Application background
With the development of China's economy and society, new requirements have been constantly put forward for hydrological information, and the number and content of hydrological observations have continuously increased. In a hydrological monitoring system, it is often necessary to monitor a large number of water levels, and most of the monitoring data needs to be stored in real time, and the back-end server performs processing. Due to the scattered monitoring points, the distribution range is wide, and most of them are set up in areas with harsh environments. Data storage through a portable RS232/485 data storage system has become one of the means of communication selected by the hydrological department. The pollution source monitoring equipment can store the collected pollution data in the SD/TF card in real time, so that it can be easily extracted and sent to the hydrological monitoring department at any time. The timely management of the pollutant discharge unit or individual can greatly improve the efficiency of the hydrological department.
An Introduction
System composition and basic working principle
As the price of high-performance embedded microprocessors gradually decreases and the storage capacity of SD/TF cards continues to increase, the use of high-performance 32-bit industrial-grade ARM microprocessors as the system core in conjunction with CPLD timing control, embedded FAT32 file system, through large The capacity memory card and USB data copy function provide unparalleled advantages for high-performance, low-power, low-cost, small-volume mass data storage and copying.
Figure 1 shows the basic structure of a portable RS232/485 data storage system:
In this system, high-performance 32-bit industrial-grade ARM microprocessors and large-capacity memory cards are the core of the system. With the continuous development of technology, it is now very easy to buy dozens of G SD/TF cards on the market. A large-capacity storage system can be realized.
In order to achieve high reliability and high efficiency of the system, a high-performance 32-bit embedded microprocessor based on the ARM architecture must be used as the management core of the system. By combining with an efficient embedded operating system, a unique dynamic memory allocation algorithm is adopted. In order to manage the memory consumption and release of the file system, improve data transmission efficiency, avoid data loss, and achieve reliable storage of real-time data.
SD/TF card and ARM interface software design:
a First initialize the SD/TF card, check the status, read and write sectors and other basic operations. The file system layer is designed in accordance with the requirements of the PC file system, such as FAT tables, file directory tables and other PC-compatible file management systems, which can greatly simplify the analysis and processing of back-end data. The file operation layer includes file creation, reading and writing, deletion, and the like.
b When serial data is detected, the system automatically creates a pre-defined folder on the SD/TF card and generates a stored data file in the directory for real-time data storage. The name of the folder can be customized by the configuration software. For example, the 2011 data, the folder name can be defined as 20111001, and the data storage file is a .TXT file. The system automatically creates the file, automatically numbers it, and does not duplicate the file for easy file management.
c Due to the limitations of the data acquisition system and the requirements of the specific environment, portable RS232/485 data storage must be suitable for long-term unattended, fast, and versatile. In order to enable long-term data storage, in addition to using a larger capacity SD/TF card, if several G or even several tens of G of data are stored in the same file at the same time, the back-end analysis and processing of a large amount of data will certainly cause huge impact on us. The trouble, therefore, requires the FAT32 file system of portable data storage to be more sophisticated and intelligent. This requires the exploration of a better file management method. After many experiments and attempts, the use of regularly created data storage files for storage is conducive to more effective data management and better analysis and processing. For example, suppose that the user creates a data storage file by setting the software to set an interval of 24 hours a day (according to the specific amount of data stored in the user's device determines the time). Then N days later, there will be N TXT files automatically created in the folder 20111001. 0001.TXT, 0002.TXT, ... N.TXT, respectively, the data for each period will be stored in the corresponding file, without losing any bytes.
d In some specific applications, data does not need to be processed and displayed in real time. Only the original data is recorded and used as a “black box†to prepare for back-end processing. This requires that the SD/TF card can be used cyclically. When the data volume reaches the set memory card capacity, it automatically overwrites the original storage file.
f In the past, large-capacity data storage systems only had the function of passively receiving data for storage. However, with the continuous updating of technology, the requirements of existing data acquisition equipment have been far from satisfied; more user equipments need to be stored by data storage systems. In the host state, the handshake signal is actively sent, and the user equipment passively feeds back information after receiving the signal, and then the data storage system stores the data. The serial communication interface is controlled by the user, and the user can set more than 10 different "polling" instructions and intervals. The system is initialized in the main program and uses the serial port work mode to make a call from the system host to the data device, and periodically reads data or writes data. The flow chart of the program is as follows:
Hardware interface design:
a Provide RS232/485 interface, support 2400~115200 wide range baud rate. Serial port transparent data transmission, no transmission protocol, transparent storage of user data, 100% reliable storage, support data storage capacity of up to 14K bytes / sec.
b has USB copy data function, U disk management, high speed USB2.0 interface; USB automatic identification, no need to install the driver.
Shock-resistant design:
Whether it is in the storage pipeline online detection data, or unmanned aerial information black box need data storage equipment has a certain strength of vibration resistance, this hardware design uses self-locking deck, embedded memory card, with shock-proof function; To avoid accidental contact between the memory card and the card holder, data cannot be stored.
Buzzer alarm function:
For important data, the loss caused by lost data is painful. The system software has designed a system error alarm. After the system is powered on, the SD/TF card is initialized. The buzzer sounds when the initialization is successful, indicating that the system is operating normally; the buzzer sounds long as an error alarm.
typical application
to sum up:
Embedded operating system has a vital role in the system, relying on the powerful features of high-performance embedded operating system, the program supports a variety of commonly used file systems to facilitate the migration of data, while the embedded operating system also achieve Automatic management of storage media, automatic error correction, and fatigue algorithms ensure high reliability of stored data.
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