Design of Sending and Controlling Timing Detection System Based on MSP430F149 MCU

For the detection of the launch and control system, there is a launch and control sequence detection device on the electromechanical detection and maintenance vehicle supporting the rocket launcher, which is used to qualitatively check the launch and control sequence of the directional tube. The detection device cannot quantify and Display the detection results. During detection, it can only be determined whether the transmission and control system is normal by turning on and off the LED. It cannot quantitatively observe the line in a critical fault state, which has certain limitations.

Since the rocket launcher is a simple control rocket, the electrical signal interface between the directional tube and the rocket has the same ignition signal interface as the ordinary uncontrolled rocket, and also has a 32-core parameter setting signal interface. In the launching procedure, if the flight control parameters of the rocket calculated by the fire control system can be accurately set in the control system of the rocket, the rocket will fly in the simple control mode, otherwise it will fly in the uncontrolled way, which will cause the rocket to fly. Shooting accuracy is greatly reduced. In order to ensure that the rocket can be launched smoothly and the accuracy of shooting, before the technical position is loaded, it is necessary to strictly test the ignition signal line and parameter setting line on the rocket to ensure that the signal line is in good working condition.

For the detection of the launch and control system, there is a launch and control sequence detection device on the electromechanical detection and maintenance vehicle supporting the rocket launcher, which is used to qualitatively check the launch and control sequence of the directional tube. The detection device cannot quantify and display the detection results. During detection, it can only be determined whether the transmission and control system is normal by turning on and off the LED. It cannot quantitatively observe the line in a critical fault state, which has certain limitations.

This text is based on MSP430F149 one-chip computer, designs a kind of sending and controlling timing detection system. The system uses digital signal processing technology, computer automatic control technology, etc. to collect the control signal at the ignition contact and the butt plug, and analyzes the voltage amplitude, current magnitude, signal noise, signal rising and falling edge width of the signal, and displays the Detect the deviation of the signal from the standard value and give the evaluation value; at the same time, check the reliability of the docking, do three docking of the same tube and analyze the difference of the signal, so as to evaluate the reliability of the docking; record the test data in detail, and each time During detection, it is compared and analyzed with historical data, and the variation law of the same number of tube data and the consistency with all other tube data are obtained, so as to determine the potential failure of the control system and give maintenance guidance. The detection system not only makes the detection data accurate, the process simplifies, but also saves time and can effectively improve the combat effectiveness of the rocket launcher.

The overall scheme design of the transmission control timing detection system

The main function of the detection system

This system mainly realizes the daily maintenance and fault detection of the rocket launch control device. The system has the following functions:

(1) Detection of directional control timing signals;

(2) Detection of ignition signal of rocket engine;

(3) Visually display the test content and test results;

(4) System self-check;

(5) Sound prompts during the detection process;

(6) Sound and light alarm for exceeding the standard parameters;

(7) On-site printing of test results;

(8) The test results are saved and checked back after the power is cut off;

(9) Communicate with the serial host.

The structure of the detection system

In order to realize the flexibility of the system, the system uses the serial port to realize the communication with the microcomputer; at the same time, the system should be easy to carry. According to the system function, the detection system structure is shown in Figure 1.

It can be seen from Figure 1 that the system is mainly composed of a DC regulated power supply module, an analog input multi-core switching unit, an analog-to-digital conversion unit, a data processing unit, an LCD display module and a serial communication interface.

Hardware Design of Sending and Controlling Timing Detecting System

Design of Sending and Controlling Timing Detection System Based on MSP430F149 MCU
Figure 1 System structure block diagram

MSP430F149 microcontroller is suitable for many more complex control applications, and this chip is selected to build the smallest system, which can fully meet the requirements of normal operation of the system. This system is based on the minimum system designed by MSP430F149 as the core control part of the hardware. In addition to the power supply circuit and reset circuit necessary for the normal operation of the single-chip microcomputer, the system also includes multi-core switching circuit, keyboard and liquid crystal display circuit, communication interface circuit, data Storage circuit and sound alarm circuit, etc.

Power circuit design

The reset signal must be provided in the application of the single-chip microcomputer to ensure that the single-chip microcomputer can be reset correctly and enter the correct working state. In addition, the microcontroller also needs a stable voltage signal, so a power supply circuit must be provided. The power circuit and reset circuit are shown in Figure 2. In the figure, the input voltage is converted into a voltage of 3.3V by the TPS70633 chip to meet the working voltage requirements of the microcontroller. The reset signal is generated by MAX809STR and sent to the microcontroller. In order to reduce interference, a 0.1μF capacitor is added to the power supply end of each chip for filtering.

