

For a high-reliability system design, the choice of crystal is very important, especially when designing a system with sleep wake-up (often using low voltage for low power consumption), this is because the low power supply voltage provides less excitation power to the crystal, Cause the crystal to vibrate very slowly or not at all. This phenomenon is not particularly noticeable at power-on reset, because the circuit has enough perturbation at power-on that it is easy to establish oscillation. When waking up from sleep, the disturbance of the circuit is much smaller than when it is powered on, and it becomes very difficult to start the oscillation. In the oscillation circuit, the crystal can neither be over-excited (easy to vibrate to higher harmonics) nor under-excited (not easy to vibrate).

MSP430F149 can be connected to 2 external oscillators, one is a low-speed crystal oscillator, which is connected through the XIN and XOUT pins, and the other is a high-speed crystal oscillator, which is connected through the XT2IN and XT2OUT pins. It can be 450KHz～8MHz.

The selection of the system frequency is closely related to the working voltage of the system. If a higher working voltage is required, it is necessary to provide a higher frequency for the system. The relationship between the system frequency and the working voltage is shown in Figure 3.

According to the relationship between the system frequency and the working voltage, the system selects a 4M crystal oscillator, and the crystal oscillator circuit is shown in Figure 4.

Fig. 3 The relationship between working frequency and working voltage

Figure 4 Schematic diagram of crystal oscillator circuit

JTAG interface circuit design

One of the advantages of MSP430F149 microcontroller is that it can download the program code through the JTAG controller, and use it to complete the online debugging of the software. JATG is a so-called boundary scan technology standard, namely IEEE1149.1, which is an interface technology that can perform online testing of chips. The JATG interface only uses a small number of pins in practical applications, mainly including: TDO (Test Data Output), TDI (Test Data Input), TMS (Test Mode Select), TCK (Test Clock Input), RST (Reset) and TCLK/XOUT, etc.

The SIPL8 circuit interface in Figure 5 is a ProgPort programmable interface. Connect it to the corresponding pin of MSP430F149, and connect the other end of the interface to the JTAG emulator, you can realize online programming and download the program to the MSP430F149 on the circuit board.

Control core circuit design

The main control circuit of the indicator controls the starting sampling of the signal acquisition circuit and the data storage and extraction after the sampling; as a lower computer, it communicates with the PC and is responsible for transferring the acquired data stored in the memory to the signal processing circuit; control the signal conditioning circuit , so that the conditioned signal does not exceed the threshold of the acquisition circuit; coordinate other peripheral circuits.

The P3.4 and P3.5 pins of MSP430F149 are used to connect with the RS232 communication interface circuit to realize online programming and communication with computers and other equipment. The input range of the analog voltage received by the A/D converter is 0~+VREF. In the target indicator, +VREF is introduced externally with a +3.3V voltage reference, and the CREF pin is coupled to ground with a 0.1pF capacitor. Its circuit schematic diagram is shown in Figure 5.

Figure 5 Schematic diagram of the core circuit of the target indicator

GPS positioning module circuit design

The GPS positioning module mainly returns the position of the target indicator to the main control station, including the ordinate, abscissa and elevation, and transmits it to the main control station through wireless communication.

(1) Features of GPS positioning system

GPS is a global satellite positioning system, which consists of a space part, a monitoring part and a user part. The characteristics of the GPS system are: ①High positioning accuracy; ②Short observation time; ③Three-dimensional coordinates can be provided; ④Easy to operate; ⑤Multiple functions , Wide application; ⑥ all-weather operation.

(2) GPS positioning module circuit implementation

Since the GPS output is RS-232 signal, the GPS module is connected to the single-chip microcomputer through the signal conversion chip MAX3232 to realize the conversion between the RS232 level and the TTL level. The data receiving pin, the 34 pin is the data sending pin of the microcontroller.

Figure 6 GPS positioning module circuit interface diagram

MAX3232 is a low-power, single-power dual RS232 transmitter/receiver produced by MAXIM Company, and one of the MAX3232 channels is now selected for transmission/reception. Because the MAX232 has the driving ability, no additional driving circuit is required. The MAX232 chip contains a capacitive voltage generator, which can convert the input +5V power supply into the ±10V voltage required by RS232, so the serial communication system using this chip interface only needs a single +5V power supply.

When designing the interface circuit, a 3-wire (RXD, TXD, GND) soft handshake method is adopted. That is, the GPS receiver and the single-chip microcomputer “transmit data line (TXD)” and “receive data line (RXD)” are cross-connected, and the ground lines (GND) of the two are directly connected, and other signal lines are not needed. The handshake signal is generated by software method. . In this way, the predetermined goal can be achieved, the circuit design can be simplified, and the cost can be saved.

The MAX3232 requires 5 capacitors, of which 4 capacitors C1, C2, C3 and C4 are the capacitors required for internal power conversion, and their value is 1µF, and another C5 is required for the decoupling capacitor, the value is 0.1µF .

Lighting Display Module Circuit Design

The light display module is used to simulate and display various types of luminous targets. Its basic task is that after receiving the target display command sent by the main control station, the single-chip microcomputer processes the command, and the light display module can display the light according to the display mode required by the indicator. .

