Application of MSP430 MCU in test system

1 Introduction

Microcontroller (or microcontroller) technology has penetrated into all aspects of life and is widely used in home appliances, communications, testing and other fields. Therefore, this technology is actively affecting people's lives. Here is a test system design based on MSP430 microcontroller. MSP430 series microcontrollers are ultra-low power mixed signal controllers produced by TI. Its flexible clock source selection can maximize battery life. It has a rich set of peripheral modules integrated inside. Different models of this series of microcontrollers are targeted at different application fields.

2 System Design

2.1 Introduction to Storage Test Principles

Storage test technology is a new test method that started in the 1970s. Storage test is a dynamic test technology that places a micro data acquisition and storage tester in the tested object without affecting it or affecting it within the permitted range, completes the rapid acquisition and memory of information on site in real time, retrieves the recorder afterwards, and processes and reproduces the test information with a computer.

2.2 System Working Principle

Figure 1 is a block diagram of the test system based on the MSP430 series microcontroller. The test system has a programmable setting function. The trigger signal starts the microcontroller to enter the sampling state and samples the A/D converter data at a certain sampling frequency. The sampling frequency is determined by the timer inside the microcontroller. The sampled data is converted to digital through the 12-bit A/D converter inside the microcontroller and then stored in the memory. When the test system is recovered, it can communicate directly with the computer through the RS232 serial port and store the data in the computer for subsequent processing. When designing the system, factors such as design requirements, performance of the devices used, electromagnetic compatibility, system stability, operability, and work reliability should be fully considered.

3 System Hardware Design

The system hardware design mainly includes sensors, analog adapter circuits, MSP430 microcontroller acquisition, storage units, and interface units. The signal from the sensor enters the A/D converter inside the microcontroller after the analog adapter circuit for conversion, and then the conversion result is stored in the memory through the I/O port of the microcontroller. The serial asynchronous RS232 communication interface is used to read the data. After the test is completed, the data communication, display, processing and other functions are completed through the computer. The power management part is controlled by the microcontroller to supply power to the memory and analog circuit, which can extend the battery life. The use of the A/D converter inside the microcontroller not only reduces the complexity of the system design, but also improves the reliability of the system, thereby avoiding the complexity of the interface design and reducing the PCB board area.

The system uses RS232 serial port asynchronous communication with the computer. The system uses MAX232 device to realize the conversion between the microcontroller and the computer interface. A 0.1μF capacitor is connected to its pins C1+, C1-, C2+, C2-, V+ and V- respectively to realize charging to meet the corresponding charging pump requirements. Pins T1OUT, T1IN, R1OUT and R1IN are the output and input pins of RS232 conversion transmission and reception, respectively, which can realize the conversion between the TTL level of the microcontroller and the interface level of the host computer. In order to reduce the interference at the input end, a 0.1μF capacitor is also required to be connected to the power input pin of the device to realize filtering. MAX232 uses a power supply voltage of 0.3~6V; the levels on the pins R1IN and T1OUT of the computer interface are ±30V and ±15V respectively, and the levels on the pins T1IN and R1OUT of the microcontroller interface are -0.3V～ (Vcc is -0.3V) and 0.3V～ (Vcc is +0.3V). The microcontroller is powered by 3.3 V, so the power supply voltage Vcc of MAX232 is 3.3 V. As shown in Figure 2.

4 System Software Design

Software design is also an important part of test system design. The general process of software design is: clarify software design tasks; divide program modules according to functions and draw flow charts; select programming languages ​​and program; debug programs.

State design is the process of determining the state organization structure of the storage test system according to the motion law of the object under test. It is the key to realize functional design, the basis of hardware design, and an effective means to establish a basic storage test system. State design can make the design idea clearly run through the design and debugging, and can simplify the originally complex design process to varying degrees.

System state transition: After the system is powered on, the MCU is in the state of knowing, waiting for the sampling start signal. At this time, the system is in an ultra-low power state, consuming only about 1μA of current. After the trigger signal arrives, the system starts cyclic sampling. After the sampling is completed and the memory is full of data, it stops sampling and enters the low-power waiting reading state. In the waiting reading state, the reading port is connected. When the I/O port of the MCU receives the rising edge sent by the computer, it starts to send data to the computer, that is, the data is first read from the memory to the MCU, and then sent to the computer by the serial port of the MCU. After the sending is completed, it enters the low-power state again. Figure 3 is a system state diagram.

5 Test Results

In the system test experiment, the signal generator generates a 1 Hz sine wave. After data acquisition, the reading is shown in Figure 4. The system fully realizes the triggering and sampling process. Figure 4 is a single-channel test waveform obtained through the experiment. The output is completely consistent with the given input signal, which fully demonstrates that this solution is feasible.

6 Conclusion

The test system is designed using the MSP430 series microcontroller, and the 12-bit A/D converter provided inside the MSP430 series microcontroller is used for data acquisition. This method greatly simplifies the circuit design and can achieve higher measurement accuracy. Moreover, due to the ultra-low power design of the MSP430 series microcontroller, the test system has the characteristics of small size, low power consumption, strong anti-interference ability, and no leads.