Multi-core automatic switching circuit design

In an automatic test system, it is often necessary to collect multi-channel data, and sometimes data signals of different channels need to be obtained in different test processes. In the past, people often solved the problem by increasing the number of analog switches on the front end of the A/D sampling. However, if the detection system contains switching of high-voltage circuits, the analog switches are no longer suitable. The relay has obvious advantages in this regard. The ability of large current and voltage can also completely isolate the drive control circuit from the controlled contact circuit, with a high safety factor.

When selecting a relay, comprehensively consider the actual technical requirements, functional characteristics and environmental adaptability, and refer to the performance parameters, size, installation method, load characteristics of the relay, etc., this scheme selects the TX2-5V relay produced by Panasonic as the measurement circuit. switching device. The relay has the advantages of fast response time, high withstand voltage, small size and low power consumption, and can meet the requirements of long-term continuous scanning and working under high voltage during testing.

Design of Sending and Controlling Timing Detection System Based on MSP430F149 MCU
Figure 2 Power supply circuit and reset circuit diagram
Design of Sending and Controlling Timing Detection System Based on MSP430F149 MCU
Figure 3 Schematic diagram of multi-core automatic switching circuit

The measurement of the terminal voltage and loop resistance of the ignition device of the 32-core cable is relative to the rocket launcher system. The detection system also needs to adjust the analog signal, analog-digital conversion, and single-chip processing data. Realize the automatic switching of constant voltage and constant current, and also realize the switching between multi-channel signals. In the circuit design, each core adopts a dual relay to realize switching, which can not only realize the constant voltage and constant current loading of the core cable, but also realize the measurement and switching of multi-channel signals. The principle of automatic switching circuit is shown in Figure 3. In the figure, IN1~IN30 are omitted before IN31, and the line connection of IN1~IN30 is the same as that of IN31; the 1 pin of J32 is connected to the 6 pin of J1.

Data Acquisition Circuit Design

A/D chip selection

The analog/digital converter is a device, referred to as A/D for short, which converts the collected sampled analog signal into a digital signal after quantization and encoding and outputs it. In order to meet the needs of high-speed and high-precision A/D converters in radar, image processing, and high-speed data acquisition systems, some IC manufacturers have successively introduced A/D converters with pipeline structure, and the ADS1241 chip of Texas Instruments is one of them. one.

ADS1241 is a high-performance, wide dynamic range, high-precision 24-bit A/D conversion chip. The chip has the following features: ①24-bit A/D conversion; ②The gain and output rate can be set by the program; ③The external reference voltage source in differential mode is provided, and the external reference voltage is 0.1V~5V; ④It has on-chip self-calibration Function; ⑤ Use SPI serial port to interface with other chips; ⑥ Low power consumption: the power consumption is only 600μW; ⑦ It has a wide working voltage, the voltage range is 2.7V~5.5V; ⑧ It can realize up to 8 channels of analog acquisition. The ADS1241 chip provides multiplexers and buffers to achieve multi-channel acquisition. In addition, the chip also performs filtering processing.

A/D chip interface circuit design

ADS1241 needs an external clock to work, so a crystal needs to be connected to the XIN and XOUT pins to provide the clock required for the chip to work. This system uses a crystal with a frequency of 2.4576MHz and a capacitance of 20pF. The choice of capacitance is related to the frequency of the crystal. The ADS1241 is connected to the microcontroller through the SPI serial port. The 4-wire method is used here, that is, the SCLK, DIN, DOUT and CS pins are connected to the microcontroller. In addition, the DRDY pin of ADS1241 is connected to the general I/O pin of the microcontroller, so that it can be judged whether it is ready or not through this pin. Since the output of this pin is active low, it is necessary to pull this pin high. The ADS1241 interface circuit is shown in Figure 4.