The light display drive circuit is shown in Figure 7. The drive chip adopts MC1413 chip, the working power supply is 12V, and the output current of the circuit is as high as 500mA.

Figure 7 Lighting display driver circuit diagram

Circuit design of pyrotechnic display module

The pyrotechnic display module is mainly used to simulate and display various types of smoking targets. Its basic task is that after receiving the target display command sent by the main control station, the single-chip microcomputer processes the command, and the pyrotechnic display circuit can display in the display mode required by the indicator. smoke. The module uses a general Electronic ignition smoke pipe for display.

The circuit design of the pyrotechnic display module should meet the following requirements: ① The smoke pipe should be able to be controlled reliably and stably; ② The circuit design should be simple, the number of components should be as few as possible, and the original executive-level circuit should be used as much as possible. Therefore, the fireworks display module and the light display module use the same drive circuit and are used comprehensively.

Wireless Communication Module Circuit Design

The requirements of the target indicator for the wireless communication module: ① a long communication distance, to meet the requirements of the large field range and different training subjects when the troops are shooting in the field; ② strong anti-interference ability; ③ low power consumption, for the application of For wireless data transmission modules in the wild, without a fixed power supply, and only rely on batteries to maintain system operation, the power consumption parameters of the chip are very important.

According to the above requirements, the indicator selects the ZT-TR43C wireless data transmission module, which is a wireless communication module launched by Shenzhen Zhentong Company. Technical indicators of TR43C: ①The carrier frequency is 433MHz, and the working frequency is 428MHz～435MHz; ②The maximum transmission power is 20mW, and the maximum transmission distance in the open area is 3km; ③It adopts FSK modulation, adopts forward channel error correction coding, and has strong anti-interference ability; Eight working channels are available; ⑤The transmission rate is 20kbps; ⑥Most functions such as noise reduction amplifier LNA, power amplifier PA, and pressure air oscillator VCO are integrated in the chip, and the peripheral circuit is simple and easy to develop.

Wireless communication module and microcontroller interface TR43C provides three interface modes: RS232/TTL/RS485. The indicator adopts TTL interface mode, which is convenient for the interface with MSP430F149 microcontroller. The circuit interface is shown in Figure 8. Among them, the RXD and TXD ports of the MSP430 microcontroller are respectively connected with the TXD and RXD ports of the wireless module, and the ground wire is connected.

Figure 8 Schematic diagram of interface between TR43C and microcontroller

Wireless modules can be used for networking, TR43C series modules are most suitable for point-to-multipoint communication, especially in line with the needs of target indicators. This method firstly sets a master control station, which is equivalent to a host; setting multiple target indicators is equivalent to a slave, and both the host and the slave set address codes. The coordination of communication is completely controlled by the master. After the slave receives the signal, it compares the received address code with the address code of the local machine. If it is different, the data will be completely discarded and no response will be made; if the address code is the same, the slave will receive data or command, and respond according to the command.

Target indicator software design

The software design of the target indicator adopts a modular design idea. The advantages of modular design are: 1. Make the complex system small and simple; 2. It is easy to modify and maintain; 3. It can improve the design efficiency of system software.

The main tasks of the target indicator software design are: initialization, light display, fireworks display, GPS positioning and wireless communication and some small tasks. Firstly, the software is divided into several large functional modules according to the main tasks to be completed by the target indicator, which are initialization module, light display module, pyrotechnic display module, GPS positioning module, and wireless communication module. In the main program, it mainly completes the work of the initialization module, and then cyclically detects the status flags of each functional module, and judges whether to enter each functional module according to the indications of various status flags, and performs corresponding operations. If the corresponding operation is performed, it will jump out of the main program and continue to execute after the operation is completed. The target indicator software function is shown in Figure 9.

Figure 9 Functional block diagram of target indicator software

The main program flow of the target indicator is shown in Figure 10. In the system software design, in order to reduce the burden of the CPU, so that the CPU has more time to process useful operations, and at the same time to reduce the power consumption of the circuit, all functions are implemented in interrupt mode, and the main program does not do too much work. . In Fig. 10, each functional module of the target indicator is initialized first. After the initialization is completed, the interrupt is then turned on, the CPU wakes up from the low-power mode, performs interrupt processing, and returns to the low-power cycle after the interrupt ends.

Figure 10 Main program flow chart

concluding remarks

This paper designs a target indicator based on MSP430F149 microcontroller. The target indicator works stably and reliably, and can meet the system requirements. It has the following characteristics:

①Through the scientific layout and combined control of target classification, lighting and pyrotechnics, etc., technical problems such as target setting and dynamic display under field conditions are effectively solved, and the training efficiency of target capture and shooting command of the troops is greatly improved.

②Using the combination of ultra-low power consumption devices and power shutdown function, the overall power consumption of the system is greatly reduced, and the working time of the system is prolonged. The system can work continuously for more than 30 hours on a single charge.

③Using mature technology and modular design, etc., effectively solve the problems of power supply fluctuation and improve the stability and reliability of the system.

④Optimize the structure design to make the overall structure small, flexible and convenient to set targets, suitable for use in field conditions.