High-precision mass data acquisition and storage system based on single-chip microcomputer

　　0 Introduction

　　With the development of information technology, especially the improvement of processing speed of various digital processing devices, it has become a reality to realize real-time processing of massive data. However, in some harsh experimental environments, data cannot be processed in real time, and storage test methods are still needed.

　　Storage testing refers to a dynamic testing technology in which a micro storage test system is built into the object being tested, with no impact on the object being tested or the impact being within the allowable range, to complete data acquisition and storage in real time on site, and the storage is recycled afterwards, with the host computer processing and reproducing the tested information.

　　According to the specific situation, this paper designs a high-precision mass data acquisition and storage system based on MSP430F1611 single-chip microcomputer. The system uses MSP430F1611 single-chip microcomputer as the main control unit, and adopts 16-bit high-precision A/D conversion chip ADS1146 and 2 GB TF storage card to realize high-precision data acquisition and designated block storage; the host computer and the single-chip microcomputer are connected through the parallel port to USB chip FT245, and the reading of the designated block data of the TF storage card and the erasing of the block data are all controlled by Lab-

　　The system is completed by the host computer program written in VIEW. Therefore, users can easily and conveniently complete the acquisition, storage and post-processing of massive high-precision data in some harsh experimental environments. At the same time, the system has the characteristics of large capacity, high precision, low power consumption and small size.

　　1 System Design

　　1.1 Basic system of single chip microcomputer

　　The microcontroller basic system is the core of the entire control system, which completes the signal processing and coordinated control of the entire system. Its structural block diagram is shown in Figure 1. Its main work is to perform initialization operations after power-on, set the sampling cycle, start the A/D sampling circuit, read the sampled data, and temporarily store it in its own RAM storage area. When the stored data reaches a certain amount, it will be stored in the specified TF storage card data block; after data acquisition and storage, the microcontroller is connected to the host computer, and when the TF storage card block data read instruction sent by the host computer is received, the corresponding block data will be uploaded to the host computer and stored as a specified type of steering file; in addition, when the host computer sends a TF storage card erase instruction to the microcontroller, a dialog box will pop up in the user interface to confirm whether to erase the specified block to confirm the block to be erased again to prevent accidental erasure.

　　The central control unit of this system uses the 16-bit low-power single-chip microcomputer MSP430F1611 produced by TI [5]. The operating voltage range of this chip is 1.8~3.6 V, with 48 KB+256 B of FLASH MEMORY and 10 KB of RAM, rich on-chip peripheral modules, such as timer A, timer B, 48 programmable I/Os, and serial port 0, 1 (UART0, 1), so it can better meet the system design requirements.

　　1.2 A/D sampling circuit

　　The 16-bit high-precision A/D conversion chip ADS1146 is selected, and its connection circuit with the microcontroller is shown in Figure 2.

　　The three-wire SPI communication mode is selected between ADS1146 and the microcontroller, that is, the microcontroller P3.1~P3.3 pins are selected as the second function: SIMO0, SOMI0 and UCLK0. The data transmission rate and the gain value of the programmable gain amplifier are set by initializing the corresponding registers. At this time, the P3.1 pin can be programmed to detect whether it is a low level. If it is low, 0001 001X is written to the microcontroller U0TXBUF register to start the single read RDATA mode, and then two NOP instructions are written to the microcontroller U0TXBUF. At the same time, the MSB of the U0RXBUF high byte data obtained by the microcontroller in this operation is placed in the high 8 bits of the pre-defined integer data, and its low byte data LSB is placed in the low 8 bits of the integer data.

　　1.3 TF memory card

　　The main function of the TF memory card is to store data. The specific implementation process is: read the A/D sampling data and temporarily store it in the RAM storage area of ​​the microcontroller. When the stored data reaches a certain amount, it is stored in the specified TF memory card data block, and this process is repeated until the storage of the predetermined data block of the TF memory card is completed. This system uses a 2 GB TF memory card produced by SanDisk, which is particularly suitable for data acquisition and storage systems with large-capacity data storage requirements. The connection circuit between the TF memory card and the MSP430F1611 is shown in Figure 3.

　　The volume of TF memory card is 15 mm×11 mm×1 mm, which is equivalent to the size of a fingernail, and includes two bus modes: SD protocol and SPI protocol. The bus mode of this system is set to SPI mode through COM0 instruction, and the corresponding control register of the microcontroller UART is set and the second function of P5.1~P5.3 pins SIMO1, SOMI1 and UCLK1 are selected. In addition, the TF memory card is initialized. Single block read. Single block write and erase operations are completed by calling COM1, COM17, COM24 and COM38 instructions and their corresponding steps respectively.

　　1.4 Communication with the host computer

　　FT245 is a parallel FIFO bidirectional data transmission USB chip from FTDI. The USB communication mode in this system is shown in Figure 4, where FT245 provides an 8-bit parallel data bus D0~D7 to the MSP430F1611 microcontroller, which is converted into a virtual serial port by installing the VCP driver on the host computer.

　　The host computer software is developed based on the VISA (Virtual Instrument Software Architecture) interface module of LabVIEW. VISA is a standard I/O application program interface used for instrument programming and a standard application program interface (API) for instrument drivers commonly used in the industry. It adopts object-oriented programming and has good compatibility. Scalability and independence [10-11]? The host computer user interface developed using it is shown in Figure 5. After the data acquisition and storage are completed, the data reading function can be selected. At this time, the microcontroller will read the data stored in the corresponding block in the TF storage card, send it to the host computer in serial mode, and save it as a steering file. txt, so as to facilitate the subsequent analysis of the data.

　　2 Conclusion

　　This system solves the problem of high-precision data acquisition and mass storage for subsequent analysis in some harsh experimental environments. In addition, after the data acquisition and storage is completed, the user can read the data instructions through the host computer software to obtain the data stored in the corresponding block in the TF storage card. txt document, and further analyze the data by calling Matlab. At the same time, the system has the advantages of small size and low power consumption.