In Figure 4, both the digital power supply and the analog power supply are powered by a 3.3V voltage. In order to reduce the interference at the power supply, a 0.1μF capacitor needs to be added for filtering. In this system, the digital ground and the analog ground are also connected together, but in some specific applications, it may be necessary to separate the digital ground and the analog ground. The external reference power supply of AS1241 can be in differential mode or non-differential mode. In this system, non-differential mode is adopted, so it is only necessary to connect the Vref+ pin to the external reference power supply and the Vref- pin to ground. In this system, connect the PWND pin to a high level, so that the chip is always in a working state; in the case of low power consumption, this pin can be connected to the general I/O of the single-chip microcomputer, and the low-level of the ADS1241 can be controlled by the single-chip microcomputer. Power state.

Design of Sending and Controlling Timing Detection System Based on MSP430F149 MCU
Figure 4 ADS1241 interface circuit diagram

Data Storage Circuit Design

The detection system data storage selects a large-capacity EEPROM CAT24WC256, which is a 256K-bit serial CMOSEEPROM with 32768 bytes inside, and each byte is 8 bits. CATALYST’s advanced CMOS technology reduces the power consumption of the device. The CAT24WC256 has a 64-byte page write buffer, and the device operates through the I2C bus interface, as shown in Figure 5.

Design of Sending and Controlling Timing Detection System Based on MSP430F149 MCU
Figure 5 Schematic diagram of data storage circuit

Measurement circuit design

Design of voltage measurement circuit for transmission and control sequence

Differential sampling is performed after the output voltage VS is divided. After sampling, it is sent to the microcontroller for AD sampling. The AD sampling value is compared with the set value to realize overvoltage warning and overvoltage protection. At the same time, the AD sampling value can be uploaded to the computer through the communication interface. The output voltage of this road is displayed, and the voltage detection circuit is shown in Figure 6.

Design of Sending and Controlling Timing Detection System Based on MSP430F149 MCU
Figure 6 Voltage measurement circuit diagram

The Design of Current Measurement Circuit for Transmitting and Controlling Sequence

The sampling current is detected by a balanced current transformer, and the output current signal is converted into a voltage signal and sent to the microcontroller for AD sampling. The overcurrent warning and overcurrent protection are realized by comparing the AD sampling value with the set value. The current detection circuit is shown in the figure. 7 is shown. The current signal generates two analog voltage signals and sends them to the microcontroller for sampling to ensure the accuracy in the full range of the current.

Design of Sending and Controlling Timing Detection System Based on MSP430F149 MCU
Figure 7 Current detection circuit diagram

Design of Ignition Load Resistance Measurement Circuit

The resistance value of the rocket engine ignition load is usually very small, and the measurement with general equipment and methods cannot achieve the required accuracy. The double-arm bridge is very accurate to measure small resistance, but the measurement uses a large current, and the cable is easy to heat up, which affects the test results. If you want to measure accurately, you need to adjust the balance, so it cannot meet the requirements of fast testing. In order to accurately measure the ignition resistance, the system uses a constant current source with temperature control feedback and a high-precision proportional op amp to measure the ignition load resistance, and the instrument eliminates system errors (including system line resistance and contact point resistance, etc.) through self-checking. ), the measurement principle of ignition circuit resistance is shown in Figure 8.

Design of Sending and Controlling Timing Detection System Based on MSP430F149 MCU
Figure 8 Schematic diagram of ignition load resistance measurement

In this system, according to the range and accuracy requirements of the measured resistance, the DH900 precision constant current triode is selected, and the resistance is adjusted to measure the standard constant current of 20mA.

The constant current triode has excellent constant current and adjustment characteristics, low temperature coefficient and high current stability. It is a precise integrated circuit constant current device.

The domestic DH900 system is a new type of ultra-precision constant current source device, the constant current range is extended to 1μA~20A, can be used in parallel, can be transmitted over long distances, and the load can be disconnected.

The Design of Single-chip Control Circuit

keyboard circuit design

In the single-chip application system, it usually has the function of man-machine dialogue, which can issue various control commands and data input at any time, and report the operation status and operation results of the application system. The main function of the human-computer interaction of this system is to select the detection content, view the detection results, control communication and printing, etc. There is no design data input, and the detection process is automatically controlled, so only a few function buttons are needed. The system adopts independent port keys, each key is connected to an interrupt pin, and the key value is obtained by the port interrupt method, as shown in Figure 9.

Design of Sending and Controlling Timing Detection System Based on MSP430F149 MCU
Figure 9 Keyboard circuit diagram

Liquid crystal display circuit design

The principle of liquid crystal display is to use the physical characteristics of liquid crystal to control its display area through voltage, and there is a display when there is electricity, so that graphics can be displayed. Liquid crystal displays are divided into dot matrix, segment, character and so on according to their display methods. The dot matrix liquid crystal display has the advantages of small size, light weight, thin appearance, low energy consumption, low operating voltage, no radiation, especially a wide field of view and a large amount of displayed information.

The LM2029-6 LCD selected in this article is a graphic dot matrix LCD, which is mainly composed of a row driver/column driver and a 320×240 full dot matrix LCD, which can display graphics and Chinese characters. Main technical parameters and performance: ① The power supply VDD is +5V, and the module has a negative voltage of -10V, which is used for the driving voltage of the LCD; ② The display content is 320 (column) × 240 (row) dots; ③ Full screen dot matrix; ④Seven kinds of instructions; ⑤The interface with CPU adopts 8-bit data bus parallel input and output and 8 control lines; ⑥Duty ratio is 1/64; ⑦The working temperature is -10℃~+55℃.

The LCD screen is connected to the main chip through a 20-pin socket, the brightness of the LCD is controlled by adjusting the driving voltage through a 50K adjustable resistor, and the backlight of the LCD is controlled by two triodes, as shown in Figure 10. P1.5 controls LCD display data/display instruction data, P1.6 controls data read/write, P1.7 controls enable signal, 8 pins of P2 are used as data pins, P3.0 and P3.1 are used as LCD The chip select signal, P4.1 controls the LCD backlight display.

Design of Sending and Controlling Timing Detection System Based on MSP430F149 MCU
Figure 10 Liquid crystal display circuit diagram

Communication interface circuit design

The communication interface is responsible for the tasks of exchanging data with the peripheral serial host and supporting printing.

Serial communication can realize the intercommunication between single-chip microcomputer and PC with less ports, which has unparalleled advantages. MSP430 series have USART module to realize serial communication. In this design, the USART module of MSP430F149 communicates with the peripheral serial host through the RS232 serial port. The system uses a dedicated level conversion chip MAX3232 to achieve level conversion, as shown in Figure 11. The MAX3232 chip is a level conversion chip produced by MAXIM, which includes two receivers and drivers, and has reliable performance.

Design of Sending and Controlling Timing Detection System Based on MSP430F149 MCU
Figure 11 Schematic diagram of the communication interface circuit

Sound buzzer alarm circuit design

The sound alarm uses a buzzer, and outputs pulse control through the I/O port, changing the frequency and action time of the pulse to give different types of prompts or alarms. In order to improve the driving ability and make the buzzer produce a certain intensity of sound, a symmetrical transistor drive is used, and its circuit is shown in Figure 12.

Design of Sending and Controlling Timing Detection System Based on MSP430F149 MCU
Figure 12 Schematic diagram of sound buzzer alarm circuit

Software Design of Sending and Controlling Timing Detecting System

In order to facilitate the maintenance of the software system and the upgrading and modification of the hardware system in the future, the software of this system adopts modularized, structured design and programming, and each hardware module independently develops the driver interface, and provides the application program interface independent of the hardware, so that if the hardware When the resource problem needs to be changed, only the driver of the hardware needs to be modified, which saves the tediousness of modifying the application software and main system software related to the hardware, and greatly improves the efficiency of software development and maintenance. The system software structure is shown in Figure 13.

Design of Sending and Controlling Timing Detection System Based on MSP430F149 MCU
Figure 13 System software structure block diagram

The system software is divided into four layers: hardware layer, driver layer, interface layer and application layer. The hardware layer provides system data acquisition, digital processing and input and output control support; the driver layer provides driver support for the use and operation of each hardware, ensuring that software functions are completed through the corresponding hardware devices; the interface layer provides application programming interfaces that are independent of each hardware module As well as system timing and logic control services; the application layer mainly completes functions such as detection tasks and related environment settings.

concluding remarks

According to the characteristics and detection requirements of a certain type of rocket launch control timing signal, this paper designs a launch control timing detection system based on MSP430F149 microcontroller. The paper gives the overall design scheme of the system, and introduces the specific implementation methods of each part of the hardware and software of the transmission control timing detection system in detail. The system works stably and reliably, has high efficiency, and has high detection data accuracy.

The Links:   LM150X08-TLA1 FZ1200R12KF1

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